| Abstract: | We investigated plants reputed in herbal encyclopedias to enhance memory or alleviate mental disorder for cholinergic activities since this transmitter system has been implicated in memory and dementia. Crude extracts were applied to human brain homogenates to determine whether any inhibit acetylcholinesterase. Of three plants with reputed memory enhancing properties (rosemary, sage and balm), extracts of sage (Salvia officinalis) inhibited the brain enzyme in a concentration dependant manner. 50% enzyme inhibition was obtained at a concentration of 0.07 μg essential oil per ml and 1.5 mg fresh herb per ml. None of the known and commercially available chemical constituents of sage oil so far tested (borneol, caffeic acid, camphor, cineol or thujone) inhibited the enzyme, indicating that the active plant constituent(s) may be an as yet unidentified compound(s). In parallel studies, plants with insecticide or vermifuge (antihelminthic) properties, which frequently depend on cholinergic activities, were examined for cholinergic receptor interactions. Crude alcoholic extracts of wormwood, balm and angelica displaced nicotine binding to the nicotinic receptor in a concentration dependant manner, with IC50 values ranging from 3–15 mg/ml. Components of these plants may be relevant in relation to dementia therapy since there is a loss of nicotinic receptors in Alzheimer's disease and related disorders and stimulation of the nicotinic receptor leads to increased receptor numbers. |
