title: Antioxidant behaviour of caffeine: efficient scavenging of hydroxyl radicals.
abstract: Considerable controversy exists in the literature regarding the toxicity of coffee, including its possible carcinogenic and anticarcinogenic properties. This study reports on the reaction of 1,3,7-trimethylxanthine (caffeine) with the hydroxyl radical (.OH), as investigated by electron spin resonance (ESR) spin trapping. The .OH was generated by the Fenton reaction (Fe2+ + H2O2) as well as by the reaction of chromium(V) with H2O2. The results show that caffeine effectively scavenges .OH with a reaction rate constant of approximately 5.9 x 10(9) M-1 sec-1 that is comparable with those of other efficient .OH radical scavengers. ESR measurements provide evidence that a caffeine-derived oxygen-centred radical is formed in the reaction of caffeine with .OH and suggest a biochemical basis for the understanding of the reported anticarcinogenic properties of caffeine and related methylxanthine compounds.
authors.affiliation: Department of Chemistry, West Virginia University, Morgantown 26506.
authors.forename: X
authors.initials: X
authors.lastname: Shi
authors.forename: N S
authors.initials: NS
authors.lastname: Dalal
authors.forename: A C
authors.initials: AC
authors.lastname: Jain
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D002110:Caffeine / Q000737:chemistry*; D003497:Cyclic N-Oxides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D000431:Ethanol / Q000737:chemistry; D005609:Free Radicals; D006861:Hydrogen Peroxide / Q000737:chemistry; D006878:Hydroxides / Q000737:chemistry*; D017665:Hydroxyl Radical; D007501:Iron / Q000737:chemistry; D009249:NADP / Q000737:chemistry
chemical_list: D000975:Antioxidants; D003497:Cyclic N-Oxides; D005609:Free Radicals; D006878:Hydroxides; D017665:Hydroxyl Radical; D002110:Caffeine; D000431:Ethanol; D009249:NADP; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D006861:Hydrogen Peroxide; D007501:Iron