title: Antioxidant activity assay based on laccase-generated radicals.
abstract: A novel antioxidant activity assay was developed using laccase-oxidized phenolics. In a three-step approach, phenolic compounds were first oxidized by laccase. Laccase was then inhibited using 80% (v/v) methanol which also stabilized the oxidized phenolics which were then used to measure antioxidant activities of ascorbic acid and Trolox. From a number of laccase-oxidized phenolics screened for potential use in the measurement of antioxidant activities, syringaldazine emerged the best, giving results comparable to the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, which is currently used in conventional methods. Like DPPH radicals, two moles of stoichiometric oxidized syringaldazine were reduced by one mole of either ascorbic acid or Trolox. For the first time we show that antioxidant activity can be correlated to oxygen consumption by laccase. Reduction of one molecule of oxygen corresponded to oxidation of four molecules of syringaldazine which in turn is reduced by two molecules of Trolox or ascorbic acid. This study therefore demonstrates the great potential of using laccase-oxidized syringaldazine for the measurement of antioxidant activity.
authors.affiliation: Department of Environmental Biotechnology, Graz University of Technology, Petersgasse 12/1, 8010, Graz, Austria.
authors.forename: Endry
authors.initials: E
authors.lastname: Nugroho Prasetyo
authors.forename: Tukayi
authors.initials: T
authors.lastname: Kudanga
authors.forename: Walter
authors.initials: W
authors.lastname: Steiner
authors.forename: Michael
authors.initials: M
authors.lastname: Murkovic
authors.forename: Gibson S
authors.initials: GS
authors.lastname: Nyanhongo
authors.forename: Georg M
authors.initials: GM
authors.lastname: Guebitz
mesh_terms: D000975:Antioxidants / Q000032:analysis* / Q000378:metabolism; D001205:Ascorbic Acid / Q000032:analysis* / Q000378:metabolism; D001681:Biological Assay / Q000379:methods*; D001713:Biphenyl Compounds; D002839:Chromans / Q000032:analysis* / Q000378:metabolism; D005609:Free Radicals / Q000737:chemistry / Q000378:metabolism; D042845:Laccase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000432:Methanol / Q000494:pharmacology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D010636:Phenols / Q000737:chemistry / Q000378:metabolism; D010851:Picrates / Q000737:chemistry / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D002839:Chromans; D005609:Free Radicals; D010636:Phenols; D010851:Picrates; C004931:1,1-diphenyl-2-picrylhydrazyl; D042845:Laccase; D001205:Ascorbic Acid; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid; D010100:Oxygen; D000432:Methanol