In vitro and in vivo studies on the radical-scavenging activity of tea

The effects of tea (Camellia sinensis L.) of three types on excessive free radicals were examined utilizing spin trapping, 1,1-diphenyl-2-picrylhydrazyl radical, lipid peroxidation, and lactate dehydrogenase leakage from cultured cells. Green tea extract presented significant antiradical effects in these four assay systems, whereas oolong tea and black tea extracts showed a rather weak protective effect against free radicals. A more potent scavenger effect using cultured cells was found with a green tea tannin mixture. Similarly to the effects of the green tea tannin mixture, (-)-epigallocatechin 3-O-gallate, its main ingredient, had an inhibitory effect on oxidative stress-induced apoptosis. The activities of the antioxidation enzymes in rats after subtotal nephrectomy were increased, suggesting a protective action against oxidative stress. The increased levels of uremic toxins in the blood were also reduced in rats given (-)-epigallocatechin 3-O-gallate. These findings indicate that (-)-epigallocatechin 3-O-gallate helps to inhibit the progression of renal failure by scavenging radicals.