Hydroxyl radical formation from Cu(II)-trolox mixtures: insights into the pro-oxidant properties of alpha-tocopherol.

Although widely recognised as the most important chain-breaking antioxidant of the lipid phase, alpha-tocopherol has also been reported to exert pro-oxidant activity, particularly during the Cu(II)-stimulated oxidation of low density lipoproteins (LDL). In the present communication, we demonstrate that hydroxyl radicals are generated following the interaction of Cu(II) with the alpha-tocopherol model compound Trolox, involving the reduction of Cu(II) by Trolox and the subsequent reduction of molecular oxygen by Cu(I). We suggest, therefore, that the hydroxyl radical may be the species responsible for the initiation of fatty acid oxidation during the Cu(II)-stimulated oxidation of hydroperoxide-free LDL.