Certain Lamiaceous and Asteraceous plants have long histories of use as restoratives of lost or declining cognitive
functions in western European systems of traditional medicine. Investigations were carried out to evaluate human
CNS cholinergic receptor binding activity in extracts of those European medicinal plants reputed to enhance or
restore mental functions including memory. Ethanolic extracts were prepared from accessions of these plants and a
number of other species related by genus. Amongst the plant extracts screened for contents able to displace
[3H]-(N)-nicotine and [3H]-(N)-scopolamine from nicotinic receptors and muscarinic receptors, respectively in
homogenates of human cerebral cortical cell membranes, the most potent extracts, prepared from one accession of
Melissa officinalis, three Sal6ia species and Artemisia absinthium had IC50 concentrations of B1 mg:ml. The
displacement curves of some extracts were comparable with that of carbamylcholine chloride, a potent acetylcholine
analogue. Choline, a weak nicotinic ligand (IC503104 M) was found in extracts of all plants studied at
concentrations of 106–105 M. These concentrations could not account for not more than 5% of the displacement
activity observed. Some extracts displayed differential displacement at nicotinic and muscarinic acetylcholine
receptors, with M. officinalis 0033 having the highest [3H]-(N)-nicotine displacement value and Sal6ia elegans with the
highest [3H]-(N)-scopolamine displacement value. There was also considerable variation in cholinoreceptor interactions
between different accessions of a single plant species. Although most plant extracts screened showed some
nicotinic and muscarinic activity, only some showed dose-dependent receptor activity typical of materials with
genuine cholinergic activity. © 2000 Elsevier Science Ireland Ltd. All rights reserved.