PPI and PPVII induce cytotoxicity in A549 and A549/DDP cells. (A) Chemical structure of PPI and PPVII. (B) A549 and A549/DDP cells were treated with different dose of PPI (0.5–8 µg/ml) and PPVII (0.5–8 µg/ml) for 24 h, respectively. In A549 cells, the cell inhibition rate of 0.5 µg/ml PPI was significantly different from other concentration groups (**P<0.01); 1.0 µg/ml was significantly different from 4.0 and 8.0 µg/ml (**P<0.01), and 2.0 µg/ml was significantly different from 8.0 µg/ml (**P<0.01). As for A549/DDP cells, the cell inhibition rates of 0.5 µg/ml PPI and 1.0 µg/ml were both significantly different from other concentration groups (##P<0.01), and 2.0 µg/ml was significantly different from 8.0 µg/ml (##P<0.01). In A549 cells, there were significant differences in cell inhibition rates of PPVII among different concentration groups (**P<0.01); as for A549/DDP cells, there were significant differences among different concentration groups except for 4.0 and 8.0 µg/ml (##P<0.01). PPI, Polyphyllin I; PPVII, polyphyllin VII; DDP, cisplatin.