Supercritical carbon dioxide treatment as a method for polymorph preparation of deoxycholic acid

A new polymorph of deoxycholic acid (DCA) was formed by using a supercritical carbon dioxide treatment. Deoxycholic acid crystals were stored in a pressure vessel purged with carbon dioxide at 12 MPa, 60degreesC for definite intervals. After storage for I h in supercritical carbon dioxide (SC-CO2), new X-ray diffraction (XRD) peaks, not found in the bulk DCA crystal, were observed at 2theta = 7.4degrees, 9.7degrees and 14.0degrees. The intensities of the new diffraction peaks increased with an increase in storage time, whereas the intensities of the diffraction peaks due to bulk DCA crystal decreased. On the DSC curves, the crystals obtained showed an exothermic peak at around 155 degreesC followed by the melting peak of bulk DCA crystal at 175 degreesC. By the temperature-control led powder XRD measurement, the crystals obtained were found to be a metastable form of DCA. The polymorphs of DCA have not been reported; therefore, the SC-CO2 treatment would be a peculiar method to obtain a DCA polymorph. (C) 2003 Elsevier B.V. All rights reserved.