Syntheses, characterization and antitumor activities of transition metal complexes with isoflavone

Five new complexes were synthesized by the reaction of 4′-methoxy-5,7-dihydroxy-isoflavone ligand (a) with transition metal ions zinc (Zn2+) (complex b), manganese (Mn2+) (complex c), copper (Cu2+) (complex d), cobalt (Co2+) (complex e) and nickel (Ni2+) (complex f). The composition of the complexes has been characterized by elemental analysis, IR, mass spectrometry (MS) and 1H NMR spectrometric techniques. Their antitumor properties were evaluated against five human cancer cell lines using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry. The results indicated that the complexes possess higher growth inhibitory effects than free isoflavone and corresponding metal ions. Complex c and f showed greater antitumor activity and selectivity than other described complexes, even more effective than the positive control cisplatin against the selected cell lines. In addition, DNA flow cytometric analysis demonstrated that complexes display a significant G2/M phase arrest, which then progressed to early apoptosis as detected by flow cytometry after double-staining with annexin V and propidium iodide (PI).