title: Inhibition of nitrous acid-dependent tyrosine nitration and DNA base deamination by flavonoids and other phenolic compounds.
abstract: Exposure of tyrosine or DNA bases to acidic nitrite at low pH results in the nitration of tyrosine and the formation of base deamination products, respectively. At pH 1, hypoxanthine and xanthine are formed from the deamination of adenine and guanine, respectively, whereas under the same conditions, uracil is not detected. The yield of 3-nitrotyrosine derived from interaction of equimolar nitrite and tyrosine at pH 1 is approximately 50% of that obtained from equimolar peroxynitrite-tyrosine interactions at pH 7. 4. The ability of a range of plant phenolic constituents to prevent damage mediated by acidic nitrite was also examined in comparison with the activity of vitamin C. The epicatechin/gallate family of flavonols, constituents of green tea, red wine, etc., demonstrates the most extensive inhibitory properties against both tyrosine nitration and base deamination. The results also show that ascorbic acid is a poor inhibitor of nitration or deamination under acidic conditions such as those of the stomach. The ability of plant phenolics to scavenge reactive nitrogen species derived from acidic nitrite may contribute to the protective effects of tea polyphenols against gastric cancer.
authors.affiliation: International Antioxidant Research Centre at UMDS-Guy's Hospital, London SE1 9RT, and International Antioxidant Research Centre at King's College, Manresa Road, London SW3 6LX, U.K.
authors.forename: C
authors.initials: C
authors.lastname: Oldreive
authors.forename: K
authors.initials: K
authors.lastname: Zhao
authors.forename: G
authors.initials: G
authors.lastname: Paganga
authors.forename: B
authors.initials: B
authors.lastname: Halliwell
authors.forename: C
authors.initials: C
authors.lastname: Rice-Evans
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000737:chemistry*; D003641:Deamination; D005419:Flavonoids / Q000737:chemistry*; D007042:Hypoxanthines / Q000737:chemistry; D009566:Nitrates / Q000737:chemistry; D009608:Nitrous Acid / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D014443:Tyrosine / Q000737:chemistry*; D014970:Xanthines / Q000737:chemistry
chemical_list: D005419:Flavonoids; D007042:Hypoxanthines; D009566:Nitrates; D010636:Phenols; D014970:Xanthines; D014443:Tyrosine; D004247:DNA; D009608:Nitrous Acid