氢化可的松催化超氧阴离子歧化及反应动力学

Dismutation of Superoxide Anion Catalyzed by Hydrocortisone and Its Reaction Kinetics

在O.1 mol@L-1NaHCO3介质中,用伏安法研究了超氧阴离子O2@-与糖皮质类甾体氢化可的松的化学反应.实验表明,氢化可的松清除O2@-的化学作用机制为氢化可的松催化O2@-的歧化反应,氢化可的松是O2@-的清除剂.氢化可的松催化O2@-歧化反应的速率对O2@-为零级表观反应,对氢化可的松则为二级表观反应,求得20℃时氢化可的松催化O2@-歧化反应表观速率常数k为8.76×105L@mol-1@s-1.本结果为医学组织研究结果提供了新的实验证据.在抗炎作用方面,氢化可的松除抑制磷脂酶A2的活性从而间接阻止O2@-的产生外,还能直接化学清除产生的O2@-,认为氢化可的松的抗炎作用应是这种生物的和化学的综合作用结果.

In 0.1 mol . L-1 NaHCO3 medium, the chemical reaction of hydrocortisone with superoxide anion O-2(.-) is studied by voltammetry. Experimental results prove that hydrocortisone, as a scavenger of O-2(.-), can catalyze the dismutation reaction of O-2(.-). The apparent reaction progression of the catalytic dismutation is zero for O-2(.-), but two for hydrocortisone. The equation of rate constant for the catalytic dismutation reaction is deduced, and the apparent rate constant obtained is 8.76 x 10(5) L . mol(-1) . s(-1). The result obtained gives new evidence for biomedical research. Besides the indirect inhibition of O-2(.-) generation by such synthesized glucocorticoids as hydrocortisone suppressing the activity of phospholipase A(2), chemically hydrocortisone can also directly scavenge O-2(.-) produced. Therefore, the activity of hydrocortisone as an anti - inflammatory drug is ascribed to the combination of its biologic effectiveness and chemical scavenging for O-2(.-).