title: Catalytic superoxide scavenging by metal complexes of the calcium chelator EGTA and contrast agent EHPG.
abstract: Metal ion chelators widely used in experimental protocols and clinical diagnosis are generally assumed to be inert. We previously reported that the ubiquitous chelator EDTA has high levels of superoxide suppressing activity. Here, we report that the common chelators calcium chelator EGTA and contrast agent EHPG have significant activities in suppressing superoxide levels depending on the nature of metal ion chelated. The most active species is Mn(II)-EGTA which exhibited an IC50 value of 0.19 microM for superoxide destruction. In addition, IC50 values for Mn(II)-EHPG and 2Cu(II)-EGTA were 0.69 and 0.60 microM, respectively. In conclusion, Mn(II) and Cu(II) complexes of the common chelators EGTA and EHPG exhibit considerable superoxide scavenging activities. Caution should be employed in their use in biological systems where superoxide has a key role and they may be useful for the development of catalytic anti-oxidants.
authors.affiliation: School of Pharmacy and Biomolecular Sciences, University of Brighton, Cockcroft Building, Moulsecoomb, Brighton BN2 4GJ, UK.
authors.forename: Anna E O
authors.initials: AE
authors.lastname: Fisher
authors.forename: Theresa A
authors.initials: TA
authors.lastname: Hague
authors.forename: Charlotte L
authors.initials: CL
authors.lastname: Clarke
authors.forename: Declan P
authors.initials: DP
authors.lastname: Naughton
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000737:chemistry; D002384:Catalysis; D002417:Cattle; D002614:Chelating Agents / Q000494:pharmacology*; D003287:Contrast Media / Q000494:pharmacology*; D003300:Copper / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000737:chemistry / Q000494:pharmacology*; D004912:Erythrocytes / Q000201:enzymology; D005029:Ethylenediamines / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D007477:Ions; D008024:Ligands; D008345:Manganese / Q000737:chemistry; D008670:Metals / Q000737:chemistry; D008956:Models, Chemical; D011485:Protein Binding; D013053:Spectrophotometry; D013482:Superoxide Dismutase; D013481:Superoxides
chemical_list: D000975:Antioxidants; D002614:Chelating Agents; D003287:Contrast Media; D005029:Ethylenediamines; D007477:Ions; D008024:Ligands; D008670:Metals; D013481:Superoxides; C011813:ethylenediamine-N,N'-bis(2-hydroxyphenylacetic acid); D008345:Manganese; D004533:Egtazic Acid; D003300:Copper; D013482:Superoxide Dismutase