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天然的类视黄醇(retinoids):维生素 A及其重要的代谢衍生物——视黄醛与维甲酸都是脂溶性不饱和的异戊间二烯化合物,由三甲基环己基与一带有四个双链的全反式多烯链组成。这些化合物的纯结晶体在氧气、光线与高温中不稳定。类胡萝卜素是存在于蔬菜中无生理活性的维生素 A 二聚体。合成的类视黄醇:为了寻求具有更大生物活性与更小毒性的化合物,维生素 A 分子的所有三个部分均曾被置换过。一般改变类视黄醇的多烯链可明显地减低其活性,而改变维甲酸的羧基使其成为乙烯胺或乙氧羰基终末基团,则可减低其毒性并保留或增强其生物活性,如再置换以某些芳香性化合物,则可使其毒性更小且活性增强达10倍之多。
Natural retinoids: Vitamin A and its important metabolic derivatives - Retinyl and retinoic acid are both fat-soluble, unsaturated isoprenoid compounds consisting of trimethylcyclohexyl and a Four double-stranded all-trans polyene chains. The pure crystals of these compounds are unstable in oxygen, light and high temperatures. Carotenoids are vitamin A dimers that are present in vegetables that are not physiologically active. Synthetic retinoids: In order to seek compounds with greater biological activity and less toxicity, all three parts of the Vitamin A molecule have been replaced. General modifications of the retinoid polyene chain can significantly reduce its activity, while the retinoic acid carboxyl to make it a vinylamine or ethoxycarbonyl terminal group, you can reduce its toxicity and retain or enhance its biological activity, If the replacement with some aromatic compounds, can make it less toxic and activity increased by up to 10 times.