Antioxidative and anti-tumour activities of solid quercetin metal(II) complexes

Six metal(II) complexes with quercetin ML2 · nH2O [L = quercetin (3-OH group deprotonated); M = Mn, Co, Ni, Cu, Zn, and Pb; n = 2 or 3] have been prepared and characterized by elemental analysis, complexometric titration, thermal analysis, conductivity, i.r., u.v., 1H-n.m.r. and fluorescence spectral techniques as well as by cyclic voltammetry. The antioxidative and anti-tumour activities of quercetin · 2H2O and the complexes were tested by both the MTT and SRB methods. The results show that the suppression ratios of the complexes against the tested tumour cells are superior to quercetin · 2H2O. The effect of ZnL2 · 3H2O reacting with calf thymus DNA was studied by fluorescence methods. The Zn-complex binding to DNA has been determined by fluorescence titration in 0.05 M Tris-HCl, 0.5 M NaCl buffer (pHb = 7.0). The results indicate that the interaction of the complex with DNA is very evident.