title: Iron and copper chelation by flavonoids: an electrospray mass spectrometry study.
abstract: Flavonoids are well known as effective free radical scavengers exhibiting therefore an antioxidant behaviour. Another antioxidant mechanism however may result from the ability they have to chelate metal ions, rendering them inactive to participate in free radical generating reactions. Electrospray mass spectrometry has been used to study metal ion interactions with a set of flavonoids from different classes. Complexes with a range of stoichiometries, of metal: flavonoid, 1:1, 1:2, 2:2, 2:3 have been observed. The stoichiometry 1:2 is in general the preferred one. It is established for flavones and for the flavanone naringenin that the binding metal sites are preferentially at the 5-hydroxyl and 4-oxo groups. Redox reactions are also observed through the change of the oxidation state of the metal, jointly with the oxidation of the flavonoid by loss of hydrogen. Structures of the oxidized species of some flavonoids are proposed.
authors.affiliation: Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Edifício C8, 1749-016 Lisbon, Portugal. terezaf@fc.ul.pt
authors.forename: M Tereza
authors.initials: MT
authors.lastname: Fernandez
authors.forename: M Lurdes
authors.initials: ML
authors.lastname: Mira
authors.forename: M Helena
authors.initials: MH
authors.lastname: Florêncio
authors.forename: Keith R
authors.initials: KR
authors.lastname: Jennings
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000494:pharmacology; D002614:Chelating Agents / Q000737:chemistry* / Q000494:pharmacology*; D003300:Copper / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry* / Q000494:pharmacology*; D007502:Iron Chelating Agents / Q000737:chemistry* / Q000494:pharmacology*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000975:Antioxidants; D002614:Chelating Agents; D005419:Flavonoids; D007502:Iron Chelating Agents; D003300:Copper