Copper(II) complexes with 4-(diethylamino)salicylaldehyde and α-diimines: Anticancer, antioxidant, antigenotoxic effects and interaction with DNA and albumins.

In this article, cytotoxicity, the mechanisms of cytotoxic activity, genotoxicity, and interaction with DNA and proteins, of two Cu(II) complexes with a salicylaldehyde derivative (4-(diethylamino)salicylaldehyde) and α-diimine (2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen)) are reported. Both Cu(II) complexes performed cytotoxic effects against all tested malignant cell lines. Complexes exerted highest cytotoxicity against HeLa and A375 malignant cell lines. The cytotoxic activity of Cu(II) complex with phen as a α-diimine co-ligand was significantly higher in comparison with cytotoxic activity of Cu(II) complex with bipy. Pretreatment with specific inhibitors of caspase-3, caspase-8 or caspase-9, in order to clear up the mode of cell death triggered by two Cu(II) complexes in HeLa cells, indicated the ability of these complexes to induce apoptosis through activation of target caspases. Cu(II)-phen complex exhibited significant antioxidant activity compared with Cu(II)-bipy complex, and showed a better effect on reducing intracellular ROS levels in HeLa cells. Tested complexes did not display genotoxic potential in human peripheral blood leucocytes, but exhibited an antigenotoxic effect in post-treatment, after H2O2 exposure. The study of the in vitro biological properties regarding their affinity towards CT (calf-thymus) DNA and serum albumins showed that the compounds can intercalate to CT DNA, and bind reversibly and tightly to the albumins. Molecular docking studies of the ability of compounds to bind to biomacromolecules are consistent with in vitro studies.

Interaction of dinuclear cadmium(II) 5-Cl-salicylaldehyde complexes with calf-thymus DNA.

Five dinuclear Cd(II) complexes with the anion of 5-Cl-salicylaldehyde (5-Cl-saloH) were synthesized in the absence or presence of the α-diimines: 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (neoc) or 2,2'-dipyridylamine (dpamH) and characterized as [Cd(5-Cl-salo)2(CH3OH)]2 (1), [Cd(5-Cl-salo)2(bipy)]2 (2), [Cd(5-Cl-salo)2(phen)]2 (3), [Cd(5-Cl-salo)(neoc)(ONO2)]2 (4) and [Cd(5-Cl-salo)(dpamΗ)(ONO2)]2 (5). The complexes were characterized by spectroscopic techniques (IR, UV-vis, (1)H-NMR and (13)C-NMR), elemental analysis and molar conductivity measurements. The structures of four complexes (1-3 and 5) were determined by X-ray crystallography, providing all three possible coordination modes of the ligand 5-Cl-salicylaldehyde, i.e. bidentate or tridentate chelating and/or bridging mode. The complexes bind to calf-thymus (CT) DNA mainly by intercalation, as concluded by the viscosity measurements and present relatively high DNA-binding constants. The complexes exhibit significant ability to displace ethidium bromide (EB) from the EB-DNA complex, thus indirectly proving the intercalation as the most possible binding mode to CT DNA.