Vitamin C contributing to the more severe symptoms of scurvy. More generally, the biochemical role of vitamin C is to act as an antioxidant (a reducing agent) by donating electrons to various enzymatic and non-enzymatic reactions. Doing so converts vitamin C to an oxidized state - either as semidehydroascorbic acid or dehydroascorbic acid. These compounds can be restored to a reduced state by glutathione and NADPH-dependent enzymatic mechanisms. In plants, vitamin C is a substrate for ascorbate peroxidase. This enzyme utilizes ascorbate to neutralize toxic hydrogen peroxide (HO) by converting it to water (HO). Scurvy is a disease resulting from a deficiency
Vitamin growth and differentiation. The B complex vitamins function as enzyme cofactors (coenzymes) or the precursors for them. Vitamin D has a hormone-like function as a regulator of mineral metabolism for bones and other organs. Vitamins C and E function as antioxidants. Both deficient and excess intake of a vitamin can potentially cause clinically significant illness; although excess intake of water-soluble vitamins is less likely to do so. Before 1935, the only source of vitamins was from food. If intake of vitamins was lacking, the result was vitamin deficiency and consequent deficiency diseases. Then, commercially produced tablets of yeast-extract vitamin B