Exploring the selective inhibitory activity of essential oils on the Alzheimer associated enzymes AChE and BChE: a comprehensive screening based on a bio-guided fractionation approach. Focus on Mentha sp. essential oils

Essential oils (EOs), complex mixtures of volatile compounds obtained from individual plant species via steam distillation, dry distillation or mechanical processes, have attracted scientific interest due to their traditional use. Their biological effects, including effects on the central nervous system, have become the focus of research. In this work, we have conducted an extensive screening of numerous essential oils and identified those that have a promising inhibitory activity on two different enzyme targets involved in Alzheimer's disease: acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Further investigation focused on the trend that most EOs exhibit selectivity towards one enzyme. The EOs found to be selectively active for AChE are primarily composed of 1,8-cineole, a compound already known in the literature for this activity [1], and it was confirmed to be solely responsible for the activity of these EOs. The same is true for Origanum vulgare L. EO, related to the compound carvacrol. Conversely, Mentha x piperita L. and Mentha arvensis L. were EOs with selective activity toward BChE, but the activity of the main compound, menthol, didn’t explain completely that of the total essential oil. Therefore, a bio-guided fractionation of the EOs was performed to finally identify the compounds to which this activity might be attributed. In addition, preliminary in vitro studies were carried out on mice cellular models (NE-4C culture purchased from ATCC) to investigate the activity of Mentha x piperita L. EO on BChE, with the aim of improving our understanding of its interesting biological effects.