Monoterpenoids found in natural plant products have been shown to have biocidal activity against agricultural, human health and veterinary pests. Specific neurological activity has been found to be highly variable between different monoterpenoids acting on different organisms and receptors. This research follows findings that carvacrol can act as an antagonist against the ACR-16 nicotinic acetylcholine receptor from Ascaris suum. We tested multiple plant derived monoterpenoids with the ACR-16 receptor. Receptors were expressed in oocytes from Xenopus lavis. We used two electrode voltage clamp to test the receptor response when exposed to monoterpenoids alongside acetylcholine, the natural agonist. Concentration response characterizations were performed at 100 µM and 10 µM concentrations of the monoterpenoid compounds. No monoterpenoids showed agonist activity on the ACR-16 receptor. Most compounds tested showed a significant inhibition of the acetylcholine response. Concentration response curves showed that the monoterpenoids tested had no significant effect on the EC50 values of the acetylcholine response. The maximal current was significantly lower than the acetylcholine only control for several compounds at the 10 µM rate. This research confirms previous findings that monoterpenoids as a class of compounds have varied but noticeable neurotoxic effects at a nicotinic acetylcholine receptor. We plan to characterize those compounds most active at our chosen target site.

Analysis of activity of monoterpenoid plant compounds on a nicotinic acetylcholine receptor

256th National Meeting (2018)

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