A study on the ability of copper complexes to act as active oxygen species scavengers

The ability of two low-molecular-weight copper complexes to influence the hemolysis of human erythrocytes caused by active oxygen species-generating systems was studied. Cu(II) (glycine)2 and Cu(II) (tyrosine)2 did not inhibit hemolysis due to O-2 and H2O2 generated by xanthine oxidase plus acetaldehyde but rather has a prooxidant effect. The same copper complexes as well as Cu(II) strongly inhibited the hemolysis caused by the 1O2-generating system (Rose Bengal + light). It was found that except for 1O2 the other active oxygen species (O-2, H2O2 and OH.) did not participate in the Rose Bengal + light-induced hemolysis. Thus we examined whether the inhibitory effect of copper complexes was due to 1O2 quenching. Cu(II) (glycine)2 inhibited the Rose Bengal + light-induced oxidation of compounds known to react chemically with 1O2 and its effects were analogous to the effects of physical 1O2 quenchers, e. g. NaN3 and NiCl2. The oxygen consumption upon NADH-photooxidation in the presence of Rose Bengal was inhibited competitively by Cu(II) (glycine)2 but when concentration of Rose Bengal or light intensity were varied the extent of Cu(II) (glycine)2-caused inhibition was not changed. It is concluded that the effects of Cu(II) (glycine)2 and possibly of Cu(II) (tyrosine)2 are due to quenching of 1O2 but quenching of the excited state of the dye could not be excluded.