title: Radical scavenging activity of antioxidants evaluated by means of electrogenerated HO radical.
abstract: A method is proposed and tested concerning the characterization of antioxidants by means of their reaction with electrogenerated HO radicals in galvanostatic assays with simultaneous O2 evolution, using a Pt anode fairly oxidized. The consumption of a set of species with antioxidant activity, ascorbic acid (AA), caffeic acid (CA), gallic acid (GA) and trolox (T), is described by a first order kinetics. The rate of the processes is limited by the kinetics of reaction with HO radicals and by the kinetics of charge transfer. Information regarding the scavenger activity of antioxidants is obtained by the relative value of the rate constant of the reaction between antioxidants and HO radicals, k(AO,HO)/k(O2). The number of HO radicals scavenged per molecule of antioxidant is also estimated and ranged from 260 (ascorbic acid) to 500 (gallic acid). The method is applied successfully in the characterization of the scavenger activity of ascorbic acid in a green-tea based beverage.
authors.affiliation: Centro de Química, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Raquel
authors.initials: R
authors.lastname: Oliveira
authors.affiliation: Centro de Química, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Dulce
authors.initials: D
authors.lastname: Geraldo
authors.affiliation: Centro de Química, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal. Electronic address: fbento@quimica.uminho.pt.
authors.forename: Fátima
authors.initials: F
authors.lastname: Bento
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D001205:Ascorbic Acid / Q000737:chemistry; D001628:Beverages; D002109:Caffeic Acids / Q000737:chemistry; D002839:Chromans / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D004563:Electrochemistry / Q000379:methods*; D004572:Electrolysis; D005504:Food Analysis; D016166:Free Radical Scavengers / Q000737:chemistry; D005707:Gallic Acid / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D019800:Phenol / Q000737:chemistry; D013662:Tea
chemical_list: D000975:Antioxidants; D002109:Caffeic Acids; D002839:Chromans; D016166:Free Radical Scavengers; D013662:Tea; D017665:Hydroxyl Radical; D019800:Phenol; D005707:Gallic Acid; D001205:Ascorbic Acid; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid; D010100:Oxygen; C040048:caffeic acid
keywords: Antioxidants; Ascorbic acid; HO radical generation; Phenolic compounds; Scavenging activity