ABSTRACT
Vitamin E functions as a potent chain-breaking antioxidant and plays a vital role as one of the defense systems in biological systems against oxygen toxicity. The sparing action of vitamin C is ascribed to the regeneration of vitamin E from tocopheroxyl radical by vitamin C. Vitamin E is effective as an antioxidant in-dependent of the initial site of radical generation and produces an induction period. On the other hand, the addition of vitamin C has little effect, suggesting vitamin C located in the aqueous phase cannot scavenge the radicals from the initiator nor lipid peroxyl radicals within the membrane. Vitamin C suppresses the consumption of vitamin E almost completely in the homogeneous solution. In addition to vitamin C, uric acid, cysteine, and glutathione may also function as water soluble, chain-breaking antioxidants. Vitamin C is itself a radical scavenger and reducing agent, but it can also function as a prooxidant under certain conditions, especially in combination with metal ions.
