Unit Definition 1 international unit according to PH EUR II, 217 (1983) Biochem/physiol Actions Retinal, retinol and retinoic acid are the aldehyde, alcohol and acid forms of vitamin A. The retinoids exist as many geometric isomers due to the unsaturated bonds in the aliphatic chain.Retinoids also exist as retinyl esters such as retinyl propionate, retinyl acetate and retinyl palmitate. Retinyl esters provide pools of vitamin A that are converted into retinol and other retinoids as needed. Retinyl propionate is used in various formulations to control wrinkles. |