Antioxidative and antitumour properties of metal(II) solid complexes with 8-acetyl-4-methyl umbelliferone

Abstract

Six transition metal(II) complexes with 8-acetyl-4-methyl umbelliferone (AMUH), ML2 (L = AMU⁻; M = Mn, Co, Ni, Cu, Zn and Cd), have been synthesized and characterized by elemental analysis, electrical conductance, i.r., 1H-n.m.r. and u.v. spectroscopic techniques. The e.s.r. spectra show that CuL2 is anisotropic, with g ⊥ ≈ 2.05 and g_∥≈2.26. The MnL2 species is characterized by a very broad g≈2 centered resonance without manganese hyperfine structure. The antioxidative and other biological activities of selected complexes were also investigated, indicating that both the ligand and complexes exhibit a scavenging effect on the superoxide radical (O₂ ^−·) and a suppressing effect on the hydroxyl radical (·OH). The suppressing effect on ·OH is greater than the scavenging effect on O₂ ⁻·. The Cu and Mn complexes exhibit very significant suppression ratios for both radicals. However, the inhibitory effect on lipid peroxides results show that, in the initial stage, the Cu and Mn complexes exhibit obvious inhibitory effects on lipid peroxides, but after one hour, they begin to accelerate the lipid peroxides. Lower catalytic activity and instability when the complexes react with active oxygen may be responsible for this dual nature. The ligand and four transition metal(II) complexes selectively, obviously, inhibit the growth of HCT-8 and HL-60 tumour cell lines. They also exhibit a minor influence on the proliferation of B cells in higher concentration (10⁻⁵ m), but only a weak effect on the proliferation of T cells of the BALB/C (nude rate) spleen cells.