Combining TEMPO and methyl undecenoate to produce an effective anti-mosquito compound with convenient spin-labeling

Authors: Doll, Kenneth - Ken; MUTURI, EPHANTUS - Former ARS Employee; Weiler, Lina

Submitted to: Experimental Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2022
Publication Date: 12/7/2022
Citation: Doll, K.M., Muturi, E.J., Flor-Weiler, L.B. 2022. Combining TEMPO and methyl undecenoate to produce an effective anti-mosquito compound with convenient spin-labeling. Experimental Parasitology. 244. Article 108440. https://doi.org/10.1016/j.exppara.2022.108440.
DOI: https://doi.org/10.1016/j.exppara.2022.108440

Interpretive Summary: Chemical insecticides have been a weapon used against disease spreading insects, such as mosquitoes, for many years. The problem is that these chemicals have a poor record of environmental safety and, as an added problem, insects are developing resistance to many of them. The use of natural oils in this battle is a growing strategy, but it has limitations. Highly expensive essential oils can be effective, but cost prohibitive. Commodity oils would be more economically viable, if only they worked. The reasons behind these differences in efficacy are not clear and significantly more study is needed to determine the exact structures of compounds that are the most effective. A tool for uncovering the mechanisms of action in a compound involves treating a target pest with it and then detecting where the compound ends up in the pest, in real time. This work reports a compound that will be useful in such a process. It contains an unpaired electron which can be rapidly detected with a specific instrument, and also a fatty acid component that will make it compatible with both the essential and commodity oils. It was synthesized through simple chemistry using a readily available fatty acid, making it much more economical than alternatives. This work will help those wishing to further understand the use of essential oils in insect control, and contribute to these much needed alternatives to synthetic chemicals.

Technical Abstract: A general method to spin-label a fatty acid was demonstrated as well as an assay of the effectiveness of methyl 10-undecenoate and the spin-labeled version, against the larvae of Aedes aegypti. The LC50s were 66 and 58 uL/120 mL (55 and 48 ppm) respectively, and the LC90s were 108 and 90 uL/120 mL (113 and 90 ppm). This shows that the spin-label has very little effect on the larvicidal activity of the compound. This opens the possibility of using spin-labeling as a tool to determine mechanisms of larvicidal effectiveness, as it can be employed without altering the system under study.