Structure and biological properties of mixed-ligand Cu(II) Schiff base complexes as potential anticancer agents

We synthesized two mixed-ligand Cu(II) complexes containing different aroylhydrazone ligands and a pyridine co-ligand, namely, [Cu(L1)(Py)] (C1) and [Cu(L2)(Py)(Br)] (C2) (L1 = (E)-2-hydroxy-N'-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide, Py = pyridine, L2 = (E)-2-hydroxy-N'-(phenyl(pyridin-2-yl)methylene)benzohydrazide), and assessed their chemical and biological properties to understand their marked activity. C2 showed better anticancer activity than C1 in various human cancer cell lines, including the cisplatin-resistant lung cancer cell line A549cisR. Both Cu(II) complexes, especially C2, displayed promising anti-metastatic activity against HepG2 cells. Spectroscopic titration and agarose gel electrophoresis experiments indicated that C2 exhibited binding affinity toward calf-thymus DNA and efficient pBR322 DNA-cleaving ability. Further mechanistic studies showed that C2 effectively induced DNA damage and thus led to cell cycle arrest at the G2/M phase, and also stimulated mitochondrial dysfunction mediated by reactive oxygen species and caspase-dependent apoptosis.