APPLICATION OF RADIOLIGAND-RECEPTOR BINDING ASSAYS IN THE SEARCH FOR THE ACTIVE PRINCIPLES OF THE TRADITIONAL CHINESE MEDICINE GOUTENG

Uncaria rhynchophylla and related species (i.e. Gouteng of the Pharmac opoeia of the People's Republic of China) have antihypertensive, sedat ive and anticonvulsant activities, A methanol extract of 'Gouteng' (U. rhynchopylla) hooks and stems was assessed for its ability to inhibit the binding of radioligands to 13 different receptors in this study, The extract inhibited ligand-receptor binding by more than 60% to alph a(2)-adrenoceptors, dopamine 1, 5-HT1A, opiate, GABA(A) and GABA(B) re ceptors. Bioassay-guided fractionation resulted in the isolation of ur solic acid (muscarinic and sulphonylureas activities), husutine (alpha (2)- and beta-adrenoceptor, 5-HT1A and 2, opiate and sulphonylureas ac tivities) and epiallocorynanthine (beta-adrenoceptor, 5-HT1A and 2, an d opiate receptor activities). These findings are discussed in relatio n to the reported pharmacological properties, clinical uses and differ ing alkaloid profiles of those Uncaria species which constitute 'Goute ng' of the Pharmacopoeia of the People's Republic of China. (C) 1997 b y John Wiley & Sons, Ltd.