Vitamin C

Vitamin C is a water-soluble vitamin that includes L-ascorbic acid and compounds with equivalent biological activity. In the body, ascorbic acid exists mainly in its ionized form, ascorbate. Humans cannot synthesize vitamin C because they lack a functional enzyme required for the final step of its biosynthesis, so it must be obtained from the diet .¹

Vitamin C functions as an electron donor, allowing it to act as a reducing agent and as a cofactor for several enzymes. It is required by enzymes involved in collagen synthesis, where it helps maintain iron in the chemical state needed for hydroxylation reactions. Vitamin C also contributes to the synthesis of carnitine and certain neurotransmitters and participates in other enzyme systems that depend on iron or copper .^1,2

Ascorbate can also act as a water-soluble antioxidant by donating electrons to reactive chemical species. In doing so, it can form the relatively stabilized ascorbyl radical and subsequently dehydroascorbic acid. These oxidized forms can be reduced back to ascorbate through cellular recycling systems. Vitamin C can also participate in reducing the tocopheroxyl radical and thereby regenerating alpha-tocopherol .^1,2

Vitamin C is distinct from the broader category of antioxidants. Antioxidant activity is one property of ascorbate, whereas vitamin C refers specifically to compounds with biological vitamin C activity. Its physiological importance therefore extends beyond antioxidant reactions to its essential roles as an enzyme cofactor .^1,2