Stability of Corticosteroids in Aqueous Solutions1

Abstract

Aqueous solutions of cortisol were spontaneously oxidized to 21-dehydrocortisol. In pH 9.1 carbonate buffer, conversion rates of 1.6-2.8% hr. were obtained; slower rates occurred at lower pH values. Rate of spontaneous oxidation was diminished by scrupulous attention to cleanliness of reagents and glassware, by addition of EDTA, or by the presence of high concentrations of plasma or plasma protein fractions. Other 17a-hydroxycorticosteroids were oxidized at the same rate as cortisol, but 17a-deoxysteroids were oxidized at a slower rate. The proportion of cortisol oxidized increased with decreasing cortisol concentration. Rate of oxidation increased as incubation temperature was raised from 3 to 37 C.