HPLC-荧光法测定土大黄苷平衡溶解度和油水分配系数

Determination of the equilibrium solubility of rhaponticin and oil-water apparent partition coefficients using HPLC-fluorometric method

目的建立测定土大黄苷平衡溶解度和油水分配系数的高效液相色谱(HPLC)-荧光法。方法采用SHIMPACK VP-ODS色谱柱;以甲醇-水(40∶60)为流动相,流速为0.8mL/min;进样量为10μL;激发波长为320nm,发射波长为410nm,测定土大黄苷在37℃水和不同pH值介质中的平衡溶解度以及在正辛醇-水、正辛醇-缓冲溶液体系中的油水分配系数。结果在37℃条件下,土大黄苷在水中的平衡溶解度为109.54mg/L;在pH为8.0时溶解度最大,为126.12mg/L;土大黄苷在正辛醇-水中的油水分配系数logP值为0.53;在pH为6.0的缓冲溶液中油水分配系数最大,logP为0.76。结论本研究建立了HPLC-荧光检测法,成功应用于测定土大黄苷平衡溶解度和油水分配系数,为土大黄苷剂型的开发及药代动力学研究提供了理论依据。

Objective To determine the equilibrium solubility and the oil-water partition coefficients of rhaponticin by HPLC-fluorometric method. Methods Separation was achieved on SHIM-PACK VP-ODS column. The mobile phase consisted of methanol-water （40∶60） with a flow rate of 0.8mL/min, detection with a fluorometric detector set at an excitation wavelength of 320nm and emission wavelength of 410nm. The equilibrium solubility at 37℃ in water and in series of buffer solutions with different pH, and oil-water partition coefficients （logP） in the octanol-water/the buffer solution system of rhaponticin were determined in the above conditions. Results The equilibrium solubility of rhaponticin in water was 109.54mg/L at 37℃ and exhibited a maximum solubility of 126.12mg/L at pH 8.0; the partition coefficient of rhaponticin was 0.53 in n-octanol-water system and the maximum partition coefficient was 0.76 in n-octanol-buffer solution system at pH 6.0. Conclusion A HPLC-fluorometric method was developed, and the method was successfully applied to determine the equilibrium solubility and oil-water partition coefficients of rhaponticin. The research results can provide the theoretical basis for development and pharmacokinetic studies of rhaponticin dosage form.