Ascorbic Acid (Vitamin C)

• The dietary essentiality of ascorbic acid is dependent upon the absence of the enzyme necessary for its synthesis: L-gulonolactone oxidase. In the majority of animals (which possess L-gulonolactone oxidase), ascorbic acid can be synthesized ultimately from glucose.  Primates (including humans), guinea pig, some species of bats, birds, fishes and invertebrates lack L-gulonolactone oxidase and thus require a dietary source of ascorbic acid.
• Ascorbic acid functions physiologically as a source of reducing equivalents.  In many cases, ascorbic acid acts indirectly in many enzymatic steps requiring metal cofactors in their reduced state(s).  Ascorbic acid also acts as an antioxidant, one role being the regeneration of a-tocopherol from tocopherol which has reacted with peroxyl free radicals.