SPECTROSCOPIC STUDIES ON THE PRODUCTION OF HYDROXYL RADICALS FROM THE REACTIONS OF COPPER(II)-POLYAMINE-N-POLYCARBOXYLATE COMPLEXES WITH HYDROGEN-PEROXIDE

Reactions of copper(II)-polyamine-N-polycarboxylate complexes such as Cu(II)(edta) (edta: ethylenediaminetetraacetic acid) and Cu(II)(dtpa) (dtpa: diethylenetriaminepentaacetic acid) with hydrogen peroxide (H2O2) were investigated spectroscopically in the presence or absence of biological reductants. In the absence of biological reductants such as L-cysteine, N-acetyl-L-cysteine, L-ascorbic acid, NADH and glutathione, no reaction occurred between Cu(II)(edta) and H2O2; but, in the presence of these biological reductants, Cu(II)(edta) was reduced to Cu(I) and then the subsequent redox reaction (Fenton-type reaction) between Cu(I) and H2O2 occurred to yield hydroxyl radicals (.OH). From these results, it is concluded that copper(II)-polyamine-N-polycarboxylate complexes cannot directly be reduced to Cu(I) by H2O2, because the redox potentials of Cu2+ ions towards H2O2 have been changed by ligation with these polyamine-N-polycarboxylate ligands.