ABSTRACT
Retinoids comprise a large class of small lipophilic molecules related to vitamin A, retinol (ROL), in their chemical structure, biological activities, or receptor binding. The naturally occurring retinoids include ROL; retinyl esters (retinyl palmitate); 11-cis-retinal, 11cRAL; 9-cis-retinoic acid, 9cRA; all trans retinoic acid, tRA (tretinoin, Retin A); 13-cis-retinoic acid, 13cRA, (isotretinoin, Accutane); and as many as a few dozen active and inactive metabolites of these molecules. The provitamin beta-carotene may be included by extension as it can furnish retinyl esters when cleaved in the intestine. The synthetic retinoids now number well over 2000, only a few of which have been successfully commercialized as etretinate (Tigason, Tegison), acitretin (Soriatane, Neotigason), tazarotene (Tazorac), adapalene (Differin), and bexarotene (Targretin). This massive synthetic effort by a number of large pharmaceutical companies has been largely an attempt to obviate the toxicity of retinoids when administered in pharmacologic doses for treatment of various skin diseases and carcinomas but has had thus far limited success in divorcing desirable and undesirable biological actions.
