Helenalin induces cytotoxicity in A2780 human ovarian cancer cell line Phase contrast micrographs of A2780 cells treated with increasing concentrations of helenalin of 0.5, 1.0 and 2uM for 24 h. Changes in cell number and morphology were observed when compared to DMSO control. (B) Percent of viable cells after treatment with increasing concentrations of helenalin (serial dilution for drug concentration ranging from 10uM to 0.001uM) using the MTT assay. (C) Clonogenic survival assay. A2780 cells were treated with increasing concentrations of helenalin and then incubated for 2 weeks. The cells were stained with crystal violet for 16 h. Representative dishes are shown. All results represent data from three independent experiments.