posted on 2023-12-15, 14:34authored byEdmund J. Norris, Jedidiah Kline, Jeffrey R. Bloomquist
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 analogues 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 those of other commercially available toxicants. The three
most toxic compounds (LC50 values) were 3-chlorobenzaldehyde
(CBA) (37 μg/cm2), biphenyl-3-carboxaldehyde (BCA)
(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 analogues
with EC50 values below 30 μg/cm2 were
3-phenoxybenzaldehyde (6.3 μg/cm2), isophthalaldehyde
(23 μg/cm2), BCA (17 μg/cm2), and
CBA (22 μg/cm2), which makes them about as active
as N,N-diethyl-3-methylbenzamide (25.4 μg/cm2). We further investigated the activity of a select group
of these benzaldehydes to block the firing of the central nervous
system of A. 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
analogues are viable candidate repellent and insecticidal molecules
and may lead to the development of future repellent and vapor toxic
vector control tools.