ISOLATION AND IDENTIFICATION OF TETRAHYDRO-COLUMBAMINE AS A DOPAMINE RECEPTOR LIGAND FROM POLYGALA TENUIFOLIA WILLD

The isolation and purification of a dopamine receptor ligand ,tetrahydro-columbamine from Polygala tenuifolia Willd is described. Tetrahydrocolumbamine was shown to inhibitthe binding of³H-SCH23390 and³H-spiroperidol to rat striatum membranes in vitro with IC₅₀values of 0.75 ± 0.08μmol·L^-1 and 0.92 ± 0. 10μmol·L^-1, respectively.The compoundinhibited the binding of³H-prazosin(IC₅₀ value of 46μmol·L^-1),while it did not change thebinding of the ligands,³H-QNB and³H-muscimol to rat cortex in vitro. Scatchard plot analysisshowed a mixture of competitive and non-competitive inhibition by the compound on both³H-SCH23390 and³H-spiroperidol binding to membranes from rat striatum.