The interaction of two bioactive components of Chinese traditional herb, palmatine (Pa) and jatrorrhizine (Ja), with β₂-adrenoceptor (β₂-AR) was investigated by high-performance affinity chromatography. The binding isotherms of two drugs were determined by frontal analysis, and the results showed that Pa had one kind of binding site, and Ja had two kinds of binding sites on β₂-AR molecular. The association constants and binding sites were determined by zonal elution, at pH 7.4 and 25 ℃. The association constant for Pa was 2.93×10⁴ L·mol^-1, and the concentration of the binding sites was 1.13×10^-4 mol·L^-1. The association constants for Ja at the low and high binding sites were 1.93×10⁴ and 1.56×105 L·mol^-1, and the concentration of the two binding sites were 1.25×10^-4 and 1.00×10^-5 mol·L^-1, respectively. The ratio of two binding sites was 93:7. It was further proved that Pa and Ja competed the low binding site on β₂-AR. Thermodynamic results indicated that the interaction between the two drugs and β₂-AR was mainly drived by electrostatic force.

Key words: small molecular-biopolymer interaction, β₂-adrenoceptor, palmatine, jatrorrhizine, high-perfor-mance affinity chromatography