Synthesis and Evaluation of New Quinoxaline Derivatives of Dehydroabietic Acid as Potential Antitumor Agents

A series of new quinoxaline derivatives of dehydroabietic acid (DAA) were designed and synthesized as potential antitumor agents. Their structures were characterized by IR, (1)H-NMR, (13)C-NMR, and MS spectra and elemental analyses. All the new compounds were screened for their in vitro antiproliferative activities against three human cancer cell lines (MCF-7, SMMC-7721 and HeLa) and noncancerous human hepatocyte cells (LO2). A cytotoxic assay manifested that compound 4b showed the most potent cytotoxic activity against the three cancer cell lines, with IC(50) values of 1.78 ± 0.36, 0.72 ± 0.09 and 1.08 ± 0.12 μM, respectively, and a substantially lower cytotoxicity to LO2 cells (IC(50): 11.09 ± 0.57 μM). Moreover, the cell cycle analysis suggested that compound 4b caused cell cycle arrest of SMMC-7721 cells at the G0/G1 phase. In a Hoechst 33258 staining assay, compound 4b caused considerable morphological changes of the nuclei of SMMC-7721 cells, correlated with cell apoptosis. In addition, an Annexin V-FITC/PI dual staining assay confirmed that compound 4b could induce the apoptosis of SMMC-7721 cells in a dose-dependent manner.