The oxidation products from two kinds of tocopherols co-existing in autoxidation system of methyl linoleate.

The oxidation products of both types of mixtures of alpha-tocopherol (alpha-Toc) and gamma-tocopherol (gamma-Toc) or alpha-Toc and delta-tocopherol (delta-Toc) during autoxidation of methyl linoleate were isolated and identified. The structures of the oxidation products were characterized by UV, IR, 1H and 13CNMR, and mass spectrometry. The 5-[2-(alpha-tocopherol-5'-yl)ethyl]-alpha-tocopherylquinone, 5-[2-(alpha-tocopherol-5'-yl)ethyl]-8a-hydroxy-alpha-tocopherone, O-[8-(5-ethoxymethyl-7-methyltocol)methyl]-alpha-tocopherol were obtained from both types of the mixtures as the oxidation products derived from alpha-Toc. gamma-Toc diphenyl ether dimer (gamma-TED) and gamma-Toc biphenyl dimer (gamma-TBD) were identified from the mixture of alpha-Toc and gamma-Toc, and delta-Toc diphenyl ether dimer (delta-TED) from the mixture of alpha-Toc and delta-Toc. However, no oxidation product composed of both alpha-Toc and gamma-Toc or delta-Toc was detected in oxidation products of both types of the mixtures. These results support the facts that, at first, oxidation of alpha-Toc proceeds during autoxidation of lipids and then gamma-Toc or delta-Toc decomposes after approximate consumption of alpha-Toc.