title: Lanthanide(III) complexes are more active inhibitors of the Fenton reaction than pure ligands.
abstract: OBJECTIVE
  This study is an extension to our finding of direct anti-oxidant activities of lanthanide(III) complexes with the heterocyclic compound, 5-aminoorotic acid (AOA). In this experiment, we used AOA and coumarin-3-carboxylic acid as the two heterocyclic compounds with anti-oxidant potential, to produce the complexes with different lanthanides.
  
  
  METHODS
  Lanthanide(III) complexes were tested on the iron-driven Fenton reaction. The product of this reaction, the hydroxyl radical, was detected by HPLC.
  
  
  RESULTS
  All complexes as well as their ligands had positive or neutral effect on the Fenton reaction but their behavior was different. Both pure ligands in low concentration ratio to iron were inefficient in contrast to some of their complexes. Complexes of neodymium, samarium, gadolinium, and partly of cerium blocked the Fenton reaction at very low ratios (in relation to iron) but the effect disappeared at higher ratios. In contrast, lanthanum complexes appeared to be the most promising. Both blocked the Fenton reaction in a dose-dependent manner.
  
  
  CONCLUSIONS
  Lanthanide(III) complexes were proven to block the iron-driven production of the hydroxyl radical. Second, the lanthanide(III) element appears to be crucial for the anti-oxidant effect. Overall, lanthanum complexes may be promising direct anti-oxidants for future testing.
authors.affiliation: a Department of Pharmacognosy, Faculty of Pharmacy in Hradec Králové , Charles University in Prague , Heyrovského 1203, 500 05 , Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Martin
authors.affiliation: b Department of Pharmacology and Toxicology , Faculty of Pharmacy in Hradec Králové, Charles University in Prague , Heyrovského 1203, 500 05 , Czech Republic.
authors.forename: Přemysl
authors.initials: P
authors.lastname: Mladěnka
authors.affiliation: c Department of Physiology and Pharmacology 'Vittorio Erspamer' , Sapienza University of Rome , Piazzale Aldo Moro 5, 00185 , Italy.
authors.forename: Luciano
authors.initials: L
authors.lastname: Saso
authors.affiliation: d Department of Chemistry , Faculty of Pharmacy, Medical University , 2 Dunav Street, Sofia 1000 , Bulgaria.
authors.forename: Irena
authors.initials: I
authors.lastname: Kostova
mesh_terms: D000975:Antioxidants; D003374:Coumarins / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008024:Ligands; D009963:Orotic Acid / Q000031:analogs & derivatives / Q000737:chemistry
chemical_list: D000975:Antioxidants; D003374:Coumarins; C045076:Fenton's reagent; D028581:Lanthanoid Series Elements; D008024:Ligands; D009963:Orotic Acid; D006861:Hydrogen Peroxide; D007501:Iron; C532756:5-aminoorotic acid; C104227:coumarin-3-carboxylic acid
keywords: 5-Aminoorotic acid; Anti-oxidant; Coumarin-3-carboxylic acid; Iron; Lanthanide(III)