PMID: 9554834Apr 29, 1998Paper

Re-appraisal of the tocopheroxyl radical reaction with beta-carotene: evidence for oxidation of vitamin E by the beta-carotene radical cation

Free Radical Research
A MortensenS A Everett

Abstract

Photobleached beta-carotene (Car) is regenerated in hexane on a microsecond timescale in the presence of alpha-tocopherol (TOH) but not when alpha-tocopherol is absent, as studied by laser flash photolysis. Beta-carotene radical cations (Car.+) likewise react with (excess) alpha-tocopherol: Car.+ + TOH-->Car + TO. + H+ (second-order rate constant of k = 1.7 +/- 0.1 x 10(7) M(-1) s(-1) in homogeneous di-tert-butylperoxide/benzene at 20 degrees C) rather than alpha-tocopheroxyl radicals (TO.) reacting with beta-carotene. In hexane, hexane radicals formed by pulse radiolysis react considerably faster with beta-carotene (k = 2.1 +/- 0.1 x 10(9) M(-1) s(-1)) than with alpha-tocopherol (k = 4.9 +/- 0.1 x 10(6) M(-1) s(-1)). No evidence was obtained for a slower rate of beta-carotene radical cation formation in beta-carotene/alpha-tocopherol mixtures resulting from alpha-tocopheroxyl radical oxidation of beta-carotene. Steady-state radiolysis experiments confirmed that alpha-tocopherol protects beta-carotene from oxidation by hexane radicals. In both solvent systems, beta-carotene is regenerated from the radical cation by alpha-tocopherol rather than alpha-tocopherol being regenerated by beta-carotene from the alpha-tocopheroxyl radical.

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Citations

May 22, 2001·Archives of Biochemistry and Biophysics·A MortensenT G Truscott
Jan 5, 2001·Bulletin of Experimental Biology and Medicine·G G KonovalovaV Z Lankin
May 24, 2003·Biochemical and Biophysical Research Communications·Norman I Krinsky, Kyung-Jin Yeum
Oct 31, 2003·Molecular Aspects of Medicine·Paola PalozzaGabriella Calviello
Oct 29, 1999·Food and Chemical Toxicology : an International Journal Published for the British Industrial Biological Research Association·J Chaudière, R Ferrari-Iliou
Dec 18, 2001·Journal of Photochemistry and Photobiology. B, Biology·M BoultonB Rózanowski
Apr 10, 2002·Journal of Clinical Periodontology·M BattinoP Bullon
Jun 23, 2005·Critical Reviews in Food Science and Nutrition·John ShiYueming Jiang
May 23, 2003·Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology·K Razi NaqviVassilia Partali
Oct 21, 2015·Free Radical Biology & Medicine·Magdalena M OlchawaTadeusz J Sarna
Mar 1, 1999·Asia Pacific Journal of Clinical Nutrition·O I Aruoma
Jun 13, 2020·Antioxidants·Antonio Pérez-GálvezMaría Roca
Nov 29, 2005·Molecular Aspects of Medicine·Norman I Krinsky, Elizabeth J Johnson
Sep 17, 2021·Critical Reviews in Food Science and Nutrition·Faye M A LangstonJohn R Bows

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