Exploring the BSA- and DNA-binding, cytotoxicity, and cell cycle evaluation of ternary copper(II)/diimine complexes with N,N-dibenzyl-N'-benzoylthiourea as promising metallodrug candidates.

Four new copper(II) complexes were synthesized and characterized with the general formula [Cu(N-N)(Th)(NO3)], where N-N corresponds to the N-heterocyclic ligands 1,10-phenanthroline (phen), 2,2'-bipyridine (bipy), 4,7-diphenyl-1,10-phenanthroline (dpp), and 4,4-dimethyl-2,2'-bipyridine (dmbp) and Th represents the N,N-dibenzyl-N'-benzoylthiourea. Cytotoxic activities of the complexes against HCT116 (human colon carcinoma), HepG2 (human hepatocellular carcinoma), and non-tumor MRC-5 (human lung fibroblast) cells were investigated. The copper(II) complexes 1-4 were characterized by spectroscopic techniques while complexes 1 and 2 were studied using single-crystal X-ray diffraction as well. The complexes possessed a five-coordinated structure with one nitrate ligand as a monodentate at the axial position and two bidentate ligands N-heterocyclic and N,N-dibenzyl-N'-benzoylthiourea. The complexes showed promising IC50 values, ranging from 0.3 to 9.0 μM. Furthermore, interaction studies with biomolecules such as calf thymus DNA (ct-DNA) and Bovine Serum Albumin (BSA), which can act as possible biological targets of the complexes, were carried out. The studies suggested that the compounds interact moderately with ct-DNA and BSA. Complexes 1, 2, and 4 did not lead to cell accumulation at any stage of the cell cycle but caused a significant increase in internucleosomal DNA fragmentation. Whereas, compound 3 caused cell cycle arrest in the S phase while doxorubicin caused cell cycle arrest in the G2/M phase. The effect of structural modifications on the metal compounds was correlated with their biological properties and it was concluded that an increase in biological activity occurred with increasing the extension of the diimine ligands. Thus, complex 3 was the most promising one.