Abstract: Objective To observe the effects of purified product trihydroxybenzoic acid dimmer in different doses from Trapa manshurica Fler on apoptosis and cell cycle progression of liver cancer SMMC-7721 cells in vitro and explore its possible mechanism of inhibiting tumor growth. Methods The changes of apoptosis and cell cycle progression were measured with flow cytometry. Results The apoptotic percentages of the cells treated with the purified products with doses of 3.125, 6.250, 12.500 and 25.000 mg•L^-1 increased significantly as compared with that in the control (P<0.001). And the percentages of G₂+M phase cells increased, those in 3.125, 6.250 and 12.500 mg•L^-1 groups were significantly higher than that in the control (P<0.01 or P<0.05); while the percentages of S phase cells decreased，especially decreased in 6.250, 12.500 and 25.000 mg•L^-1 group(P<0.05). Conclusion The inhibitory effect of purified product trihydroxybenzoic acid dimmer from Trapa manshurica Fler on tumor growth could be due to cell apoptosis caused by G₂+M phase arrest.

Key words: trihydroxybenzoic acid dimmer, apoptosis, cell cycle