Abstract: OBJECTIVE: To evaluate the anti-tumor activity of ethyl acetate fraction(EFA), extracted with ethanol from the root of "Dai-Bai-Jie" in A549 cancer cells and its underlying mechanism.METHODS: "Dai-Bai-Jie" was extracted with 95%ethanol-aqueous(DBJ-1), 50% ethanol-aqueous(DBJ-2), and water(DBJ-3) by reflux method. 95%ethanol-aqueous extract was separated byethyl acetate(EFA) and n-butyl alcohol(DBJ-5), consecutively. The SRB method was used to evaluate the cytotoxic activity. Annexin V-FITC staining was applied to observe the apoptosis and analyze the cell cycle activated by EFA in A549 tumor cell. Western blot was used to detect the apoptosis/related pro-teins expressions. A549 tumor cellsbearing nude mice model was employed to measure the tumor volume, mice weight, and tumor inhibition ratio in order to verify the antitumor activity in vivo.RESULTS: DBJ-1 and EFA showed better cytotoxic activity on A549 tumor cells with IC5025 and 3.5 μg/mL, respectively. EFA can exhibit the proliferation,arrest cell cycle at G0/G1 phase, and induce apoptosis in A549 tumor cells in vitro. The mechanisms of apoptosis induced by EFA may be associated with decreasing Bcl-2 protein expression and increasing p53, Bax, Caspase-3, and Caspase-8 proteins expression. EFA also possessed significant anti-tumor efficacy in nude mice, and little toxicity was observed in the host.CONCLUSION: EAF could induce A549 tumor cells apoptosis and G0/G1 cell cycle arrest. A549 tumor cells apoptosis induced by EAF may be associated with the decrease in the ratio of Bcl-2 and Bax mRNA levels, and increase in the expression of p53,Caspase-3, and Caspase-8 proteins.

Key words: Dai-Bai-Jie, Antineoplastic agents, Apoptosis, In vitro techniques, In vivo