Binuclear silver(I) complexes with the non-steroidal anti-inflammatory drug tolfenamic acid: Synthesis, characterization, cytotoxic activity and evaluation of cellular mechanism of action

Abstract

In this study, two new binuclear silver(I)-tolfenamic acid complexes including picoline derivative ligands, [Ag2(μ-tolf)2(2-pic)2] 1and [Ag2(μ-tolf)2(4-pic)2] 2, were synthesized and identified by elemental analysis, FT-IR, 1H NMR and thermal analysis techniques. The in vitro cytotoxicity of the complexes was investigated against human breast cancer cell lines by XTT, flow cytometry, enzyme activity and western blot studies. The structures of 1 and 2 were clarified by single-crystal X-ray diffraction determination. The data clearly indicated that the Ag(I) ion is coordinated to one auxiliary ligand (2-pic or 4-pic), two tolfenamato ligands and another Ag(I) ion, demonstrating a distorted tetrahedral geometry. The tolfenamato ligands act as a bridging bidentate ligands. The chains are stabilized by intramolecular Ag(I)⋯π and π···π interactions. The 1H NMR and thermal analyses displayed the presence of picoline and tolfenamato ligands in the coordination sphere and the purity of the complexes. Both complexes exhibited potent cytotoxicity against cancer cell lines with higher selectivity than carboplatin. Flow cytometry and enzyme activity studies indicated that both complexes caused an increase in apoptosis, ROS and NO levels, cell cycle arrest, mitochondrial membrane damage and caspase activity, as well as inhibiting PI3K/Akt phosphorylation and modulating the oxidant/antioxidant balance system. Western blot analyses revealed the up-regulation of bax, caspase-3, caspase-9 and p53 proteins, but the down-regulation of bcl-2. These results demonstrate the vigorous apoptotic potential of the novel Ag(I) complexes in human breast cancer MDA-MB-453 cells.