Determination of Equilibrium Solubility and Apparent Oil-water Partition Coefficients of Nicotinate-curcu-min Ester / 中国药师

ABSTRACT

Objective:To determine the equilibrium solubility and the apparent oil/water partition coefficients of nicotinate-curcu-min ester,so as to provide basis for the new formula design. Methods:Nicotinate-curcumin ester was dissolved in buffer solution with pH of 1.2-7.8. HPLC was used to detect the equilibrium solubility of nicotinate-curcumin ester in various solutions. The apparent oil/water partition coefficients in octanol-water and octanol-buffer solution system were measured by a shaking-flask method. Results:The solubility of nicotinate-curcumin ester in pH 6.8 was the highest. The apparent oil-water partition coefficients of nicotinate-curcumin ester in pH 1.2,5.8,6.5 and 7.8 were lgPapvalues within the range(lgPap=1.69-1.98) beneficial to the absorption in vivo. But in pH 2,5 and 6.8,the lgPapvalues were greater than 2 with strong lipophilicity. Conclusion:The equilibrium solubility as well as ap-parent oil/water partition coefficients of nicotinate-curcumin ester is greatly influenced by the pH value of media. In the pH value with relatively high solubility,lipophilicity is stronger,suggesting it is difficult to be absorbed by the body and needs to be further studied on dosage forms.