New manganese(II), iron(II), cobalt(II), nickel(II) and copper(II) saccharinate complexes of 2,6-bis(2-benzimidazolyl) pyridine as potential anticancer agents

Abstract

New mononuclear complexes [Mn(NO3)(sac)(H2O)(bzimpy)]center dot 2DMF (Mn), [Fe(sac)(2)(H2O)(bzimpy)]center dot 2H(2)O (Fe), [Co(bzimpy)(2)](sac)(2)center dot 2H(2)O (Co), [Ni(bzimpy)(2)](sac)(2)center dot H2O center dot i-PrOH (Ni) and [Cu(sac)(2)(bzimpy)]center dot 3DMF (Cu) (sac = saccharinate and bzimpy = 2,6-bis(2-benzimidazolyl)pyridine) were synthesized and structurally characterized by elemental analysis, UV-Vis, IR, ESI-MS and X-ray diffraction. The anticancer activity of the metal complexes against A549 (lung), MCF-7 (breast), HT29 (colon) cancer cells and MCF10A (normal human breast epithelial) cells was tested and compared with those of cisplatin and bzimpy. The complexes displayed potent cytotoxic activity especially in MCF-7 and A549 cell lines, but they were practically inactive against the normal cells. Mechanistic studies with Mn and Cu complexes on A549 cells indicated that the complexes induced G0/G1 arrest. Both complexes increased intracellular ROS (reactive oxygen species) levels and successfully caused both mitochondrial dysfunction and doublestrand DNA breaks. The up-regulated Bax and down-regulated Bcl-2 expression levels, caspase-3/7 activation and reduced Fas expression indicated that Mn and Cu induced ROS-dependent mitochondria-mediated intrinsic apoptosis in A549 cells.