灯盏花乙素解离常数的测定

Determination of Dissociation Constants of Scutellarin

采用紫外分光光度法测定灯盏花乙素解离常数pK_a值.将灯盏花乙素溶于一系列pH值磷酸缓冲盐溶液中,选择合适波长测定吸光度并计算其pK_a值.结果表明:灯盏花乙素在一系列pH值缓冲盐溶液中表现为二次解离,在pH值5.86～8.62的缓冲盐溶液中,选择335、385和395 nm作为测定波长,计算得到pK_(a1)为7.77;在pH值8.78～12.28的缓冲盐溶液中,选择260、320和330 nm作为测定波长,计算得到pK_(a2)为10.19.研究结果为预测灯盏花乙素的吸收、分布、代谢和排泄等奠定了理论基础.

The dissociation constants of scutellarin were determined using ultraviolet spectrometry. Scutellarin was dissolved in phosphate buffer solutions （PBS） of different pH values, and the pK,values were calculated according to the measured absorbances of the solutions. The results showed that scutellarin dissociated in PBS solutions of different pH ranges. The pKa1 value was found to be 7. 77 in PBS solutions at pH range of 5. 86-8. 62 using wavelengths 335, 385 and 395 nm for the determination, and the pKa2 value was found to be 10. 19 in PBS solutions at pH range of 8. 78-12. 28 using wavelengths 260, 320 and 330 nm for the determination. This study lay the foundation for the investigations of absorption, distribution, metabolism and excretion of the drug.