title: Exploration of pro-oxidant and antioxidant activities of the flavonoid myricetin.
abstract: OBJECTIVE
  Flavonoids are ubiquitous phenolic plant metabolites. Many of them are well known for their pro- and antioxidant properties. Myricetin has been reported to be either a potent antioxidant or a pro-oxidant depending on the conditions. The reaction conditions for the pro- and antioxidant activities were therefore investigated using variations of the deoxyribose degradation assay systems.
  
  
  METHODS
  The deoxyribose degradation assay systems were conducted as follows; H(2)O(2)/Fe(III)/ascorbic acid, H(2)O(2)/Fe(III), Fe(III)/ascorbic acid, and Fe(III). Each system was carried out in two variants, FeCl(3) (iron ions added as FeCl(3)) and FeEDTA (iron added in complex with ethylenediaminetetraacetic acid).
  
  
  RESULTS
  When ascorbic acid was present, myricetin showed antioxidant properties, especially when it occurred in complex with iron. In ascorbic acid-free systems, pro-oxidant activities prevailed, which where enhanced if iron was in complex with EDTA.
  
  
  CONCLUSIONS
  Myricetin's antioxidant activity depends on both the reactive oxygen species (ROS) scavenging and iron ions chelation properties. The pro-oxidative properties are caused by reduction of molecular oxygen to ROS and iron(III) to iron(II). Myricetin is able to substitute for ascorbic acid albeit less efficiently.
authors.affiliation: Department of Chemical Ecology and Ecosystem Research, University of Vienna, Vienna, Austria. vladimir.chobot@univie.ac.at
authors.forename: Vladimir
authors.initials: V
authors.lastname: Chobot
authors.forename: Franz
authors.initials: F
authors.lastname: Hadacek
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D001205:Ascorbic Acid / Q000737:chemistry; D002712:Chlorides / Q000737:chemistry; D003855:Deoxyribose / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D005419:Flavonoids / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D015394:Molecular Structure; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D002712:Chlorides; D005290:Ferric Compounds; D005296:Ferrous Compounds; D005419:Flavonoids; D017382:Reactive Oxygen Species; D003855:Deoxyribose; C040015:myricetin; D004492:Edetic Acid; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid; C024555:ferric chloride