Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Deflazacort (DFZ) is an oxazoline derivative of prednisolone with anti-inflammatory and immunosuppressive activity. The aim of this study was to investigate and to identify the main degradation product of DFZ, and to evaluate the anti-inflammatory effect of both DFZ and its major degradation product (namely DDP1). DFZ was subjected to alkaline and acid degradation. In 0.1 N NaOH, DFZ was immediately degraded and 99.0% of product DDP1 was detected by high performance liquid chromatography (HPLC). The HPLC method was ideal to separate the primary and other minor degradation products and was carried out using C-18 column, mobile phase consisting of water: acetonitrile: (60:40, v/v) with flow rate of 1.0 mL/min and detection at 244 nm. DDP1 was isolated and identified as 21-hydroxy deflazacort (21-OH-DFZ) by NMR, IR and LCMS. The in vivo pharmacological assays showed that both DFZ as 21-OH-DFZ are active in in vivo and in vitro inflammatory models, but 21-OH-DFZ is more potent than DFZ.676495499Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)