Design and elucidation of an insecticide from natural compounds targeting mitochondrial proteins of Aedes aegypti.

Developing new pesticides poses a significant challenge in designing next-generation natural insecticides that selectively target specific pharmacological sites while ensuring environmental friendliness. In this study, we aimed to address this challenge by formulating novel natural pesticides derived from secondary plant metabolites, which exhibited potent insecticide activity. Additionally, we tested their effect on mitochondrial enzyme activity and the proteomic profile of Ae. aegypti, a mosquito species responsible for transmitting diseases. Initially, 110 key compounds from essential oils were selected that have been reported with insecticidal properties; then, to ensure safety for mammals were performed in silico analyses for toxicity properties, identifying non-toxic candidates for further investigation. Subsequently, in vivo tests were conducted using these non-toxic compounds, focusing on the mosquito's larval stage. Based on the lethal concentration (LC), the most promising compounds as insecticidal were identified as S-limonene (LC50 = 6.4 ppm, LC95 = 17.2 ppm), R-limonene (LC50 = 9.86 ppm, LC95 = 27.7 ppm), citronellal (LC50 = 40.5 ppm, LC95 = 68.6 ppm), R-carvone (LC50 = 61.4 ppm, LC95 = 121 ppm), and S-carvone (LC50 = 62.5 ppm, LC95 = 114 ppm). Furthermore, we formulated a mixture of R-limonene, S-carvone, and citronellal with equal proportions of each compound based on their LC50. This mixture specifically targeted mitochondrial proteins and demonstrated a higher effect that showed by each compound separately, enhancing the insecticidal activity of each compound. Besides, the proteomic profile revealed the alteration in proteins involved in proliferation processes and detoxification mechanisms in Ae. aegypti. In summary, our study presents a formulation strategy for developing next-generation natural insecticides using secondary plant metabolites with the potential for reducing the adverse effects on humans and the development of chemical resistance in insects. Our findings also highlight the proteomic alteration induced by the formulated insecticide, showing insight into the mechanisms of action and potential targets for further exploration in vector control strategies.

Synthesis of new series of quinoline derivatives with insecticidal effects on larval vectors of malaria and dengue diseases.

Mosquito borne diseases are on the rise because of their fast spread worldwide and the lack of effective treatments. Here we are focusing on the development of a novel anti-malarial and virucidal agent with biocidal effects also on its vectors. We have synthesized a new quinoline (4,7-dichloroquinoline) derivative which showed significant larvicidal and pupicidal properties against a malarial and a dengue vector and a lethal toxicity ranging from 4.408 µM/mL (first instar larvae) to 7.958 µM/mL (pupal populations) for Anopheles stephensi and 5.016 µM/mL (larva 1) to 10.669 µM/mL (pupae) for Aedes aegypti. In-vitro antiplasmodial efficacy of 4,7-dichloroquinoline revealed a significant growth inhibition of both sensitive strains of Plasmodium falciparum with IC50 values of 6.7 nM (CQ-s) and 8.5 nM (CQ-r). Chloroquine IC50 values, as control, were 23 nM (CQ-s), and 27.5 nM (CQ-r). In vivo antiplasmodial studies with P. falciparum infected mice showed an effect of 4,7-dichloroquinoline compared to chloroquine. The quinoline compound showed significant activity against the viral pathogen serotype 2 (DENV-2). In vitro conditions and the purified quinoline exhibited insignificant toxicity on the host system up to 100 µM/mL. Overall, 4,7-dichloroquinoline could provide a good anti-vectorial and anti-malarial agent.

Mitochondrial affectation, DNA damage and AChE inhibition induced by Salvia officinalis essential oil on Aedes aegypti larvae.

The aim of this research study was to understand the mechanism of action of Salvia officinalis (Lamiaceae) essential oil (EO) on Aedes aegypti larvae. We evaluated the effect on DNA damage, acetylcholinesterase (AChE) inhibition and mitochondrial enzymatic alterations. The major components were analyzed in silico using OSIRIS and Molispiration free software. Aedes aegypti DNA was extracted from mosquito larvae between third (L3) and fourth (L4) instars to determine the DNA fragmentation or degradation at S. officinalis EO lethal concentrations (LC10, LC20, LC50, and LC90). DNA integrity was assessed in both LCs in larvae treated for 24 h and in larvae homogenized with EO; we also assessed purified DNA larvae by a densitometric analysis. The AChE inhibition was quantified in protein larvae L3-L4 following Ellman's method and the enzymatic activities related to the mitochondrial respiratory chain of mitochondrial proteins was estimated by spectrophotometry. In silico analysis of 1,8-cineol and of α-thujone, major EO components, showed that they were highly permeable in biological membranes without mutagenic risks. Alterations in the integrity of DNA were observed in larvae exposed and homogenized with S. officinalis EO. The EO induced an AChE inhibition of 37 ±â€¯2.6% to IC50. On the other hand, mitochondrial bioenergetics suggest that EO inhibits electrons entry to the respiratory chain, via Complex II. AChE activity alteration causes mortality of individuals, by blocking the insect cholinergic functions. These results indicate that EO affects the integrity of DNA, the mitochondrial respiration chain and the AChE activity.

[Insecticidal action of synthetic girgensohnine analogues and essential oils on Rhodnius prolixus (Hemiptera: Reduviidae)].

INTRODUCTION: The alkaloid girgensohnine has been used as a natural model in the synthesis of new alkaloid-like alpha-aminonitriles with insecticidal effect against disease vectors. OBJECTIVE: To evaluate the biocide activity of girgensohnine analogues and essential oils of Cymbopogon flexuosus, Citrus sinensis and Eucalyptus citriodora in stage I and stage V Rhodnius prolixus nymphs. MATERIALS AND METHODS: We used a topical application model in tergites and sternites, as well as exposure to treated surfaces with different exploratory doses of each of the molecules and essential oils to determine the lethal doses (LD50 and LD95). RESULTS: Analogue 3 showed the highest insecticidal activity with 83.3±16.7% of mortality when applied on tergites, 38.9±4.8% on sternites and 16.7±0% on treated surfaces in stage I nymphs at 72 hours (h) and 500 mg.L-1. In stage V nymphs, the compounds induced mortality only in sternums (11.1±9.6% for analogue 6 and 5.5±4.7% for analogues 3 and 7 at 72 h and 1500 mg.L-1). The lethal doses for molecule 3 on tergites in stage I nymphs were LD50 225.60 mg.L-1 and LD95 955.90 mg.L-1. The insecticidal effect of essential oils was observed only in stage I nymphs, with 11.1±4.8% for C. flexuosus when applied in sternites, while using exposure to surfaces treated it was 5.6±4.8% for C. sinensis applied on tergites and 8.3±0% on sternites at 72 h and 1000 mg.L-1. CONCLUSION: Synthetic girgensohnine analogues, and C. flexuosus and C. sinensis essential oils showed insecticidal activity in R. prolixus. Analogue 3 showed the greatest insecticidal activity among all molecules and oils evaluated under our laboratory conditions.

Insecticidal action of synthetic girgensohnine analogues and essential oils on Rhodnius prolixus (Hemiptera: Reduviidae) / Acción insecticida de análogos sintéticos de girgensohnina y de aceites esenciales sobre Rhodnius prolixus (Hemiptera: Reduviidae)

ABSTRACT Introduction: The alkaloid girgensohnine has been used as a natural model in the synthesis of new alkaloid-like alpha-aminonitriles with insecticidal effect against disease vectors. Objective: To evaluate the biocide activity of girgensohnine analogues and essential oils of Cymbopogon flexuosus, Citrus sinensis and Eucalyptus citriodora in stage I and stage V Rhodnius prolixus nymphs. Materials and methods: We used a topical application model in tergites and sternites, as well as exposure to treated surfaces with different exploratory doses of each of the molecules and essential oils to determine the lethal doses (LD50 and LD95). Results: Analogue 3 showed the highest insecticidal activity with 83.3±16.7% of mortality when applied on tergites, 38.9±4.8% on sternites and 16.7±0% on treated surfaces in stage I nymphs at 72 hours (h) and 500 mg.L-1. In stage V nymphs, the compounds induced mortality only in sternums (11.1±9.6% for analogue 6 and 5.5±4.7% for analogues 3 and 7 at 72 h and 1500 mg.L-1). The lethal doses for molecule 3 on tergites in stage I nymphs were LD50 225.60 mg.L-1 and LD95 955.90 mg.L-1. The insecticidal effect of essential oils was observed only in stage I nymphs, with 11.1±4.8% for C. flexuosus when applied in sternites, while using exposure to surfaces treated it was 5.6±4.8% for C. sinensis applied on tergites and 8.3±0% on sternites at 72 h and 1000 mg.L-1. Conclusion: Synthetic girgensohnine analogues, and C. flexuosus and C. sinensis essential oils showed insecticidal activity in R. prolixus. Analogue 3 showed the greatest insecticidal activity among all molecules and oils evaluated under our laboratory conditions.

RESUMEN Introducción. El alcaloide natural girgensohnina se ha usado como modelo en la síntesis de nuevos análogos de alcaloidales alfa-aminonitrílicos con efecto insecticida en vectores de enfermedades. Objetivo. Evaluar la actividad biocida de análogos de girgensohnina y de aceites esenciales de las plantas Cymbopogon flexuosus, Citrus sinensis y Eucalyptus citriodora en ninfas de estadios I y V de Rhodnius prolixus. Materiales y métodos. Se empleó la aplicación tópica en terguitos, esternitos y superficies tratadas con diferentes dosis exploratorias de cada una de las moléculas y aceites esenciales para determinar las dosis letales (LD50 y LD95). Resultados. El análogo 3 tuvo la mayor actividad insecticida, con una mortalidad de 83,3±16,7% en los terguitos, de 38,9±4,8 % en los esternitos y de 16,7±0 % a las 72 horas en ninfas de estadioI expuestas a superficies tratadas y 500 mg.L-1. En las ninfas de estadio V solo se presentó mortalidad en los esternitos (11,1±9,6 % con el análogo 6 y 5,5±4,7 % con los análogos 3 y 7 a las 72 h y 1.500 mg.L-1). Las dosis letales para la molécula 3 en los terguitos de ninfas de estadio I fueron las siguientes: DL50, 225,60 mg.L-1 y DL95, 955,90 mg.L-1. En cuanto a los aceites esenciales, el efecto insecticida solo se presentó con C. flexuosus (11,1±4,8%) en los esternitos de ninfas de estadio I expuestas a superficies tratadas; con C. sinensis (5,6±4,8%) en los terguitos y en los esternitos (8,3±0%) a las 72 horas y 1.000 mg.L-1. Conclusión. Los análogos sintéticos del alcaloide girgensohnina y los aceites esenciales de C. flexuosus y C. sinensis exhibieron actividad insecticida en R. prolixus. El análogo 3 exhibió la mayor actividad insecticida de todas las moléculas evaluadas bajo las condiciones de laboratorio.

Insecticidal and Repellent Activity of Several Plant-Derived Essential Oils Against Aedes aegypti.

We examined the pupicidal, adulticidal, repellent, and oviposition-deterrent activities of essential oils (EOs) from Lippia alba, L. origanoides, Eucalyptus citriodora, Cymbopogon citratus, Cymbopogon flexuosus, Citrus sinensis , Cananga odorata , Swinglea glutinosa, and Tagetes lucida plants against Aedes aegypti under laboratory conditions. Pupicidal and adulticidal activities were assessed at exploratory concentrations of 250, 310, and 390 parts per million (ppm); and 30, 300, and 1,000 ppm, respectively. The greatest pupicidal activity was exhibited at 390 ppm with a 24-h exposure by L. origanoides, and 390 ppm with a 48-h exposure by Citrus sinensis . Lippia origanoides killed all adult mosquitoes at 300 ppm after 120 min of exposure. Only L. origanoides and E. citriodora EOs, applied at 1,000 ppm to human skin, produced the greatest repellency (100%) to host-seeking Ae. aegypti after 2 min of exposure; the repellency decreased between 12% and 10% after 15 min. Complete oviposition deterrence by gravid Ae. aegypti was observed for E. citriodora EOs at 200 ppm with an oviposition activity index of -1.00. These results confirm that the EOs assessed in this study have insecticidal, repellent, and oviposition-deterrent activities against the dengue vector, Ae. aegypti.

Larvicidal action of ethanolic extracts from fruit endocarps of Melia azedarach and Azadirachta indica against the dengue mosquito Aedes aegypti.

Ethanolic extracts from the kernels of ripe fruits from the Indian Lilac Melia azedarach and from the well-known Neem tree, Azadirachta indica were assayed against larvae of Aedes aegypti, the mosquito vector of dengue fever. The lethality bioassays were carried out according to the recommendations of the World Health Organization. Extracts were tested at doses ranging from 0.0033 to 0.05 g% in an aqueous medium for 24 and 48 h, at 25 or 30 degrees C, with or without feeding of the larvae. LC50, LC95 and LC99 were determined. Both seed extracts proved lethal for third to fourth instar larvae. Non-fed A. aegypti larvae were more susceptible to Azadirachta extracts at both temperatures. Under a more realistic environmental situation, namely with fed larvae at 25 degrees C, the death rates caused by the Melia extract were higher, although at 30 degrees C the extract of Azadirachta had an even higher lethality. Inter allia, the LC50 values for the crude extracts of these two members of the Meliaceae ranged from 0.017 to 0.034 g% while the LC99 values ranged from 0.133 to 0.189 g%. Since no downstream processing was undertaken to purify the active agents in the extracts, our findings seem very promising, suggesting that it may be possible to increase the larvicidal activity further by improving the extraction and the fractionation of the crude limonoids, for instance removing the co-extracted natural fats.