目的 筛查中药白头翁抗肝癌有效成分，探索其抗癌机制。方法 分离白头翁皂苷成分，以人肝癌细胞HepG2为作用靶细胞，MTT法测定其对细胞增殖的抑制，流式细胞术检测细胞周期阻滞，DNA片断化方法检测细胞凋亡情况，检测半胱氨酸蛋白酶3酶活性，从信号通路的角度探寻其诱导凋亡的机制。结果 白头翁药材含量较高的成分白头翁皂苷B4对HepG2具有显著的抑制作用，最大抑制率达到71.5%；通过细胞周期分布分析，发现最多有83.2%的细胞被阻滞在G2期；用流式细胞仪研究其凋亡情况发现，在40 mg/mL药物浓度作用下，细胞凋亡与孵育时间呈现依赖关系，随着时间从0到48 h，初期凋亡比例从接近于零最高增长到14.3%，并且发生了DNA片段化；进一步研究发现，白头翁皂苷B4处理后的HepG2细胞半胱氨酸蛋白酶3活性显著升高。结论 白头翁皂苷B4调控肝癌细胞周期，阻滞G2/M期更替，诱导细胞凋亡，是肝癌治疗的潜在候选分子，奠定了白头翁药材用于肝癌治疗的理论基础。

Objective To screen the potential effective components in Pulsatilla chinensis for treatment for liver cancer, and explore the anti-cancer mechanism. Methods Pulchinenoside was isolated from Pulsatilla chinensis, human liver cancer cell line HepG2 was served as target cell, and the inhibiting effects of pulchinenoside on HepG2 cells were evaluated by MTT assay. Cell cycle arrest was determined by flow cytometry, cell apoptosis was detected by DNA fragmentation method, and Caspase 3 activity was measured. The possible responsible signal pathway for cell apoptosis was explored. Results Pulchinenoside B4 significantly inhibited proliferation of HepG2 cells, and the maximum inhibitory rate was 71.5%. Cell cycle analysis indicated that 83.2% of cells were arrested at G2 phase at most. Flow cytometry revealed that cell apoptosis was dependent of time of incubation with 40 mg/mL pulchinenoside B4, cell apoptosis rate increased from nearly 0 to 14.3% at most with time increase from 0 to 48 h, and DNA fragmentation occurred. Further study indicated that pulchinenoside B4 significantly upregulated Caspase 3 activity in HepG2 cells. Conclusion Pulchinenoside B4 regulates the cell cycle of liver cancer cells, causes cell cycle arrest at G2/M, and induces cell apoptosis, which is a potential chemical for the treatment of liver cancer.