Design,Synthesis And Biological Activities Evaluation Of Novel Topo ? Inhibitors Based On Quinoxaline Skeleton

Quinoxaline is a nitrogen-containing heterocycle compound,which consisted of a benzene and a pyrazine ring.Quinoxaline derivatives exhibit broad-spectrum bioactivities such as anti cancer,antibacterial and anti-HIV activities,which are widely used in medicinal,agricultural and optoelectronic material sciences.Benzo-five-membered heterocycles derivatives(such as benzoimidazole,benzooxazole and benzothiazole),are also extraordinary important heterocycles compounds,which possessed a wide range of biological activities including antitumor,antifungal,antiinflammatory antiviral activities and Topoisomerase ?(Topo?)inhibition.Topo ? represents a very important molecular target of anticancer agents.Drugs targeted to Topo ? such as camptothecin and its derivatives are wide clinical application.As many benzo-five-membered heterocycles derivatives exhibit potent Topo ? inhibited activities,and the promising potential of the quinoxaline moiety in drug development,twenty-one novel compounds whose scaffold were coined by the combination of quinoxaline and benzo-five-membered heterocycles derivatives under the guidance of the Topo ?pharmacophore model were designed and synthesized.Their structures were characterized and confirmed by 1H NMR,13C NMR and HRMS.The results of the antiproliferative activities evaluation in vitro on some common human cancer cell lines indicated that most of them exbibited potent anticancer activity,among them the selected compound 8a and 8e inhibited the proliferation of MGC-803 cells lines with an IC50 value of 1.49±0.18 and 2.93±0.47 ?M,respectively,more potent than the positive control(11.1 9±0.82 ?M).Detailed biological exploration of the selected compound on MGC-803 cells lines via flow cytometry revealed that 8a could induces G2 phase cell cycle arrest,decrease the mitochondrial membrane potential(??m),raise the reactive oxygen species(ROS)and intracellular Ca2+concentration level.The western blot analysis showed that 8a could down-regulate the level of anti-apoptosis protein Bcl-2,Bcl-x1 while up-regulate the levels of bax,bak,bim,caspasc-3,caspase-9,Cytochrome c,Cyclin B1 and P21.The results of agarose gel electrophorsis assay aimed to explore the interaction of compound 8a with pBR322 DNA and the DNA/Topo ? showed that 8a could remarkablely inhibit the at the Topo ? to catalyze the unwinding of DNA but not directly interact with DNA.