Vitamin C (Ascorbic Acid)

Vitamin C (Ascorbic Acid)

1. Both have vitamin activity

   • ascorbic acid (reduced form)
   • and dehydroascorbic acid (oxidized form)

2. Acts as a hydrogen carrier

3. 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”

4. 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

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