A series of novel coumarin-containing α-aminophosphonates were synthesized and evaluated for their antitumor activities against Human colorectal (HCT-116), human nasopharyngeal carcinoma (human KB) and human lung adenocarcinoma (MGC-803) cell lines in vitro. Compared with 7-hydroxy-4-methylcoumarin (4-MU), most of the derivatives showed an improved antitumor activity. Compound 8j (diethyl 1-(3-(4-methyl-2-oxo-2H-chromen-7-yloxy) propanamido)-1-phenylethyl-Phosphonate), with IC50 value of 8.68 μM against HCT-116 cell lines, was about 12 fold than that of unsubstituted parent compound. The mechanism investigation proved that 8c, 8d, 8f and 8j were achieved through the induction of cell apoptosis by G1 cell-cycle arrest. In addition, the further mechanisms of compound 8j-induced apoptosis in HCT-116 cells demonstrated that compound 8j induced the activations of caspase-9 and caspase-3 for causing cell apoptosis, and altered anti-and pro-apoptotic proteins. DNA-binding experiments suggested that some derivatives bind to DNA through intercalation. The results seem to imply the presence of an important synergistic OPEN ACCESSMolecules 2015, 20 14792 effect between coumarin and aminophosphonate, which could contribute to the strong chelating properties of aminophosphonate moiety.

A series of novel asiatic acid (AA) derivatives containing α-aminophosphonate were designed and synthesized as antitumor agents. In vitro antitumor activities of these compounds against five cancer cell lines (A549, Hct-116, T24, Spca-2 and SK-OV-3 cell) and a normal cell line (HUVEC cell) were evaluated, employing standard MTT assay. Antitumor activities screening result indicated that many target compounds displayed moderate to high levels of antitumor activities compared with AA, 5-fluorouracil (5-FU) and cisplatin, and exhibited much lower cytotoxicy against normal cell than 5-FU and cisplatin. In addition, the mechanism of representative compound 3d was preliminarily investigated by AO/EB staining, Hoechst 33258 staining, JC-1 mitochondrial membrane potential staining, flow cytometry and western blot.Compound 3d inducing apoptosis involved intracellular Ca 2+ production, the loss of mitochondrial membrane potential and intracellular reactive oxygen species (ROS) production. Western blot analysis also demonstrated that compound 3d treatment triggered the mitochondrial apoptotic pathway, indicating by changing Bax/Bcl-2 ratios, cytochrome c release, and caspase-9 activation.Moreover, the cell cycle analysis showed that compound 3d may confine T24 cells in G 1 /S phase mainly through the p53-dependent pathway. Together, these results implied a critical role of ROS, caspase-9 and p53 in compound 3d-inducing G 1 /S arrest and apoptosis of T24 cells.

Compound 4l exerts significant anticancer effects on NCI-H460 cells in vitro through targeting of mitochondria-dependent apoptotic pathway. These results indicate that the strategy for rational design of 4-MU derivatives may identify potential anticancer agents.