Noam Gadelha

Mosquitoes are responsible for serious public health problems worldwide, and as such, Aedes aegypti and Aedes albopictus are important vectors in the transmission of dengue, chikungunya, and Zika in Brazil and other countries of the world. Due to growing resistance to chemical insecticides among populations of vectors, environmentally friendly strategies for vector management are receiving ever more attention. Essential oils (EOs) extracted from plants have activities against insects with multiple mechanisms of action. These mechanisms hinder the development of resistance, and have the advantages of being less toxicity and biodegradable. Thus, the present study aimed to evaluate the chemical composition of the EOs obtained from Piper capitarianum Yunck, as well as evaluating their insecticidal potential against Aedes aegypti and A. albopictus, and their toxicity in relation to Artemia salina. The yields of the EOs extracted from the leaves, stems, and inflorescences of P. capitarianum were 1.2%, 0.9%, and 0.6%, respectively, and their main constituents were trans-caryophyllene (20.0%), α-humulene (10.2%), β-myrcene (10.5%), α-selinene (7.2%), and linalool (6.0%). The EO from the inflorescences was the most active against A. aegypti and A. albopictus, and exhibited the respective larvicidal (LC50 = 87.6 μg/mL and 76.1 μg/mL) and adulticide activities (LC50 = 126.2 μg/mL and 124.5 μg/mL). This EO was also the most active in the inhibition of AChE, since it presented an IC50 value of 14.2 μg/mL. Its larvicidal effect was observed under optical and scanning electron microscopy. Additionally, non-toxic effects against A. salina were observed. Docking modeling of trans-caryophyllene and α-humulene on sterol carrier protein-2 (SCP-2) suggests that both molecules have affinity with the active site of the enzyme, which indicates a possible mechanism of action. Therefore, the essential oil of P. capitarianum may be used in the development of new insecticide targets for the control of A. aegypti and A. albopictus in the Amazonian environment.

Abstract The high incidence of dengue, chikungunya, and Zika indicates the importance of controlling the vector of these arboviruses in the tropical and subtropical regions of the world. However, vector control is hindered by pesticide resistance and the limited success of biocontrol programs against Aedes mosquitoes. Despite these difficulties, the study of common plant species, including those with commercial value, can offer effective and ecological tools in the fight against mosquitoes. In the present study, the essential oils obtained from the aerial parts of Origanum vulgare L. and Thymus vulgaris L. were analyzed by GC–MS and evaluated for their larvicidal, adulticidal and repellent activities against  Aedes aegypti L. The main constituents of the O. vulgare essential oil were terpinen-4-ol (17.4%), carvacrol (16.0%) and thymol (10.4%), and the main constituents of the T. vulgaris essential oil were thymol (40.0%), p-cymene (19.3%) and γ-terpinene (17.3%). Both essential oils were toxic to Ae. aegypti larvae with LC50 values of 37.5 μg/mL for O. vulgare and 38.9 μg/mL for T. vulgaris. For adult mosquitoes, the LC50 values were 14.3 and 11.7 μg/mL, respectively. The essential oils of O. vulgare and T. vulgaris showed a significant repellency effect, with values ranging from 8.9% to 37.8% and 4.4% to 68.9%, respectively. In addition, morphological differences between larvae treated with the EOs and the control group were evidenced by optical microscopy. Thus, the results suggest that the essential oils of O. vulgare and T. vulgaris have potential use as an ecofriendly source to develop new insecticides for the control of Ae. aegypti.