Effect of honokiol on the cell viability. The cell viability was examined by CCK8 assay when the human gastric carcinoma MGC-803 cells were incubated with various concentrations of honokiol (0-40 μM) for 24 h (A) and 48 h (B). Human neuroglioma cells were incubated with honokiol (10 μM) for 0, 6, 12, 24, 36 and 48 h, and the cell viability was examined by CCK8 assay (C). Values are expressed as mean ± SEM, n = 3 in each group. *P < 0.05 versus control group.