Nonenzymatic oxidation products of methyl arachidonate.

Six monohydroperoxide isomers were obtained on autoxidation of methyl arachidonate. In the isomeric mixture of monohydroperoxides, the amount ratio of outer isomers (5- and 15-isomers) was especially high. However, in the presence of 1.0% of α-tocopherol, the isomeric composition of monohydroperoxides was approximately homogeneous.Furthermore, no significant difference was observed in the susceptibility to decomposition between the isomers. From these results, it was suggested that the predominance of outer isomers was based on the difference in stability between their peroxy radicals. With the accelerated oxidation of methyl arachidonate with ferrous ion-AsA catalyst, further oxygenated products, diOH, triOH and tetraOH compounds (after reduction and hydrogenation), were detected by GC-MS analysis.