The Oxidation Products from Two Kinds of Tocopherols Co-Existing in Autoxidation System of Methyl Linoleate

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Abstract
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 13C NMR, and mass spectrometry. The 5-[2-(.alpha.-tocopherol-5''-yl)ethyl]-.alpha.-tocopherylquinone, 5-[2-(.alpha.-tocopherol-5''-yl)ethyl]-8a-hydroxy-.alpha.-tocopherone, and 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 mixutres. 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.

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