Evidence for α-tocopherol regeneration reaction of green tea polyphenols in SDS micelles

The synergistic antioxidant mechanism of α-tocopherol (vitamin E) with green tea polyphenols, i.e., (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin gallate (EGCG), and gallic acid (GA), was studied by assaying the kinetics of the reaction of α-tocopheroxyl radical with green tea polyphenols by stopped-flow electron paramagnetic resonance, the inhibition of linoleic acid peroxidation by these antioxidants, and the decay of α-tocopherol during the peroxidation. It was found that the green tea polyphenols could reduce α-tocopheroxyl radical to regenerate α-tocopherol with rate constants of 0.45, 1.11, 1.31, 1.91, and 0.43 × 102 M−1 s−1 for EC, EGC, ECG, EGCG, and GA, respectively, in sodium dodecyl sulfate micelles. In addition, these second-order rate constants exhibited a good linear correlation with their oxidation potentials, suggesting that electron transfer might play a role in the reaction.