Synthesis, characterization and the antioxidative activity of copper(II), zinc(II) and nickel(II) complexes with naringenin

New complexes of Cu-(II), Zn-(II) and Ni-(II) with naringenin have been synthesized and characterized on the basis of elemental analyses, molar conductivities, H-1-n.m.r., i.r. spectra, u.v. spectra, thermal analyses, and fluorescence spectra. In addition, the suppression ratio for O-2(-center dot) (a) and OH center dot (b) of the complexes were studied by spectrophotometric methods. The results show that the effect of the Cu-(II)-complex IC50 (a) = 0.003 mu M, IC50 (b) = 0.06 mu M is the most remarkable, and the average scavenger ability of the complexes (IC50=0.06-2.67 mu M) against OH center dot is higher than that of the ligand (IC50 = 28.5 mu M). Taken together, these results indicate that the scavenger effect can be enhanced by the formation of metal-ligand coordination complexes, and the transition-metal ions may have differential and selective roles.