title: Iron-chelating agents never suppress Fenton reaction but participate in quenching spin-trapped radicals.
abstract: Hydroxyl radical formation by Fenton reaction in the presence of an iron-chelating agent such as EDTA was traced by two different assay methods; an electron spin resonance (ESR) spin-trapping method with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and high Performance liquid chromatography (HPLC)-fluorescence detection with terephthalic acid (TPA), a fluorescent probe for hydroxyl radicals. From the ESR spin-trapping measurement, it was observed that EDTA seemed to suppress hydroxyl radical formation with the increase of its concentration. On the other hand, hydroxyl radical formation by Fenton reaction was not affected by EDTA monitored by HPLC assay. Similar inconsistent effects of other iron-chelating agents such as nitrylotriacetic acid (NTA), diethylenetriamine penta acetic acid (DTPA), oxalate and citrate were also observed. On the addition of EDTA solution to the reaction mixture 10 min after the Fenton reaction started, when hydroxyl radical formation should have almost ceased but the ESR signal of DMPO-OH radicals could be detected, it was observed that the DMPO-OH* signal disappeared rapidly. With the simultaneous addition of Fe(II) solution and EDTA after the Fenton reaction ceased, the DMPO-OH* signal disappeared more rapidly. The results indicated that these chelating agents should enhance the quenching of [DMPO-OH]* radicals by Fe(II), but they did not suppress Fenton reaction by forming chelates with iron ions.
authors.affiliation: Kyoritsu University of Pharmacy, 1-5-30 Shibakoen, Minato, Tokyo 105-8512, Japan.
authors.forename: Linxiang
authors.initials: L
authors.lastname: Li
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Abe
authors.forename: Kiyotada
authors.initials: K
authors.lastname: Kanagawa
authors.forename: Tomoko
authors.initials: T
authors.lastname: Shoji
authors.forename: Tadahiko
authors.initials: T
authors.lastname: Mashino
authors.forename: Masataka
authors.initials: M
authors.lastname: Mochizuki
authors.forename: Miho
authors.initials: M
authors.lastname: Tanaka
authors.forename: Naoki
authors.initials: N
authors.lastname: Miyata
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003497:Cyclic N-Oxides / Q000737:chemistry; D004492:Edetic Acid / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005453:Fluorescence; D016166:Free Radical Scavengers / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000138:chemical synthesis*; D007501:Iron / Q000737:chemistry*; D007502:Iron Chelating Agents / Q000737:chemistry*; D010795:Phthalic Acids / Q000737:chemistry; D013113:Spin Labels
chemical_list: D003497:Cyclic N-Oxides; C045076:Fenton's reagent; D016166:Free Radical Scavengers; D007502:Iron Chelating Agents; D010795:Phthalic Acids; D013113:Spin Labels; D017665:Hydroxyl Radical; C011363:terephthalic acid; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D004492:Edetic Acid; D006861:Hydrogen Peroxide; D007501:Iron