黄芩苷在不同pH值缓冲液中理化常数的测定

Physicochemical properties of baicalin in different pH phosphate buffer solutions

目的考察黄芩苷在不同pH值中的平衡溶解度与表观油水分配系数,为制剂研究奠定基础。方法采用摇瓶-紫外分光光度法测定温度为25和37℃时,黄芩苷在不同pH值磷酸盐缓冲溶液中的平衡溶解度及在正辛醇/缓冲液体系中的表观油水分配系数。结果 25℃时,黄芩苷在pH=2.0,3.0,4.0,5.0,6.0,6.8,7.4,8.0和9.0缓冲液中的平衡溶解度分别为0.032,0.034,0.119,0.873,3.329,12.96,11.49,4.605和11.87mg.mL-1,相应条件下表观油水分配系数(P)值分别为0.363,0.244,0.292,0.137,0.057,0.046,0.036,0.028和0.029。37℃时,黄芩苷在pH=2.0,3.0,4.0,5.0,6.0,6.8,7.4,8.0和9.0缓冲液中的平衡溶解度分别为0.028,0.048,0.095,0.950,4.881,14.15,26.65,14.48和17.89mg.mL-1,相应条件下表观油水分配系数(P)值分别为0.234,0.224,0.365,0.103,0.074,0.049,0.034,0.034和0.035。结论黄芩苷的平衡溶解度在酸性及中性条件下受温度影响很小,在碱性条件下随着温度升高而增加;黄芩苷在酸性条件下的P值比在碱性条件下大,Pmax=0.363(T=25℃,pH=2),Pmax=0.365(T=37℃,pH=4),随着碱性的增加P值变化不明显,且温度对黄芩苷的P值几乎无影响。

Objective To determine the equilibrium solubility of baicalin in different pH phosphate buffer solutions,to determine its apparent partition coefficient for the n-octanol/buffer solution systems in different pH value,and to lay the foundation for further pharmaceutical research.Method A shake flask-ultraviolet spectrophotometry method was applied to measure the equilibrium solubility and partition coefficient of baicalin with temperature of 25 and 37 ℃.Result At 25 ℃,the equilibrium solubility of baicalin were 0.032,0.034,0.119,0.873,3.329,12.96,11.49,4.605 and 11.87 mg·mL^-1 in buffer solutions with pH values of 2.0,3.0,4.0,5.0,6.0,6.8,7.4,8.0 and 9.0,respectively.The oil/water partition coefficient（P） of baicalin were 0.363,0.244,0.292,0.137,0.057,0.046,0.036,0.028 and 0.029 in buffer solutions with different pH values.At 37 ℃,the equilibrium solubility of baicalin were 0.028,0.048,0.095,0.950,4.881,14.15,26.65,14.48 and 17.89 mg·mL^-1 in buffer solutions with pH values of 2.0,3.0,4.0,5.0,6.0,6.8,7.4,8.0 and 9.0,respectively.The oil/water partition coefficient（P） of baicalin were 0.234,0.224,0.365,0.103,0.074,0.049,0.034,0.034 and 0.035 in buffer solutions with different pH values.Conclusion The equilibrium solubility of baicalin was little affected by temperature in acidic and neutral environment while it was increased with the increasing of temperature under alkaline condition.The apparent oil/water partition coefficient（P） of baicalin was higher in acidic environment than in alkaline environment.Pmax=0.363（T=25 ℃,pH=2）,Pmax=0.365（T=37 ℃,pH=4）.The difference of apparent oil/water partition coefficient（P） were not obvious with the increasing of pH values.On the other hand,partition coefficient was little influenced by temperature.