Biochemical Roles of Ascorbic Acid (Vitamin C)

Vitamin C serves the following biochemical role:
  1. It is present in large amounts in glandular tissues especially adrenal cortex and corpus luteum; in these tissues it appears to take part in reducing reactions involved in the synthesis of steroid hormone. Depletion of adrenal cortex ascorbic acid occurs on injecting ACTH and in stressful conditions showing that ascorbic acid has been fully utilized.

  2. Ascorbic acid helps in reducing Fe+++ to Fe++ and helps in the absorption of iron from the intestine and in its utilization (iron is absorbed in Fe++ form). It also takes part in oxidation-reduction reaction systems coupled with glutathione, cytochrome, NAD, NADP and FAD. Due to reducing properties ascorbic acid is of use in the treatment of methemoglobinemia.

  3. Ascorbic acid is involved in the metabolism of tyrosine. However, this function is important only when tyrosine metabolism is abnormally increased as after excessive intake of tyrosine and/or phenylalanine; such a condition is seen in premature infants who are on cow’s milk.

  4. The reaction, folic acid —> tetrahydrofolic acid needs the presence of ascorbic acid. This reaction is necessarily for the utilization of folic acid in the body. Ascorbic acid deficiency in infants has been found to result in megaloblastic anemia due to a non-utilization of folic acid.

  5. Ascorbic acid is involved in the conversion of proline into hydroxyproline; the latter is found abundantly in collagen which the main protein of the connective tissue. This reaction is catalyzed by the enzyme collagen-proline-hydroxylase for whose activity ascorbic acid appear to essential.