Ethnomedicinally selected plants as sources of potential analgesic compounds: indication of in vitro biological activity in receptor binding assays.

A number of plant species used in traditional medicine for the relief of pain have been selected from the medicinal and scientific literature of China, South America, Asia and West Africa. Extracts were prepared and tested in three in vitro receptor radioligand binding assays to determine whether there was an indication of biological activity, in particular their selectivity to a single receptor implicated in the mediation of pain. The three neuropeptide receptors chosen were Bradykinin (BK II), expressed in Chinese hamster ovary cells (CHO), neurokinin 1 (NK 1) expressed in astrocytoma cells, and calcitonin gene related peptide (CGRP) which were all implicated in the mediation of acute pain in the mammaliancentral nervous system. The plant species chosen to investigate were Ageratum conyzoides, Barringtonia edulis, Croton tiglium, Ipomea pes-caprae, Panax ginseng, Physostigma venenosum, Sinomenium acutum, Solidago virgaurea, Symplocos leptophylla and Typhonium giganteum. The results showed that there was a strong indication of biological activity for some of the plants which are used ethnomedicinally to treat pain, in the three in vitro receptor binding assays used, and particular plant extracts exhibited selective action to a single receptor.