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.