OXIDATIVE-DEGRADATION OF ANTIFLAMMIN-2

Purpose. To study the oxidation of the methionine residue of antiflamm in 2 (HDMNKVLDL, AF2) as a function of pH, buffer concentration, ionic strength, and temperature using different concentrations of hydrogen peroxide and to determine the accessibility of methionine residue to o xidation. Methods. Reversed-phase high-performance liquid chromatograp hy (RPHPLC) was used as the main analytical method in determining the oxidation rates of AF2. Calibration curves for AF2 and the oxidation p roduct, methionine sulfoxide of AF2 (Met(O)-3-AF2), were constructed f or each measurement using standard materials. Fast Atom Bombardment Ma ss Spectroscopy (FABMS) was used to characterize the product. Results. Met(O)-3-AF2 was the only oxidation product detected at pH 3.0 to 8.0 . The oxidation rates were independent of buffer concentrations, ionic strength, and pH from 3.0 to 7.0. However, there was an acceleration of the rates at basic pHs, and small amounts of degradation products o ther than Met(O)-3-AF2 were observed in this alkaline region. Conclusi ons. Oxidation of methionine in AF2 does not cause the biological inac tivation reported by other laboratories since this drug is relatively stable under neutral conditions in the absence of oxiding agent.