Effect of isorhamnetin, cisplatin, carboplatin and their combinations on A-549 cancer cell proliferation. The cells were treated with DMSO as vehicle control and with isorhamnetin (IR, 25 μM), cisplatin (CP, 0.5 μM), carboplatin (CB, 0.5 μM) and their combinations (IR+CP and IR+CB) for 24 h and cell viability was determined by MTT assay. *P = 0.05, **P = 0.01 vs. vehicle control.