Prooxidant role of vitamin E in copper induced lipid peroxidation.

When exposed to Cu2+, alpha-tocopherol, in detergent dispersion, is rapidly oxidised. Moreover, if phospholipids and traces of their hydroperoxide derivatives are included in these dispersions, Cu2+ initiates lipid peroxidation, the rate of which is dramatically stimulated by alpha-tocopherol. The observation that the rate of alpha-tocopherol consumption is identical in the absence and in the presence of lipids undergoing peroxidation, apparently rules out any antioxidant effect. These results are consistent with a prooxidant effect of vitamin E, mediated by its capability to reduce Cu2+ to Cu+ which, in turn, produces, from lipid hydroperoxides, the highly reactive alkoxyl radicals. Present data highlight the risk of misleading results in interpreting the significance of lags in peroxidation of LDL challenged with Cu2+.