title: In vitro analysis of iron chelating activity of flavonoids.
abstract: Flavonoids have been demonstrated to possess miscellaneous health benefits which are, at least partly, associated with iron chelation. In this in vitro study, 26 flavonoids from different subclasses were analyzed for their iron chelating activity and stability of the formed complexes in four patho/physiologically relevant pH conditions (4.5, 5.5, 6.8, and 7.5) and compared with clinically used iron chelator deferoxamine. The study demonstrated that the most effective iron binding site of flavonoids represents 6,7-dihydroxy structure. This site is incorporated in baicalein structure which formed, similarly to deferoxamine, the complexes with iron in the stoichiometry 1:1 and was not inferior in all tested pH to deferoxamine. The 3-hydroxy-4-keto conformation together with 2,3-double bond and the catecholic B ring were associated with a substantial iron chelation although the latter did not play an essential role at more acidic conditions. In agreement, quercetin and myricetin possessing all three structural requirements were similarly active to baicalein or deferoxamine at the neutral conditions, but were clearly less active in lower pH. The 5-hydroxy-4-keto site was less efficient and the complexes of iron in this site were not stable at the acidic conditions. Isolated keto, hydroxyl, methoxyl groups or an ortho methoxy-hydroxy groups were not associated with iron chelation at all.
authors: Department of Pharmacology and Toxicology, Faculty of Pharmacy in Hradec Králové, Charles University in Prague, Hradec Králové, Czech Republic. mladenkap@faf.cuni.cz
authors: Přemysl
authors: P
authors: Mladěnka
authors: Kateřina
authors: K
authors: Macáková
authors: Tomáš
authors: T
authors: Filipský
authors: Libuše
authors: L
authors: Zatloukalová
authors: Luděk
authors: L
authors: Jahodář
authors: Paolo
authors: P
authors: Bovicelli
authors: Ilaria Proietti
authors: IP
authors: Silvestri
authors: Radomír
authors: R
authors: Hrdina
authors: Luciano
authors: L
authors: Saso
mesh_terms: D001665:Binding Sites; D003676:Deferoxamine / Q000737:chemistry; D044950:Flavanones / Q000737:chemistry; D047309:Flavones / Q000737:chemistry; D005419:Flavonoids / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007502:Iron Chelating Agents / Q000737:chemistry*; D007529:Isoflavones / Q000737:chemistry; D013329:Structure-Activity Relationship
chemical_list: D044950:Flavanones; D047309:Flavones; D005419:Flavonoids; D007502:Iron Chelating Agents; D007529:Isoflavones; C004742:daidzein; C059353:7-hydroxyflavanone; D003676:Deferoxamine; C043562:flavone