Three novel copper(II), cobalt(II), and nickel(II) complexes of lapachol (Lap) containing 1,10-phenanthroline (phen) ligand, [M(Lap) 2 (phen)] (M = Cu(II), Co(II), and Ni(II)), have been synthesized and characterized using, elemental analysis and spectroscopic studies. Their interactions with calf thymus DNA (CT DNA) were investigated using viscosity, thermal denaturation, circular dichorism, fluorescence quenching and electronic absorption spectroscopy. The catalytic activities on DNA cleavage of the complexes Cu, Co, and Ni were studied, which copper complex Cu showed better catalyst activity in the DNA cleavage process than complexes Co and Ni. The in vitro cytotoxic potential of the complexes Cu, Co, and Ni against human cervical carcinoma (HeLa), human liver hepatocellular carcinoma (HepG-2), and human colorectal adenocarcinoma (HT-29) cells indicated their promising antitumor activity with quite low IC 50 values in the range of 0.15–2.41 ?M, which are lower than those of cisplatin.
