title: Iron reduction potentiates hydroxyl radical formation only in flavonols.
abstract: Flavonoids, substantial components of the human diet, are generally considered to be beneficial. However, they may possess possible pro-oxidative effects, which could be based on their reducing potential. The aims of this study were to evaluate the ability of 26 flavonoids to reduce ferric ions at relevant pH conditions and to find a possible relationship with potentiation of hydroxyl radical production. A substantial ferric ions reduction was achieved under acidic conditions, particularly by flavonols and flavanols with the catecholic ring B. Apparently corresponding bell-shaped curves displaying the pro-oxidant effect of flavonols quercetin and kaempferol on iron-based Fenton reaction were documented. Several flavonoids were efficient antioxidants at very low concentrations but rather inefficient or pro-oxidative at higher concentrations. Flavonols, morin and rutin were progressively pro-oxidant, while 7-hydroxyflavone and hesperetin were the only flavonoids with dose-dependent inhibition of hydroxyl radical production. Conclusively, administration of flavonoids may lead to unpredictable consequences with few exceptions.
authors.affiliation: Department of Pharmaceutical Botany and Ecology, Faculty of Pharmacy in Hradec Králové, Charles University in Prague, Heyrovského 1203, 500 05 Hradec Králové, Czech Republic.
authors.forename: Kateřina
authors.initials: K
authors.lastname: Macáková
authors.forename: Přemysl
authors.initials: P
authors.lastname: Mladěnka
authors.forename: Tomáš
authors.initials: T
authors.lastname: Filipský
authors.forename: Michal
authors.initials: M
authors.lastname: Říha
authors.forename: Luděk
authors.initials: L
authors.lastname: Jahodář
authors.forename: František
authors.initials: F
authors.lastname: Trejtnar
authors.forename: Paolo
authors.initials: P
authors.lastname: Bovicelli
authors.forename: Ilaria
authors.initials: I
authors.lastname: Proietti Silvestri
authors.forename: Radomír
authors.initials: R
authors.lastname: Hrdina
authors.forename: Luciano
authors.initials: L
authors.lastname: Saso
mesh_terms: D044948:Flavonols / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction
chemical_list: D044948:Flavonols; D017665:Hydroxyl Radical; D007501:Iron