Effect of α-tocopherol on the hemin-catalyzed decomposition of 1-palmitoyl-2-linoleoyl-3-sn-phosphatidylcholine 13-hydroperoxide in micelles and liposomes.

The secondary process of lipid peroxidation produces some toxic aldehydes. Since this process takes place via free radical reaction in lipophilic circumstances, α-tocopherol would suppress the formation of such aldehydes by trapping free-radical intermediates. This study reports the effect of α-tocopherol on the hemin-catalyzed decomposition of 1-palmitoyl-2-linoleoyl-3-sn-phosphatidylcholine 13-hydroperoxide (PLPC-OOH) in micelles and liposomes. PLPC-OOH and α-tocopherol were reacted with hemin in micelles, and the reaction products were characterized to be 1-palmitoyl-2-(α-tocopheroxy-12,13-epoxyoctadecenoyl)-3-sn-phosphatidylcholines (T-epoxyPLPC) and known compounds, 1-palmitoyl-2-[(8a-dioxy-α-tocopherone)-12,13-epoxyoctadecenoyl]-3-sn-phosphatidylcholines (TOO-epoxyPLPC) and α-tocopherol dimer. The hemin-catalyzed decomposition of PLPC-OOH in micelles produced hexanal as one of secondary aldehydic products. α-Tocopherol suppressed the formation of hexanal, and α-tocopherylquinone, α-tocopherol dimer, TOO-epoxyPLPC, and T-epoxyPLPC were detected during the reaction. In liposomes, α-tocopherol could partially suppress the formation of hexanal, and the main products were TOO-epoxyPLPC and α-tocopherol dimer. The results indicate that α-tocopherol may suppress the formation of hexanal by trapping the epoxyperoxyl and epoxyalkyl radicals derived from PLPC-OOH.