Ascorbic Acid / Vitamin C
Vitamin C is a water soluble versatile vitamin. It plays an important role in human health and disease.
Most of the functions of Vitamin C are related to its property to undergo reversible oxidation-reduction, i.e., interconversion of ascorbic acid and dehydroascorbic acid.
1. Collagen formation: Vitamin C plays the role of a coenzyme in hydroxylation of proline and lysine while protocollagen is converted to collagen (i.e., posttranslational modification). The hydroxylation reaction is catalyzed by lysyl hydroxylase (for lysine) and prolyl hydroxylase (for proline). This reaction is dependent on Vitamin C.
Hydroxyproline and hydroxylysine are essential for the collagen cross-linking and the strength of the fiber. In this way, vitamin C is necessary for maintenance of normal connective tissue and wound healing process.
2. Bone formation: Bone tissues possess an organic matrix, collagen, and the inorganic calcium, phosphate, etc. Vitamin C is required for bone formation.
3. Iron and hemoglobin metabolism: Ascorbic acid enhances iron absorption by keeping it in the ferrous form. This is due to the reducing property of vitamin C.
4. Tryptophan metabolism: Vitamin C is essential for the hydroxylation of tryptophan (enzyme, hydroxylase) to hydroxytryptophan in the synthesis of serotonin.
5. Tyrosine metabolism: Ascorbic acid is required for the oxidation of p-hydroxy phenyl pyruvate (enzyme, hydroxylase) to homogentisic acid in tyrosine metabolism.
6. Folic acid metabolism: The active form of the vitamin folic acid is tertrahydrofolate (FH4). Vitamin C is needed for the formation of FH4 (enzyme, folic acid reductase).
7. Synthesis of corticosteroid hormones: Adrenal gland possesses high levels of ascorbic acid, particularly in periods of stress. It is believed that vitamin C is necessary for the hydroxylation reactions in the synthesis of corticosteroid hormones.
8. Sparing action of other vitamins: Ascorbic acid is strong antioxidant. It spares Vitamin A, Vitamin E and some B-complex vitamins from oxidation.
9. Immunological function: Vitamin C enhances the synthesis of immunoglobulin’s (antibodies) and increases the phagocytic action of leukocytes.
10. Preventive action of chronic diseases: Free radicals are constantly produced in the normal metabolism. They cause serious damage to proteins, lipids, DNA, and the cell membranes. The free radicals are implicated in the development of cancer, heart diseases, and also ageing. Vitamin C is a strong biological antioxidant, besides vitamin E and β-carotene.
The deficiency of ascorbic acid results in scurvy. This disease is characterized by spongy and sore gums, loose teeth, anemia, swollen joints, decreased immunocompetence, delayed wound healing, hemorrhage, osteoporosis, etc.