Figure 4: Concentration-inhibition curves of the active compounds against the proliferation of prostate ((a) PC3 and BPH1 cells), melanoma ((b) WM9 cells), and leukemia ((c) K562 and HEL cells) cell lines in vitro. Different concentrations of tested compounds were added to 96-well microculture plates and cells were incubated for 48 h at 37°C. The inhibition ratio (%) was calculated as described in Materials and Methods.