Studies on bio-antioxidants--prooxidation of vitamin E on the autoxidation of linoleic acid in sodium dodecyl sulfate micelles

The reaction of vitamin E (alpha-tocopherol) with linoleic acid containing peroxidized linoleic acid has been studied. No significant reaction was found in ethanol solution, whereas in sodium dodecyl sulfate micelles vitamin E reacted rapidly with peroxidized linoleic acid, and thereby induced the peroxidation of linoleic acid, leading to oxygen absorption. The reaction kinetics was studied in detail by u.v. spectroscopy, HPLC and ESR spectroscopy. It was found that the main product was alpha-tocopherone with alpha-tocopheroxy radical as the reaction intermediate. A mechanism involving two consecutive bimolecular reactions between peroxidized linoleic acid and alpha-tocopherol and between peroxidized linoleic acid and alpha-tocopheroxy radical, with rate constant 2.93 and 6.21 mol/L-1s-1 respectively is proposed. The micellar effect on the reaction is discussed.