Lipid antioxidants: how they may act in biological systems.

Chain breaking antioxidants scavenge the chain carrying oxygen radicals and suppress the peroxidation of liposomal and biological membranes in aqueous dispersions. Vitamin E scavenges peroxyl radicals rapidly and its lateral diffusion is suggested to be fast, but its antioxidant efficiency in the liposomal and bio-membranes appears to be considerably smaller than in homogeneous solution. Water soluble chain breaking antioxidants, such as uric acid, cysteine, glutathione, and vitamin C, scavenge radicals in the aqueous region and suppress the peroxidation. However, they cannot scavenge the peroxyl radicals within the lipid region of the membranes. Nevertheless, vitamin C can interact with vitamin E radical, probably at membrane-water interface, and regenerate vitamin E.