Okonogi S, Puttipipatkhachorn S, Yamamoto K
Faculty of Pharmacy, Chiang Mai University, Thailand.
Drug Dev Ind Pharm. 2001 Sep;27(8):819-23. doi: 10.1081/ddc-100107245.
The objective of this study was to clarify the thermal behavior of ursodeoxycholic acid (UDCA) in mixtures with urea. Physical mixtures of UDCA and urea in various ratios were prepared, and the thermal analysis of these sample mixtures was investigated using conventional differential scanning calorimetry (DSC) and variable-temperature powder X-ray diffractometry (VTXRD). The hot-stage microscopy (HSM) and powder X-ray diffractometry (PXRD) were used as complementary techniques. From the DSC results of all sample mixtures, it was found that there was no endothermic peak at the melting temperature of intact UDCA crystals. The DSC thermograms of each ratio showed only the endothermic peak at about 136 degrees C due to the melt of urea and the anomalous endothermic peak at about 155 degrees C 157 degrees C. The VTXRD study revealed that the crystals of urea completely disappeared at a temperature of 140 degrees C. At this temperature, it was identified that the VTXRD pattern obtained was of UDCA crystals. The crystalline peaks gradually decreased in intensity at a temperature of 150 degrees C When the temperature was up to 160 degrees C, the identical crystalline peaks of UDCA crystals completely disappeared. It was concluded that the anomalous endothermic peak at 155 degrees C-157 degrees C was the peak due to the dissolution of UDCA crystals in the surrounding melted urea.
本研究的目的是阐明熊去氧胆酸（UDCA）与尿素混合物的热行为。制备了不同比例的UDCA与尿素的物理混合物，并使用常规差示扫描量热法（DSC）和变温粉末X射线衍射法（VTXRD）对这些样品混合物进行热分析。热台显微镜（HSM）和粉末X射线衍射法（PXRD）用作补充技术。从所有样品混合物的DSC结果发现，完整UDCA晶体的熔点处没有吸热峰。每个比例的DSC热谱图仅显示由于尿素熔化在约136℃处的吸热峰以及在约155℃至157℃处的异常吸热峰。VTXRD研究表明，尿素晶体在140℃时完全消失。在此温度下，确定获得的VTXRD图谱是UDCA晶体的图谱。在150℃时结晶峰强度逐渐降低。当温度升至160℃时，UDCA晶体相同的结晶峰完全消失。得出的结论是，155℃至157℃处的异常吸热峰是由于UDCA晶体在周围熔化的尿素中溶解所致的峰。
