In o.1 mol·L^-1 NaHCO3 medium, the chemical reaction of hydrocortisone with superoxide anion O2^.- is studied by voltammetry. Experimental results prove that hydrocortisone, as a scavenger of O2^. -, can catalyze the dismutation reaction of O2^.-. The apparent reaction progression of the catalytic dismutation is zero for O2^.-, but two for hydrocortisone. The equation of rate constant for the catalytic dismutation reaction is deduced, and the apparent rate constant obtained is 8.76×10^5L·mol^-1·s^-1. The result obtained gives new evidence for biomedical research. Besides the indirect inhibition of O2^.- generation by such synthesized glucocorticoids as hydrocortisone suppressing the activity ofphospholipase A2, chemically hydrocortisone can also directly scavenge O2^.- produced. Therefore, the activity of hydrocortisone as an anti - inflammatory drug is ascribed to the combination of its biologic effectiveness and chemical scavenging for O2^.-.

Key words: HYDROCORTISONE, APPARENT, VOLTAMMETRY, GLUCOCORTICOID, DISPROPORTIONATION REACTION, REACTION KINETICS, RADICALS SCAVENGING