岩白菜素理化性质的研究

Studies on the Physicochemical Properties of Bergenin

目的研究岩白菜素的理化性质。方法通过X-射线粉末衍射(powder X-ray diffraction patterns,PXRD),差示扫描量热分析(differential scanning calorimetry,DSC),热重量分析法(thermogravimetric analysis,TGA),吸湿性实验以及湿、热稳定性实验研究岩白菜素的固态理化性质;在不同pH、不同温度条件下研究岩白菜素的溶解度;采用非水滴定法测定解离常数pKa;采用正辛醇-水系统测定岩白菜素的表观油/水分配系数。结果PXRD研究结果表明,岩白菜素在溶解过程以及潮湿环境下均未发生晶型转变;DSC,TGA研究结果表明,岩白菜素为一水合物;在湿热条件下该药能稳定存在;其水中溶解度较低,解离常数为pKa1(5.46±0.13)和pKa2(5.74±0.18),为极弱酸;表观油/水分配系数具有pH依赖性,但亲脂性较差。结论本实验确定了岩白菜素的主要理化性质,有利于其生物药剂学的研究以及新剂型的开发。

OBJECTIVE To investigate the physicochemical properties ofbergenin. METHODS Bergenin was characterized by powder X-ray diffraction （PXRD）, differential scanning calorimetry （DSC）, thermogravimetric analysis （TGA）, moisture sorption and solid state stability studies. Solubilities were determined at different pHs and different temperatures. Dissociation constant （pKa） was investigated using non-aqueous titration and partition coefficient was studied with n-octanol-buffers system. RESULTS PXRD showed the crystalline ofbergenin did not change in the solution process and under the humidity conditions, and DSC, TGA showed it was monohydrate. Bergenin was stable under the humidity and high temperature. The solubilities in buffers were poor. Dissociation constants were （5.46±0.13） of pKa1 and （5.74± 0.18 ） of pKa2, suggesting bergenin was a very weak acid. The partition coefficients were pH dependent and its lipophilicity was poor. CONCLUSION The present study revealed the physicochemical properties of bergenin. These results will be of significance for the investigation of biopharmaceutics and the development of new formulations of bergenin.