Protective role of black tea against oxidative damage of human red blood cells.

The purpose of our study was to explore the possible scavenging property of black tea and catechins, the major flavonols of tea-leaf, against damage by oxidative stress. For this purpose, human red blood cell (rbc) was taken as the model and the oxidative damage was induced by a variety of inducers, e.g. phenylhydrazine (PHX), Cu(2+)-ascorbic acid, and xanthine/xanthine oxidase systems. Lipid peroxidation of pure erythrocyte membrane and of whole red blood cell could be completely prevented by black tea extract. Similarly, black tea provided total protection against degradation of membrane proteins. Finally, membrane fluidity studies as monitored by the fluorescent probe 1,6 diphenyl hexa 1,3,5-triene (DPH) showed considerable disorganization of its architecture that could be restored back to normal on addition of black tea or free catechins. Black tea extract in comparison to free catechins seemed to be a better protecting agent against various types of oxidative stress. Apparently, conversion of catechins to partially polymerized products such as theaflavin or thearubigin during 'fermentation' process for making black tea has no deleterious effect on its scavenging properties.