Oxidation of Lipids. VIII. Synergistic Inhibition of Oxidation of Phosphatidylcholine Liposome in Aqueous Dispersion by Vitamin E and Vitamin C

Abstract

Vitamin E acted as an efficient antioxidant in the oxidation of soybean phosphatidylcholine liposome in an aqueous dispersion initiated by free radicals generated initially either in the aqueous phase or in the lipid phase. Vitamin E decayed linearly with time, and when it was exhausted, the oxidation proceeded rapidly at a similar rate to that in the absence of vitamin E. Vitamin C was also effective by itself in scavenging radicals in an aqueous phase, but it could not scavenge the radicals efficiently in a lipid bilayer. However, when vitamin E was located in phosphatidylcholine bilayer, the addition of vitamin C into an aqueous phase prolonged the period of suppression of oxidation and vitamin C reduced the rate of decay of vitamin E markedly even when the radicals were generated initially in the lipid region. Vitamin C was predominantly consumed linearly at first and vitamin E began to decay after vitamin C was exhausted. It was suggested that vitamin C could regenerate vitamin E by reacting with vitamin E radical during the oxidation of phosphatidylcholine liposome in an aqueous dispersion as observed in a homogeneous solution.