STUDY ON THE ANTI-TUMOR ABILITY OF NIAOWANGZHONG GREEN TEA

It has been known that green tea not only possesses certain chemo-preventive effects on cancer, but also can kill directly some types of tumor cells. Niaowangzhong tea (C. sinensis), a special tea resource growing in Qiannan Buyi, a Miao Minority Autonomous Prefecture in Guizhou province, China, is one of the most popular medicinal beverages for local people there. The aims of this study were to analyze the quality components and their relative contents present in Niaowangzhong green tea and to investigate whether or not the water extract of this green tea has the antitumor capability in vitro and in vivo. Biochemical analysis indicated that this green tea extract contained relatively higher levels of tea polyphenols, alkaloids, flavonoids compounds and polysaccharides. In the MTT (3-(4,5-dimethyl-2-thiazolyl) 22,5-diphenyl-2-H-tetrazolium bromide) assay, this green tea extract showed inhibitory activity against several types of tumor cells, including breast, prostate, colorectal and gastric cancer cell lines, with higher selectivity toward human gastric cancer cell line MGC-803. Its 50% inhibition concentration (IC50) of MGC-803 was 32.5 mu M as compared to that (367.9 mu M) of normal vascular endothelial cells. Cell cycle and apoptosis analyses showed that the proportion of cells arrested at the G0/G1 phase was increased with the increase in concentration, and the proportion of apoptotic cells was also increased. Niaowangzhong green tea extract could significantly inhibit tumor-sphere formation in the in vivo antitumor experiment and the growth of MGC-803-derived tumor in nude mice. At the concentration of 500 mg/kg/day, inhibition rate was 31.0% without causing obvious toxic side effects. This study revealed a potent anti-cancer activity of this special green tea and its promising potential as chemo-preventive agent and proper dietary practice for prevention and control of cancers.