Studies On Synthesis, DNA Interaction And In Vitro Antitumor Activities Of Halogen-oxovanadium Complexes

Oxovanadium complexes are potential antibacterial,antidiabetic HIV,anti-malarial,antiviral and anti-tumor agents.It has been reported that thesecomplexes have potent antitumor activities,however,theirspecific anti-tumor mechanism is sitll unclear.Experimental results had showed that with alarger ?-conjugated planar structure,the vanadium complexes exhibit better DNA binding and cleavage abilities,and its anti-tumor activity is better in vitro.To get more information about its anti-tumor mechanism,new oxovanadium complexes have been synthesized.The main work is as follows:1.Five new oxovanadium complexes with thiosemicarbazide derivatives as primary ligand,[VO(MAST)(phen)](1),[VO(MAST)(BrPIP)](2),[VO(MAAST)(CF3PIP)](3),[VO(FAST)(phen)](4),[VO(ClAST)(phen)](5)have been synthesized and characterized by elemental analysis,IR,ESI-MS,1H NMR,13 C NMR and conductivity.Their interaction with DNA were performed by using UV-Vis,steady-state fluorescence quenching,viscosity testing and gel electrophoresis.The results showed that these novel complexes could interact with CT-DNA through an intercalative model and can efficiently cleave pBR322 DNA.The binding constants Kb are as follows: 2>3> 5>1>4.2.[VO(MASI)(phen)](6),[VO(FASI)(phen)](7),[VO(ClASI)(phen)](8)and [VO(ClASPT)(phen)](9)were synthesized by using isoflurane azobenzene schiff base as the main ligand and 1,10-phenanthroline as the auxiliary ligand.The structures of thesecomplexes were characterized by elemental analysis,IR,ESI-MS,H1 NMR,C13 NMR and conductivity properties.The interaction between these complexes and DNA were studied by UV-Vis,fluorescence spectrophotometry,viscosity test and gel electrophoresis.The experimental results show that all these complexes could break plasmid DNA and were binded to CT-DNA by an intercalative model manner with Kb 7>9>6>8,which is similar to those thiosemicarbazide derivatives.3.MTT assay was used to screen the antitumor activity of Hela and A549 tumor cell lines with cisplatin as a positive control.The results showed that the compounds had good cytotoxic activities against Hela and HepG2 cell lines.Besides,Hela cells were more sensitive to vanadiumcomplexes.Meanwhile,complexes 2 and 3 have better anticancer activities than that of cis-platinum,under the same conditions.To further understand the antitumor mechanism of vanadium complexes,the apoptosis and cycle arrest of complex 2 and 3 were detected by flow cytometry.The results suggested that all of the complexes can induce apoptotic and complexes 2 and 3 block the cell cycle in G0/G1 with concentration dependent.According to the above results,the western blot was used to study the expression of protein p53.It turned out that p53 accumulate by dose-dependent manner when the cells were treated with different concentration of [VO(MAST)(BrPIP)](2)and [VO(MAAST)(CF3PIP)](3),respectively.Consequently,the results showed that total amount of ROS were significantly risen up with the increase of concentration [VO(MAST)(BrPIP)](2)and [VO(MAAST)(CF3PIP)](3),respectively.Finally,the mitochondrial membrane potential of Hela cells decreased significantly,in the presence of [VO(MAST)(BrPIP)](2)and [VO(MAAST)(CF3PIP)](3).Thus,the mechanisms of apoptosis in tumor cells may be owing to the complexes could damage DNA,which leads to the increase of p53 expression and the increase of intracellular ROS,and then made the damage of mitochondria.