DNA binding, DNA cleavage, antioxidant and cytotoxicity studies on ruthenium(II) complexes of benzaldehyde 4-methyl-3-thiosemicarbazones

Four new ruthenium(II) complexes with N(4)-methyl thiosemicarbazone ligands, (E)-2-(2-chlorobenzylidene)-N-methylhydrazinecarbothioamide (HL1) and (E)-N-methyl-2-(2-nitrobenzylidene)hydrazinecarbothioamide (HL2), were prepared and fully characterized by various spectro-analytical techniques. The Schiff bases act as bidentate, monobasic chelating ligands with S and N as the donor sites and are preferably found in the thiol form in all the complexes studied. The molecular structure of HL1 and HL2 were determined by single crystal X-ray diffraction method. DNA binding of the compounds was investigated by absorption spectroscopy which indicated that the complexes bind to DNA via intercalation. The oxidative cleavage of the complexes with CT-DNA inferred that the effects of cleavage are dose dependent. Antioxidant studies of the ligands and complexes showed the significant antioxidant activity against DPPH radical. In addition, the in vitro cytotoxicity of the ligands and complexes against MCF-7 cell line was assayed which showed higher cytotoxic activity with the lower IC50 values indicating their efficiency in killing the cancer cells even at low concentrations.

Four new ruthenium(II) complexes with benzaldehyde 4-methyl-3-thiosemicarbazones were prepared and fully characterized by various spectro-analytical techniques. The molecular structure of HL1 and HL2 were determined by single crystal X-ray diffraction method. The ligands act as bidentate, monobasic chelating ligands with S and N as the donor sites in all the complexes studied. DNA binding of the ligands and complexes were investigated by absorption spectroscopy which indicated that the complexes bind to DNA via intercalation. The oxidative cleavage of the complexes with CT-DNA inferred that the effects of cleavage are dose dependent. Further, in vitro antioxidant and anticancer studies were carried out for the ligands and ruthenium(II) complexes.Figure optionsDownload as PowerPoint slideHighlights
► Molecular structure of Ligands was elucidated by X-ray diffraction study.
► The ligands and complexes interact with CT-DNA, intercalatively.
► The complexes can efficiently cleave CT-DNA via oxidative cleavage.
► The complexes possess significant antioxidative property against DPPH radical.
► The complex 3 shows higher IC50 value than the other complexes against tumor cells.