title: Effects of flavonoids and vitamin C on oxidative DNA damage to human lymphocytes.
abstract: This study assessed the antioxidant potencies of several widespread dietary flavonoids across a range of concentrations and compared with vitamin C as a positive control. The antioxidant effects of pretreatment with flavonoids and vitamin C, at standardized concentrations (7.6, 23.2, 93, and 279.4 micromol/L), on oxygen radical-generated DNA damage from hydrogen peroxide (100 micromol/L) in human lymphocytes were examined by using the single-cell gel electrophoresis assay (comet assay). Pretreatment with all flavonoids and vitamin C produced dose-dependent reductions in oxidative DNA damage. At a concentration of 279 micromol/L, they were ranked in decreasing order of potency as follows: luteolin (9% of damage from unopposed hydrogen peroxide), myricetin (10%), quercetin (22%), kaempferol (32%), quercitrin (quercetin-3-L-rhamnoside) (45%), apigenin (59%), quercetin-3-glucoside (62%), rutin (quercetin-3-beta-D-rutinoside) (82%), and vitamin C (78%). The protective effect of vitamin C against DNA damage at this concentration was significantly less than that of all the flavonoids except apigenin, quercetin-3-glucoside, and rutin. The ranking was similar with estimated ED50 (concentration to produce 50% protection) values. The protective effect of quercetin and vitamin C at a concentration of 23.2 micromol/L was found to be additive (quercetin: 71% of maximal DNA damage from unopposed hydrogen peroxide; vitamin C: 83%; both in combination: 62%). These data suggest that the free flavonoids are more protective than the conjugated flavonoids (eg, quercetin compared with its conjugate quercetin-3-glucoside, P < 0.001). Data are also consistent with the hypothesis that antioxidant activity of free flavonoids is related to the number and position of hydroxyl groups.
authors.affiliation: Department of Human Nutrition, Glasgow University, Royal Infirmary, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Noroozi
authors.forename: W J
authors.initials: WJ
authors.lastname: Angerson
authors.forename: M E
authors.initials: ME
authors.lastname: Lean
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000145:classification / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D004249:DNA Damage / Q000187:drug effects*; D004032:Diet; D004305:Dose-Response Relationship, Drug; D004586:Electrophoresis; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D044949:Kaempferols; D008214:Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D011794:Quercetin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D044949:Kaempferols; C006552:kaempferol; D011794:Quercetin; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid