Biological evaluation of copper(II) complex with nalidixic acid and 2,2′-bipyridine (bpy)

A copper(II) complex with the first antibacterial quinolone drug nalidixic acid (= nal) has been synthesized and characterized in the presence of N-donor heterocyclic ligand 2,2'-bipyridyl (= bpy). The molecular structure of the complex reveals a distorted square pyramidal based geometry in Cu(II) atom which is confirmed by the X-ray crystallography technique. Study of the antibacterial activity showed that the complex exhibited promising antibacterial activity against both Escherichia coli and Staphylococcus aureus. The binding affinity of the complex towards calf thymus DNA (CT DNA) has been investigated by electronic absorption, circular dichroism and fluorescence spectroscopy techniques. The binding results revealed an intercalation binding mode of the complex with CT DNA. This complex has a superior ability to quench the intrinsic fluorescence of both HSA and BSA proteins via a static quenching mode and it has been observed at two different temperatures (30 and 40 degrees C). Molecular docking analysis reveals that the interaction of the complex with proteins was stabilized by hydrogen bonding and hydrophobic interaction. Furthermore, the complex was subjected to cytotoxicity tests against human breast cancer cell lines (MCF-7) and showed potential cytotoxicity with IC50 value of 79.05 mu M.