What Is the 'Areca' in 'Areca Nuts'? Extraction and Neuroactive Bioassay of Arecoline

摘要

A series of three practical sessions are designed to give students firsthand experience with the preparation of natural product extracts and assay using a live tissue preparation. Areca or betel nuts are the seeds from the fruit of the Areca catechu palm tree that is known to contain a number of pharmacologically active alkaloids. The principal of these is arecoline that makes up to 1% of the dry nut. Arecoline is a potent spasmogenic agent, causing smooth muscle contraction via muscarinic acetylcholine receptor (mAChR) activation. The first session involves the preparation of methanolic extracts from whole areca nuts and TLC for the 20 qualitative identification of arecoline present in the extract. The second session utilizes the spasmodic effects of arecoline on smooth muscle to allow students to perform a live tissue bioassay using guinea-pig ileum. This response is subsequently blocked by the mAChR antagonist atropine to investigate the mechanism underlying the measured response. The final session gives students the opportunity to construct arecoline dose response curves based on their experimentally derived data. From this curve and the obtained antagonist results, they are able to calculate an estimate of the arecoline content in the extracts they prepared and the original betel nut samples.