Mosquiticidal and repellent potential of formulations containing wood residue extracts of a Neotropical plant, Tabebuia heptaphylla

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The use of wood residues and their extracts as sources for bioactive molecules not only helps to reduce the environmental impacts of the wastage produced by timber industry but also provide innumerous biotechnological application opportunities, including the development of novel insecticide products. Here, the insecticidal and repellent (in gel and cream formulations) potential of wood extracts of the Neotropical plant “purple ipê”, Tabebuia heptaphylla (Bignoniaceae) against the mosquitoes Aedes aegypti are investigated. Firstly, the chemical composition of the chloroform and hexane extracts obtained from T. heptaphylla residues is analyzed and their insecticidal activities are assessed against A. aegypti larvae. Furthermore, the repellence and oviposition deterrence actions of these extracts were evaluated against adult mosquito females. Computational docking analysis was also conducted to predict the physical interactions between the major constituents of the T. heptaphylla residue extracts and the odorant binding receptor of A. aegypti. Despite the fact that the 2,6-di-tert-butylnaphthalene was the major constituent (53.3%) in the T. heptaphylla hexanoic extract, the presence of lapachol, 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthalenedione, as major constituent in both wood extracts combined with the computational docking analysis, strongly suggest the lapachol as the major factor of the insecticidal/repellent effects of T. heptaphylla wood extracts. The computational docking analysis predicted significant binding of lapachol with the internal active pocket of the mosquito odorant binding receptor, which helps to explain the up to 3 h protection against bites of A. aegypti females provided by gel and cream formulations containing the T. heptaphylla residue extracts. Collectively, the findings demonstrated relevant biotechnological and environmentally-friend opportunities (i.e., production of biopesticides) for the wood residues produced by timber activities during the extraction and processing of T. heptaphylla trees.