title: Metalloporphyrins are potent inhibitors of lipid peroxidation.
abstract: The objectives of these studies were to determine whether metalloporphyrins could inhibit lipid peroxidation, characterize factors that influence their potency and compare their potency to prototypical antioxidants. Lipid peroxidation was initiated with iron and ascorbate in rat brain homogenates and the formation of thiobarbituric acid reactive species was used as an index of lipid peroxidation. Metalloporphyrins were found to be a novel and potent class of lipid peroxidation inhibitors. Inhibition of lipid peroxidation by metalloporphyrins was dependent on the transition metal ligated to the porphyrin, indicating that metal centered redox chemistry was important to the mechanism of their antioxidant activities. Manganese porphyrins with the highest superoxide dismutase (SOD) activities, MnOBTM-4-PyP and MnTM-2-PyP (charges are omitted throughout text for clarity), were the most potent inhibitors of lipid peroxidation with calculated IC50s of 1.3 and 1.0 microM, respectively. These manganese porphyrins were 2 orders of magnitude more potent than either trolox (IC50 = 204 microM) or rutin (IC50 = 112 microM). The potencies of the manganese porphyrins were related not only to their redox potentials and SOD activities, but also to other factors that may contribute to their ability to act as electron acceptors. The broad array of antioxidant activities possessed by metalloporphyrins make them attractive therapeutic agents in disease states that involve the overproduction of reactive oxygen species.
authors.affiliation: Department of Medicine, National Jewish Medical and Research Center, Denver, CO 80206, USA. DAYB@NJC.ORG
authors.forename: B J
authors.initials: BJ
authors.lastname: Day
authors.forename: I
authors.initials: I
authors.lastname: Batinic-Haberle
authors.forename: J D
authors.initials: JD
authors.lastname: Crapo
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002839:Chromans / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D007700:Kinetics; D015227:Lipid Peroxidation / Q000187:drug effects*; D008345:Manganese; D008665:Metalloporphyrins / Q000138:chemical synthesis / Q000494:pharmacology*; D010084:Oxidation-Reduction; D051381:Rats; D017207:Rats, Sprague-Dawley; D012431:Rutin / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000378:metabolism / Q000494:pharmacology; D015032:Zinc
chemical_list: D000975:Antioxidants; D002839:Chromans; D016166:Free Radical Scavengers; D008665:Metalloporphyrins; C097284:manganese(III)-tetrakis(4-benzoic acid)porphyrin; C097283:zinc(II)-tetrakis(4-benzoic acid)porphyrin; D008345:Manganese; D012431:Rutin; D013482:Superoxide Dismutase; D015032:Zinc; D001205:Ascorbic Acid; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid