Pulse radiolysis study on free radical scavenger edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one)

• Published in: Journal of photochemistry and photobiology. B, Biology Vol. 89; no. 1; pp. 36 - 43
• Main Authors: Lin, Mingzhang, Katsumura, Yosuke, Hata, Kuniki, Muroya, Yusa, Nakagawa, Keichi
• Format: Journal Article
• Language: English
• Published: Switzerland Elsevier B.V 12.11.2007
• Subjects: Absorption; Antioxidant; Antipyrine - analogs & derivatives; Antipyrine - chemistry; Edaravone; Free radical; Free Radical Scavengers - chemistry; Free Radicals - chemistry; Hydrogen-Ion Concentration; Kinetics; Oxidation-Reduction; Pulse Radiolysis; Radiation therapy; Edaravone; Radiation therapy; Antioxidant; Pulse radiolysis; Free radical
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2007.08.001

The reactions between edaravone and various one-electron oxidants such as OH, N 3 , Br 2 - , and SO 4 - , have been studied by pulse radiolysis techniques. The transient species produced by the reaction of edaravone with OH radical shows an absorption band with λ max = 320 nm, while the oxidation by N 3 , Br 2 - , SO 4 - and CCl 3OO results in an absorption band with λ max = 345 nm. Different from the previous reports, the main transient species by the reaction of edaravone with OH radical in the absence of O 2 is attributed to OH-adducts. At neutral condition (pH 7), the rate constants of edaravone reacting with OH, N 3 , SO 4 - , CCl 3OO , and e aq - are estimated to be 8.5 × 10 9, 5.8 × 10 9, 6 × 10 8, 5.0 × 10 8 and 2.4 × 10 9 dm 3 mol −1 s −1, respectively. From the pH dependence on the formation of electron adducts and on the rate constant of edaravone with hydrated electron, the p K a of edaravone is estimated to be 6.9 ± 0.1.