油脂の変敗に関する研究 (第4報)

リノール酸メチルハイドロパーオキサイドの分解

抄録

Methyl linoleate hydroperoxide (ML-HPO) was separated from methyl linoleate autoxidized at about 10°C by the combination method of simple countercurrent extraction and column chromatography. The peroxide value of ML-HPO was more than 5, 780meq/kg. This value indicated that the material was essential pure monoperoxide. ML-HPO had a conjugated diene and a hydroperoxide group. Being hydrogenated with platinum oxide, ML-HPO absorbed 3.11 mole of hydrogen, and was converted into a mixture of great quantity of hydroxystearic acid methyl esters and slight unknown material. The methyl esters contained equal amount of 9 and 13 hydroxystearic acid methyl esters.
When ML-HPO stored in air and in nitrogen at 25°C, the contents of conjugated diene and peroxide value of ML-HPO decreased respectively. This fact evidences that decomposition of ML-HPO occurred in those atmospheric conditions. Methyl 8-formyloctanoate (MFO) was detected in oxidized ML-HPO, was not detected in the substance that decomposed under nitrogen, by gasliquid chromatographic analysis.
ML-HPO and hydroxyoctadecadienoic acid methyl ester (HODE) which was obtained from reduction of ML-HPO with stannous chloride absorbed about 1 mole of oxygen at 45°C, respectively. In the oxidation process, the contents of peroxide value and conjugated diene of ML-HPO decreased proportionately with oxygen uptake. MFO and malonaldehyde were found in oxidized ML-HPO. One mole of oxidized ML-HPO released 0.393 mole of MFO at maximal rate. The quantity of malonaldehyde found was about one-tenth of MFO. MFO and malonaldehyde were found in case of HODE as well as ML-HPO. Thier quantity, however were less than in case of ML-HPO.
The above results indicated that MFO was not formed from ML-HPO that was the first product of autoxidation of methyl linoleate, but formed from furthermore oxidized ML-HPO.