Enhancement of biological activities of copper(II) complexes containing guanidine derivatives by enrofloxacin

Two new copper(II) chloride complexes from guanidine derivatives containing a deprotonated enrofloxacin (erx(-)) as the second ligand, [CuL1(erx)]Cl (1) and [CuL2(erx)]Cl (2), were synthesized and characterized by elemental analysis and several spectroscopic methods. Crystallographic data of the single crystal of 1 gave a monoclinic with P2(1)/n space group of [Cu(L-1-H+)(erx)]center dot 2MeOH with a slightly distorted square-planar CuN2O2 geometry. The DNA binding studies of 1 and 2 toward calf thymus (CT) DNA by absorption titration, fluorescence, viscosity measurements and circular dichroism spectroscopy showed non-intercalative binding mode with the K-b values of 1 > 2. Their cleaving ability toward plasmid pBR322 DNA was investigated by gel electrophoresis and atomic force microscopy (AFM). From these results, an oxidative mechanism is possible to be the main cleaving pathway of 1 and 2. The antibacterial activity of 1 and 2 was then tested against three human-food poisoning bacteria (E. coli, Salmonella and Campylobacter) by disc diffusion method. Both complexes exhibit inhibitory activity against E. coli and Salmonella greater than their corresponding starting complexes, [(CuLCl2)-Cl-1](2) (for 1) and [CuL2Cl2](2) (for 2). Study on the cytotoxicity of 1 and 2 against three human cancer cell lines including oral cavity (KB), breast (MCF-7) and small cell lung (NCI-H187) cell lines was determined using Resazurin Microplate assay (REMA). Results have shown that both complexes display much higher cytotoxicity against MCF-7 than their corresponding starting complexes. The better biological activities of the complexes in this system can be probably ascribed to the presence of erx(-). (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Two new copper(II) chloride complexes containing deprotonated enrofloxacin ligands were synthesized and characterized. Studies showed that these complexes exhibited binding to DNA, antibacterial activity against E. coli and Salmonella, and cytotoxicity against cancer cell lines, potentially due to the presence of enrofloxacin ligands.