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

Lin, M.; Katsumura, Yosuke; Hata, Kuniki ; Muroya, Yusa*; Nakagawa, Keiichi*

The reactions between edaravone and various one-electron oxidants such as OH, N, Br, and SO radical have been studied by pulse radiolysis techniques. The transient species produced by the reaction of edaravone with OH radical shows an absorption band with = 320 nm, while the oxidation by N, Br, SO and CClOO results in an absorption band with = 345 nm. Different from the previous reports, the main transient species by the reaction of edaravone with OH radical in the absence of O is attributed to OH-adducts. At neutral condition (pH 7), the rate constants of edaravone reacting with OH, N, SO, CClOO, and are estimated to be 8.510, 5.810, 610, 5.010 and 2.410 dm mols, respectively. From the pH dependence on the formation of electron adducts and on the rate constant of edaravone with hydrated electron, the pKa of edaravone is estimated to be 6.90.1.