Reaction of alpha-tocopherol with alkyl and alkylperoxyl radicals of methyl linoleate.

alpha-Tocopherol was reacted with alkyl and alkylperoxyl radicals at 37 degrees C in bulk phase. The lipid-free radicals were generated by the reaction of methyl linoleate with the free radical initiator, 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN) under air-insufficient conditions. The products were isolated by high-performance liquid chromatography. Their structures were identified as 2-(alpha-tocopheroxy)-2,4- dimethylvaleronitrile (1), a mixture of methyl 9-(8a-peroxy-alpha-tocppherone)-10(E),12(Z)-octadecadienoate and methyl 13-(8a-peroxy-alpha-tocopherone)-9(Z),11(E)-octadecadienoate (2), methyl 9-(alpha-tocopheroxy)-10(E),12(Z)-octadecadienoate (3a), methyl 13-(alpha-tocopheroxy)-9(Z),12(E)-octadecadienoate (3b), alpha-tocopherol spirodiene dimer (4) and alpha-tocopherol trimer (5). When methyl linoleate containing alpha-tocopherol was oxidized with AMVN under air-sufficient conditions, the main products were 8a-alkylperoxy-alpha-tocopherones (2). In addition to these compounds, 6-O-alkyl-alpha-tocopherols (1, 3a and 3b) were formed when the reaction was carried out under air-insufficient conditions. The results indicate that alpha-tocopherol can react with both alkyl and alkylperoxyl radicals during the autoxidation of polyunsaturated lipids.