人血清白蛋白与手性药物相互作用的毛细管电泳研究Ⅱ.药物对映体竞争结合参数的测定

Albumin-Drug Binding Study by Capillary Electrophoresis Ⅱ. Determination of Drug Enantiomeric Binding Constants

运用毛细管电泳（CE）技术，在对碱性药物Verapamil（VER）手性拆分的基础上对Verapamil与人血清白蛋白（HSA）平行体系进行了相互作用研究。通过定量HSA－VER体系中VER对映体的浓度，建立对映体对结合位点竞争的理论方程，获得了R和S型药物对映体与HSA的结合常数，其值分别为K（R）-VER=2．7×103×（±4．4×102）和K（S）-VER=8．5×102（±1.0×102）。实验证实，HSA具有手性选择性，与（R）－VER的结合强于与（S）-VER的结合，结合比随着HSA与（±）VER的浓度比而变化。

A capillary electrophoresis (CE) method was applied to determine the binding constants of the basic racemic drug, verapamil (VER) to human serum albumin (HSA) under drug-HSA binding equilibrium (in phosphae buffer pH 7. 4, ionic strength = 0. 17). In coated capillary, the unbound basic drug eluted as two zonal plateau peaks due to enantiomers separated by chiral selector (45 mmol/L trimethy-β-cyclodextrin dissolved in pH 2. 5 phosphate buffer) at 15 kV, and their concentrations can be determined from the peak heights. To avoid disturbing the VER-HSA equilibrium, the pH 7. 4 solution was used as the inlet vial buffer, and a plug(about 3 cm long) of this buffer was introduced to the capillary before injection of analyte.The binding constants were obtained from linear regression plots. The unbound concentration of S-VER was 1. 67 times higher than that of the antipode for the solution 300 μmol/L (±)VER-500 μmol/L HSA, while 1. 13 for 100 μmol/L (±)VER-100 μmol/L HSA. The study confidently provides the binding constants of VER enantiomers to HSA, which are KR = 2. 7 ×103 (±4. 4 × 102) and Ks = 8. 5 × 103 (± 1. 0 × 102 ).