Emodin-induced apoptosis in HeLa cells was determined by flow cytometry using annexin FITC-PI staining method. The cells were treated with Emodin (0, 20, 40, and 80 μM) for 48 h (a, b). (a) Emodin-induced apoptosis analyzed by flow cytometry. The lower right quadrant (Q4) indicates the percentage of early apoptotic cells (FITC-stained cells) and the upper right quadrant (Q2) indicates the percentage of late apoptotic cells (FITC+PI-stained cells). (b) Emodin-induced apoptosis rate shown by bar graph. The experiment was repeated three times and the percentage of apoptotic cells (means± SEM) for each treatment group is shown in b. *P<0.05 versus control group (0 μM) (one-way ANOVA followed by the Tukey post hoc test).