Equilibria in the aqueous system of cobalt(II) based on 2-picolinehydroxamic acid and N-(2-hydroxybenzyl)phenylalanine and its ability to inhibit the propagation of cancer cells

Abstract

Mixed-ligand complexes of cobalt(II) with two bioligands, viz. 2-picolinehydroxamic acid and the reduced Schiff base N-(2-hydroxybenzyl)phenylalanine, were studied in aqueous solution by potentiometry and UV-Vis spectroscopic analysis. The coordination mode of the complexes and their stability were determined and compared to their parent species. Stacking interactions between the rings present in the ligands influence the stability of the complexes. Also, UV-Vis spectroscopy revealed that the stacking interactions affected the intercalation of DNA and mixed-ligand complexes. The in vitro anticancer activity of the free ligand 2-picolinehydroxamic acid and the complexes was tested against cervical and gastric human adenocarcinoma epithelial cell lines. At concentrations of 0.06 and 0.11 mM, the mixed-ligand structures showed the ability to reduce gastric cancer cells with no inhibitory effect on mouse fibroblasts. The cytotoxic effect was accompanied by damage to the cell nuclei, which may confirm that the complexes demonstrate effective binding to DNA. No determination of minimal inhibitory and bactericidal/fungicidal concentrations against the test organisms was possible at higher complex concentrations due to precipitation.

Keywords: Anticancer activity; Cobalt(II) complex; DNA-binding; Hydroxamic acid; Schiff base; Stability constant.