Synergistic antioxidant effect of green tea polyphenols with α-tocopherol on free radical initiated peroxidation of linoleic acid in micelles

The antioxidant effect of the main polyphenolic components extracted from green tea leaves, i.e., (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG) and gallic acid (GA), against peroxidation of linoleic acid has been studied in sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) micelles. The peroxidation was initiated thermally by a water-soluble azo initiator 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AMPAD) and the reaction kinetics were followed by formation of linoleic acid hydroperoxides and consumption of the antioxidant. Kinetic analysis of the antioxidation process demonstrates that these green tea polyphenols are effective antioxidants in micelles used either alone or in combination with α-tocopherol (vitamin E). The antioxidative action may involve trapping the initiating radicals in the bulk water phase, trapping the propagating lipid peroxyl radicals on the surface of the micelle and regenerating α-tocopherol by reducing α-tocopheroxyl radical. The antioxidant activity of these green tea polyphenols depends significantly on the microenvironment of the reaction medium, the oxidation potential and the size of the molecule.