Dismutation of superoxide anion catalyzed by hydrocortisone and its reaction kinetics

In 0.1 mol . L-1 NaHCO3 medium, the chemical reaction of hydrocortisone wit h superoxide anion O-2(.-) is studied by voltammetry. Experimental results prove that hydrocortisone, as a scavenger of O-2(.-), can catalyze the dism utation reaction of O-2(.-). The apparent reaction progression of the catal ytic dismutation is zero for O-2(.-), but two for hydrocortisone. The equat ion 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). T he result obtained gives new evidence for biomedical research. Besides the indirect inhibition of O-2(.-) generation by such synthesized glucocorticoi ds as hydrocortisone suppressing the activity of phospholipase A(2), chemic ally 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 fo r O-2(.-).