Chromone-Based Copper(II) Complexes as Potential Antitumour Agents: Synthesis, Chemical Characterisation and In Vitro Biological Evaluation

Three new complexes of copper(II) and chromone-2-carboxylic acid, a ligand from the group of hydroxypyrones, were synthesised according to the principles of green chemistry. The complexes were characterised by FT–IR and NMR spectroscopy, thermal and electrochemical analysis, and their structures are proposed. The results show the formation of mononuclear (1) and dinuclear hydroxo-bridged dinuclear copper(II) complexes (2 and 3). The results of cyclic voltammetry show that the copper in all complexes is in the +2-oxidation state. The antiproliferative activity was determined by MTT assay on 2D cell models in vitro on seven cell lines. The activity spectrum of complexes 1–3 ranged from the highest to the lowest value in the tumour cell lines tested, in the following order: Hep G2 > NCI-H358 > HT-29 > KATO III > MDA-MB 231 > Caco-2. The most effective concentration was 10−5 mol dm−3, which suppressed the growth of Hep G2 cells as follows: 69.5% (1), 64.8% (2) and 64% (3). The calculated selectivity index clearly shows that Hep G2 is the most sensitive cell line to copper complexes (SI = 1.623 (1); 1.557 (2), 1.431 (3).