Vanadium(IV) and copper(II) complexes of salicylaldimines and aromatic heterocycles: Cytotoxicity, DNA binding and DNA cleavage properties

•VIVO and CuII ternary complexes of the type [M(sal-AA)(NN)], where NN are planar N-donor heterocyclic bases, were prepared.•Complexes interact with calf-thymus DNA and two CuII complexes efficiently cleave plasmid DNA in the absence of additives.•Phen-containing CuII and VIVO compounds display stronger DNA interaction ability and cytotoxicity than the corresponding bipy analogues.•The copper complexes show much higher cytotoxic activity than the corresponding vanadium complexes and the reference drug Cisplatin.

Five copper(II) complexes, [Cu(sal-Gly)(bipy)](1), [Cu(sal-Gly)(phen)] (2), [Cu(sal-l-Ala)(phen)] (3), [Cu(sal-D-Ala)(phen)] (4), [Cu(sal-l-Phe)(phen)] (5) and five oxidovanadium(IV) complexes, [VIVO(sal-Gly)(bipy)] (6), [VIVO(sal-Gly)(phen)] (7), [VIVO(sal-l-Phe)(H2O)] (8), [VIVO(sal-l-Phe)(bipy)] (9), [VIVO(sal-l-Phe)(phen)] (10) (sal = salicylaldehyde, bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline) were synthesized and characterized, and their interaction with DNA was evaluated by different techniques: gel electrophoresis, fluorescence, UV–visible and circular dichroism spectroscopy. The complexes interact with calf-thymus DNA and efficiently cleave plasmid DNA in the absence (only 2 and 5) and/or presence of additives. The cleavage ability is concentration-dependent as well as metal and ligand-dependent. Moreover, DNA binding experiments show that the phen-containing CuII and VIVO compounds display stronger DNA interaction ability than the corresponding bipy analogues. The complexes present cytotoxic activity against human ovarian (A2780) and breast (MCF7) carcinoma cells. Cell-growth inhibition (IC50) of compounds 1, 2 and 5 in human promyelocytic leukemia (HL60) and human cervical cancer (HeLa) cells were also determined. The copper complexes show much higher cytotoxic activity than the corresponding vanadium complexes and the reference drug cisplatin (except for the sal-Gly complexes); namely, the phenanthroline copper complexes 2–5 are ca. 10-fold more cytotoxic than cisplatin and more cytotoxic than their bipyridine analogues.

Graphical abstractVIVO and CuII ternary complexes of the type [M(sal-AA)(NN)] were prepared and its cytotoxicity and ability to interact and cleave DNA were evaluated by several techniques. Phen-containing CuII compounds display stronger nuclease and cytotoxicity activity than corresponding bipy and VIVO analogues.Figure optionsDownload full-size imageDownload as PowerPoint slide