As an extension for our earlier effort in the field of discovery of anticancer agents acting on DNA and Topo II, eighteen quinoxaline derivatives were designed and synthesized. Such members were designed to possess the main essential pharmacophoric features of DNA intercalators. The cytotoxic potential of the synthesized compounds was assessed against a group of human cancer cell lines (HCT-116, HepG2, and MCF-7). Doxorubicin as potential intercalative Topo II inhibitor, was used as a positive reference. In general, compounds 12, 15, 19, 21, and 22 showed promising anti-proliferative activities against the three cell lines with IC50 values ranging from 2.81 to 10.23 µM. The cytotoxicities of the most active compounds against normal human cells (WI-38) were evaluated, and the results revealed that these compounds have low toxicity. Further examination for the most active anti-proliferative members as Topo II inhibitors was also performed, showing a narrow range of the inhibitory activities (from 0.45 to 1.06 µM). In addition, DNA/methyl green assay was carried out to evaluate DNA-binding potential of such compounds. The results indicated that these compounds have strong to moderate DNA-binding affinities ranging from 33.48 to 51.23 µM. Further studies exhibited the capability of compound 22 to induce apoptosis in HepG2 cells and can arrest growth of such cells at G2/M phase. Also, compound 22 produced a significant increase in the level of caspase- 3 (10 folds) and caspase-9 (7 folds) compared to the control cells. Molecular docking studies were also conducted to investigate possible binding interactions between the target compounds and the DNA-Topo II complex.
Keywords: Anticancer; Apoptosis; DNA-intercalator; Molecular docking; Quinoxaline; Topoisomerase II.
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