Preparation and in vitro properties of oleanolic acid hemiphthalate disodium-hydroxypropylmethylcellulose acetate succinate microspheres

Purpose: To prepare oleanolic acid hemiphthalate disodium (OAHPDS)-hydroxypropylmethyl-cellulose acetate succinate (HPMCAS) microspheres and investigate their in vitro properties. Methods: The OAHPDS-HPMCAS microspheres were prepared by the emulsionsolvent evaporation method, and the in vitro drug release profiles of the microspheres were determined. DSC, XRPD, FTIR and SEM measurements were performed to characterize the physicochemical properties of the microspheres. Results: All the microspheres prepared exhibited perfect enteric dissolution. The XRPD results showed that the drug dispersed in the microspheres in the amorphous state. The DSC and FTIR measurements revealed the formation of hydrogen bonds between the drug and the polymer molecules. The initial drug/polymer ratio and the morphology (related to the evaporation pressure) of the microspheres may affect drug release profiles in acidic medium. Conclusion: Enteric OAHPDS-HPMCAS microspheres were prepared successfully by the emulsion-solvent evaporation method. The drug within microspheres played the role of “plasticizer”, becoming inserted between the glucose chains of HPMCAS and promoted the immigration of the glucose chain. The evaporation pressure affected the microsphere surface morphology and influenced the acidic release. The investigation revealed that HPMCAS microspheres can be used as an ideal carrier for the delayed release of drugs in the small intestine.