BACKGROUND: Black tea is known to have protective effects against plasma lipid and lipoprotein oxidation, but its influence on lipid peroxidation in tissue has been less studied. The effect of oral black tea consumption on protein oxidation has also not been demonstrated. The present study investigated the antioxidant effects of oral black tea consumption. MATERIAL/ METHODS: Male Sprague-Dawley rats were fed a regular murine chow diet. The controls were supplied with water ad libitum, while the black tea group received aqueous black tea extract as the sole source of liquids. At the end of the ten-week experimental period, intestinal brush border, liver and kidney reduced-glutathione concentrations were evaluated as an index of cellular antioxidant defence. Plasma and tissue malondialdehyde concentrations and plasma protein carbonyl content were measured to evaluate lipid peroxidation and protein oxidation, respectively. RESULTS: The plasma malondialdehyde and protein carbonyl contents of rats consuming the black tea were significantly less than in controls. Similarly, liver and kidney malondialdehyde concentrations were significantly lower in the experimental group, while jejunoileal mucosa were not affected. Ten weeks of black tea administration caused significantly higher reduced-glutathione levels in the kidneys of black tea-administered rats, and a significant negative correlation was observed between kidney malondialdehyde and glutathione concentrations. CONCLUSIONS: These findings provide evidence that long term black tea supplementation is capable of protecting both plasma proteins and plasma lipids from oxidative injury, and demonstrate that chronic black tea administration protects both liver and kidney tissues - but not the jejunoileal mucosa - against oxidation.
BACKGROUND:Black tea is known to have protective effects against plasma lipid and lipoprotein oxidation, but its influence on lipid peroxidation in tissue has been less studied. The effect of oral black tea consumption on protein oxidation has also not been demonstrated. The present study investigated the antioxidant effects of oral black tea consumption. MATERIAL/ METHODS: Male Sprague-Dawley rats were fed a regular murine chow diet. The controls were supplied with water ad libitum, while the black tea group received aqueous black tea extract as the sole source of liquids. At the end of the ten-week experimental period, intestinal brush border, liver and kidney reduced-glutathione concentrations were evaluated as an index of cellular antioxidant defence. Plasma and tissue malondialdehyde concentrations and plasma protein carbonyl content were measured to evaluate lipid peroxidation and protein oxidation, respectively. RESULTS: The plasma malondialdehyde and protein carbonyl contents of rats consuming the black tea were significantly less than in controls. Similarly, liver and kidney malondialdehyde concentrations were significantly lower in the experimental group, while jejunoileal mucosa were not affected. Ten weeks of black tea administration caused significantly higher reduced-glutathione levels in the kidneys of black tea-administered rats, and a significant negative correlation was observed between kidney malondialdehyde and glutathione concentrations. CONCLUSIONS: These findings provide evidence that long term black tea supplementation is capable of protecting both plasma proteins and plasma lipids from oxidative injury, and demonstrate that chronic black tea administration protects both liver and kidney tissues - but not the jejunoileal mucosa - against oxidation.