BIOLOGICAL ACTIVITY OF GREEN TEA EXTRACTS

The purpose of our study was to determine effects of green tea extracts on the Jurkat cells incubated under oxidative stress conditions. The research was conducted on leukemic human mature T cells (Jurkat cells). For the modelling of oxidative stress 30% hydrogen peroxide (H2O2) (Sigma) (10 μl, 25 μl 50 μl and 100 μl) was added to Jurkat cell suspension with subsequent incubation for 4, 6, 8 and 24 h. Control group was represented by intact Jurkat cells. The assessment of cells proliferation activity (viability) was performed by MTT test. The viability of Jurkat cells incubated for 24 hours under acquit oxidative stress conditions dose-depenently, monotonically decreased (irreversibly at 100 μM of H2O2 and reaches the 30% of intact Jurkat cells viability level at 50 μM of H2O2). Low doses of H2O2 (10 μl, 25 μl H2O2) revealed cytotoxicity only within short term (8 hours) of the incubation, afterward the viability of Jurkat cells monotonically increased and after 24 hours it reached 43% and 56% of control level, respectively. Vitamins C and E revealed cytotoxic effect on intact Jurkat cells, while the C+V vitamins complex induced 2-fold stimulation of Jurkat cells viability. Under a moderate oxidative stress condition (25 μl of H2O2) the complex of C + E vitamins revealed cytoprotective effect on Jurkat cells which may be related to ability of vitamin C to induce regeneration and to transform E vitamin tocopheroxyl free radicals into tocopherol. Green tea had no effect, green tea catechins revealed stimulatory effect, while green tea pectin - weak cytotoxic effect on intact Jurkat cells. Green tea and especially extracted catechins (but not pectin) revealed stimulatory effect on the viability of the Jurkat cells incubated under an oxidative stress condition. Our study results confirm the opinion that the natural compounds (green tea extracts) are harmless for normal cellular metabolism. Their differential effects on the "diseased", incubated under an oxidative stress cells are mediated via impact on signaling regulatory systems. On the basis of screening of green tea extracts it will be possible to select new high effective cytotoxic and cytoprotective compounds.