BIOLOGICAL ACTIVITY OF GREEN TEA EXTRACT

Lursmanashvili L., Gulua L., Turmanidze T., Enukidze M., Machavariani M., Sanikidze T. and Jgenti M

Department of Food Technology, Agricultural University of Georgia, Tbililsi, Georgia

Abstract

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 modeling of oxidative stress 30% hydrogen peroxide solution (10 μl, 25 μl 50 μl and 100 μl of H₂O₂) was added to 1 ml 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 μl 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 extract (23% catechins) had no effect, green tea catechins preparation (80% catechins) revealed stimulatory effect, while green tea pectin revealed weak cytotoxic effect on intact Jurkat cells. Our study results confirm the opinion that the green tea extract catechins 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 for therapy. Acknowledgement: This research was partly conducted by financial support of Shota Rustaveli National Science Foundaiton (SRNSF), project # 217416/128.

Keywords: Green tea, Jurkat cells, oxidative stress.