Skin irritation has been reported to be the main adverse effect of excessive use of N,N-diethyl-m-toluamide (DEET) and ethyl 3-acetyl(butyl)amino (IR3535) commercial repellents. Therefore, there is an interest in alternatives of natural origin such as essential oils (EOs) and major compounds, which have repellent effects but have no contraindications. The main purpose of the present study was to identify the repellent effect of selected terpenes on Aedes aegypti Linnaeus, 1762 (Diptera: Culicidae) by in silico analysis based on their affinity with the odorant protein AaegOBP1. The protein-metabolite interactions in 20 terpenes were analyzed using the SwissDock tool. Terpenes presenting the highest affinity compared with commercial repellents were selected to evaluate repellent activity at concentrations 0.1, 10, and 25% against Ae. aegypti. Different periods (0–2, 2–15, 15–60 min) were evaluated with DEET as a positive control. The toxicity of terpenes was verified through Osiris and Molinspiration Cheminformatics Software, and cytotoxicity assays in Vero and HepaRG cells were performed using the MTT method. Two formulations were prepared with polyethylene glycol to evaluate skin long-lasting in vivo assay. The results showed four terpenes: geranyl acetate, nerolidol, α-bisabolol, and nerol, with affinity to AaegOBP1 comparable with DEET and IR3535. Geranyl acetate, nerolidol, and their mixtures showed no cytotoxicity and protection percentages close to 100% during the test at concentrations 10 and 25%. Long-lasting assays with geranyl acetate and nerolidol formulate showed 3 h as maximum protection time with 100% protection percentage. These metabolites and their mixtures are candidates to repellent formulations with times and protection percentages similar to DEET.

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The current study describes the effects of sub-lethal concentrations and constituent compounds (citral and geranyl acetate) of Cymbopogon flexuosus essential oil (EO) on the development of Aedes aegypti. We treated eggs with 6, 18, or 30 mg L−1 and larvae with 3 or 6 mg L−1 of EO and its major compounds (citral and geranyl acetate). Citral and geranyl acetate were evaluated at 18, 30, and 42 mg L−1 and compared with commercial growth inhibitors (diflubenzuron and methoprene). We measured larval head diameter, siphon length, and larval length. Finally, we examined concentrations of molt hormone (MH) and juvenile hormone III (JH III) using high-performance liquid chromatography coupled to mass spectrometry. All geranyl acetate concentrations decreased egg hatching, while EO altered molting among larval instars and between larvae and pupae, with an increase in the larval length (3 mg L−1: 6 ± 0.0 mm; 6 mg L−1: 6 ± 0.7 mm) and head width (3 mg L−1: 0.8 ± 0 mm; 6 mg L−1: 0.8 ± 0.0 mm) compared with the control group. We did not detect chromatographic signals of MH and JH III in larvae treated with C. flexuosus EO or their major compounds. The sub-lethal concentrations C. flexuosus EO caused a similar effect to diflubenzuron, namely decreased hormone concentrations, an extended larval period, and death.

Diferentes estudios han evaluado la actividad biocida de aceites esenciales (AEs) en larvas de mosquitos de importancia médica. Sin embargo, son limitadas las investigaciones que analizan los efectos de los AEs en todos los estadíos del ciclo de vida de Aedes aegypti. Este estudio evalúa la actividad biológica del AE de Salvia officinalis frente a Ae. aegypti. Se evaluó la actividad ovicida a concentraciones de 1, 5, 37 y 50 mg.L-1 en huevos de 0-12 h y huevos de 0-72 h. La actividad larvicida, pupicida y adulticida fue evaluada a concentraciones exploratorias (CE) y múltiples. Para la actividad repelente se empleó una CE de 1.000 mg.L-1 en intervalos de 0-2 min y de 2-15 min de exposición en antebrazos de voluntarios. La actividad disuasiva de oviposición se estimó a CE de 5, 50 y 200 mg.L-1. El AE causó malformaciones en embriones y alteración de las larvas. La mayor actividad larvicida fue a 63 y 76 mg.L-1 (27 ± 13,4 y 37 ± 18,6 %) a 24 h. La mayor mortalidad pupicida fue a 310 y 390 mg.L-1 (89 ± 1,53 and 100 ± 0 %) a las 48 h. La mortalidad adulticida a 300 mg.L-1 fue de 57,5 ± 0 % y el porcentaje de repelencia fue de 42 ± 4,7 %. La acción disuasiva a 200 mg.L-1 fue de 97 ± 4,81 %, con un índice de actividad de ovipostura de -0,94. S. officinalis mostró un efecto biocida en embriones y mortalidad de pupas y adultos, lo que revela que tiene un uso potencial en programas de control focalizados en estos estadios de desarrollo.

The current study describes the effects of sub-lethal concentrations and constituent compounds (citral and geranyl acetate) of Cymbopogon flexuosus essential oil (EO) on the development of Aedes aegypti (L.) eggs and larvae. To demonstrate the ovicidal activity of EO, we treated embryonated eggs with 6, 18, and 30 mg.L-1 and larvae with 3 and 6 mg.L-1 EO concentrations. Citral and geranyl acetate were evaluated at 18, 30, and 42 mg.L-1 and compared with commercial growth inhibitors (diflubenzuron and methoprene) at 3 and 6 mg.L-1 concentrations. For each treatment, we measured larval head diameter, siphon length, and body length. To complement the morphological analysis, we examined concentrations of moult hormone (MH) and juvenile hormone III (JH III) using high-performance liquid chromatography (HPLC) coupled to mass spectrometry. The EO decreased egg hatching at all concentrations: 6 mg.L-1 in 45.3%; 18 mg.L-1 in 23.3%, and 30 mg.L-1 in 34.6%. EO also altered molting among larval instars and between larvae and pupae, with an increase in the length (3 mg.L-1: 6 ± 0.0 mm; 6 mg.L-1: 6 ± 0.7 mm) and head width (3 mg.L-1: 0.8 ± 0 mm; 6 mg.L-1: 0.8 ± 0.0 mm) compared with the control group (length: 5.3 ± 0 mm; head width: 0.7 ± 0.0 mm). We did not detect chromatographic signals of MH and JH III in larvae treated with C. flexuosus EO or their major compounds. The sub-lethal concentrations C. flexuosus EO caused a similar effect to diflubenzuron, decreasing hormone concentration, extending the larval period, and death.