A Study on rate constants of free radical scavenging reaction of edaravone and its derivatives
エダラボンとその誘導体のラジカル捕捉の反応速度定数に関する研究
端 邦樹 ; 勝村 庸介; Lin, M.; 室屋 裕佐*; Fu, H.*; 工藤 久明*; 中川 恵一*; 中川 秀彦*
Hata, Kuniki; Katsumura, Yosuke; Lin, M.; Muroya, Yusa*; Fu, H.*; Kudo, Hisaaki*; Nakagawa, Keiichi*; Nakagawa, Hidehiko*
Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) is known as a neuroprotective as well as a radioprotective drug, and some edaravone derivatives are also studied and developed as a radioprotector. These are thought to be due to their potent free radical scavenging activity. Pulse radiolysis technique was performed to examine the reactivity of edaravone and its derivatives (Fig.1) towards OH in aqueous solution. The rate constants of the reaction of some edaravone derivatives with OH were measured by both buildup kinetics and competition method using CO and DMPO (5,5-dimethyl-1-pyrroline-N-oxide) as competitors. The experimental results showed all derivatives were good OH scavengers (10 dmmols). Moreover, the rate constants of derivative No.1 and No.5 by competition method with the DMPO were estimated twice as high as that by buildup kinetics. This might be due to a possible interaction between the pyridine ring and DMPO. The interaction between the derivative and DMPO was also implied by UV spectroscopy. Since the DMPO is widely used as a competitor for the determination of reactivity of antioxidants in an ESR spin trapping method, this result suggests that much care should be paid for using the DMPO, which might induce a certain interaction with the pyridine ring.