Mechanism and kinetics for scavenging superoxide anion by progesterone

The chemical reaction of progesterone with superoxide anion O.-2 in 0.1 mol/L NaHCO3 medium is studied by polarography. Differing from the indirect inhibition of O.-2 generation by synthesized glucocorticoids in mechanism, the function that progesterone scavenges O.-2 is ascribed to that O.-2 directly oxidizes the C == C double bond conjugated with the carbonyl moiety of progesterone molecule to a free radical, and then is reduced to H2O2. The result obtained in this work gives new evidence for biomedical research. The equation of rate constant of the oxidization reaction is deduced, and the apparent rate constant obtained is 308 L·mol-1·s-1.