Effect of BBR on cell apoptosis in A549 cells. A549 cells were treated with 0, 20, 40 and 80 μM BBR for 6 h (A), 12 h (B) and 24 h (C). Apoptotic rates were measured using flow cytometry (D). Values are expressed as mean ± SD of three experiments. *P <0.05, **P < 0.01, as compared with control.