Design and Discovery of Novel Quinoxaline Derivatives as Dual DNA Intercalators and Topoisomerase II Inhibitors

In attempt to develop new potent anti-tumor agents, a series of quinoxaline derivatives was designed and synthesized. The novel compounds were tested in vitro for their anti-proliferative activities against HePG-2, MCF-7 and HCT-116 cell lines. Additionally, DNA binding affinities as well as DNA-top II inhibitory activities of the synthesized compounds were investigated as potential mechanism for the anticancer activity. Compounds 13, 15, 16 and 19 exhibited good cytotoxicity activities against the three cell lines (IC50 ranging from 7.6 to 32.4 µM) comparable to that of doxorubicin (IC50 = 9.8 µM). Interestingly, the results of DNA binding and DNA-top II inhibition assays were in agreement with that of the cytotoxicity tests, where the most potent anticancer compounds showed good DNA binding affinities (IC50 ranging from 25.1 to 32.4 µM) and DNA-top II inhibitory activities (IC50 ranging from 6.4 to 15.3 µM) comparable to that of doxorubicin (IC50 = 28.1 and 3.8 µM, respectively). Furthermore, molecular docking studies were carried out for the new compounds in order to investigate their binding pattern with the prospective target, DNA-top II complex (PDB-code: 3qx3).