What are the precursors of vitamin A?
The precursors of vitamin A (retinol) are the carotenoids (most commonly beta-carotene). The term retinoid refers to any compound that is structurally similar to retinal (aldehyde), retinol (alcohol), or any other substance that exhibits vitamin A activity . Retinoic acid, which is a metabolite of retinal , is such a substance that is often studied. Synthetic compounds within the vitamin A family have similar structures as the natural form, but may have few or no functions that the natural vitamin posses . Most compounds within the vitamin A family are soluble in fat and essential to numerous processes within the body. There have been several water-soluble retinoids, extracted from plasma, bile, and other tissue . For the purposes of this literature review any discussion of vitamin A will focus on those retinoids with fat-soluble properties. The main discussion will involve retinol. Retinol is chemically a “pale yellow crystalline solid” . The solid and its metabolites exist in nature
