title: Reduction in free-radical-induced DNA strand breaks and base damage through fast chemical repair by flavonoids.
abstract: This paper provides evidence that dietary flavonoids can repair a range of oxidative radical damages on DNA, and thus give protection against radical-induced strand breaks and base alterations. We have irradiated dilute aqueous solutions of plasmid DNA in the absence and presence of flavonoids (F) in a "constant *OH radical scavenging environment", k of 1.5 x 10(7) s(-1) by decreasing the concentration of TRIS buffer in relation to the concentration of added flavonoids. We have shown that the flavonoids can reduce the incidence of single-strand breaks in double-stranded DNA as well as residual base damage (assayed as additional single-strand breaks upon post-irradiation incubation with endonucleases) with dose modification factors of up to 2.0+/-0.2 at [F] < 100 microM by a mechanism other than through direct scavenging of *OH radicals. Pulse radiolysis measurements support the mechanism of electron transfer or H* atom transfer from the flavonoids to free radical sites on DNA which result in the fast chemical repair of some of the oxidative damage on DNA resulting from *OH radical attack. These in vitro assays point to a possible additional role for antioxidants in reducing DNA damage.
authors.affiliation: Department of Chemistry, The University of Auckland, New Zealand. r.anderson@auckland.ac.nz
authors.forename: R F
authors.initials: RF
authors.lastname: Anderson
authors.forename: C
authors.initials: C
authors.lastname: Amarasinghe
authors.forename: L J
authors.initials: LJ
authors.lastname: Fisher
authors.forename: W B
authors.initials: WB
authors.lastname: Mak
authors.forename: J E
authors.initials: JE
authors.lastname: Packer
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D002392:Catechin / Q000494:pharmacology; D004249:DNA Damage; D004032:Diet; D005419:Flavonoids / Q000494:pharmacology*; D016166:Free Radical Scavengers / Q000494:pharmacology; D005609:Free Radicals / Q000633:toxicity; D006801:Humans; D066298:In Vitro Techniques; D010957:Plasmids / Q000187:drug effects
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D016166:Free Radical Scavengers; D005609:Free Radicals; D002392:Catechin