Synergistic Effect of Trimethylamine Oxide on the Inhibition of the Autoxidation of Methyl Linoleate by δ-Tocopherol

Abstract

The synergistic effect of tri methyl amine oxide (TMAO) on the antioxidative activity of δ-tocopherol (δ-Toc) to inhibit the autoxidation of methyl linoleate was investigated. The peroxide value of methyl linoleate incubated with δ-Toc and TMAO at 50°C was maintained at constant values of 25~30, while a drastic increase in the peroxide value was observed in the absence of TMAO. An oxidation product of methyl linoleate, which was formed only in the presence of δ-Toc and TMAO, was isolated and identified to be a mixture of methyl 9-keto-10, 12-octadeca- dienoate and methyl 13-keto-9,11-octadecadienoate. δ-Toc diphenyl ether dimer and two δ-Toc biphenyl dimers were identified, and the latters were thought to be atropisomers with each other. The amounts of reducing dimers of δ-Toc formed were larger in the presence of TMAO than in the absence of TMAO, and it was found that these dimers were likely to play an important role in synergism between δ-Toc and TMAO.