Insecticidal activity of essential oils from American native plants against Aedes aegypti (Diptera: Culicidae): an introduction to their possible mechanism of action (original) (raw)

Searching for new bioactive molecules to design insecticides is a complex process since pesticides should be highly selective, active against the vector, and bio-safe for humans. Aiming to find natural compounds for mosquito control, we evaluated the insecticidal activity of essential oils (EOs) from 20 American native plants against Aedes aegypti larvae using bioassay, biochemical, and in silico analyses. The highest larvicide activity was exhibited by EOs from Steiractinia aspera (LC 50 = 42.4 µg/ mL), Turnera diffusa (LC 50 = 70.9 µg/mL), Piper aduncum (LC 50 = 55.8 µg/mL), Lippia origanoides (chemotype thymol/carvacrol) (LC 50 = 61.9 µg/mL), L. origanoides (chemotype carvacrol/thymol) (LC 50 = 59.8 µg/mL), Hyptis dilatata (LC 50 = 61.1 µg/mL), Elaphandra quinquenervis (LC 50 = 61.1 µg/mL), and Calycolpus moritzianus (LC 50 = 73.29 µg/mL) after 24 h. This biological activity may be related to the disruption of the electron transport chain through the mitochondrial protein complexes. We hypothesized that the observed EOs' effect is due to their major components, where computational approaches such as homology modeling and molecular docking may suggest the possible binding pose of secondary metabolites that inhibit the mitochondrial enzymes and acetylcholinesterase activity (AChE). Our results provided insights into the possible mechanism of action of EOs and their major compounds for new insecticide designs targeting the mitochondria and AChE activity in A. aegypti for effective and safe insecticide. The new way to design green insecticides includes plant extracts (PE) and essential oils (EOs), focusing on environmentally eco-friendly products 1-3. Therefore, it is crucial to begin pesticide design with a selective screening to know if the product is suitable for insect control and then to continue its refinement processes to support a future commercial insecticidal formulation. In this sense, and due to the necessity of discovering new products for mosquito control that are environmentally safe and fit into a philosophy of sustainability from a safety perspective, further findings on bioinsecticides must bring information about the toxicity of their components 3-5. Fortunately, there is extensive documentation about plants with insecticidal activity against A. aegypti, even with comprehensive details on their chemical characterization to make them commercial biopesticides 6-8. Within this extensive documentation, some studies highlight features that should have a botanical insecticide against mosquito larvae. In the first instance, to acquire this connotation, the lethal concentration (LC) LC 50 of EO or PE should be less than 100 ppm, also considering their physicochemical properties 9. Classification for the mechanism of action of insecticide substances has also been described and includes protein denaturalization, enzymatic inhibition, and membrane disintegration 7 .