ABSTRACT
Vitamin A was the žrst fat-soluble vitamin to be discovered and has been known chemically since 1927, when its structure was determined.
The term “vitamin A” is reserved to designate any substance or mixture of substances that possesses activity similar to vitamin A. Retinol (also known as vitamin A alcohol and vitamin A1) is the most commonly known and the most abundant of all naturally occurring vitamin A compounds. Other compounds of biological interest include retinal (also called retinaldehyde) and retinoic acid. The more general term, retinoids, includes both naturally occurring compounds with vitamin A activity and synthetic analogs of retinol, irrespective of whether they have biological activity.
