不和飽度の異なる脂肪酸メチルの自動酸化に伴うトコフェロールの二量化 (第1報)
γ-トコフェロールのA.O.M.条件下における二量化
1981 年 30 巻 3 号 p. 145-150
詳細
1981 年 30 巻 3 号 p. 145-150
The oxidative decomposition of γ-γ-tocopherol (γ-Toc) and the formation of its dimers during the course of autoxidation of methyl laurate (Me-La) and methyl linoleate (Me-Li) under A.O.M. conditions were investigated. Twenty mililiters of fatty acid methyl esters, in which γ-Toc dissolved in the concentration of 0.5%, were oxidized by blowing in dry air at a flow rate of 2.33 ml/s in a glycerol bath controlled at 97.8 0.2°C.
Five oxidation products were obtained from the reaction mixture in Me-Li by the chromatography on a silicic acid column eluted with hexane-diethyl ether mixtures (Fig.-4). Products [I], [II], and [III] were identified as the dimers of γ-Toc by means of UV absorption, IR absorption, NMR, and MS spectroscopy : the former one 5- (γ-tocopheroxy) -γ-tocopherol (γ-TED), and the latter two 5- (γ-tocopherol-5-yl) -γ-tocopherol [γ-TBD (H) and (L)] as the atropisomer each other. These three compounds were also confirmed by TLC and HPLC (Figs.-1 and 3). Products [N] and [V], which were formed especially in Me-Li, were red substances.
The oxidative dimerization of γ-Toc during the course of autoxidation in Me-La and in Me-Li was followed by HPLC. The decomposition of γ-Toc was more rapid in Me-Li than in Me-La (Fig.-5). γ-TED was formed more abundantly than γ-TBD, especially in Me-Li (Fig.-6). Each amount of the dimers formed in Me-La reached maximum by the autoxidation for 2 h : on the other hand, that in Me-Li reached maximum by the autoxidation for 5 h (Figs.-6 and 7). The formation of the red substances from the dimers was caused by further oxidation in Me-Li.
