Behavior of alpha, gamma, and delta tocopherols with linoleic acid in aqueous media

Tocopherols can exhibit opposite effects in aqueous media on linoleic acid autoxidation rate. The effect which was observed depended on tocopherol concentration and on the tocopherol itself. At 0.05 mole of tocopherol per mole of linoleic acid, α‐tocopherol was prooxidant while in similar conditions, δ‐tocopherol was anti‐oxidant as well as γ‐tocopherol. However, this latter one exhibited a slight antioxidant activity. When tocopherol concentration decreased (twice as weak), α‐tocopherol still exhibited the same pro‐oxidant activity, while the antioxidant effect of γ and δ tocopherols was increased. The study of tocopherol stability by HPLC has shown that tocopherol oxidation increased in order δ < γ < α. There was a relationship between the ability for a tocopherol to be easily oxidized by air and its prooxidant activity. Tocopherol oxidation would enhance the formation of a perhydroxyl radical ([·OOH] or one of this type [O20=, ·OH]) which was responsible for the prooxidant effect.