title: Chitosan gallate as a novel potential polysaccharide antioxidant: an EPR study.
abstract: A novel biopolymer-based antioxidant, chitosan conjugated with gallic acid (chitosan galloylate, chitosan-GA), is proposed. Electron paramagnetic resonance (EPR) demonstrates a wide range of antioxidant activity for chitosan-GA as evidenced from its reactions with oxidizing free radicals, that is, 1,1-diphenyl-2-picryl-hydrazyl (DPPH), horseradish peroxidase (HRP)-H(2)O(2), carbon-centered alkyl radicals, and hydroxyl radicals. The EPR spectrum of the radical formed on chitosan-GA was attributed to the semiquinone radical of the gallate moiety. The stoichiometry and effective concentration (EC(50)) of the DPPH free radical with chitosan-GA show that the radical scavenging capacity is maintained even after thermal treatment at 100 degrees C for an hour. Although the degree of substitution of GA on chitosan was about 15%, its antioxidant capacity, that is, the reaction with carbon-centered and hydroxyl radicals, is comparable to that of GA.
authors.affiliation: The Department of Applied Radiation and Isotopes, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand. wanvimol.p@ku.ac.th
authors.forename: Wanvimol
authors.initials: W
authors.lastname: Pasanphan
authors.forename: Garry R
authors.initials: GR
authors.lastname: Buettner
authors.forename: Suwabun
authors.initials: S
authors.lastname: Chirachanchai
mesh_terms: D016227:Benzoquinones / Q000737:chemistry; D001713:Biphenyl Compounds / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D048271:Chitosan / Q000031:analogs & derivatives* / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D010851:Picrates / Q000737:chemistry; D013696:Temperature
chemical_list: D016227:Benzoquinones; D001713:Biphenyl Compounds; C045076:Fenton's reagent; D016166:Free Radical Scavengers; D010851:Picrates; C547764:chitosan gallate; C025232:semiquinone radicals; D017665:Hydroxyl Radical; D002244:Carbon; D006859:Hydrogen; D048271:Chitosan; D006861:Hydrogen Peroxide; C004931:1,1-diphenyl-2-picrylhydrazyl; D007501:Iron