title: Practical problems when using ABTS assay to assess the radical-scavenging activity of peptides: Importance of controlling reaction pH and time.
abstract: Effects of reaction pH and time on the antioxidant behaviors of Tyr, Trp, Cys, and their related peptides (Tyr-Gly, Tyr-Glu, Tyr-Lys, Trp-Gly, Trp-Glu, Trp-Lys, Cys-Gly and Cys-Gly) in ABTS assay were investigated. Results showed that all these amino acids and peptides displayed a biphasic kinetic pattern with a fast initial step and a slow secondary step. The initial reaction rates of Tyr, Trp and their related peptides were strongly dependent on pH, while those of Cys and Cys-containing peptides were unaffected by pH. They failed to reach equilibrium over the short incubation period of 6-10 min typically used in this assay. Longer incubation time was needed for most of the peptides to approach equilibrium at lower pH. The observed biphasic kinetic pattern as well as the high TEAC values for these amino acids and peptides, could be a result of combined antioxidant behaviors of themselves plus the generated reaction products.
authors: College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, China; Guangdong Food Green Processing and Nutrition Regulation Technologies Research Center, Guangzhou 510640, China.
authors: Lin
authors: L
authors: Zheng
authors: College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, China; Guangdong Food Green Processing and Nutrition Regulation Technologies Research Center, Guangzhou 510640, China; State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China.
authors: Mouming
authors: M
authors: Zhao
authors: College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, China; Guangdong Food Green Processing and Nutrition Regulation Technologies Research Center, Guangzhou 510640, China.
authors: Chuqiao
authors: C
authors: Xiao
authors: College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, China; Guangdong Food Green Processing and Nutrition Regulation Technologies Research Center, Guangzhou 510640, China.
authors: Qiangzhong
authors: Q
authors: Zhao
authors: College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, China; Guangdong Food Green Processing and Nutrition Regulation Technologies Research Center, Guangzhou 510640, China. Electronic address: sgw1981@126.com.
authors: Guowan
authors: G
authors: Su
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D052160:Benzothiazoles / Q000737:chemistry*; D004151:Dipeptides / Q000032:analysis / Q000737:chemistry; D016166:Free Radical Scavengers / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010455:Peptides / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D013451:Sulfonic Acids / Q000737:chemistry*; D013997:Time Factors
chemical_list: D000596:Amino Acids; D052160:Benzothiazoles; D004151:Dipeptides; D016166:Free Radical Scavengers; D010455:Peptides; D010940:Plant Proteins; D013451:Sulfonic Acids; C114808:tyrosyl-lysine; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; C057081:alpha-glutamyltryptophan; C028505:cysteinylglycine; C024164:N2-tryptophyllysine; C022013:glycyltyrosine; C016810:tryptophylglycine
keywords: ABTS assay; Amino acids; Antioxidant activity; Peptides; TEAC value