Effects of magnolol on apoptosis in A431 cells as assessed by annexin-V/PI staining. Cells were treated with magnolol (0-150 μM) for 48 h, at the end of the treatment adherent and non-adherent cells were collected and treated with annexin-V labeled with a fluorophore, which can identify apoptotic cells by binding to phosphatidylserine exposed on apoptotic cells; and with propidium iodide that stained dead cells. Dot plot of annexin-V (FL1-H)/PI (FL2-H) staining of A431 cells by flow cytometry. The lower right quadrant shows early apoptotic cells that are labeled with annexin-V, having green fluorescence. The upper right quadrant stained by annexin-V and PI indicates late apoptotic cells. The lower left quadrant contains viable cells which exclude PI and are negative for annexin-V staining, and the upper left quadrant are necrotic cells stained by PI only. The bar graph describes the percentages of apoptotic cells after each treatment. In each case data represent mean ± SE of three observations. *p < 0.05 indicates statistical significant difference in magnolol treated groups compared with the control.