Screening of traditional European herbal medicines for acetylcholinesterase and butyrylcholinesterase inhibitory activity

Acetylcholinesterase (AChE) inhibitors are widely used for the symptomatic treatment of Alzheimer's disease (AD) to enhance central cholinergic transmission. On the other hand, butyrylcholinesterase (BuChE) inhibitors were reported to produce a significant increase in brain extracellular AChE without triggering severe peripheral or central side effects. In the present study, we selected twelve plants used in traditional European medicine to treat different central nervous system (CNS) disorders or to improve memory.

Methanolic and hexane extracts of these plants were tested for the AChE and BuChE inhibitory activity using Ellman's colorimetric method. The most potent AChE and BuChE inhibition was observed in the hexane extracts of the flowers of Arnica chamissonis Less. subs. foliosa and Ruta graveolens L. herb at a concentration of 400 μg mL^-1. However, methanolic extracts of the flowers of Arnica chamissonis Less. subs. foliosa and the Hypericum perforatum L. herb demonstrated at the same concentration, selective inhibition only against AChE but not against BuChE. The other extracts did not show any significant AChE or BuChE inhibitory activity. Our results show that further investigations of the extracts of arnica, rue and St. John's Wort are needed to identity the compounds responsible for the AChE and BuChE inhibitory activity.