The Isomeric Composition of Hydroperoxides Formed by Autoxidation of Unsaturated Triglycerides and Vegetable Oils

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Abstract
Trioleoylglycerol (TO), trilinoleoylglycerol (TL), and trilinolenoylglycerol (TLN)were autoxi-dized in the dark at 37°C. Monohydroperoxides (MHP), the primary products, were isolated by preparative thin-layer chromatography (TLC). The isomeric compositions of their hydroperoxy fatty acid components were determined by gas chromatography-mass spectrometry (GC-MS) as follows—TO: the 8-, 9-, 10-, and 11-isomers; TL: the 9-, and 13-isomers; and TLN: the 9-, 12-, 13-, and 16-isomers. The proportions of isomers in each MHP did not vary with the oxidation time. The isomeric compositions of hydroperoxy fatty acid components obtained from autoxidized soybean and olive oils indicated that each unsaturated fatty acyl group of triacylglycerol (TG) in vegetable oils produced isomeric hydroperoxides during autoxidation in a way similar to the corresponding fatty acid methyl esters. The proportions of the isomers obtained from autoxidized oils changed with the level of oxidation. Isomers coming from linolenic acid in soybean oil and those from linoleic acid in olive oil decreased remarkably at a high level of oxidation.