α‐Tocopherol prooxidant effect in aqueous media: Increased autoxidation rate of linoleic acid

The prooxidant effect of a‐tocopherol was investigated during linoleic acid autoxidation in an aqueous media, at pH 6.9. α‐Tocopherol (1.25 x 10 −4 M) was added to linoleic acid (2.5 x 10 −3 M) and the linoleic acid autoxidation rate was evaluated using 2 methods: spectrophotometric measurement at 234 nm exhibited an important increase of conjugated dienes after α‐tocopherol addition, especially during the first 4 days, and gas Chromatographie measurement of unoxidized linoleic acid showed an important degradation of linoleic acid in the presence of a‐tocopherol. During the pro‐oxidant reaction, α‐tocopherol was rapidly oxidized ; it was detected as traces by thin layer chromatography after 4 days of experimentation. Two oxidation products of α‐tocopherol have been identified: α‐tocopherylquinone and a dimer of α‐tocopherol.