葛根素和大豆甙元抑制~3H-氟硝西泮和体外大鼠脑膜的结合

目的从中药葛根中提取脑内苯并二氮杂卓(BZ)受体活性化合物。方法用体外的放射配体-受体结合法(RRA)和高压液相法(HPLC)提取、分离、纯化BZ受体活性化合物,用核磁共振和质谱仪确定活性化合物的结构。后用GABA比和Scatchardplot分析确定它们的作用特性。结果从葛根中提取、分离到葛根素和大豆甙元2种活性化合物。它们在体外可抑制3H-氟硝西泮和脑细胞膜的结合,IC50值分别为(18.46±2.34)μmol/L和(15.4±31.89)μmol/L。大豆甙元还可抑制3H-呱唑嗪和α1-肾上腺素受体的结合(IC50值为89μmol/L)。2种化合物的GABA比分别为1.11和1.12,提示2种黄酮化合物是BZ受体的拮抗剂或部分激动剂。Scatchardplot分析显示2种化合物对3H-氟硝西泮和脑膜结合的抑制是通过竞争性与非竞争性混合机制而实现的。结论葛根素和大豆甙元是脑内BZ受体的拮抗剂或部分激动剂。它们的抑制作用是通过竞争性与非竞争性混合机制而实现的。

INHIBITION OF 3H-FLUNITRAZEPAM BINDING TO RAT BRAIN MEMBRANES IN VITRO BY PUERARIN AND DAIDZEIN

Objective: To isolate and purify the active compounds at the benzodiazepine recptor from Chinese medicinal herb,Radix Puerariae. Methods: The extracts from Radix Puerariae were isolated and identified by radio-receptor binding assay with HPLC methods.The chemical structures of the compounds were identified by NMR and mass spectrometry. Results: Two active compounds,puerarin and daidzein,were got and the both inhibited the bindings of 3H-flunitrazepam to rat brain membranes in vitro with IC50 values of (18.46±2.34) μmol/L and (15.43±1.89) μmol/L for puerarin and daidzein respectively. Daidzein also inhibited the binding of prazosin to α1 -adrenoceptor in vitro with value of 89 μmol/L. The GABA-ratios were 1.11 and 1.12 for puerarin and daidzein respectively. Scatchard plot analysis showed a mixed competitive and noncompetitive inhibition by both compounds. Conclusion: Both flavone compounds are antagonists or weak partial agonists of the benzodiazepine receptors and they inhibit the binding of 3H-flunitrazepam to rat brain membranes in vitro by a mixed competitive and noncompetitive mechanism.