Vitamin A2

Vitamin A2 is a subcategory of vitamin A.

As with all vitamin A forms, A2 can exist as an aldehyde, Dehydroretinal (3,4-dehydroretinal), an alcohol, 3,4-dehydroretinol (vitamin A2 alcohol) or an acid, 3,4-dehydroretinoic acid (vitamin A2 acid). Many cold-blooded vertebrates use the aldehyde for their visual system to obtain a red-shifted sensitive spectrum.

Human skin naturally contains the alcohol form. In humans, CYP27C1 converts ordinary A1 (all-trans retinoids) to A2. The enzyme also converts 11-cis-retinal.

Vitamin A2 was first identified by Richard Alan Morton using newly-developed absorption spectroscopy in 1941.