Hemin- and myoglobin-catalyzed reaction of 1-palmitoyl-2-linoleoyl-3-sn-phosphatidylcholine 13-hydroperoxide with γ-tocopherol in micelles and liposomes.

The secondary process of lipid peroxidation proceeds by the free radical reaction to produce some toxic aldehydes. Since γ-tocopherol (γ-TH), one of the major forms of vitamin E in some vegetable oils, acts as a free radical scavenger, γ-TH may suppress the formation of such aldehydes. This study reports the effect and reaction products of γ-TH on the hemin- or myoglobin-catalyzed decomposition of 1-palmitoyl-2-linoleoyl-3-sn-phosphatidylcholine 13-hydroperoxide (PLPC-OOH) in micelles and liposomes. γ-TH and PLPC-OOH in micelles were reacted in the presence of hemin, and the reaction products were characterized as 1-palmitoyl-2-[(8a-dioxy-γ-tocopherone)-12,13-epoxyoctadecenoyl]-3-sn-phosphatidylcholines (γT-OO-epoxyPLPC), 1-palmitoyl-2-[(γ-tocopheroxy)-12,13-epoxyoctadecenoyl]-3-sn-phosphatidylcholines (γT-epoxyPLPC), and the adducts of γ-TH dimer with PLPC-OOH derived epoxyperoxyl and epoxyalkyl radicals (γTD-OO-epoxyPLPC and γTD-epoxyPLPC). The hemin- and myoglobin-catalyzed decomposition of PLPC-OOH in micelles produced hexanal and 4-hydroxy-2-nonenal as the major aldehydic products. γ-TH suppressed the formation of these aldehydes as the same level as α-TH did, and γ-tocopherylquinone, tocored, γ-TH dimers, and the addition products (γT-OO-epoxyPLPC, γT-epoxyPLPC, γTD-OO-epoxyPLPC, and γTD-epoxyPLPC) were formed during the reaction. In liposomes, hexanal was detected as the major aldehyde and its suppression by γ-TH was less effective than that by α-TH. The results indicate that γ-TH may suppress the formation of aldehydes by trapping the epoxyperoxyl and epoxyalkyl radicals derived from PLPC-OOH although its ability is weak in liposomal systems.