Repellency and toxicity of vapor-active benzaldehydes against Aedes aegypti

Authors: Norris, Edmund; Kline, Jedidiah; BLOOMQUIST, JEFFREY - University Of Florida

Submitted to: ACS Infectious Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2023
Publication Date: 12/15/2023
Citation: Norris, E.J., Kline, J.D., Bloomquist, J.R. 2023. Repellency and toxicity of vapor-active benzaldehydes against Aedes aegypti. ACS Infectious Diseases. 10:120-126. https://doi.org/10.1021/acsinfecdis.3c00294.
DOI: https://doi.org/10.1021/acsinfecdis.3c00294

Interpretive Summary: Chemical screening efforts recently found that 3-phenoxybenzaldehyde, a breakdown product of alpha-cyano pyrethroids, was a potent spatial repellent against Aedes aegypti mosquitoes in a glass tube repellency assay. In order to characterize this molecule further and identify structure-activity relationships, a set of 12 benzaldehyde analogs were screened for their repellency and toxicity in vapor phase exposures at 100 µg/cm2. Dose-response analyses were performed for the most active compounds in order to better characterize their repellent potency and toxicity compared to other commercially available toxicants. This testing resulted in the characterization of several compounds that were broadly active as both spatial repellents and insecticides, which may demonstrate their potential to be used to control wild mosquitoes in the future.

Technical Abstract: Chemical screening efforts recently found that 3-phenoxybenzaldehyde, a breakdown product of alpha-cyano pyrethroids, was a potent spatial repellent against Aedes aegypti mosquitoes in a glass tube repellency assay. In order to characterize this molecule further and identify structure-activity relationships, a set of 12 benzaldehyde analogs were screened for their repellency and toxicity in vapor phase exposures at 100 µg/cm2. Dose-response analyses were performed for the most active compounds in order to better characterize their repellent potency and toxicity compared to other commercially available toxicants. The three most toxic compounds were 3-chlorobenzaldehyde (37 µg/cm2), biphenyl-3-carboxaldehyde (48 µg/cm2), and 3-vinylbenzaldehyde (66 µg/cm2), which makes them less toxic than bioallethrin (6.1 µg/cm2) but more toxic than sandalwood oil (77 µg/cm2), a repellent/toxic plant essential oil. The most repellent analogs with EC50 values below 30 µg/cm2 were 3-phenoxybenzaldehyde (6 µg/cm2), biphenyl-3-carboxaldehyde (17 µg/cm2), and 3-chlorobenzaldehyde (22 µg/cm2), and isophthalaldehyde (23 µg/cm2), which makes them about as active as DEET (25.4 µg/cm2). We further investigated the activity of a select group of these benzaldehydes to block the central nervous system of Aedes aegypti larvae. Compounds most capable of repelling and killing mosquitoes in the vapor phase were also those most capable of blocking nerve firing in the larval mosquito nervous system. The results demonstrate that benzaldehyde analogs are viable candidate repellent and insecticidal molecules and may lead to the development of future repellent and vapor toxic vector control tools.