Objective: To isolate and purify the active compounds at the dopamine receptor from Chinese medicinal herb,Polygala Tenuifolia
Willd. Methods: The extracts from Polygala Ten-uifolia Willd were isolated and identified by radio-receptor binding assay with HPLC methods. The chemical structures of the compound was identified by NMR and mass spectrometry. Results: One active compound,
tetrahydrocolumbamine,was got and it inhibited the bindings of 3H-SCH23390 (DA1 subtype)and 3H-spiroperidol(DA2 subtype)to rat striatum membranes in vitro with IC50 values of (0.75±0.08) μmol/L and(0.92±0.10) μmol/L,respectively. The compound also inhibited the binding of prazosin to α1-adrenoceptor in vitro with IC50 value of 46 μmol/L. While it did not change the binding of ligands,3H-QNB and 3H-muscimol to rat cortex in vitro. Scatchard plot analysis showed a mixed competitive and noncompetitive inhibition by the compound on both 3H-SCH23390 and 3H-spiroperidol bindings to membranes from rat striatum. Conclusion: Tetrahydrocolumbamine from Chinese medicinal herb,
Polygala Tenuifolia Willd is an active compound which inhibits the bindings of 3H-SCH23390 and 3H-spiroperidol to rat striatum membranes by a mixed competitive and noncom-petitive mechanisms.