Antitumor activities of quercetin and quercetin-5′,8-disulfonate in human colon and breast cancer cell lines

► Quercetin dose-dependently exhibited anticancer effects in LoVo and MCF-7 cells. ► QS sharply enhanced water-solubility and anticancer effects of quercetin. ► Quercetin and QS induced apoptosis and arrest at S phase in the cancer cells. ► ROS as H2O2 and O2− generation is involved in the growth inhibition and apoptosis.