Vitamin E analogue Trolox C. E.s.r. and pulse-radiolysis studies of free-radical reactions.
The reactions between Trolox C, a water-soluble vitamin E analogue, and several oxidizing free radicals including the hydroxyl radical and various peroxy radicals were examined by using the pulse-radiolysis technique. The results demonstrate that Trolox C may undergo rapid one-electron-transfer reactions as well as hydrogen-transfer processes; the resulting phenoxyl radical is shown to be relatively stable, in common with the phenoxyl radical derived from vitamin E. The reactions between the Trolox C phenoxyl radical and a variety of biologically relevant reducing compounds were examined by using both pulse radiolysis and e.s.r. The results demonstrate that the Trolox C phenoxyl radical is readily repaired by ascorbate (k = 8.3 x 10(6) dm3.mol-1.s-1) and certain thiols (k less than 10(5) dm3.mol-1.s-1) but not by urate, NADH or propyl gallate. Evidence from e.s.r. studies indicates that thiol-containing compounds may also enter into similar repair reactions with the alpha-tocopherol phenoxyl radical. Kinetic evidence is presented that suggests that Trolox C may 'repair' proteins that have been oxidized by free radicals.
Davies
M J
MJ
Department of Biochemistry, Brunel University, Uxbridge, Middlesex, U.K.
Forni
L G
LG
Willson
R L
RL
D001205:Ascorbic Acid / Q000378:metabolism; D001578:Benzopyrans / Q000378:metabolism*; D052160:Benzothiazoles; D001667:Binding, Competitive; D002839:Chromans / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D005609:Free Radicals; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D010084:Oxidation-Reduction; D011675:Pulse Radiolysis; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013451:Sulfonic Acids
D001578:Benzopyrans; D052160:Benzothiazoles; D002839:Chromans; D005609:Free Radicals; D007202:Indicators and Reagents; D013438:Sulfhydryl Compounds; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D001205:Ascorbic Acid; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid