title: Kinetic study of the electron-transfer oxidation of the phenolate anion of a vitamin E model by molecular oxygen generating superoxide anion in an aprotic medium.
abstract: Electron-transfer reduction of molecular oxygen (O2) by the phenolate anion (1-) of a vitamin E model, 2,2,5,7,8-pentamethylchroman-6-ol (1H), occurred to produce superoxide anion, which could be directly detected by a low-temperature EPR measurement. The rate of electron transfer from 1- to O2 was relatively slow, since this process is energetically unfavourable. The one-electron oxidation potential of 1- determined by cyclic voltammetric measurements is sufficiently negative to reduce 2,2-bis(4-tert-octylphenyl)-1-picrylhydrazyl radical (DOPPH*) to the corresponding one-electron reduced anion, DOPPH-, suggesting that 1- can also act as an efficient radical scavenger.
authors.affiliation: Redox Regulation Research Group, Research Center for Radiation Safety, National Institute of Radiological Sciences, Inage-ku, Chiba 263-8555, Japan. nakanis@nirs.go.jp
authors.forename: Ikuo
authors.initials: I
authors.lastname: Nakanishi
authors.forename: Kentaro
authors.initials: K
authors.lastname: Miyazaki
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Shimada
authors.forename: Yuko
authors.initials: Y
authors.lastname: Iizuka
authors.forename: Keiko
authors.initials: K
authors.lastname: Inami
authors.forename: Masataka
authors.initials: M
authors.lastname: Mochizuki
authors.forename: Shiro
authors.initials: S
authors.lastname: Urano
authors.forename: Haruhiro
authors.initials: H
authors.lastname: Okuda
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ozawa
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
authors.forename: Nobuo
authors.initials: N
authors.lastname: Ikota
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Fukuhara
mesh_terms: D000838:Anions; D002839:Chromans / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005609:Free Radicals; D007700:Kinetics; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry*; D019800:Phenol / Q000737:chemistry*; D013053:Spectrophotometry; D013481:Superoxides / Q000737:chemistry; D013696:Temperature; D014810:Vitamin E / Q000737:chemistry*
chemical_list: C048427:2,2,5,7,8-pentamethylchroman; D000838:Anions; D002839:Chromans; D005609:Free Radicals; D013481:Superoxides; D014810:Vitamin E; D019800:Phenol; D010100:Oxygen