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

This study is designed to compare the anticancer effects of quercetin and its water-soluble sulfated derivative, quercetin-5′,8-disulfonate (QS), in human colon cancer LoVo cells and breast cancer MCF-7 cells. It was found that both quercetin and QS can inhibit the growth of cancer cells in a dose-dependent manner, with the IC50 values of 40.2 and 28.0 μM for LoVo cells and 30.8 and 19.9 μM for MCF-7 cells, respectively, suggesting QS was more effective against the cancer cells than quercetin. Moreover, flow cytometric assay revealed that quercetin and QS could mediate the cell-cycle arrest principally in the S phase after 24 h of treatment with the two tumor cells. It was also found that 69.6% of LoVo cells and 90.6% of MCF-7 cells entered the early phase of apoptosis when treated with 100 μM QS for 48 h. Furthermore, we firstly found the generation of ROS is a critical mediator in QS-induced cell growth inhibition. Taken together, the novel sulfated derivative of quercetin possesses strong antitumor activity via a ROS-dependent apoptosis pathway, and has the excellent potential to be developed into an antitumor precursor compound.