For clonogenic assay, 1000 cells per well were plated in single cell suspension in a 6-well plate. After 24 h, attached cells were treated with different concentrations of EOs (25, 50, and 90 μg/mL). 5-FU (5 μg/mL) and media containing 0.5% DMSO were used as the positive and negative control, respectively. After 48 h of treatment, old medium was aspirated, cells were washed twice with PBS, and fresh medium without any test sample/drugs was added. On the 10th day, the cells were fixed with 4% paraformaldehyde and stained with 0.2% crystal violet for 30 min at room temperature. Colonies of 50 cells or more were counted, and the plating efficiency (PE) and the survival fraction (SF) were calculated using standard equations. The results were expressed as mean ± SD (n = 3)