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Vitamin C (Ascorbic Acid)

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Both have vitamin activity
- ascorbic acid (reduced form)
- and dehydroascorbic acid (oxidized form)
Acts as a hydrogen carrier
Both forms are interconvertable and the reversibility of the reaction is key to vitamin C’s role as an antioxidant, maintain redox state “oxidation-reduction equilibrium”
Vitamin C Functions:
- 1. Important for dietary Fe absorption, by maintaining the reduced state and chelating it (Fe3+ Therefore, deficiency can lead to anaemia → Fe2+).
  - 2. Interaction exists between vitamin C, Fe and Cu that influences normal heme function through the oxidation-reduction of Fe or by regulating Fe absorption and availability at intestinal level
    - 3. Collagen is important protein of connective tissue, matrix of bone and teeth, wound healing, and capillary walls elasticity. Hydroxyproline and hydroxylysine facilitate collagen fibers binding together → strong rope-like structure
      - 4. Increased requirements during stress (e.g.) infections, smoking, common cold prevention
        5. Reducing agent. It can be reversibly oxidized in biological systems to dehydroascorbate
        6. Synthesis of vasoactive amines and microsomal drugs metabolism.
        7. Folate metabolism
        8. Protects other antioxidant vitamins like A and E
        9. Reduces histamine release (allergic action )
        10. Immune functions
        11. Blood clotting factors synthesis
        12. Glycosaminoglycans formation (chondroitin sulfate)
        13. Vitamin C is a coenzyme for 8 enzymes; Cu- containing and Fe-containing hydroxylases
        14. Carnitine synthesis
        15. Dopamine hydroxylation in synthesis of catecholamines
        16. Hydroxylation of steroid hormones, aromatic drugs (barbiturates) or carcinogens through the microsomal monooxygenase systems
        17. Amidation of glycine residues of polypeptide hormones (e.g.) growth hormone, calcitonin