title: Fluorimetric study of the pro-oxidant activity of EUK8 in the presence of hydrogen peroxide.
abstract: The catalase mimetic complex Mn(III)-salen chloride (EUK8) was found to be pro-oxidant under low hydrogen peroxide concentrations. The increase in the fluorescence rate of the probe 1,2,3-dihydrorhodamine (DHR) in solution, as well as the carbonyl content of human serum albumin were found to be maximum at H2O2:EUK8 molar ratios ranging from 0 to 2, supporting previous findings regarding the mechanism of EUK8 catalase activity and the formation of highly oxidative Mn(V)-O2- species. This pro-oxidant effect is precluded by the presence of glutathione. Cytotoxicity to HeLa cells, as probed by increased rate of oxidation of intracellular DHR, was not observed. Our findings suggest that the combination of H2O2 and EUK8 at specific molar ratios, in the absence of reductants/antioxidants, induces the oxidation of organic molecules. It is shown that the fluorimetric determination of pro-oxidant activity of metal complexes is more sensitive than the colorimetric quantification of protein carbonyl content. The implications of our findings with respect to the somewhat confusing results arising from in vivo studies of EUK8 and other Mn(III) anti-oxidant metal complexes are discussed.
authors.affiliation: Instituto de Química, Universidade de São Paulo, Av Lineu Prestes 748, Sao Paulo, SP, Brazil.
authors.forename: Samanta
authors.initials: S
authors.lastname: Do Amaral
authors.forename: Breno Pannia
authors.initials: BP
authors.lastname: Espósito
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000737:chemistry*; D005029:Ethylenediamines / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry*; D017895:Manganese Compounds / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D000975:Antioxidants; D005029:Ethylenediamines; D017895:Manganese Compounds; D009942:Organometallic Compounds; D016877:Oxidants; D017382:Reactive Oxygen Species; C090577:N,N'-bis(salicylideneamino)ethane-manganese(II); D006861:Hydrogen Peroxide