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class="vector-toc-list"> </ul> </li> <li id="toc-Stem_cell_biology" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Stem_cell_biology"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Stem cell biology</span> </div> </a> <ul id="toc-Stem_cell_biology-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Vision" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Vision"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Vision</span> </div> </a> <ul id="toc-Vision-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Glycoprotein_synthesis" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Glycoprotein_synthesis"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.4</span> <span>Glycoprotein synthesis</span> </div> </a> <ul id="toc-Glycoprotein_synthesis-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Immune_system" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Immune_system"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.5</span> <span>Immune system</span> </div> </a> <ul id="toc-Immune_system-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Skin" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Skin"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.6</span> <span>Skin</span> </div> </a> <ul id="toc-Skin-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Red_blood_cells" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Red_blood_cells"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.7</span> <span>Red blood cells</span> </div> </a> <ul id="toc-Red_blood_cells-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Units_of_measurement" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Units_of_measurement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Units of measurement</span> </div> </a> <ul id="toc-Units_of_measurement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Nutrition" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Nutrition"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Nutrition</span> </div> </a> <button aria-controls="toc-Nutrition-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Nutrition subsection</span> </button> <ul id="toc-Nutrition-sublist" class="vector-toc-list"> <li id="toc-Dietary_intake" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Dietary_intake"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Dietary intake</span> </div> </a> <ul id="toc-Dietary_intake-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Deficiency" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Deficiency"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>Deficiency</span> </div> </a> <ul id="toc-Deficiency-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Sources" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Sources"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3</span> <span>Sources</span> </div> </a> <ul id="toc-Sources-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Chemistry" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Chemistry"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Chemistry</span> </div> </a> <ul id="toc-Chemistry-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Synthesis" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Synthesis"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Synthesis</span> </div> </a> <button aria-controls="toc-Synthesis-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Synthesis subsection</span> </button> <ul id="toc-Synthesis-sublist" class="vector-toc-list"> <li id="toc-Biosynthesis" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Biosynthesis"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.1</span> <span>Biosynthesis</span> </div> </a> <ul id="toc-Biosynthesis-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Industrial_synthesis" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Industrial_synthesis"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.2</span> <span>Industrial synthesis</span> </div> </a> <ul id="toc-Industrial_synthesis-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-History" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#History"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>History</span> </div> </a> <ul id="toc-History-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Retinol</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 37 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-37" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">37 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%B1%D8%AA%D9%8A%D9%86%D9%88%D9%84" title="رتينول – Arabic" lang="ar" hreflang="ar" data-title="رتينول" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%B0%E0%A7%87%E0%A6%9F%E0%A6%BF%E0%A6%A8%E0%A6%B2" title="রেটিনল – Bangla" lang="bn" hreflang="bn" data-title="রেটিনল" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Retinol" title="Retinol – Bosnian" lang="bs" hreflang="bs" data-title="Retinol" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Retinol" title="Retinol – Catalan" lang="ca" hreflang="ca" data-title="Retinol" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Retinol" title="Retinol – German" lang="de" hreflang="de" data-title="Retinol" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Retinool" title="Retinool – Estonian" lang="et" hreflang="et" data-title="Retinool" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Retinol" title="Retinol – Spanish" lang="es" hreflang="es" data-title="Retinol" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Retinolo" title="Retinolo – Esperanto" lang="eo" hreflang="eo" data-title="Retinolo" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Erretinol" title="Erretinol – Basque" lang="eu" hreflang="eu" data-title="Erretinol" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%B1%D8%AA%DB%8C%D9%86%D9%88%D9%84" title="رتینول – Persian" lang="fa" hreflang="fa" data-title="رتینول" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/R%C3%A9tinol" title="Rétinol – French" lang="fr" hreflang="fr" data-title="Rétinol" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/Reitean%C3%B3l" title="Reiteanól – Irish" lang="ga" hreflang="ga" data-title="Reiteanól" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EB%A0%88%ED%8B%B0%EB%86%80" title="레티놀 – Korean" lang="ko" hreflang="ko" data-title="레티놀" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%8C%D5%A5%D5%BF%D5%AB%D5%B6%D5%B8%D5%AC" title="Ռետինոլ – Armenian" lang="hy" hreflang="hy" data-title="Ռետինոլ" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Retinol" title="Retinol – Indonesian" lang="id" hreflang="id" data-title="Retinol" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Retinolo" title="Retinolo – Italian" lang="it" hreflang="it" data-title="Retinolo" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-ks mw-list-item"><a href="https://ks.wikipedia.org/wiki/%D8%B1%DB%8C%D9%B9%DB%8C%D9%86%D9%88%D9%84" title="ریٹینول – Kashmiri" lang="ks" hreflang="ks" data-title="ریٹینول" data-language-autonym="कॉशुर / کٲشُر" data-language-local-name="Kashmiri" class="interlanguage-link-target"><span>कॉशुर / کٲشُر</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%A0%D0%B5%D1%82%D0%B8%D0%BD%D0%BE%D0%BB" title="Ретинол – Kazakh" lang="kk" hreflang="kk" data-title="Ретинол" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-ku mw-list-item"><a href="https://ku.wikipedia.org/wiki/R%C3%AAt%C3%AEnol" title="Rêtînol – Kurdish" lang="ku" hreflang="ku" data-title="Rêtînol" data-language-autonym="Kurdî" data-language-local-name="Kurdish" class="interlanguage-link-target"><span>Kurdî</span></a></li><li class="interlanguage-link interwiki-ky mw-list-item"><a href="https://ky.wikipedia.org/wiki/%D0%A0%D0%B5%D1%82%D0%B8%D0%BD%D0%BE%D0%BB" title="Ретинол – Kyrgyz" lang="ky" hreflang="ky" data-title="Ретинол" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target"><span>Кыргызча</span></a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/Retinol" title="Retinol – Luxembourgish" lang="lb" hreflang="lb" data-title="Retinol" data-language-autonym="Lëtzebuergesch" data-language-local-name="Luxembourgish" class="interlanguage-link-target"><span>Lëtzebuergesch</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Retinol" title="Retinol – Malay" lang="ms" hreflang="ms" data-title="Retinol" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Retinol" title="Retinol – Dutch" lang="nl" hreflang="nl" data-title="Retinol" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-or mw-list-item"><a href="https://or.wikipedia.org/wiki/%E0%AC%B0%E0%AD%87%E0%AC%9F%E0%AC%BF%E0%AC%A8%E0%AD%8B%E0%AC%B2" title="ରେଟିନୋଲ – Odia" lang="or" hreflang="or" data-title="ରେଟିନୋଲ" data-language-autonym="ଓଡ଼ିଆ" data-language-local-name="Odia" class="interlanguage-link-target"><span>ଓଡ଼ିଆ</span></a></li><li class="interlanguage-link interwiki-uz mw-list-item"><a href="https://uz.wikipedia.org/wiki/Retinol" title="Retinol – Uzbek" lang="uz" hreflang="uz" data-title="Retinol" data-language-autonym="Oʻzbekcha / ўзбекча" data-language-local-name="Uzbek" class="interlanguage-link-target"><span>Oʻzbekcha / ўзбекча</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Retinol" title="Retinol – Polish" lang="pl" hreflang="pl" data-title="Retinol" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Retinol" title="Retinol – Portuguese" lang="pt" hreflang="pt" data-title="Retinol" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Retinol" title="Retinol – Romanian" lang="ro" hreflang="ro" data-title="Retinol" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%A0%D0%B5%D1%82%D0%B8%D0%BD%D0%BE%D0%BB" title="Ретинол – Russian" lang="ru" hreflang="ru" data-title="Ретинол" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Retinol" title="Retinol – Slovak" lang="sk" hreflang="sk" data-title="Retinol" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sr badge-Q70893996 mw-list-item" title=""><a href="https://sr.wikipedia.org/wiki/%D0%A0%D0%B5%D1%82%D0%B8%D0%BD%D0%BE%D0%BB" title="Ретинол – Serbian" lang="sr" hreflang="sr" data-title="Ретинол" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Retinol" title="Retinol – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Retinol" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Retinol" title="Retinol – Swedish" lang="sv" hreflang="sv" data-title="Retinol" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%A0%D0%B5%D1%82%D0%B8%D0%BD%D0%BE%D0%BB" title="Ретинол – Ukrainian" lang="uk" hreflang="uk" data-title="Ретинол" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vec mw-list-item"><a href="https://vec.wikipedia.org/wiki/Retino%C5%82o" title="Retinoło – Venetian" lang="vec" hreflang="vec" data-title="Retinoło" data-language-autonym="Vèneto" data-language-local-name="Venetian" class="interlanguage-link-target"><span>Vèneto</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Retinol" title="Retinol – Vietnamese" lang="vi" hreflang="vi" data-title="Retinol" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E8%A7%86%E9%BB%84%E9%86%87" title="视黄醇 – Chinese" lang="zh" hreflang="zh" data-title="视黄醇" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q424976#sitelinks-wikipedia" title="Edit interlanguage links" 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searchaux" style="display:none">Chemical compound</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="/wiki/Retinal" title="Retinal">Retinal</a>.</div> <p class="mw-empty-elt"> </p> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox" style="border-spacing:2px;"><caption class="infobox-title"><span title="International nonproprietary name (INN): Retinol">Retinol</span></caption><tbody><tr><td colspan="2" class="infobox-image notheme" style="background-color: #f8f9fa;"><span class="mw-default-size" typeof="mw:File/Frameless"><a href="/wiki/File:All-trans-Retinol2.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5c/All-trans-Retinol2.svg/220px-All-trans-Retinol2.svg.png" decoding="async" width="220" height="68" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5c/All-trans-Retinol2.svg/330px-All-trans-Retinol2.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5c/All-trans-Retinol2.svg/440px-All-trans-Retinol2.svg.png 2x" data-file-width="457" data-file-height="141" /></a></span></td></tr><tr><td colspan="2" class="infobox-image notheme" style="background-color: #f8f9fa;"><span class="mw-default-size" typeof="mw:File/Frameless"><a href="/wiki/File:Retinol_3D_balls.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Retinol_3D_balls.png/220px-Retinol_3D_balls.png" decoding="async" width="220" height="105" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Retinol_3D_balls.png/330px-Retinol_3D_balls.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Retinol_3D_balls.png/440px-Retinol_3D_balls.png 2x" data-file-width="2094" data-file-height="1000" /></a></span><div class="infobox-caption">Retinol</div></td></tr><tr><th colspan="2" class="infobox-header" style="background:#ddd">Clinical data</th></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/American_Society_of_Health-System_Pharmacists" title="American Society of Health-System Pharmacists">AHFS</a>/<a href="/wiki/Drugs.com" title="Drugs.com">Drugs.com</a></th><td class="infobox-data"><span title="www.drugs.com"><a rel="nofollow" class="external text" href="https://www.drugs.com/monograph/vitamin-a.html">Monograph</a></span></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Regulation_of_therapeutic_goods" title="Regulation of therapeutic goods">License data</a></th><td class="infobox-data"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style><div class="plainlist"> <ul><li><small><abbr class="country-name" title="United States">US</abbr></small> <a href="/wiki/DailyMed" title="DailyMed">DailyMed</a>: <span title="dailymed.nlm.nih.gov"><a rel="nofollow" class="external text" href="https://dailymed.nlm.nih.gov/dailymed/search.cfm?labeltype=all&query=Retinol">Retinol</a></span></li></ul></div> </td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Route_of_administration" title="Route of administration">Routes of<br />administration</a></th><td class="infobox-data"><a href="/wiki/By_mouth" class="mw-redirect" title="By mouth">By mouth</a>, <a href="/wiki/Intramuscular" class="mw-redirect" title="Intramuscular">intramuscular</a><sup id="cite_ref-drugs_1-0" class="reference"><a href="#cite_note-drugs-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Drug_class" title="Drug class">Drug class</a></th><td class="infobox-data"><a href="/wiki/Vitamin" title="Vitamin">vitamin</a></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Anatomical_Therapeutic_Chemical_Classification_System" title="Anatomical Therapeutic Chemical Classification System">ATC code</a></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><a href="/wiki/ATC_code_A11" title="ATC code A11">A11CA01</a> (<span title="www.whocc.no"><a rel="nofollow" class="external text" href="https://www.whocc.no/atc_ddd_index/?code=A11CA01">WHO</a></span>) <a href="/wiki/ATC_code_D10" title="ATC code D10">D10AD02</a> (<span title="www.whocc.no"><a rel="nofollow" class="external text" href="https://www.whocc.no/atc_ddd_index/?code=D10AD02">WHO</a></span>), <a href="/wiki/ATC_code_R01" title="ATC code R01">R01AX02</a> (<span title="www.whocc.no"><a rel="nofollow" class="external text" href="https://www.whocc.no/atc_ddd_index/?code=R01AX02">WHO</a></span>), <a href="/wiki/ATC_code_S01" title="ATC code S01">S01XA02</a> (<span title="www.whocc.no"><a rel="nofollow" class="external text" href="https://www.whocc.no/atc_ddd_index/?code=S01XA02">WHO</a></span>)</li></ul></div></td></tr><tr><th colspan="2" class="infobox-header" style="background:#ddd">Legal status</th></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Regulation_of_therapeutic_goods" title="Regulation of therapeutic goods">Legal status</a></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"> <ul><li><small><abbr class="country-name" title="United States">US</abbr>:</small> <a href="/wiki/Over-the-counter_drug" title="Over-the-counter drug">OTC</a></li></ul></div> </td></tr><tr><th colspan="2" class="infobox-header" style="background:#ddd">Identifiers</th></tr><tr><td colspan="2" class="infobox-full-data"><div class="collapsible-list mw-collapsible mw-collapsed" style="text-align: left;"> <div style="line-height: 1.6em; font-weight: bold;"><div><a href="/wiki/IUPAC_nomenclature_of_chemistry" title="IUPAC nomenclature of chemistry">IUPAC name</a></div></div> <ul class="mw-collapsible-content" style="margin-top: 0; margin-bottom: 0; line-height: inherit; list-style: none; margin-left: 0; word-break:break-all; text-align:left; padding-left:1.5em; text-indent:-1.5em;"><li style="line-height: inherit; margin: 0"><div style="font-size: 97%;">(2<i>E</i>,4<i>E</i>,6<i>E</i>,8<i>E</i>)-3,7-dimethyl-9-(2,6,6-trimethylcyclohex-1-en-1-yl)nona-2,4,6,8-tetraen-1-ol</div></li></ul> </div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/CAS_Registry_Number" title="CAS Registry Number">CAS Number</a></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><span title="commonchemistry.cas.org"><a rel="nofollow" class="external text" href="https://commonchemistry.cas.org/detail?cas_rn=68-26-8">68-26-8</a></span></li><li>mixture: <span title="commonchemistry.cas.org"><a rel="nofollow" class="external text" href="https://commonchemistry.cas.org/detail?cas_rn=11103-57-4">11103-57-4</a></span></li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/PubChem#CID" title="PubChem">PubChem</a> <span style="font-weight:normal"><abbr title="Compound ID">CID</abbr></span></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><span title="pubchem.ncbi.nlm.nih.gov"><a rel="nofollow" class="external text" href="https://pubchem.ncbi.nlm.nih.gov/compound/445354">445354</a></span></li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Guide_to_Pharmacology" title="Guide to Pharmacology">IUPHAR/BPS</a></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><span title="www.guidetopharmacology.org"><a rel="nofollow" class="external text" href="https://www.guidetopharmacology.org/GRAC/LigandDisplayForward?ligandId=4053">4053</a></span></li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/DrugBank" title="DrugBank">DrugBank</a></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><span title="www.drugbank.ca"><a rel="nofollow" class="external text" href="https://www.drugbank.ca/drugs/DB00162">DB00162</a></span></li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/ChemSpider" title="ChemSpider">ChemSpider</a></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><span title="www.chemspider.com"><a rel="nofollow" class="external text" href="https://www.chemspider.com/Chemical-Structure.393012.html">393012</a></span></li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Unique_Ingredient_Identifier" title="Unique Ingredient Identifier">UNII</a></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><span title="precision.fda.gov"><a rel="nofollow" class="external text" href="https://precision.fda.gov/uniisearch/srs/unii/G2SH0XKK91">G2SH0XKK91</a></span></li><li>mixture: <span title="precision.fda.gov"><a rel="nofollow" class="external text" href="https://precision.fda.gov/uniisearch/srs/unii/81G40H8B0T">81G40H8B0T</a></span></li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/KEGG" title="KEGG">KEGG</a></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><span title="www.kegg.jp"><a rel="nofollow" class="external text" href="https://www.kegg.jp/entry/D00069">D00069</a></span></li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/ChEBI" title="ChEBI">ChEBI</a></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><span title="www.ebi.ac.uk"><a rel="nofollow" class="external text" href="https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:17336">CHEBI:17336</a></span></li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/ChEMBL" title="ChEMBL">ChEMBL</a></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><span title="www.ebi.ac.uk"><a rel="nofollow" class="external text" href="https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/ChEMBL986">ChEMBL986</a></span></li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Protein_Data_Bank" title="Protein Data Bank">PDB ligand</a></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li>RTL (<span title="www.ebi.ac.uk"><a rel="nofollow" class="external text" href="https://www.ebi.ac.uk/pdbe-srv/PDBeXplore/ligand/?ligand=RTL">PDBe</a></span>, <span title="www.rcsb.org"><a rel="nofollow" class="external text" href="https://www.rcsb.org/ligand/RTL">RCSB PDB</a></span>)</li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/CompTox_Chemicals_Dashboard" title="CompTox Chemicals Dashboard">CompTox Dashboard</a> <span style="font-weight:normal">(<abbr title="U.S. Environmental Protection Agency">EPA</abbr>)</span></th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><span title="comptox.epa.gov"><a rel="nofollow" class="external text" href="https://comptox.epa.gov/dashboard/chemical/details/DTXSID3023556">DTXSID3023556</a> <span class="mw-valign-text-top noprint" typeof="mw:File/Frameless"><a href="https://www.wikidata.org/wiki/Q424976#P3117" title="Edit this at Wikidata"><img alt="Edit this at Wikidata" src="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/10px-OOjs_UI_icon_edit-ltr-progressive.svg.png" decoding="async" width="10" height="10" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/15px-OOjs_UI_icon_edit-ltr-progressive.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/20px-OOjs_UI_icon_edit-ltr-progressive.svg.png 2x" data-file-width="20" data-file-height="20" /></a></span></span></li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/ECHA_InfoCard" class="mw-redirect" title="ECHA InfoCard"><span title="echa.europa.eu">ECHA InfoCard</span></a></th><td class="infobox-data"><a rel="nofollow" class="external text" href="https://echa.europa.eu/substance-information/-/substanceinfo/100.000.621">100.000.621</a> <span class="mw-valign-text-top noprint" typeof="mw:File/Frameless"><a href="https://www.wikidata.org/wiki/Q424976#P2566" title="Edit this at Wikidata"><img alt="Edit this at Wikidata" src="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/10px-OOjs_UI_icon_edit-ltr-progressive.svg.png" decoding="async" width="10" height="10" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/15px-OOjs_UI_icon_edit-ltr-progressive.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/20px-OOjs_UI_icon_edit-ltr-progressive.svg.png 2x" data-file-width="20" data-file-height="20" /></a></span></td></tr><tr><th colspan="2" class="infobox-header" style="background:#ddd">Chemical and physical data</th></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Chemical_formula" title="Chemical formula">Formula</a></th><td class="infobox-data"><span title="Carbon">C</span><sub>20</sub><span title="Hydrogen">H</span><sub>30</sub><span title="Oxygen">O</span></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Molar_mass" title="Molar mass">Molar mass</a></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7002286459000000000♠"></span>286.459</span> g·mol<sup>−1</sup></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;">3D model (<a href="/wiki/JSmol" class="mw-redirect" title="JSmol">JSmol</a>)</th><td class="infobox-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"><div class="plainlist"><ul><li><span title="chemapps.stolaf.edu (3D interactive model)"><a rel="nofollow" class="external text" href="https://chemapps.stolaf.edu/jmol/jmol.php?model=OC%2FC%3DC%28C%29%2FC%3DC%2FC%3DC%28C%29%2FC%3DC%2FC1%3DC%28C%29%2FCCCC1%28C%29C">Interactive image</a></span></li></ul></div></td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Melting_point" title="Melting point">Melting point</a></th><td class="infobox-data">62–64 °C (144–147 °F)</td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Boiling_point" title="Boiling point">Boiling point</a></th><td class="infobox-data">137–138 °C (279–280 °F) (<span class="nowrap"><span data-sort-value="6994100000000000000♠"></span>10<sup>−6</sup> mm Hg</span>)</td></tr><tr><th scope="row" class="infobox-label" style="line-height:1.2em;"><a href="/wiki/Aqueous_solution" title="Aqueous solution">Solubility in water</a></th><td class="infobox-data">0.000017<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> mg/mL (20 °C)</td></tr><tr><td colspan="2" class="infobox-full-data"><div class="collapsible-list mw-collapsible mw-collapsed" style="text-align: left;"> <div style="line-height: 1.6em; font-weight: bold;"><div><a href="/wiki/Simplified_molecular-input_line-entry_system" class="mw-redirect" title="Simplified molecular-input line-entry system">SMILES</a></div></div> <ul class="mw-collapsible-content" style="margin-top: 0; margin-bottom: 0; line-height: inherit; list-style: none; margin-left: 0; word-break:break-all;"><li style="line-height: inherit; margin: 0"><div style="word-wrap:break-word; text-indent:-1.5em; text-align:left; padding-left:1.5em; font-size:97%; line-height:120%;">OC/C=C(C)/C=C/C=C(C)/C=C/C1=C(C)/CCCC1(C)C</div></li></ul> </div></td></tr><tr><td colspan="2" class="infobox-full-data"><div class="collapsible-list mw-collapsible mw-collapsed" style="text-align: left;"> <div style="line-height: 1.6em; font-weight: bold;"><div><a href="/wiki/International_Chemical_Identifier" title="International Chemical Identifier">InChI</a></div></div> <ul class="mw-collapsible-content" style="margin-top: 0; margin-bottom: 0; line-height: inherit; list-style: none; margin-left: 0; word-break:break-all;"><li style="line-height: inherit; margin: 0"><div style="word-wrap:break-word; text-indent:-1.5em; text-align:left; padding-left:1.5em; font-size:97%; line-height:120%;">InChI=1S/C20H30O/c1-16(8-6-9-17(2)13-15-21)11-12-19-18(3)10-7-14-20(19,4)5/h6,8-9,11-13,21H,7,10,14-15H2,1-5H3/b9-6+,12-11+,16-8+,17-13+</div></li><li style="line-height: inherit; margin: 0"><div style="word-wrap:break-word; text-indent:-1.5em; text-align:left; padding-left:1.5em; font-size:97%; line-height:120%;">Key:FPIPGXGPPPQFEQ-OVSJKPMPSA-N</div></li></ul> </div></td></tr></tbody></table> <p><b>Retinol</b>, also called <b>vitamin A<sub>1</sub></b>, is a fat-soluble <a href="/wiki/Vitamin" title="Vitamin">vitamin</a> in the <a href="/wiki/Vitamin_A" title="Vitamin A">vitamin A</a> family that is found in food and used as a <a href="/wiki/Dietary_supplement" title="Dietary supplement">dietary supplement</a>.<sup id="cite_ref-ods_3-0" class="reference"><a href="#cite_note-ods-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Retinol or other forms of vitamin A are needed for vision, cellular development, maintenance of skin and <a href="/wiki/Mucous_membranes" class="mw-redirect" title="Mucous membranes">mucous membranes</a>, immune function and reproductive development.<sup id="cite_ref-ods_3-1" class="reference"><a href="#cite_note-ods-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Dietary sources include fish, <a href="/wiki/Dairy_products" class="mw-redirect" title="Dairy products">dairy products</a>, and meat.<sup id="cite_ref-ods_3-2" class="reference"><a href="#cite_note-ods-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> As a supplement it is used to treat and prevent <a href="/wiki/Vitamin_A_deficiency" title="Vitamin A deficiency">vitamin A deficiency</a>, especially that which results in <a href="/wiki/Xerophthalmia" title="Xerophthalmia">xerophthalmia</a>.<sup id="cite_ref-drugs_1-1" class="reference"><a href="#cite_note-drugs-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> It is taken <a href="/wiki/By_mouth" class="mw-redirect" title="By mouth">by mouth</a> or by <a href="/wiki/Intramuscular_injection" title="Intramuscular injection">injection into a muscle</a>.<sup id="cite_ref-drugs_1-2" class="reference"><a href="#cite_note-drugs-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> As an ingredient in skin-care products, it is used to reduce wrinkles and other effects of skin aging.<sup id="cite_ref-Kong_2015_4-0" class="reference"><a href="#cite_note-Kong_2015-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>Retinol at normal doses is well tolerated.<sup id="cite_ref-drugs_1-3" class="reference"><a href="#cite_note-drugs-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> High doses may cause <a href="/wiki/Hepatomegaly" title="Hepatomegaly">enlargement of the liver</a>, dry skin, and <a href="/wiki/Hypervitaminosis_A" title="Hypervitaminosis A">hypervitaminosis A</a>.<sup id="cite_ref-drugs_1-4" class="reference"><a href="#cite_note-drugs-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-BNF69_5-0" class="reference"><a href="#cite_note-BNF69-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> High doses during <a href="/wiki/Pregnancy" title="Pregnancy">pregnancy</a> may harm the fetus.<sup id="cite_ref-drugs_1-5" class="reference"><a href="#cite_note-drugs-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The body converts retinol to <a href="/wiki/Retinal" title="Retinal">retinal</a> and <a href="/wiki/Retinoic_acid" title="Retinoic acid">retinoic acid</a>, through which it acts.<sup id="cite_ref-ods_3-3" class="reference"><a href="#cite_note-ods-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>Retinol was discovered in 1909, isolated in 1931, and first made in 1947.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> It is on the <a href="/wiki/WHO_Model_List_of_Essential_Medicines" title="WHO Model List of Essential Medicines">World Health Organization's List of Essential Medicines</a>.<sup id="cite_ref-WHO23rd_8-0" class="reference"><a href="#cite_note-WHO23rd-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> Retinol is available as a <a href="/wiki/Generic_medication" class="mw-redirect" title="Generic medication">generic medication</a> and <a href="/wiki/Over_the_counter" class="mw-redirect" title="Over the counter">over the counter</a>.<sup id="cite_ref-drugs_1-6" class="reference"><a href="#cite_note-drugs-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> In 2021, vitamin A was the 298th most commonly prescribed medication in the United States, with more than 500,000 prescriptions.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Medical_uses">Medical uses</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=1" title="Edit section: Medical uses"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Retinol is used to treat <a href="/wiki/Vitamin_A_deficiency" title="Vitamin A deficiency">vitamin A deficiency</a>. </p><p>Three approaches may be used when populations have low vitamin A levels:<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p> <ol><li>Through dietary modification involving the adjustment of menu choices of affected persons from available food sources to optimize vitamin A content.</li> <li>Enriching commonly eaten and affordable foods with vitamin A, a process called fortification. It involves addition of synthetic vitamin A to staple foods like <a href="/wiki/Margarine" title="Margarine">margarine</a>, bread, flours, cereals, and infant formula during processing.</li> <li>By giving high-doses of vitamin A to the targeted deficient population, a method known as supplementation. In regions where deficiency is common, a single large dose is recommended to those at high risk twice a year.<sup id="cite_ref-WHO2008_12-0" class="reference"><a href="#cite_note-WHO2008-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup></li></ol> <p>Retinol is also used to reduce the risk of complications in <a href="/wiki/Measles" title="Measles">measles</a> patients.<sup id="cite_ref-WHO2008_12-1" class="reference"><a href="#cite_note-WHO2008-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Side_effects">Side effects</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=2" title="Edit section: Side effects"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Hypervitaminosis_A" title="Hypervitaminosis A">Hypervitaminosis A</a></div> <p>The <a href="/wiki/Dietary_Reference_Intake" title="Dietary Reference Intake">Recommended Daily Intake</a> (RDA) for preformed supplemental vitamin A for adult men and women is 900 and 700 Retinol Activity Units(RAE)/day, respectively, or about 3,000 IU and 2,300 IU.<sup id="cite_ref-ods_3-4" class="reference"><a href="#cite_note-ods-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> In pregnancy, the vitamin A RDA is 750–770 RAE/day (about 2,500–2,550 IU).<sup id="cite_ref-ods_3-5" class="reference"><a href="#cite_note-ods-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> During <a href="/wiki/Lactation" title="Lactation">lactation</a>, the RDA increases to 1,200–1,300 RAE/day (about 4,000–4,300 IU, with differences depending on age).<sup id="cite_ref-ods_3-6" class="reference"><a href="#cite_note-ods-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>Retinol Activity Units can only be converted to IU (International Units) when the source of the vitamin A is known.<sup id="cite_ref-ods_3-7" class="reference"><a href="#cite_note-ods-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> The IU values listed above do not apply to food sources of vitamin A.<sup id="cite_ref-ods_3-8" class="reference"><a href="#cite_note-ods-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>Too much vitamin A in retinoid form can be harmful. The body converts the dimerized form, <a href="/wiki/Carotene" title="Carotene">carotene</a>, into vitamin A as it is needed, so high levels of carotene are not toxic, whereas the ester (animal) forms are. The livers of certain animals, especially those adapted to polar environments, such as polar bears and seals,<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> often contain amounts of vitamin A that would be toxic to humans. Thus, vitamin A toxicity is typically reported in Arctic explorers and people taking large doses of synthetic vitamin A. The first documented death possibly caused by vitamin A poisoning was that of <a href="/wiki/Xavier_Mertz" title="Xavier Mertz">Xavier Mertz</a>, a <a href="/wiki/Switzerland" title="Switzerland">Swiss</a> scientist, who died in January 1913 on an <a href="/wiki/Antarctica" title="Antarctica">Antarctic</a> expedition that had lost its food supplies and fell to eating its sled dogs. Mertz may have consumed lethal amounts of vitamin A by eating the dogs' livers.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p><p>Vitamin A acute toxicity occurs when a person ingests vitamin A in large amounts more than the daily recommended value in the threshold of 25,000 IU/kg or more. Often, the patient consumes about 3–4 times the RDA's specification.<sup id="cite_ref-Gropper_15-0" class="reference"><a href="#cite_note-Gropper-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> Toxicity of vitamin A is believed to be associated with the methods of increasing vitamin A in the body, such as food modification, fortification, and supplementation, all of which are used to combat vitamin A deficiency.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> Toxicity is classified into two categories: acute and chronic. The former occurs a few hours or days after ingestion of a large amount of vitamin A. Chronic toxicity takes place when about 4,000 IU/kg or more of vitamin A is consumed for a long time. Symptoms of both include nausea, blurred vision, fatigue, weight-loss, and menstrual abnormalities.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p><p>Excess vitamin A is suspected to be a contributor to <a href="/wiki/Osteoporosis" title="Osteoporosis">osteoporosis</a>. This seems to happen at much lower doses than those required to induce acute intoxication. Only preformed vitamin A can cause these problems, because the conversion of carotenoids or retinyl esters into vitamin A is downregulated when physiological requirements are met;<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> but excessive uptake of carotenoids can cause <a href="/wiki/Carotenosis" title="Carotenosis">carotenosis</a>. </p><p>Excess preformed vitamin A during early pregnancy is associated with a significant increase in birth defects.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> These defects may be severe, even life-threatening. Even twice the daily recommended amount can cause severe birth defects.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> The FDA recommends that pregnant women get their vitamin A from foods containing beta carotene and that they ensure that they consume no more than 5,000 IU of preformed vitamin A (if any) per day. Although vitamin A is necessary for fetal development, most women carry sufficient stores of vitamin A in their liver cells,<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> so over-supplementation should be strictly avoided. </p><p>A review of all randomized controlled trials in the scientific literature by the <a href="/wiki/Cochrane_Collaboration" class="mw-redirect" title="Cochrane Collaboration">Cochrane Collaboration</a> published in <i><a href="/wiki/Journal_of_the_American_Medical_Association" class="mw-redirect" title="Journal of the American Medical Association">JAMA</a></i> in 2007 found that supplementation with beta carotene or vitamin A <i>increased</i> mortality by 5% and 16%, respectively.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> This effect has been attributed to the role of retinol and retinoic acid in increasing circulating cholesterol and triglycerides as well as promoting cancer incidence.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p><p>Studies emerging from developing countries India, Bangladesh, and Indonesia strongly suggest that, in populations in which vitamin A deficiency is common and maternal mortality is high, dosing expectant mothers with retinol can greatly reduce maternal mortality.<sup id="cite_ref-Sommer_24-0" class="reference"><a href="#cite_note-Sommer-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> Similarly, dosing newborn infants with 50,000 IU (15 mg) of vitamin A within two days of birth can significantly reduce neonatal mortality.<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Biological_roles">Biological roles</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=3" title="Edit section: Biological roles"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Retinol or other forms of vitamin A are needed for eyesight, maintenance of the skin, and human development.<sup id="cite_ref-drugs_1-7" class="reference"><a href="#cite_note-drugs-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Other than for vision, which requires 11-cis retinal, the active compound is retinoic acid, synthesized from retinal, in turn synthesized from retinol. The differing biological roles of retinoic acid depend on its <a href="/wiki/Stereochemistry" title="Stereochemistry">stereochemistry</a> and whether it is present in the all-trans, 9-cis or 13-cis forms.<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Embryology">Embryology</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=4" title="Edit section: Embryology"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Retinoic acid via the retinoic acid receptor influences the process of cell differentiation, hence, the growth and development of embryos. During development, there is a concentration gradient of retinoic acid along the anterior-posterior (head-tail) axis. Cells in the embryo respond to retinoic acid differently depending on the amount present. For example, in vertebrates, the hindbrain transiently forms eight <a href="/wiki/Rhombomeres" class="mw-redirect" title="Rhombomeres">rhombomeres</a> and each rhombomere has a specific pattern of genes being expressed. If retinoic acid is not present the last four rhombomeres do not develop. Instead, rhombomeres 1–4 grow to cover the same amount of space as all eight would normally occupy. Retinoic acid has its effects by turning on a differential pattern of Homeobox (Hox) genes that encode different homeodomain transcription factors which in turn can turn on cell type specific genes.<sup id="cite_ref-gd_28-0" class="reference"><a href="#cite_note-gd-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> Deletion of the Homeobox (Hox-1) gene from rhombomere 4 makes the neurons growing in that region behave like neurons from rhombomere 2. Retinoic acid is not required for patterning of the retina as originally proposed, but retinoic acid synthesized in the retina is secreted into surrounding <a href="/wiki/Mesenchyme" title="Mesenchyme">mesenchyme</a> where it is required to prevent overgrowth of perioptic mesenchyme which can cause microphthalmia, defects in the cornea and eyelid, and rotation of the optic cup.<sup id="cite_ref-Duester_2008_29-0" class="reference"><a href="#cite_note-Duester_2008-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Stem_cell_biology">Stem cell biology</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=5" title="Edit section: Stem cell biology"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Synthetic retinoic acid is used in <a href="/wiki/Cellular_differentiation" title="Cellular differentiation">differentiation</a> of stem cells to more committed fates, echoing retinoic acid's importance in natural embryonic developmental pathways. It is thought to initiate differentiation into a number of different cell lineages through activation of the <a href="/wiki/Retinoic_acid_receptor" title="Retinoic acid receptor">Retinoic acid receptor</a>. It has numerous applications in the experimental induction of stem cell differentiation; amongst these are the differentiation of human <a href="/wiki/Embryonic_stem_cell" title="Embryonic stem cell">embryonic stem cells</a> to posterior foregut lineages.<sup id="cite_ref-gd_28-1" class="reference"><a href="#cite_note-gd-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Vision">Vision</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=6" title="Edit section: Vision"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Visual_cycle" title="Visual cycle">Visual cycle</a></div> <p>Retinol is an essential compound in the cycle of light-activated chemical reactions called the "<a href="/wiki/Visual_cycle" title="Visual cycle">visual cycle</a>" that underlies vertebrate vision. Retinol is converted by the protein <a href="/wiki/RPE65" title="RPE65">RPE65</a> within the <a href="/wiki/Pigment_epithelium" class="mw-redirect" title="Pigment epithelium">pigment epithelium</a> of the <a href="/wiki/Retina" title="Retina">retina</a> into 11-<i>cis</i>-retinal. This molecule is then transported into the <a href="/wiki/Retina" title="Retina">retina</a>'s <a href="/wiki/Photoreceptor_cell" title="Photoreceptor cell">photoreceptor cells</a> (the <a href="/wiki/Rod_cell" title="Rod cell">rod</a> or <a href="/wiki/Cone_cell" title="Cone cell">cone</a> cells in mammals) where it binds to an <a href="/wiki/Opsin" title="Opsin">opsin</a> protein and acts as a light-activated molecular switch. When 11-<i>cis</i>-retinal absorbs light it <a href="/wiki/Cis-trans_isomerism" class="mw-redirect" title="Cis-trans isomerism">isomerizes</a> into all-<i>trans</i>-retinal. The change in the shape of the molecule in turn changes the configuration of the opsin in a cascade that leads to the <a href="/wiki/Action_potential" title="Action potential">neuronal firing</a>, which signals the detection of light.<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> The opsin then splits into the protein component (such <a href="/wiki/Metarhodopsin" class="mw-redirect" title="Metarhodopsin">metarhodopsin</a>) and the cofactor all-<i>trans</i>-retinal. The regeneration of active opsin requires conversion of all-<i>trans</i>-retinal back to 11-<i>cis</i>-retinal via retinol. The regeneration of 11-<i>cis</i>-retinal occurs in vertebrates via conversion of all-<i>trans</i>-retinol to 11-<i>cis</i>-retinol in a sequence of chemical transformations that occurs primarily in the pigment epithelial cells.<sup id="cite_ref-bs_31-0" class="reference"><a href="#cite_note-bs-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> </p><p>Without adequate amounts of retinol, regeneration of rhodopsin is incomplete and <a href="/wiki/Night_blindness" class="mw-redirect" title="Night blindness">night blindness</a> occurs. Night blindness, the inability to see well in dim light, is associated with a deficiency of <a href="/wiki/Vitamin_A" title="Vitamin A">vitamin A</a>, a class of compounds that includes retinol and retinal. In the early stages of <a href="/wiki/Vitamin_A" title="Vitamin A">vitamin A</a> deficiency, the more light-sensitive and abundant <a href="/wiki/Rod_cell" title="Rod cell">rods</a>, which have <a href="/wiki/Rhodopsin" title="Rhodopsin">rhodopsin</a>, have impaired sensitivity, and the <a href="/wiki/Cone_cell" title="Cone cell">cone cells</a> are less affected. The cones are less abundant than rods and come in three types, each contains its own type of <a href="/wiki/Iodopsin" class="mw-redirect" title="Iodopsin">iodopsin</a>, the opsins of the cones. The cones mediate <a href="/wiki/Color_vision" title="Color vision">color vision</a>, and vision in bright light (day vision). </p> <div class="mw-heading mw-heading3"><h3 id="Glycoprotein_synthesis">Glycoprotein synthesis</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=7" title="Edit section: Glycoprotein synthesis"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Glycoprotein" title="Glycoprotein">Glycoprotein</a> synthesis requires adequate vitamin A status. In severe vitamin A deficiency, lack of glycoproteins may lead to <a href="/wiki/Corneal_ulcer" title="Corneal ulcer">corneal ulcers</a> or liquefaction.<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Immune_system">Immune system</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=8" title="Edit section: Immune system"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Vitamin A is involved in maintaining a number of immune cell types from both the innate and acquired immune systems.<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> These include the <a href="/wiki/Lymphocytes" class="mw-redirect" title="Lymphocytes">lymphocytes</a> (<a href="/wiki/B-cells" class="mw-redirect" title="B-cells">B-cells</a>, <a href="/wiki/T-cells" class="mw-redirect" title="T-cells">T-cells</a>, and <a href="/wiki/Natural_killer_cells" class="mw-redirect" title="Natural killer cells">natural killer cells</a>), as well as many myelocytes (<a href="/wiki/Neutrophils" class="mw-redirect" title="Neutrophils">neutrophils</a>, <a href="/wiki/Macrophages" class="mw-redirect" title="Macrophages">macrophages</a>, and myeloid <a href="/wiki/Dendritic_cells" class="mw-redirect" title="Dendritic cells">dendritic cells</a>). Vitamin A maintains immune barriers in the gut through its activity as retinoic acid.<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Skin">Skin</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=9" title="Edit section: Skin"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Deficiencies in vitamin A have been linked to an increased susceptibility to skin infection and inflammation.<sup id="cite_ref-Roche2021_35-0" class="reference"><a href="#cite_note-Roche2021-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> Vitamin A appears to modulate the <a href="/wiki/Innate_immune_response" class="mw-redirect" title="Innate immune response">innate immune response</a> and maintains homeostasis of <a href="/wiki/Epithelial_tissues" class="mw-redirect" title="Epithelial tissues">epithelial tissues</a> and mucosa through its metabolite, retinoic acid (RA). As part of the innate immune system, <a href="/wiki/Toll-like_receptors" class="mw-redirect" title="Toll-like receptors">toll-like receptors</a> in skin cells respond to pathogens and cell damage by inducing a pro-inflammatory immune response which includes increased RA production.<sup id="cite_ref-Roche2021_35-1" class="reference"><a href="#cite_note-Roche2021-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> The epithelium of the skin encounters bacteria, fungi and viruses. Keratinocytes of the epidermal layer of the skin produce and secrete <a href="/wiki/Antimicrobial_peptides" title="Antimicrobial peptides">antimicrobial peptides</a> (AMPs). Production of AMPs <a href="/wiki/Resistin" title="Resistin">resistin</a> and <a href="/wiki/Cathelicidin" class="mw-redirect" title="Cathelicidin">cathelicidin</a>, are promoted by RA.<sup id="cite_ref-Roche2021_35-2" class="reference"><a href="#cite_note-Roche2021-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> Another way that vitamin A helps maintain a healthy skin and hair follicle <a href="/wiki/Microbiome" title="Microbiome">microbiome</a>, especially on the face, is by reduction of <a href="/wiki/Sebum" class="mw-redirect" title="Sebum">sebum</a> secretion, which is a nutrient source for bacteria.<sup id="cite_ref-Roche2021_35-3" class="reference"><a href="#cite_note-Roche2021-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> Retinol has been the subject of clinical studies related to its ability to reduce the appearance of fine lines on the face and neck.<sup id="cite_ref-Kong_2015_4-1" class="reference"><a href="#cite_note-Kong_2015-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Red_blood_cells">Red blood cells</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=10" title="Edit section: Red blood cells"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Vitamin A may be needed for normal <a href="/wiki/Haematopoiesis" title="Haematopoiesis">red blood cell formation</a>;<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup> deficiency causes abnormalities in <a href="/wiki/Iron_metabolism" class="mw-redirect" title="Iron metabolism">iron metabolism</a>.<sup id="cite_ref-39" class="reference"><a href="#cite_note-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> Vitamin A is needed to produce the red blood cells from stem cells through retinoid differentiation.<sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Units_of_measurement">Units of measurement</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=11" title="Edit section: Units of measurement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>When referring to dietary allowances or <a href="/wiki/Nutrition" title="Nutrition">nutritional</a> science, retinol is usually measured in <a href="/wiki/International_unit" title="International unit">international units</a> (IU). IU refers to biological activity and therefore is unique to each individual compound, however 1 IU of retinol is equivalent to approximately 0.3 micrograms (300 nanograms). </p> <div class="mw-heading mw-heading2"><h2 id="Nutrition">Nutrition</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=12" title="Edit section: Nutrition"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <table class="wikitable" style="width:300px; float:right; margin:0 0 0 0.5em; background:#fff; border-collapse:collapse;"> <tbody><tr> <th style="background:#fda;" colspan="2">Vitamin properties </th></tr> <tr> <td style="background:#fed;"><a href="/wiki/Solubility" title="Solubility">Solubility</a> </td> <td>Fat </td></tr> <tr> <td style="background:#fed;"><a href="/wiki/Recommended_Dietary_Allowance" class="mw-redirect" title="Recommended Dietary Allowance">RDA</a> (adult male) </td> <td>900 <a href="/wiki/Microgram" title="Microgram">μg</a>/day </td></tr> <tr> <td style="background:#fed;">RDA (adult female) </td> <td>700 <a href="/wiki/Microgram" title="Microgram">μg</a>/day </td></tr> <tr> <td style="background:#fed;">RDA upper limit (adult male) </td> <td>3,000 <a href="/wiki/Microgram" title="Microgram">μg</a>/day </td></tr> <tr> <td style="background:#fed;">RDA upper limit (adult female) </td> <td>3,000 <a href="/wiki/Microgram" title="Microgram">μg</a>/day </td></tr> <tr> <th style="background:#fed;" colspan="2">Deficiency symptoms </th></tr> <tr> <td colspan="2"> <ul><li><a href="/wiki/Night_blindness" class="mw-redirect" title="Night blindness">Night blindness</a></li> <li><a href="/wiki/Keratomalacia" title="Keratomalacia">Keratomalacia</a></li> <li>Pale, dry skin</li></ul> </td></tr> <tr> <th style="background:#fed;" colspan="2">Excess symptoms </th></tr> <tr> <td colspan="2"> <ul><li>Liver toxicity</li> <li>Dry skin</li> <li>Hair loss</li> <li><a href="/wiki/Teratogenesis" class="mw-redirect" title="Teratogenesis">Teratological</a> effects</li> <li><a href="/wiki/Osteoporosis" title="Osteoporosis">Osteoporosis</a> (suspected, long-term)</li></ul> </td></tr> <tr> <th style="background:#fda;" colspan="2">Common sources </th></tr> <tr> <td colspan="2"> <ul><li><a href="/wiki/Liver" title="Liver">Liver</a> and other organs</li> <li>fortified <a href="/wiki/Dairy_products" class="mw-redirect" title="Dairy products">Dairy products</a></li></ul> </td></tr></tbody></table> <p>This vitamin plays an essential role in vision, particularly night vision, normal bone and tooth development, reproduction, and the health of skin and mucous membranes (the mucus-secreting layer that lines body regions such as the respiratory tract). While Vitamin A is often considered to be an antioxidant that prevents cancers, it does not have antioxidant activity<sup id="cite_ref-41" class="reference"><a href="#cite_note-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> and is shown to promote the development of many cancers.<sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> </p><p>There are two sources of dietary vitamin A. Retinyl ester or retinol forms, which are immediately available to the body or <a href="/wiki/Carotene" title="Carotene">carotene</a> precursors, also known as provitamins, which must be converted to active forms by the body. These are obtained from fruits and vegetables containing yellow, orange and dark green pigments, known as <a href="/wiki/Carotenoid" title="Carotenoid">carotenoids</a>, the most well-known being β-carotene.<sup id="cite_ref-44" class="reference"><a href="#cite_note-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup> For this reason, amounts of vitamin A are measured in Retinol Equivalents (RE). One RE is equivalent to 0.001 mg of retinol, or 0.006 mg of β-carotene, or 3.3 International Units of vitamin A. </p><p>Vitamin A is fat-soluble and is stored in the liver and fat tissue.<sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> When required by a particular part of the body, the liver releases some vitamin A, which is carried by the blood and delivered to the target cells and tissues.<sup id="cite_ref-46" class="reference"><a href="#cite_note-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Dietary_intake">Dietary intake</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=13" title="Edit section: Dietary intake"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Dietary_Reference_Intake" title="Dietary Reference Intake">Dietary Reference Intake</a> (DRI) Recommended Daily Amount (RDA) for vitamin A for a 25-year-old male is 900 micrograms/day, or 3000 IU. <a href="/wiki/National_Health_Service" title="National Health Service">National Health Service</a> daily recommended values are slightly lower at 700 micrograms for men and 600 micrograms for women.<sup id="cite_ref-47" class="reference"><a href="#cite_note-47"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> </p><p>During the absorption process in the <a href="/wiki/Intestine" class="mw-redirect" title="Intestine">intestines</a>, retinol is incorporated into <a href="/wiki/Chylomicron" title="Chylomicron">chylomicrons</a> as the ester form, and it is these particles that mediate transport to the <a href="/wiki/Liver" title="Liver">liver</a>. Liver cells store vitamin A as the ester, and when retinol is needed in other tissues, it is de-esterifed and released into the blood as the alcohol. Retinol then attaches to a serum carrier, <a href="/wiki/Retinol_binding_protein" class="mw-redirect" title="Retinol binding protein">retinol binding protein</a>, for transport to target tissues.<sup id="cite_ref-48" class="reference"><a href="#cite_note-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> A binding protein inside cells, cellular retinoic acid binding protein, serves to store and move retinoic acid <a href="/wiki/Intracellular" class="mw-redirect" title="Intracellular">intracellularly</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Deficiency">Deficiency</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=14" title="Edit section: Deficiency"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Vitamin_A_deficiency" title="Vitamin A deficiency">Vitamin A deficiency</a></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Vitamin_A_deficiency.PNG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7d/Vitamin_A_deficiency.PNG/360px-Vitamin_A_deficiency.PNG" decoding="async" width="360" height="167" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7d/Vitamin_A_deficiency.PNG/540px-Vitamin_A_deficiency.PNG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7d/Vitamin_A_deficiency.PNG/720px-Vitamin_A_deficiency.PNG 2x" data-file-width="1357" data-file-height="628" /></a><figcaption>Prevalence of vitamin A deficiency in 1995</figcaption></figure> <p>Vitamin A deficiency is common in developing countries but rarely seen in developed countries. Approximately 250,000 to 500,000 malnourished children in the developing world go blind each year from a deficiency of vitamin A.<sup id="cite_ref-49" class="reference"><a href="#cite_note-49"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> Vitamin A deficiency in expecting mothers increases the mortality rate of children shortly after childbirth.<sup id="cite_ref-50" class="reference"><a href="#cite_note-50"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Night_blindness" class="mw-redirect" title="Night blindness">Night blindness</a> is one of the first signs of vitamin A deficiency. Vitamin A deficiency contributes to blindness by depleting the necessary form needed for rhodopsin.<sup id="cite_ref-bs_31-1" class="reference"><a href="#cite_note-bs-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Sources">Sources</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=15" title="Edit section: Sources"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Vitamin_A#Sources" title="Vitamin A">Vitamin_A § Sources</a></div> <p>Retinoids are found naturally only in foods of animal origin. Each of the following contains at least 0.15 mg of retinoids per 1.75–7 oz (50–198 g): </p> <ul><li><a href="/wiki/Cod_liver_oil" title="Cod liver oil">Cod liver oil</a></li> <li><a href="/wiki/Butter" title="Butter">Butter</a></li> <li><a href="/wiki/Liver_(food)" title="Liver (food)">Liver</a> (beef, pork, chicken, turkey, fish)</li> <li><a href="/wiki/Egg_(food)" class="mw-redirect" title="Egg (food)">Eggs</a></li> <li><a href="/wiki/Cheese" title="Cheese">Cheese</a>, <a href="/wiki/Milk" title="Milk">milk</a><sup id="cite_ref-51" class="reference"><a href="#cite_note-51"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup></li></ul> <div class="mw-heading mw-heading2"><h2 id="Chemistry">Chemistry</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=16" title="Edit section: Chemistry"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Many different geometric isomers of retinol, retinal and retinoic acid are possible as a result of either a <i><a href="/wiki/Trans_isomer" class="mw-redirect" title="Trans isomer">trans</a></i> or <i><a href="/wiki/Cis-trans_isomerism" class="mw-redirect" title="Cis-trans isomerism">cis</a></i> configuration of four of the five <a href="/wiki/Double_bond" title="Double bond">double bonds</a> found in the <a href="/wiki/Polyene" title="Polyene">polyene</a> chain. The <i>cis</i> isomers are less stable and can readily convert to the all-<i>trans</i> configuration (as seen in the structure of all-<i>trans</i>-retinol shown at the top of this page). Nevertheless, some <i>cis</i> isomers are found naturally and carry out essential functions. For example, the 11-<i>cis</i>-retinal isomer is the <a href="/wiki/Chromophore" title="Chromophore">chromophore</a> of <a href="/wiki/Rhodopsin" title="Rhodopsin">rhodopsin</a>, the <a href="/wiki/Vertebrate" title="Vertebrate">vertebrate</a> <a href="/wiki/Photoreceptor_protein" title="Photoreceptor protein">photoreceptor</a> molecule. Rhodopsin is composed of the 11-cis-retinal covalently linked via a <a href="/wiki/Schiff_base" title="Schiff base">Schiff base</a> to the <a href="/wiki/Opsin" title="Opsin">opsin</a> protein (either rod opsin or blue, red or green cone opsins). The process of vision relies on the light-induced isomerisation of the chromophore from 11-<i>cis</i> to all-<i>trans</i> resulting in a change of the conformation and activation of the photoreceptor molecule.<sup id="cite_ref-bs_31-2" class="reference"><a href="#cite_note-bs-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> </p><p>Many of the non-visual functions of vitamin A are mediated by retinoic acid, which regulates gene expression by activating nuclear <a href="/wiki/Retinoic_acid_receptor" title="Retinoic acid receptor">retinoic acid receptors</a>.<sup id="cite_ref-Duester_2008_29-1" class="reference"><a href="#cite_note-Duester_2008-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> The non-visual functions of vitamin A are essential in the immunological function, reproduction and embryonic development of vertebrates as evidenced by the impaired growth, susceptibility to infection and birth defects observed in populations receiving suboptimal vitamin A in their diet. </p> <div class="mw-heading mw-heading2"><h2 id="Synthesis">Synthesis</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=17" title="Edit section: Synthesis"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Biosynthesis">Biosynthesis</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=18" title="Edit section: Biosynthesis"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size skin-invert-image" typeof="mw:File/Thumb"><a href="/wiki/File:Chem_157_vitamin_a_synthesis_project.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4b/Chem_157_vitamin_a_synthesis_project.png/220px-Chem_157_vitamin_a_synthesis_project.png" decoding="async" width="220" height="253" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4b/Chem_157_vitamin_a_synthesis_project.png/330px-Chem_157_vitamin_a_synthesis_project.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4b/Chem_157_vitamin_a_synthesis_project.png/440px-Chem_157_vitamin_a_synthesis_project.png 2x" data-file-width="1850" data-file-height="2124" /></a><figcaption>Vitamin A biosynthesis</figcaption></figure> <p>Retinol is synthesized from the breakdown of <a href="/wiki/%CE%92-carotene" class="mw-redirect" title="Β-carotene">β-carotene</a>. First, the <a href="/wiki/%CE%92-carotene_15,15%27-monooxygenase" class="mw-redirect" title="Β-carotene 15,15'-monooxygenase">β-carotene 15,15'-monooxygenase</a> cleaves β-carotene at the central double bond, creating an <a href="/wiki/Epoxide" title="Epoxide">epoxide</a>. This epoxide is then attacked by water creating two hydroxyl groups in the center of the structure. The cleavage occurs when these alcohols are oxidized to the aldehydes using <a href="/wiki/NADH" class="mw-redirect" title="NADH">NADH</a>. This compound is called retinal. Retinal is then reduced to retinol by the enzyme <a href="/wiki/Retinol_dehydrogenase" title="Retinol dehydrogenase">retinol dehydrogenase</a>. Retinol dehydrogenase is an enzyme that is dependent on NADH.<sup id="cite_ref-52" class="reference"><a href="#cite_note-52"><span class="cite-bracket">[</span>52<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Industrial_synthesis">Industrial synthesis</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=19" title="Edit section: Industrial synthesis"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left skin-invert-image" typeof="mw:File/Thumb"><a href="/wiki/File:Ionone_beta.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Ionone_beta.svg/220px-Ionone_beta.svg.png" decoding="async" width="220" height="147" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Ionone_beta.svg/330px-Ionone_beta.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Ionone_beta.svg/440px-Ionone_beta.svg.png 2x" data-file-width="854" data-file-height="570" /></a><figcaption>β-ionone ring</figcaption></figure> <p>Retinol is made industrially via <a href="/wiki/Total_synthesis" title="Total synthesis">total synthesis</a> using either a method developed by <a href="/wiki/BASF" title="BASF">BASF</a><sup id="cite_ref-β-Carotin-1_53-0" class="reference"><a href="#cite_note-β-Carotin-1-53"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-β-Carotin-2_54-0" class="reference"><a href="#cite_note-β-Carotin-2-54"><span class="cite-bracket">[</span>54<span class="cite-bracket">]</span></a></sup> or a <a href="/wiki/Grignard_reaction" title="Grignard reaction">Grignard reaction</a> utilized by <a href="/wiki/Hoffman-La_Roche" class="mw-redirect" title="Hoffman-La Roche">Hoffman-La Roche</a>.<sup id="cite_ref-55" class="reference"><a href="#cite_note-55"><span class="cite-bracket">[</span>55<span class="cite-bracket">]</span></a></sup> The two major suppliers, DSM and BASF, are believed to use total synthesis.<sup id="cite_ref-Parker2016_56-0" class="reference"><a href="#cite_note-Parker2016-56"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> </p><p>The world market for synthetic retinol is primarily for animal feed, leaving approximately 13% for a combination of food, prescription medication and dietary supplement use.<sup id="cite_ref-Parker2016_56-1" class="reference"><a href="#cite_note-Parker2016-56"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> The first industrialized synthesis of retinol was achieved by the company Hoffmann-La Roche in 1947. In the following decades, eight other companies developed their own processes. β-ionone, synthesized from acetone, is the essential starting point for all industrial syntheses. Each process involves elongating the unsaturated carbon chain.<sup id="cite_ref-Parker2016_56-2" class="reference"><a href="#cite_note-Parker2016-56"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> Pure retinol is extremely sensitive to oxidization and is prepared and transported at low temperatures and oxygen-free atmospheres. When prepared as a dietary supplement or food additive, retinol is stabilized as the <a href="/wiki/Ester" title="Ester">ester</a> derivatives <a href="/wiki/Retinyl_acetate" title="Retinyl acetate">retinyl acetate</a> or <a href="/wiki/Retinyl_palmitate" title="Retinyl palmitate">retinyl palmitate</a>. Prior to 1999, three companies, Roche, <a href="/wiki/BASF" title="BASF">BASF</a> and <a href="/wiki/Rhone-Poulenc" class="mw-redirect" title="Rhone-Poulenc">Rhone-Poulenc</a> controlled 96% of global vitamin A sales. In 2001, the European Commission imposed total fines of 855.22 Euros on these and five other companies for their participation in eight distinct market-sharing and price-fixing cartels that dated back to 1989. Roche sold its vitamin division to <a href="/wiki/DSM_(company)" title="DSM (company)">DSM</a> in 2003. DSM and BASF have the major share of industrial production.<sup id="cite_ref-Parker2016_56-3" class="reference"><a href="#cite_note-Parker2016-56"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=20" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Frederick_Gowland_Hopkins_nobel.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/75/Frederick_Gowland_Hopkins_nobel.jpg/220px-Frederick_Gowland_Hopkins_nobel.jpg" decoding="async" width="220" height="311" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/7/75/Frederick_Gowland_Hopkins_nobel.jpg 1.5x" data-file-width="280" data-file-height="396" /></a><figcaption>Frederick Gowland Hopkins, 1929 Nobel Prize for Physiology or Medicine</figcaption></figure> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:George_Wald_nobel.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/George_Wald_nobel.jpg/220px-George_Wald_nobel.jpg" decoding="async" width="220" height="311" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/7/70/George_Wald_nobel.jpg 1.5x" data-file-width="280" data-file-height="396" /></a><figcaption>George Wald, 1967 Nobel Prize for Physiology or Medicine</figcaption></figure> <p>In 1912, <a href="/wiki/Frederick_Gowland_Hopkins" title="Frederick Gowland Hopkins">Frederick Gowland Hopkins</a> demonstrated that unknown accessory factors found in milk, other than <a href="/wiki/Carbohydrate" title="Carbohydrate">carbohydrates</a>, <a href="/wiki/Protein" title="Protein">proteins</a>, and <a href="/wiki/Fat" title="Fat">fats</a> were necessary for growth in rats. Hopkins received a Nobel Prize for this discovery in 1929.<sup id="cite_ref-Semba_57-0" class="reference"><a href="#cite_note-Semba-57"><span class="cite-bracket">[</span>57<span class="cite-bracket">]</span></a></sup> One year later, <a href="/wiki/Elmer_McCollum" title="Elmer McCollum">Elmer McCollum</a>, a <a href="/wiki/Biochemist" title="Biochemist">biochemist</a> at the <a href="/wiki/University_of_Wisconsin%E2%80%93Madison" title="University of Wisconsin–Madison">University of Wisconsin–Madison</a>, and colleague <a href="/wiki/Marguerite_Davis" title="Marguerite Davis">Marguerite Davis</a> identified a fat-soluble nutrient in <a href="/wiki/Butterfat" title="Butterfat">butterfat</a> and <a href="/wiki/Cod_liver_oil" title="Cod liver oil">cod liver oil</a>. Their work confirmed that of <a href="/wiki/Thomas_Burr_Osborne_(chemist)" title="Thomas Burr Osborne (chemist)">Thomas Burr Osborne</a> and <a href="/wiki/Lafayette_Mendel" title="Lafayette Mendel">Lafayette Mendel</a>, at <a href="/wiki/Yale_University" title="Yale University">Yale</a>, also in 1913, which suggested a fat-soluble nutrient in butterfat.<sup id="cite_ref-Semba2_58-0" class="reference"><a href="#cite_note-Semba2-58"><span class="cite-bracket">[</span>58<span class="cite-bracket">]</span></a></sup> The "accessory factors" were termed "fat soluble" in 1918 and later "vitamin A" in 1920. In 1931, Swiss chemist <a href="/wiki/Paul_Karrer" title="Paul Karrer">Paul Karrer</a> described the chemical structure of vitamin A.<sup id="cite_ref-Semba_57-1" class="reference"><a href="#cite_note-Semba-57"><span class="cite-bracket">[</span>57<span class="cite-bracket">]</span></a></sup> Retinoic acid and retinol were first synthesized in 1946 and 1947 by two Dutch chemists, <a href="/wiki/David_Adriaan_van_Dorp" title="David Adriaan van Dorp">David Adriaan van Dorp</a> and Jozef Ferdinand Arens.<sup id="cite_ref-59" class="reference"><a href="#cite_note-59"><span class="cite-bracket">[</span>59<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-60" class="reference"><a href="#cite_note-60"><span class="cite-bracket">[</span>60<span class="cite-bracket">]</span></a></sup> </p><p><br /> In 1967, <a href="/wiki/George_Wald" title="George Wald">George Wald</a> was a co-recipient of the Nobel Prize in Physiology and Medicine "..."for their discoveries concerning the primary physiological and chemical visual processes in the eye."<sup id="cite_ref-nobel-1967_61-0" class="reference"><a href="#cite_note-nobel-1967-61"><span class="cite-bracket">[</span>61<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Photoreceptor_cell" title="Photoreceptor cell">Photoreceptor cells</a> in the eye contain a <a href="/wiki/Chromophore" title="Chromophore">chromophore</a> composed of the protein <a href="/wiki/Opsin" title="Opsin">opsin</a> and <a href="/wiki/11-cis_retinal" class="mw-redirect" title="11-cis retinal">11-cis retinal</a>. When struck by light, 11-cis retinal undergoes photoisomerization to all-trans retinal and via signal transduction cascade send a nerve signal to the brain. The all-trans retinal is reduced to all-trans retinol and travels back to the retinal pigment epithelium to be recycled to 11-cis retinal and conjugated to opsin.<sup id="cite_ref-62" class="reference"><a href="#cite_note-62"><span class="cite-bracket">[</span>62<span class="cite-bracket">]</span></a></sup> </p><p>Although vitamin A was not confirmed as an essential nutrient and a chemical structure described until the 20th century, written observations of conditions created by deficiency of this nutrient appeared much earlier in history. Sommer classified historical accounts related to vitamin A and/or manifestations of deficiency as follows: "ancient" accounts; 18th- to 19th-century clinical descriptions (and their purported etiologic associations); early 20th-century laboratory animal experiments, and clinical and epidemiologic observations that identified the existence of this unique nutrient and manifestations of its deficiency.<sup id="cite_ref-Sommer_24-1" class="reference"><a href="#cite_note-Sommer-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=21" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-drugs-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-drugs_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-drugs_1-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-drugs_1-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-drugs_1-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-drugs_1-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-drugs_1-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-drugs_1-6"><sup><i><b>g</b></i></sup></a> <a href="#cite_ref-drugs_1-7"><sup><i><b>h</b></i></sup></a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.drugs.com/monograph/vitamin-a.html">"Vitamin A"</a>. 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title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Progress+in+Retinal+and+Eye+Research&rft.atitle=Vertebrate+photoreceptors&rft.volume=20&rft.issue=1&rft.pages=49-94&rft.date=2001-01&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A2789591%23id-name%3DS2CID&rft_id=info%3Apmid%2F11070368&rft_id=info%3Adoi%2F10.1016%2FS1350-9462%2800%2900014-8&rft.aulast=Ebrey&rft.aufirst=T&rft.au=Koutalos%2C+Y&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARetinol" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Retinol&action=edit&section=22" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Jane Higdon, "<a rel="nofollow" class="external text" href="http://lpi.oregonstate.edu/infocenter/vitamins/vitaminA/">Vitamin A</a>", Micronutrient Information Center, <i><a href="/wiki/Linus_Pauling_Institute" title="Linus Pauling Institute">Linus Pauling Institute</a>, <a href="/wiki/Oregon_State_University" title="Oregon State University">Oregon State University</a></i></li> <li><a rel="nofollow" class="external text" href="http://ods.od.nih.gov/factsheets/cc/vita.html">NIH Office of Dietary Supplements – Vitamin A</a></li> <li><a rel="nofollow" class="external text" href="http://www.merck.com/mrkshared/mmanual/section1/chapter3/3b.jsp">Vitamin A Deficiency</a> at the <i><a href="/wiki/Merck_Manual_of_Diagnosis_and_Therapy" title="Merck Manual of Diagnosis and Therapy">Merck Manual of Diagnosis and Therapy</a></i></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist 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.navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Vitamins" title="Template:Vitamins"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Vitamins" title="Template talk:Vitamins"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Vitamins" title="Special:EditPage/Template:Vitamins"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Vitamins_(A11)" style="font-size:114%;margin:0 4em"><a href="/wiki/Vitamin" title="Vitamin">Vitamins</a> (<a href="/wiki/ATC_code_A11" title="ATC code A11">A11</a>)</div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Fat <br />soluble</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Vitamin_A" title="Vitamin A">A</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/%CE%91-Carotene" title="Α-Carotene">α-Carotene</a></li> <li><a href="/wiki/%CE%92-Carotene" title="Β-Carotene">β-Carotene</a></li> <li><a class="mw-selflink selflink">Retinol</a><sup>#</sup></li> <li><a href="/wiki/Tretinoin" title="Tretinoin">Tretinoin</a><sup>#</sup></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Vitamin_D" title="Vitamin D">D</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>D<sub>2</sub> <ul><li><a href="/wiki/Ergosterol" title="Ergosterol">Ergosterol</a></li> <li><a href="/wiki/Ergocalciferol" title="Ergocalciferol">Ergocalciferol</a><sup>#</sup></li></ul></li> <li>D<sub>3</sub> <ul><li><a href="/wiki/7-Dehydrocholesterol" title="7-Dehydrocholesterol">7-Dehydrocholesterol</a></li> <li><a href="/wiki/Previtamin_D3" title="Previtamin D3">Previtamin D<sub>3</sub></a></li> <li><a href="/wiki/Cholecalciferol" title="Cholecalciferol">Cholecalciferol</a><sup>#</sup></li> <li><a href="/wiki/Calcifediol" title="Calcifediol">25-hydroxycholecalciferol</a></li> <li><a href="/wiki/Calcitriol" title="Calcitriol">Calcitriol (1,25-dihydroxycholecalciferol)</a></li> <li><a href="/wiki/Calcitroic_acid" title="Calcitroic acid">Calcitroic acid</a></li></ul></li> <li>D<sub>4</sub> <ul><li><a href="/wiki/22-Dihydroergocalciferol" title="22-Dihydroergocalciferol">Dihydroergocalciferol</a></li></ul></li> <li><a href="/wiki/Vitamin_D5" title="Vitamin D5">D<sub>5</sub></a></li> <li>D analogues <ul><li><a href="/wiki/Alfacalcidol" title="Alfacalcidol">Alfacalcidol</a></li> <li><a href="/wiki/Dihydrotachysterol" title="Dihydrotachysterol">Dihydrotachysterol</a></li> <li><a href="/wiki/Calcipotriol" title="Calcipotriol">Calcipotriol</a></li> <li><a href="/wiki/Tacalcitol" title="Tacalcitol">Tacalcitol</a></li> <li><a href="/wiki/Paricalcitol" title="Paricalcitol">Paricalcitol</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Vitamin_E" title="Vitamin E">E</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Tocopherol" title="Tocopherol">Tocopherol</a> <ul><li><a href="/wiki/%CE%91-Tocopherol" title="Α-Tocopherol">Alpha</a></li> <li><a href="/wiki/%CE%92-Tocopherol" title="Β-Tocopherol">Beta</a></li> <li><a href="/wiki/%CE%93-Tocopherol" title="Γ-Tocopherol">Gamma</a></li> <li><a href="/wiki/%CE%94-Tocopherol" title="Δ-Tocopherol">Delta</a></li></ul></li> <li><a href="/wiki/Tocotrienol" title="Tocotrienol">Tocotrienol</a> <ul><li><a href="/wiki/%CE%91-Tocotrienol" title="Α-Tocotrienol">Alpha</a></li> <li><a href="/wiki/%CE%92-Tocotrienol" title="Β-Tocotrienol">Beta</a></li> <li><a href="/wiki/%CE%93-Tocotrienol" title="Γ-Tocotrienol">Gamma</a></li> <li>Delta</li></ul></li> <li><a href="/wiki/Tocofersolan" title="Tocofersolan">Tocofersolan</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Vitamin_K" title="Vitamin K">K</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/1,4-Naphthoquinone" title="1,4-Naphthoquinone">Naphthoquinone</a></li> <li><a href="/wiki/Phytomenadione" title="Phytomenadione">Phylloquinone (K<sub>1</sub>)</a><sup>#</sup></li> <li><a href="/wiki/Vitamin_K2" title="Vitamin K2">Menaquinones (K<sub>2</sub>)</a></li> <li><a href="/wiki/Menadione" title="Menadione">Menadione (K<sub>3</sub>)</a><sup>‡</sup></li> <li><a href="/wiki/Vitamin_K4" class="mw-redirect" title="Vitamin K4">Various (K<sub>4</sub>)</a></li> <li><a href="/wiki/4-Amino-2-methyl-1-naphthol" title="4-Amino-2-methyl-1-naphthol">4-Amino-2-methyl-1-naphthol (K<sub>5</sub>)</a><sup>‡</sup></li> <li><a href="/wiki/2-Methylnaphthalene-1,4-diamine" title="2-Methylnaphthalene-1,4-diamine">2-Methylnaphthalene-1,4-diamine (K<sub>6</sub>)</a></li> <li><a href="/wiki/4-Amino-3-methyl-1-naphthol" title="4-Amino-3-methyl-1-naphthol">4-Amino-3-methyl-1-naphthol (K<sub>7</sub>)</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Water <br />soluble</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/B_vitamins" title="B vitamins">B</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>B<sub>1</sub> <ul><li><a href="/wiki/Thiamine" title="Thiamine">Thiamine</a><sup>#</sup></li></ul></li> <li><a href="/wiki/Vitamin_B1_analogues" title="Vitamin B1 analogues">B<sub>1</sub> analogues</a> <ul><li><a href="/wiki/Acefurtiamine" title="Acefurtiamine">Acefurtiamine</a></li> <li><a href="/wiki/Allithiamine" title="Allithiamine">Allithiamine</a></li> <li><a href="/wiki/Benfotiamine" title="Benfotiamine">Benfotiamine</a></li> <li><a href="/wiki/Fursultiamine" title="Fursultiamine">Fursultiamine</a></li> <li><a href="/wiki/Octotiamine" title="Octotiamine">Octotiamine</a></li> <li><a href="/wiki/Prosultiamine" title="Prosultiamine">Prosultiamine</a></li> <li><a href="/wiki/Sulbutiamine" title="Sulbutiamine">Sulbutiamine</a></li></ul></li> <li>B<sub>2</sub> <ul><li><a href="/wiki/Riboflavin" title="Riboflavin">Riboflavin</a><sup>#</sup></li></ul></li> <li><a href="/wiki/Vitamin_B3" title="Vitamin B3">B<sub>3</sub></a> <ul><li><a href="/wiki/Niacin" title="Niacin">Niacin</a></li> <li><a href="/wiki/Nicotinamide" title="Nicotinamide">Niacinamide</a><sup>#</sup></li></ul></li> <li>B<sub>5</sub> <ul><li><a href="/wiki/Pantothenic_acid" title="Pantothenic acid">Pantothenic acid</a></li> <li><a href="/wiki/Panthenol" title="Panthenol">Dexpanthenol</a></li> <li><a href="/wiki/Pantethine" title="Pantethine">Pantethine</a></li></ul></li> <li><a href="/wiki/Vitamin_B6" title="Vitamin B6">B<sub>6</sub></a> <ul><li><a href="/wiki/Pyridoxine" title="Pyridoxine">Pyridoxine</a><sup>#</sup>, <a href="/wiki/Pyridoxal_phosphate" title="Pyridoxal phosphate">Pyridoxal phosphate</a></li> <li><a href="/wiki/Pyridoxamine" title="Pyridoxamine">Pyridoxamine</a></li> <li><a href="/wiki/Pyritinol" title="Pyritinol">Pyritinol</a></li></ul></li> <li>B<sub>7</sub> <ul><li><a href="/wiki/Biotin" title="Biotin">Biotin</a></li></ul></li> <li>B<sub>9</sub> <ul><li><a href="/wiki/Folate" title="Folate">Folic acid</a><sup>#</sup></li> <li><a href="/wiki/Dihydrofolic_acid" title="Dihydrofolic acid">Dihydrofolic acid</a></li> <li><a href="/wiki/Folinic_acid" title="Folinic acid">Folinic acid</a></li> <li><a href="/wiki/Levomefolic_acid" title="Levomefolic acid">Levomefolic acid</a></li></ul></li> <li><a href="/wiki/Vitamin_B12" title="Vitamin B12">B<sub>12</sub></a> <ul><li><a href="/wiki/Adenosylcobalamin" title="Adenosylcobalamin">Adenosylcobalamin</a></li> <li><a href="/wiki/Cyanocobalamin" title="Cyanocobalamin">Cyanocobalamin</a></li> <li><a href="/wiki/Hydroxocobalamin" title="Hydroxocobalamin">Hydroxocobalamin</a><sup>#</sup></li> <li><a href="/wiki/Methylcobalamin" title="Methylcobalamin">Methylcobalamin</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Vitamin_C" title="Vitamin C">C</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Vitamin_C" title="Vitamin C">Ascorbic acid</a><sup>#</sup></li> <li><a href="/wiki/Dehydroascorbic_acid" title="Dehydroascorbic acid">Dehydroascorbic acid</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Combinations</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Multivitamin" title="Multivitamin">Multivitamins</a></li></ul> </div></td></tr><tr><td colspan="2" class="navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"><div class="hlist"> <ul><li><sup>#</sup><a href="/wiki/WHO_Model_List_of_Essential_Medicines" title="WHO Model List of Essential Medicines">WHO-EM</a></li> <li><sup>‡</sup><a href="/wiki/List_of_withdrawn_drugs" title="List of withdrawn drugs">Withdrawn</a> from market</li> <li><a href="/wiki/Clinical_trial" title="Clinical trial">Clinical trials</a>: <ul><li><sup>†</sup><a href="/wiki/Phases_of_clinical_research#Phase_III" title="Phases of clinical research">Phase III</a></li> <li><sup>§</sup>Never to phase III</li></ul></li></ul> </div></div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Carotenoids" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Carotenoids" title="Template:Carotenoids"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Carotenoids" title="Template talk:Carotenoids"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Carotenoids" title="Special:EditPage/Template:Carotenoids"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Carotenoids" style="font-size:114%;margin:0 4em"><a href="/wiki/Carotenoid" title="Carotenoid">Carotenoids</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Carotene" title="Carotene">Carotenes</a> (C<sub>40</sub>)</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Alpha-Carotene" class="mw-redirect" title="Alpha-Carotene">α-Carotene</a></li> <li><a href="/wiki/Beta-Carotene" class="mw-redirect" title="Beta-Carotene">β-Carotene</a></li> <li><a href="/wiki/Gamma-Carotene" class="mw-redirect" title="Gamma-Carotene">γ-Carotene</a></li> <li><a href="/wiki/Delta-Carotene" class="mw-redirect" title="Delta-Carotene">δ-Carotene</a></li> <li><a href="/wiki/Epsilon-Carotene" class="mw-redirect" title="Epsilon-Carotene">ε-Carotene</a></li> <li><a href="/wiki/Zeta-Carotene" class="mw-redirect" title="Zeta-Carotene">ζ-Carotene</a></li> <li><a href="/wiki/Lycopene" title="Lycopene">Lycopene</a></li> <li><a href="/wiki/Neurosporene" title="Neurosporene">Neurosporene</a></li> <li><a href="/wiki/Phytoene" title="Phytoene">Phytoene</a></li> <li><a href="/wiki/Phytofluene" title="Phytofluene">Phytofluene</a></li> <li><a href="/wiki/Torulene" title="Torulene">Torulene</a></li> <li><a href="/wiki/Lycopersene" title="Lycopersene">Lycopersene</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Xanthophyll" title="Xanthophyll">Xanthophylls</a> (C<sub>40</sub>)</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Antheraxanthin" title="Antheraxanthin">Antheraxanthin</a></li> <li><a href="/wiki/Astaxanthin" title="Astaxanthin">Astaxanthin</a></li> <li><a href="/wiki/Canthaxanthin" title="Canthaxanthin">Canthaxanthin</a></li> <li><a href="/wiki/Citranaxanthin" title="Citranaxanthin">Citranaxanthin</a></li> <li><a href="/wiki/Cryptoxanthin" class="mw-redirect" title="Cryptoxanthin">Cryptoxanthin</a></li> <li><a href="/wiki/Diadinoxanthin" title="Diadinoxanthin">Diadinoxanthin</a></li> <li><a href="/wiki/Diatoxanthin" title="Diatoxanthin">Diatoxanthin</a></li> <li><a href="/wiki/Dinoxanthin" title="Dinoxanthin">Dinoxanthin</a></li> <li><a href="/wiki/Echinenone" title="Echinenone">Echinenone</a></li> <li><a href="/wiki/Flavoxanthin" title="Flavoxanthin">Flavoxanthin</a></li> <li><a href="/wiki/Fucoxanthin" title="Fucoxanthin">Fucoxanthin</a></li> <li><a href="/wiki/Lutein" title="Lutein">Lutein</a></li> <li><a href="/wiki/Neoxanthin" title="Neoxanthin">Neoxanthin</a></li> <li><a href="/wiki/Rhodoxanthin" title="Rhodoxanthin">Rhodoxanthin</a></li> <li><a href="/wiki/Rubixanthin" title="Rubixanthin">Rubixanthin</a></li> <li><a href="/wiki/Violaxanthin" title="Violaxanthin">Violaxanthin</a></li> <li><a href="/wiki/Zeaxanthin" title="Zeaxanthin">Zeaxanthin</a></li> <li><a href="/w/index.php?title=Zeinoxanthin&action=edit&redlink=1" class="new" title="Zeinoxanthin (page does not exist)">Zeinoxanthin</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Apocarotenoid" title="Apocarotenoid">Apocarotenoids</a> (C<sub><40</sub>)</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Abscisic_acid" title="Abscisic acid">Abscisic acid</a></li> <li><a href="/wiki/Apocarotenal" title="Apocarotenal">Apocarotenal</a></li> <li><a href="/wiki/Bixin" title="Bixin">Bixin</a></li> <li><a href="/wiki/Crocetin" title="Crocetin">Crocetin</a></li> <li><a href="/wiki/Food_orange_7" title="Food orange 7">Food orange 7</a></li> <li><a href="/wiki/Ionone" title="Ionone">Ionones</a></li> <li><a href="/wiki/Peridinin" title="Peridinin">Peridinin</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Vitamin A retinoids (C<sub>20</sub>)</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Retinal" title="Retinal">Retinal</a></li> <li><a href="/wiki/Retinoic_acid" title="Retinoic acid">Retinoic acid</a></li> <li><a class="mw-selflink selflink">Retinol</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Retinoid" title="Retinoid">Retinoid drugs</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Acitretin" title="Acitretin">Acitretin</a></li> <li><a href="/wiki/Alitretinoin" title="Alitretinoin">Alitretinoin</a></li> <li><a href="/wiki/Bexarotene" title="Bexarotene">Bexarotene</a></li> <li><a href="/wiki/Etretinate" title="Etretinate">Etretinate</a></li> <li><a href="/wiki/Fenretinide" title="Fenretinide">Fenretinide</a></li> <li><a href="/wiki/Isotretinoin" title="Isotretinoin">Isotretinoin</a></li> <li><a href="/wiki/Tazarotene" title="Tazarotene">Tazarotene</a></li> <li><a href="/w/index.php?title=Temarotene&action=edit&redlink=1" class="new" title="Temarotene (page does not exist)">Temarotene</a></li> <li><a href="/wiki/Tretinoin" title="Tretinoin">Tretinoin</a></li> <li><a href="/w/index.php?title=Zuretinol_acetate&action=edit&redlink=1" class="new" title="Zuretinol acetate (page does not exist)">Zuretinol acetate</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Retinoid_receptor_modulators" style="padding:3px"><table class="nowraplinks hlist mw-collapsible mw-collapsed navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Retinoid_receptor_modulators" title="Template:Retinoid receptor modulators"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Retinoid_receptor_modulators" title="Template talk:Retinoid receptor modulators"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Retinoid_receptor_modulators" title="Special:EditPage/Template:Retinoid receptor modulators"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Retinoid_receptor_modulators" style="font-size:114%;margin:0 4em"><a href="/wiki/Retinoid_receptor" title="Retinoid receptor">Retinoid receptor</a> <a href="/wiki/Receptor_modulator" title="Receptor modulator">modulators</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:center;"><a href="/wiki/Retinoic_acid_receptor" title="Retinoic acid receptor"><abbr title="Retinoic acid receptor">RAR</abbr></a><span class="sr-only" style="border: 0; clip: rect(0, 0, 0, 0); clip-path: polygon(0px 0px, 0px 0px, 0px 0px); height: 1px; margin: -1px; overflow: hidden; padding: 0; position: absolute; width: 1px; white-space: nowrap;">Tooltip Retinoic acid receptor</span></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><i>Agonists:</i> <a href="/w/index.php?title=9-cis-13,14-Dihydro-retinoic_acid&action=edit&redlink=1" class="new" title="9-cis-13,14-Dihydro-retinoic acid (page does not exist)">9CDHRA</a></li> <li><a href="/wiki/Alitretinoin" title="Alitretinoin">9-<i>cis</i>-Retinoic acid (alitretinoin)</a></li> <li><a href="/w/index.php?title=AC-261066&action=edit&redlink=1" class="new" title="AC-261066 (page does not exist)">AC-261066</a></li> <li><a href="/w/index.php?title=AC-55649&action=edit&redlink=1" class="new" title="AC-55649 (page does not exist)">AC-55649</a></li> <li><a href="/wiki/Acitretin" title="Acitretin">Acitretin</a></li> <li><a href="/wiki/Adapalene" title="Adapalene">Adapalene</a></li> <li><a href="/wiki/Tretinoin" title="Tretinoin">all-<i>trans</i>-Retinoic acid (tretinoin)</a></li> <li><a href="/w/index.php?title=AM-580&action=edit&redlink=1" class="new" title="AM-580 (page does not exist)">AM-580</a></li> <li><a href="/w/index.php?title=BMS-493&action=edit&redlink=1" class="new" title="BMS-493 (page does not exist)">BMS-493</a></li> <li><a href="/w/index.php?title=BMS-753&action=edit&redlink=1" class="new" title="BMS-753 (page does not exist)">BMS-753</a></li> <li><a href="/w/index.php?title=BMS-961&action=edit&redlink=1" class="new" title="BMS-961 (page does not exist)">BMS-961</a></li> <li><a href="/w/index.php?title=CD-1530&action=edit&redlink=1" class="new" title="CD-1530 (page does not exist)">CD-1530</a></li> <li><a href="/w/index.php?title=CD-2314&action=edit&redlink=1" class="new" title="CD-2314 (page does not exist)">CD-2314</a></li> <li><a href="/w/index.php?title=CD-437&action=edit&redlink=1" class="new" title="CD-437 (page does not exist)">CD-437</a></li> <li><a href="/w/index.php?title=Ch-55&action=edit&redlink=1" class="new" title="Ch-55 (page does not exist)">Ch-55</a></li> <li><a href="/w/index.php?title=EC_23&action=edit&redlink=1" class="new" title="EC 23 (page does not exist)">EC 23</a></li> <li><a href="/wiki/Etretinate" title="Etretinate">Etretinate</a></li> <li><a href="/wiki/Fenretinide" title="Fenretinide">Fenretinide</a></li> <li><a href="/wiki/Isotretinoin" title="Isotretinoin">Isotretinoin</a></li> <li><a href="/wiki/Palovarotene" title="Palovarotene">Palovarotene</a></li> <li><a href="/wiki/Retinoic_acid" title="Retinoic acid">Retinoic acid</a></li> <li><a class="mw-selflink selflink">Retinol</a> (<a href="/wiki/Vitamin_A" title="Vitamin A">vitamin A</a>)</li> <li><a href="/wiki/Tamibarotene" title="Tamibarotene">Tamibarotene</a></li> <li><a href="/wiki/Tazarotene" title="Tazarotene">Tazarotene</a></li> <li><a href="/w/index.php?title=Tazarotenic_acid&action=edit&redlink=1" class="new" title="Tazarotenic acid (page does not exist)">Tazarotenic acid</a></li> <li><a href="/wiki/Trifarotene" title="Trifarotene">Trifarotene</a></li> <li><a href="/w/index.php?title=TTNPB&action=edit&redlink=1" class="new" title="TTNPB (page does not exist)">TTNPB</a></li></ul> <ul><li><i>Antagonists:</i> <a href="/w/index.php?title=BMS-195614&action=edit&redlink=1" class="new" title="BMS-195614 (page does not exist)">BMS-195614</a></li> <li><a href="/w/index.php?title=BMS-493&action=edit&redlink=1" class="new" title="BMS-493 (page does not exist)">BMS-493</a></li> <li><a href="/w/index.php?title=CD-2665&action=edit&redlink=1" class="new" title="CD-2665 (page does not exist)">CD-2665</a></li> <li><a href="/w/index.php?title=ER-50891&action=edit&redlink=1" class="new" title="ER-50891 (page does not exist)">ER-50891</a></li> <li><a href="/w/index.php?title=LE-135&action=edit&redlink=1" class="new" title="LE-135 (page does not exist)">LE-135</a></li> <li><a href="/w/index.php?title=MM-11253&action=edit&redlink=1" class="new" title="MM-11253 (page does not exist)">MM-11253</a></li></ul> <ul><li><i>Retinoic acid metabolism inhibitors:</i> <a href="/wiki/Liarozole" title="Liarozole">Liarozole</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:center;"><a href="/wiki/Retinoid_X_receptor" title="Retinoid X receptor"><abbr title="Retinoid X receptor">RXR</abbr></a><span class="sr-only" style="border: 0; clip: rect(0, 0, 0, 0); clip-path: polygon(0px 0px, 0px 0px, 0px 0px); height: 1px; margin: -1px; overflow: hidden; padding: 0; position: absolute; width: 1px; white-space: nowrap;">Tooltip Retinoid X receptor</span></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><i>Agonists:</i> <a href="/w/index.php?title=9-cis-13,14-Dihydro-retinoic_acid&action=edit&redlink=1" class="new" title="9-cis-13,14-Dihydro-retinoic acid (page does not exist)">9CDHRA</a></li> <li><a href="/wiki/Alitretinoin" title="Alitretinoin">9-<i>cis</i>-Retinoic acid (alitretinoin)</a></li> <li><a href="/wiki/Tretinoin" title="Tretinoin">all-<i>trans</i>-Retinoic acid (tretinoin)</a></li> <li><a href="/wiki/Bexarotene" title="Bexarotene">Bexarotene</a></li> <li><a href="/w/index.php?title=CD_3254&action=edit&redlink=1" class="new" title="CD 3254 (page does not exist)">CD 3254</a></li> <li><a href="/wiki/Docosahexaenoic_acid" title="Docosahexaenoic acid">Docosahexaenoic acid</a></li> <li><a href="/w/index.php?title=Fluorobexarotene&action=edit&redlink=1" class="new" title="Fluorobexarotene (page does not exist)">Fluorobexarotene</a></li> <li><a href="/wiki/Isotretinoin" title="Isotretinoin">Isotretinoin</a></li> <li><a href="/w/index.php?title=LG-100268&action=edit&redlink=1" class="new" title="LG-100268 (page does not exist)">LG-100268</a></li> <li><a href="/w/index.php?title=LG-101506&action=edit&redlink=1" class="new" title="LG-101506 (page does not exist)">LG-101506</a></li> <li><a href="/w/index.php?title=LG-100754&action=edit&redlink=1" class="new" title="LG-100754 (page does not exist)">LG-100754</a></li> <li><a href="/wiki/Retinoic_acid" title="Retinoic acid">Retinoic acid</a></li> <li><a class="mw-selflink selflink">Retinol</a> (<a href="/wiki/Vitamin_A" title="Vitamin A">vitamin A</a>)</li> <li><a href="/w/index.php?title=SR-11237&action=edit&redlink=1" class="new" title="SR-11237 (page does not exist)">SR-11237</a></li></ul> <ul><li><i>Antagonists:</i> <a href="/w/index.php?title=HX-531&action=edit&redlink=1" class="new" title="HX-531 (page does not exist)">HX-531</a></li> <li><a href="/w/index.php?title=HX-630&action=edit&redlink=1" class="new" title="HX-630 (page does not exist)">HX-630</a></li> <li><a href="/w/index.php?title=LG-100754&action=edit&redlink=1" class="new" title="LG-100754 (page does not exist)">LG-100754</a></li> <li><a href="/w/index.php?title=PA-452&action=edit&redlink=1" class="new" title="PA-452 (page does not exist)">PA-452</a></li> <li><a href="/w/index.php?title=UVI-3003&action=edit&redlink=1" class="new" title="UVI-3003 (page does not exist)">UVI-3003</a></li> <li><a href="/w/index.php?title=HX-603&action=edit&redlink=1" class="new" title="HX-603 (page does not exist)">HX-603</a></li> <li><a href="/w/index.php?title=LE135_(RAR_beta_selective)&action=edit&redlink=1" class="new" title="LE135 (RAR beta selective) (page does not exist)">LE135 (RAR beta selective)</a></li> <li><a href="/w/index.php?title=LE-540&action=edit&redlink=1" class="new" title="LE-540 (page does not exist)">LE-540</a></li> <li><a href="/w/index.php?title=CD3254&action=edit&redlink=1" class="new" title="CD3254 (page does not exist)">CD3254</a></li> <li><a href="/w/index.php?title=PA-451&action=edit&redlink=1" class="new" title="PA-451 (page does not exist)">PA-451</a></li> <li><a href="/w/index.php?title=PA-452&action=edit&redlink=1" class="new" title="PA-452 (page does not exist)">PA-452</a></li> <li><a href="/wiki/Rhein_(molecule)" title="Rhein (molecule)">Rhein</a></li> <li><a href="/w/index.php?title=HX-711&action=edit&redlink=1" class="new" title="HX-711 (page does not exist)">HX-711</a></li> <li><a href="/w/index.php?title=6-(N-ethyl-N-(5-isobutoxy-4-isopropyl-2-(E)-styrylphenyl)amino)nicotinic_acid&action=edit&redlink=1" class="new" title="6-(N-ethyl-N-(5-isobutoxy-4-isopropyl-2-(E)-styrylphenyl)amino)nicotinic acid (page does not exist)">6-(N-ethyl-N-(5-isobutoxy-4-isopropyl-2-(E)-styrylphenyl)amino)nicotinic acid</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <dl><dt>See also</dt> <dd><i><a href="/wiki/Template:Receptor_modulators" title="Template:Receptor modulators">Receptor/signaling modulators</a></i></dd></dl> </div></td></tr></tbody></table></div> <style data-mw-deduplicate="TemplateStyles:r1130092004">.mw-parser-output .portal-bar{font-size:88%;font-weight:bold;display:flex;justify-content:center;align-items:baseline}.mw-parser-output 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