[Prooxidant effect of alpha-tocopherol on essential fatty acids in aqueous media]

Linoleic, linolenic and arachidonic acids, dispersed at a concentration of 2.5 x 10-3 M in an aqueous media pH 7.3, exhibited increasing of their autoxidation rate in presence of 1.5 x 10-5M alpha-tocopherol or more. Cosidering linolenic and arachidonic acids, prooxidant effect increased with alpha-tocopherol level while for linoleic acid this effect was similar with all alpha-tocopherol concentrations. During the prooxidant reaction, alpha-tocopherol was rapidly oxidized. Its oxidation rate depended on hydroperoxides level. It was the most important in presence of arachidonic acid. After 24 hours, alpha-tocopherol was completly oxidized whatever its initial concentration and the type of the fatty acid. Two oxidation products have been identified : alpha-tocopherylquinone for the most part and a dimer of alpha-tocopherol which was detected at the beginning of the reaction.