金合欢素平衡溶解度、油水分配系数和解离常数的测定

Determination of equilibrium solubility, oil-water partition coefficient and dissociation constant of acacia

目的考察金合欢素的解离常数(pKa)以及不同pH下的平衡溶解度(S)和油水分配系数(lgP O/W)。方法采用紫外分光光度法测定金合欢素在不同pH值缓冲液的平衡溶解度,结合摇瓶法、正辛醇-水系统测定金合欢素的油水分配系数。根据等摩尔浓度分光光度法测定酸碱解离常数的原理,采用紫外分光光度法测定金合欢素的解离常数。结果在pH为2~9条件下,金合欢素S值为6.99~32.06μg/mL、lgP O/W为0.14~0.802,实验测得金合欢素的pKa为(6.25±0.007)。结论紫外分光光度法操作简便,准确性好,可作为金合欢素解离常数、平衡溶解度和油水分配系数测定的方法。

Objective To investigate the dissociation constant(pKa) of acacia and the equilibrium solubility(S) and oil-water partition coefficient(lgP O/W) at different pHs.Methods Determination of the equilibrium solubility of Acacetin in different pH buffers by UV spectrophotometry, combined with shake flask method, n-octanol-water system to determine the oil-water partition coefficient of Acacetin. The principle of the acid-base dissociation constant was determined by spectrophotometry according to the equimolar concentration. The dissociation constant of acacetin was determined by ultraviolet spectrophotometry.Results The equilibrium solubility of acacetin was 6.99~32.06μg/mL and the lgP O/W was 0.14~0.802 under the condition of pH 2~9. The pKa of acacetin was 6.25±0.007.Conclusion Ultraviolet spectrophotometry is easy to operate and has good accuracy. It can be used as a method for determining the dissociation constant, equilibrium solubility and oil-water partition coefficient of acacia.