High-content phenotypic screening reveals natural product bioactives that disrupt mosquito activity, development and serotonergic signaling.

Mosquitoes are one of the most prolific disease vectors in nature, transmitting many infectious diseases, such as dengue, malaria, and yellow fever. Vector eradication campaigns are failing due to the increasing insecticide resistance shown by mosquito populations, causing efficacy loss of currently available chemistries due to their limited mode of action. Natural products (NPs) are chemistries with diverse chemical structures and potential unique modes of action for mosquito control. Here, we report the results of a high-content phenotypic screen of 3680 chemistries from the AnalytiCon Discovery MEGx and NATx collections against the first instar larvae of Aedes aegypti L., the yellow fever mosquito. The electrophysiological effects of bioactive chemistries were investigated using Blattella germanica (German cockroach) nerve cord preparations and the suction electrode technique. Our approach led to the identification of five active chemistries: rotenone, 6-hydroxysumatrol, aureothin and two uncharacterized chemistries, NP-3 and -5. Among these chemistries, aureothin showed the highest larvicidal activity with a LC50 of 31.1 μM. The screen also identified 140 plant metabolites associated with increased larval cuticular pigmentation and morphometric changes. Eighty percent of these chemistries were classified as terpenoids, flavonoids, phenylpropanoids, alkaloids, and polyketides, and 30 % were glycosylated. The electrophysiological results evidenced neuroinhibition effects of aureothin, while metergoline was not associated with any neurophysiological effect. Results of the phenotypic screen are considered in the context of developing new, safer mosquito control technologies with efficacy against insecticide-resistant populations. Lastly, based on electrophysiological recordings and published studies, a molecular model for metergoline-induced modulation of invertebrate serotonergic receptors and associated signaling processes was proposed.