Óleos essenciais e extratos vegetais como ferramentas alternativas ao controle químico de larvas de Aedes spp, Anopheles spp e Culex spp / Essential oils and plant extracts as alternative tools for chemical control of Aedes spp, Anopheles spp, and Culex spp

Objetivos: Realizar um levantamento das contribuições científicas produzidas entre 2017 e 2021 acerca do efeito larvicida de óleos essenciais e extratos vegetais no controle de Aedes spp, Anopheles spp e Culex spp. Métodos: de setembro a outubro de 2022, foi realizado um levantamento de artigos científicos publicados entre os anos de 2017 e 2021, nas bases de dados Portal Periódicos Capes, Scielo, Science Direct e Scopus. Foram utilizados os descritores "larvicide", "essential oil" e "plant extracts" com a interposição do operador boleano "AND". Resultados: inicialmente, foram obtidos 246 artigos, dos quais 110 foram excluídos (68 não estavam disponíveis na íntegra e 42 apareceram em mais de uma base de dados). Dos 136 artigos restantes, 36 foram excluídos por não terem realizado ensaio larvicida. Dos 100 artigos remanescentes, 63 foram excluídos por não mencionarem valores de CL50, enquanto 3 não especificaram a estrutura vegetal de obtenção dos produtos naturais, restando, portanto, 34 artigos para análise. Foram utilizadas 57 espécies vegetais para a obtenção dos produtos vegetais utilizados contra larvas de Aedes spp; 11 espécies nos ensaios contra Anopheles spp, e 36 espécies nos ensaios contra Culex spp. Os óleos essenciais predominaram nos ensaios contra Aedes spp, enquanto os extratos, contra Anopheles spp. A maior parte dos produtos testados exibiu CL50 < 100 ppm. Conclusão: a atividade larvicida demonstrada por uma grande variedade de extratos vegetais e óleos essenciais representa uma alternativa promissora ao tradicional controle químico feito à base de inseticidas sintéticos em programas de manejo integrado de vetores.

Objectives: Conduct a survey of the scientific contributions produced between 2017 and 2021 on the larvicidal effect of essential oils and plant extracts in the control of Aedes spp, Anopheles spp, and Culex spp. Methods: from September to October 2022, a survey was carried out of scientific articles published between 2017 and 2021 in the Portal Periódicos Capes, Scielo, Science Direct, and Scopus databases. The descriptors "larvicide", "essential oil" and "plant extracts" were used with the Boolean operator "AND". Results: initially, 246 articles were obtained, of which 110 were excluded (68 were not available, and 42 appeared in more than one database). Of the remaining 136 articles, 36 were excluded because they did not perform a larvicide assay. Of the 100 remaining articles, 63 were excluded for not mentioning LC50 values, while three did not specify the plant structure for obtaining natural products, thus leaving 34 articles for analysis. A total of 57 plant species were used to obtain plant products used against Aedes spp larvae; 11 species in the tests against Anopheles spp, and 36 species in the tests against Culex spp. Essential oils predominated in the tests against Aedes spp, while extracts against Anopheles spp. Most of the products tested exhibited an LC50 < 100 ppm. Conclusion: the larvicidal activity demonstrated by a wide variety of plant extracts and essential oils represents a promising alternative to traditional chemical control based on synthetic insecticides in integrated vector management programs.

Biotechnological potential of essential oils from different chemotypes of Lippia alba(Mill.) N.E.Br. ex Britton & P. Wilson / Potencial biotecnológico de los aceites esenciales de diferentes quimiotipos de Lippia alba(Mill.) N.E.Br. ex Britton y P. Wilson

This study reports the biotechnological importance of seven Lippia albaspecimens collected in different places in Brazil, and evaluation of some activities as larvicidal against Aedes spp., antifungal against dermatophytes; cytotoxicity against SNB-19 (astrocytoma), HCT-116 (human colon) and PC-3 (human prostate) cancer cell lines, and inhibition of the enzyme acetylcholinesterase (AChE). The essential oils, whose extraction yield was about 1.24 w/w ± 0.9%, showed differences in their chemical composition and considered as chemotypes. The essential oils containing neral and geranial as main constituents showed better action against HCT-116 cell lines (IC50 value was 9.22 µg/mL), larvicidal activity against arbovirus vectors (LC50 value against A. aegypti was 1.59 µg/mL) and inhibition of AChE (halo inhibition zone was 1 cm). The essential oils containing mainly monoterpenoids showed better antifungal action with MIC values range from 0.15 to 1.25 mg/mL. This chemical and biological characterization may be useful for biotechnological applications.

Este estudio reporta la importancia biotecnológica de siete especímenes de Lippia alba recolectados en diferentes lugares de Brasil, y evaluación de algunas actividades como larvicida contra Aedes spp., Antifúngico contra dermatofitos; citotoxicidad contra líneas celulares de cáncer SNB-19 (astrocitoma), HCT-116 (colon humano) y PC-3 (próstata humana), e inhibición de la enzima acetilcolinesterasa (AChE). Los aceites esenciales, cuyo rendimiento de extracción fue de aproximadamente 1,24 p/p ± 0,9%, mostraron diferencias en su composición química y se consideraron quimiotipos. Los aceites esenciales que contienen neral y geranial como constituyentes principales mostraron una mejor acción contra las líneas celulares HCT-116 (el valor de CI50 fue de 9.22 µg/mL), actividad larvicida contra los vectores de arbovirus (el valor de LC50 contra A. aegypti fue de 1.59 µg/mL) e inhibición de AChE (la zona de inhibición del halo era de 1 cm). Los aceites esenciales que contienen principalmente monoterpenoides mostraron una mejor acción antifúngica con valores de CMI en el rango de 0.15 a 1.25 mg/mL. Esta caracterización química y biológica puede ser útil para aplicaciones biotecnológicas.

Toxicity of Ulva lactuca and green fabricated silver nanoparticles against mosquito vectors and their impact on the genomic DNA of the dengue vector Aedes aegypti.

Marine seaweeds are known to have a potential role against microbial and pesticidal activities. Ulva lactuca, a green macroalgae extract analysed through gas chromatography mass spectrometry reveals 31 compounds. Resistance of mosquito vectors to synthetic insecticides remains a major problem. Discovering and applying natural agents to act against disease vectors is challenging. The activities of the extract and nano-fabricated green synthesised silver nanoparticles were checked for use against Aedes aegypti and Culex pipiens. The crude extract and synthesised silver nanoparticles exhibited a notable larvicidal effect, and very effective inhibition of pupal and adult emergence. Inhibition of adult emergence of Ae.aegypti was 97.7% and in Cu.pipiens, it was 93.3%. Our genotypic study of Deoxyribonucleic acid from treated larvae utilising random primers MA-09, MA-12 and MA-26 revealed damaged nucleotide sequences when compared with the controls. The antimicrobial activity of both the extract and green synthesised nanomaterials showed prominent activity against pathogenic drug resistant bacteria. Our results contribute to further development of eco-friendly insecticides with lower cost of preparation. This could further contribute to further research helping future generations to be free from these deadly disease-causing vectors and pathogenic microbes.

Chemical composition and larvicidal activity of the essential oil of Pimenta dioica leaves / Composición química y actividad larvicida del aceite esencial de hojas de Pimenta dioica

In this study, we investigated the main constituent, the predominant class and biological activity of the essential oil extracted from the leaves of Pimenta dioica and the pattern of the major constituent against larvae in the third stage of Aedes aegypti. For this reason, we extracted the oil by hydrodistillation, identified its components by gas chromatography coupled with mass spectrometry (GC/MS) and calculated the lethal concentration (LC50) of the larvicidal activity using the Reed-Muench method. The results show that the oil consists mainly of eugenol, in which the phenylpropanoid class predominated and the lethal concentration, LC50, was 38.86 µg mL-1at a confidence level of 2.25 µg mL-1, while the eugenol standard presented LC5079.75 µg mL-1at a confidence level of 2.10 µg mL-1. Given the facts, we conclude that the oil is more active than the standard and that it has the potential to replace chemical larvicides.

En este estudio, investigamos el constituyente principal, la clase predominante y la actividad biológica del aceite esencial extraído de las hojas de Pimenta dioica y el patrón del constituyente principal contra las larvas en la tercera etapa de Aedes aegypti. Por este motivo, extrajimos el aceite por hidrodestilación, identificamos sus componentes mediante cromatografía de gases acoplada a espectrometría de masas (GC/MS) y calculamos la concentración letal (CL50) de la actividad larvicida mediante el método Reed-Muench. Los resultados muestran que el aceite está constituido principalmente por eugenol, en el que predominó la clase fenilpropanoide y la concentración letal, CL50, fue de 38,86 µg.mL-1 a un nivel de confianza de 2,25 µg.mL-1, mientras que el estándar de eugenol presentó CL50 79,75 µg.mL -1 a un nivel de confianza de 2,10 µg.mL-1. Dados los hechos, concluimos que el aceite es más activo que el estándar y que tiene el potencial de reemplazar los larvicidas químicos.

Bioguided Phytochemical Study of Ipomoea cairica Extracts with Larvicidal Activity against Aedes aegypti.

Vector-borne diseases, such as those transmitted by Aedes aegypti, are a constant threat to inhabitants of tropical regions of the planet. Synthetic chemicals are commonly used as a strategy to control them; however, these products are known to persist in ecosystems and drive the appearance of resistance genes in arthropod vectors. Thus, the use of natural products has emerged as an environmentally friendly alternative in integrated vector control strategies. The present bioguided study investigated the larvicidal potential of Ipomoea cairica extracts, fractionated using thin-layer and open-column chromatography, because this species has been shown to exert larvicidal effects on the genus Aedes. The objective of this study was to evaluate the nonvolatile components in ethanolic extract of I. cairica stems as a potential natural larvicidal, and coumarins, such as 7-hydroxy-6-methoxychromen-2-one (scopoletin) and 7-hydroxychromen-2-one (umbelliferone), were identified as major compounds; however, they were not shown to be responsible for the larvicidal activity. Based on the results of the larvicidal action tests, these coumarins are not directly responsible for the larvicidal activity, but this activity might be attributed to a synergistic effect of all the compounds present in the most active secondary fraction, called F.DCM, which had an LC50 value of 30.608 mg/L. This type of study has yet not been conducted in the region; therefore, it is an important contribution to recognizing a natural and easy-to-cultivate source of vector control, such I. cairica.

Evaluating Volatile Plant Compounds of Psidium galapageium (Myrtales: Myrtaceae) as Repellents Against Invasive Parasitic Diptera in the Galapagos Islands.

Plant-based repellents represent a safe, economic, and viable alternative to managing invasive insects that threaten native fauna. Observations of self-medication in animals can provide important cues to the medicinal properties of plants. A recent study in the Galapagos Islands found that Darwin's finches apply the leaves of Psidium galapageium (Hooker 1847) to their feathers, extracts of which were repellent to mosquitoes and the parasitic fly Philornis downsi (Dodge & Aitkens 1968; Diptera: Muscidae). Introduced mosquitoes are suspected vectors of avian pathogens in the Galapagos Islands, whereas the larvae of P. downsi are blood-feeders, causing significant declines of the endemic avifauna. In this study, we investigated the volatile compounds found in P. galapageium, testing each against a model organism, the mosquito Anopheles arabiensis (Patton 1905; Diptera: Culicidae), with the aim of singling out the most effective compound for repelling dipterans. Examinations of an ethanolic extract of P. galapageium, its essential oil and each of their respective fractions, revealed a mixture of monoterpenes and sesquiterpenes, the latter consisting mainly of guaiol, trans-nerolidol, and ß-eudesmol. Of these, trans-nerolidol was identified as the most effective repellent to mosquitoes. This was subsequently tested at four different concentrations against P. downsi, but we did not find a repellence response. A tendency to avoid the compound was observed, albeit significance was not achieved in any case. The lack of repellence suggests that flies may respond to a combination of the volatile compounds found in P. galapageium, rather than to a single compound.

Short-term changes related to autotetraploidy in essential oil composition of Eucalyptus benthamii Maiden & Cambage and its applications in different bioassays.

Some forest trees have been polyploidized to improve their traits and to supply new germplasms for breeding programs. As trees have a long juvenile stage, the early characterization of the chromosome set doubling effects is crucial for previous selection. Thus, we aimed to characterize the chemical variability of essential oils from diploid and autotetraploid germplasms (autotetraploid A and B) of Eucalyptus benthamii, as well as to evaluate their larvicidal and allelopathic effects. Autotetraploid A showed a higher essential oil yield than diploid and autotetraploid B, which did not differ quantitatively. Aromadendrene, viridiflorol and α-pinene were the major compounds in the diploid essential oil. In contrast, compounds were present in autotetraploids, such as 1,8-cineole, limonene, α-terpineol, and α-terpinyl-acetate. Essential oils from the diploid at 50-200 ppm were twice as larvicidal than those from autotetraploids against Aedes aegypti larvae. Considering the phytotoxicity bioassays using Lactuca sativa, essential oils from both ploidy levels affected root growth. Moreover, the essential oils inhibited shoot growth at all concentrations tested (187.5; 375; 750; 1500; and 3000 ppm). Autotetraploid A and B had the same effect on shoot growth as glyphosate. The essential oils had no cytogenotoxic effect on root meristematic cells of L. sativa, whereas phytotoxic potential was identified mainly in shoot growth. This work demonstrated a dramatic change in secondary metabolism (terpene composition) related to an increase in the ploidy level in Eucalyptus germplasms. In addition, we report the novelty of the chemical composition of essential oils among germplasms and their potential use as larvicidal and post-emergence weed control agents.

Analysis of chemical compositions and larvicidal activity of nut extracts from Areca catechu Linn against Aedes (Diptera: Culicidae).

BACKGROUND: There is a growing need to use green alternative larvicidal control for Aedes larvae compared to chemical insecticides. Substantial reliance on chemical insecticides caused insecticide resistance in mosquito populations. Thus, research for alternate chemical compounds from natural products is necessary to control Aedes larvae. This study explores the analysis of chemical compositions from Areca catechu nut as a potential larvicide for Aedes (Diptera: Culicidae). METHODS: The Areca catechu nut collected from Ipoh, Perak, Malaysia was grounded into powder and used for Soxhlet extraction. The chemical analysis of the extracts and their structures were identified using the GCMS-QP2010 Ultra (Shimadzu) system. National Institute of Standards and Technology (NIST) Chemistry WebBook, Standard Reference Database 69 (https://webbook.nist.gov/chemistry/) and PubChem (https://pubchem.ncbi.nlm.nih.gov/), the two databases used to retrieve the synonyms, molecular formula, molecular weight, and 2-dimensional (2D) structure of chemical compounds. Next, following WHO procedures for larval bioassays, the extracts were used to asses larvicidal activity against early 4th instar larvae of Aedes aegypti and Aedes albopictus. RESULTS: The larvicidal activities were observed against early 4th stage larvae with different concentrations in the range from 200 mg/L to 1600 mg/L. The LC50 and LC95 of Aedes aegypti were 621 mg/L and 2264 mg/L respectively; whereas the LC50 and LC95 of Aedes albopictus were 636 mg/L and 2268 mg/L respectively. Mortality was not observed in the non-target organism test. The analysis using gas chromatography and mass spectrometer recovered several chemical compounds such as Arecaidine, Dodecanoic acid, Methyl tetradecanoate, Tetradecanoic acid , and n-Hexadecanoic acid bioactive components. These chemical constituents were used as additive formulations in pesticides, pest control, insect repellent, and insecticidal agents. CONCLUSIONS: Our study showed significant outcomes from the extract of Areca catechu nut and it deserves further investigation in relation to chemical components and larvicidal actions between different species of Aedes mosquitoes. Even though all these findings are fundamental, it may have some interesting potentials to be developed as natural bio-larvicidal products.

Biocidal Activity of a Nanoemulsion Containing Essential Oil from Protium heptaphyllum Resin against Aedes aegypti (Diptera: Culicidae).

This work aimed to prepare a nanoemulsion containing the essential oil of the Protium heptaphyllum resin and evaluate its biocidal activities against the different stages of development of the Aedes aegypti mosquito. Ovicide, pupicide, adulticide and repellency assays were performed. The main constituents were p-cymene (27.70%) and α-pinene (22.31%). The developed nanoemulsion showed kinetic stability and monomodal distribution at a hydrophilic-lipophilic balance of 14 with a droplet size of 115.56 ± 1.68 nn and a zeta potential of -29.63 ± 3.46 mV. The nanoemulsion showed insecticidal action with LC50 0.404 µg·mL-1 for the ovicidal effect. In the pupicidal test, at the concentration of 160 µg·mL-1, 100% mortality was reached after 24 h. For adulticidal activity, a diagnostic concentration of 200 µg·mL-1 (120 min) was determined. In the repellency test, a concentration of 200 µg·mL-1 during the 180 min of the test showed a protection index of 77.67%. In conclusion, the nanobiotechnological product derived from the essential oil of P. heptaphyllum resin can be considered as a promising colloid that can be used to control infectious disease vectors through a wide range of possible modes of applications, probably as this bioactive delivery system may allow the optimal effect of the P. heptaphyllum terpenes in aqueous media and may also induce satisfactory delivery to air interfaces.

The determination of effective concentration of acethonilic Ipomoea cairica leaves extract against laboratory and field strains of Aedes albopictus and Aedes aegypti mosquito larvae.

Inundated with escalating dengue outbreaks, there is an urgent call to find alternate potential vector control methods as the currently employed method fails to curb the expanding of dengue virus transmission in Malaysia. Supported by this aim, we are interested in exploiting the potential of Ipomoea cairica leaves extract towards primary and secondary vectors of dengue fever, Aedes aegypti and Aedes albopictus. To assess the effectiveness of this plant extracts towards Aedes larvae, we carried out two complementary analyses. First, we observed the comparative effectiveness of larvicidal activity I. cairica extract against the laboratory and field strains of Ae. aegypti and Ae. albopictus. Then, we determined the effective lethal dose of this plant extract against Aedes larvae using log-probit regression analysis of the SPSS 20.0 programme. Results from bioassay demonstrated that I. cairica leaves extract was highly effective to induce larvicidal mortality of Ae. albopictus and Ae. aegypti within 24 and 48 hours post-treatment. Results from the factorial analysis of variance (ANOVA) also indicated that there were significant differences in larvicidal activity between species and strains used (P<0.05). It is interesting to notify that the sequence of effectiveness for the larvicidal activities of I. cairica acethonilic leaves extract is in the manner; Ae. albopictus field strain > Ae. aegypti laboratory strain > Ae. aegypti field strain > Ae. albopictus laboratory strain. The I. cairica leaves extract displayed high larvicidal activity against Ae. albopictus as compared to Ae. aegypti. This is the first evaluation involving the comparison of I. cairica leaves extract effects for the laboratory strain and field strain of Ae. albopictus and Ae. Aegypti.

Chemical composition and insecticidal activity of Garcinia gardneriana (Planchon & Triana) Zappi (Clusiaceae) essential oil / Composición química y actividad insecticida del aceite esencial de Garcinia gardneriana (Planchon & Triana) Zappi (Clusiaceae)

The present study aimed to analyze the chemical composition of the essential oil from Garcinia gardneriana (Planchon & Triana) Zappi leaves and fruits, and to determine its acaricidal activity on Rhipicephalus microplusy larval packet test and larvicidal action on Aedes aegyptiby larval immersion test. The chemical analysis of the essential oil by gas chromatography-mass spectrometry identified sesquiterpene hydrocarbons and oxygenated sesquiterpenes in bacupari leaves and fruits, and α-cedrene, α-chamigrene, α-trans-bergamotene, and ß-curcumene as major compounds. Essential oil from leaves of G. gardneriana presented acaricidal activity on R. microplus (LC50= 4.8 mg/mL; LC99= 10.8 mg/mL) and larvicidal effect on A. aegypti (LC50= 5.4 mg/mL; LC99 = 11.6 mg/mL), where as essential oil from the fruits of G. gardneriana showed LC50= 4.6 mg/mL and LC99= 8.9 mg/mL against R. microplus and LC50= 6.4 mg/mL and LC99= 13.9 mg/mL against A. aegypti. These results thus demonstrate the potential acaricidal and larvicidal activity of essential oil of G. gardneriana, offering new perspectives for the realization of bioassays from this essential oil.

El presente estudio tuvo como objetivo analizar la composición química del aceite esencial de las hojas y frutos de Garcinia gardneriana (Planchon & Triana) Zappi, y determinar su actividad acaricida en Rhipicephalus microplus y larvicida en Aedes aegypti empleando la prueba de inmersión de larvas. El análisis químico del aceite esencial por cromatografía de gases-espectrometría de masas identificó hidrocarburos sesquiterpénicos y sesquiterpenos oxigenados en hojas y frutos de bacupari, y α-cedreno, α-chamigreno, α-trans-bergamoteno y ß-curcumeno como compuestos principales. El aceite esencial obtenido de las hojas de G. gardneriana presentó actividad acaricida en la garrapata del ganado (LC50= 4,8 mg/mL; LC99= 10,8 mg/mL) y actividad larvicida en A. aegypti (LC50= 5,4 mg/mL; LC99= 11,6 mg/mL), así como, el aceite esencial obtenido de los frutos de G. gardneriana mostró LC50= 4,6 mg/mL y LC99= 8,9 mg/mL contra las larvas de garrapatas de ganado y LC50= 6,4 mg/mL y LC99= 13,9 mg/mL en las larvas de A. aegypti. Por lo tanto, estos resultados demuestran la actividad acaricida y larvicida del aceite essencial de G. gardneriana, ofreciendo nuevas perspectivas para la realización de bioensayos a partir de este aceite esencial.

Transcriptomic analysis and molecular docking reveal genes involved in the response of Aedes aegypti larvae to an essential oil extracted from Eucalyptus.

BACKGROUND: Aedes aegypti (L.) is an urban mosquito, vector of several arboviruses that cause severe diseases in hundreds of million people each year. The resistance to synthetic insecticides developed by Ae. aegypti populations worldwide has contributed to failures in vector control campaigns, increasing the impact of arbovirus diseases. In this context, plant-derived essential oils with larvicidal activity could be an attractive alternative for vector control. However, the mode of action and the detoxificant response of mosquitoes to plant derived compounds have not been established, impairing the optimization of their use. METHODS AND FINDINGS: Here we compare gene expression in Ae. aegypti larvae after 14 hrs of exposure to Eucalyptus camaldulensis essential oil with a control group exposed to vehicle (acetone) for the same lapse, by using RNA-Seq. We found differentially expressed genes encoding for cuticle proteins, fatty-acid synthesis, membrane transporters and detoxificant related gene families (i.e. heat shock proteins, cytochromes P450, glutathione transferases, UDP-glycosyltransferases and ABC transporters). Finally, our RNA-Seq and molecular docking results provide evidence pointing to a central involvement of chemosensory proteins in the detoxificant response in mosquitoes. CONCLUSIONS AND SIGNIFICANCE: Our work contributes to the understanding of the physiological response of Ae. aegypti larvae to an intoxication with a natural toxic distilled from Eucalyptus leafs. The results suggest an involvement of most of the gene families associated to detoxification of xenobiotics in insects. Noteworthy, this work provides important information regarding the implication of chemosensory proteins in the detoxification of a natural larvicide. Understanding the mode of detoxification of Eucalyptus distilled compounds could contribute to their implementation as a tool in mosquito control.

Bioefficacy of Epaltes divaricata (L.) n-Hexane Extracts and Their Major Metabolites against the Lepidopteran Pests Spodoptera litura (fab.) and Dengue Mosquito Aedes aegypti (Linn.).

The present research investigated the chemical characterization and insecticidal activity of n-Hexane extracts of Epaltes divaricata (NH-EDx) along with their chief derivatives n-Hexadecanoic acid (n-HDa) and n-Octadecanoic acid (n-ODa) against the dengue vector Aedes aegypti and lepidopteran pest Spodoptera litura. Chemical screening of NH-EDx through GC-MS analysis delivered nine major derivatives, and the maximum peak area percentage was observed in n-Hexadecanoic acid (14.63%) followed by n-Octadecadienoic acid (6.73%). The larvicidal activity of NH-EDx (1000 ppm), n-HDa (5 ppm), and n-ODa (5 ppm) against the A. aegypti and S. litura larvae showed significant mortality rate in a dose-dependent way across all the instars. The larvicidal activity was profound in the A. aegypti as compared to the S. litura across all the larval instars. The sublethal dosages of NH-EDx (500 ppm), n-HDa (2.5 ppm), and n-ODa (2.5 ppm) also showed alterations in the larval/pupal durations and adult longevity in both the insect pests. The enzyme activity revealed that the α- and ß-carboxylesterase levels were decreased significantly in both the insect pests, whereas the levels of GST and CYP450 uplifted in a dose-dependent manner of NH-EDx, n-HDa, and n-ODa. Correspondingly, midgut tissues such as the epithelial layer (EL), gut lumen (GL), peritrophic matrix (Pm), and brush border membrane (BBM) were significantly altered in their morphology across both A. aegypti and S. litura against the NH-EDx and their bioactive metabolites. NH-EDx and their bioactive metabolites n-HDa and n-ODa showed significant larvicidal, growth retardant, enzyme inhibition, and midgut toxicity effects against two crucial agriculturally and medically challenging insect pest of ecological importance.

Change in susceptibility response of Aedes aegypti (Diptera: Culicidae) to organophosphate insecticide and Copaifera oleoresin.

The growth of resistance in vector mosquitoes to insecticides, especially the organophosphate Temephos can facilitate the transmission of various disease agents worldwide. Consequently, it arises a challenge to public health agencies, which is the urgency use of other possibilities as botanical insecticides. Such insecticides have specific properties against insects due to the plant's ability to synthesize products derived from its secondary metabolism. The diversity and complexity of active compounds of botanical insecticides can help reduce the selection of resistant individuals and consequently not change susceptibility. To corroborate this hypothesis, the aim of this study was to compare two populations of Aedes aegypti treated with Temephos and Copaifera oleoresin. Thus, Ae. aegypti larvae were exposed from (F1) up to tenth generation (F10) with sublethal doses (±LC25) of these products (Copaifera oleoresin: 40 mg/L and Temephos: 0.0030 mg/L). The triplicates and control groups were monitored every 48 hours and the surviving larvae were separated until the emergence of the adults. Each new population were then subjected to a series of concentrations (LC50 and LC95) of Temephos and Copaifera oleoresin to calculate the Resistance Ratio (RR) of each exposed generation. The population of Ae. aegypti exposed to Temephos had an increase in RR from 05 (considered low) to 13 (considered high). Those population exposed to Copaifera oleoresin, had no increasing in RR and continued susceptible to the oil in all generations. There was a significant difference in mortality between the generations exposed to the two products. The results presented here show that the change in the susceptibility status of Ae. aegypti population to Temephos was already expected. So, we believe that this work will be of great contribution to research related to mosquito control with plant products, and resistance to chemical insecticides.

Development of cellulose nanocrystal-stabilized Pickering emulsions of massoia and nutmeg essential oils for the control of Aedes albopictus.

We investigated the larvicidal potential of 10 plant essential oils (EOs) against the Asian tiger mosquito Aedes albopictus. Among the EOs, larvicidal activity against Ae. albopictus was strongest in those derived from massoia (Massoia aromatica) and nutmeg (Myristica fragrans). Larvicidal activities of massoia and nutmeg EOs against Ae. albopictus were 95.0% and 85.0% at 50 µg/mL, respectively. A total of 4 and 14 compounds were identified from massoia and nutmeg, respectively, and two massoia lactones, C10 and C12, were isolated from massoia EO. Among the identified compounds, benzyl salicylate, terpinolene, C12 massoia lactone, sabinene, benzyl benzoate, methyl eugenol, and C10 massoia lactone exhibited the strong larvicidal activity. Cellulose nanocrystal (CNC)-stabilized Pickering emulsions of massoia and nutmeg EOs were developed to overcome the insolubility of EOs in water. CNC/massoia and CNC/nutmeg emulsions were stable for at least 10 days, and larvicidal activities of CNC/massoia PE and CNC/nutmeg were higher than those of crude massoia and nutmeg EOs. This study presents a CNC-stabilized PE, a suitable formulation for EOs, as a potential larvicide against Ae. albopictus.

High larvicidal efficacy of yeast-encapsulated orange oil against Aedes aegypti strains from Brazil.

BACKGROUND: Botanical substances such as essential oils (EOs) have demonstrated insecticidal properties and are a valid option for vector control. However, free EOs are unreliable as mosquito larvicides due their easy degradation by environmental exposure to ultraviolet light and higher temperatures. Here, we assessed the efficacy of a mosquito larvicide based on orange oil in a yeast-based delivery system against Aedes aegypti strains with different resistance status towards chemical neurotoxic insecticides. This larvicide preparation was physicochemically characterized in a previous report. METHODS: Larvae of four Ae. aegypti strains from different regions of Brazil and different resistance profiles for deltamethrin (pyrethroid) and temephos (organophosphate) were tested against yeast-encapsulated orange oil (YEOO) in laboratory conditions for measurement of LC50 and LC90 values. The same assays were performed with the Belo Horizonte strain under environmental conditions (natural light and temperature). The resistance profiles of these strains were compared to the Rockefeller reference strain in all conditions. RESULTS: YEOO was found to be a highly active larvicide (LC50 < 50 mg/L) against all Ae. aegypti strains tested in both laboratory conditions (LC50 = 8.1-24.7 mg/L) and environmental conditions with natural light and temperature fluctuation (LC50 = 20.0-49.9 mg/L). Moreover, all strains were considered susceptible (RR < 5) to YEOO, considering resistance ratios calculated based on the Rockefeller strain. The resistance ratios were only higher than 2.5 for LC90-95 of Belo Horizonte in the laboratory, probably due the higher heterogeneity associated with older egg papers (> 5 months). CONCLUSION: YEOO demonstrates high larvicidal activity against Ae. aegypti strains with resistant phenotypes for deltamethrin (PY) and temephos (OP). This larvicidal activity suggests the potential for the development of YEOO as an alternative intervention to synthetic insecticides in integrated vector management programs, for populations with resistance to commonly used insecticides.

Bioactivities of rose-scented geranium nanoemulsions against the larvae of Anopheles stephensi and their gut bacteria.

Anopheles stephensi with three different biotypes is a major vector of malaria in Asia. It breeds in a wide range of habitats. Therefore, safer and more sustainable methods are needed to control its immature stages rather than chemical pesticides. The larvicidal and antibacterial properties of the Pelargonium roseum essential oil (PREO) formulations were investigated against mysorensis and intermediate forms of An. stephensi in laboratory conditions. A series of nanoemulsions containing different amounts of PREO, equivalent to the calculated LC50 values for each An. stephensi form, and various quantities of surfactants and co-surfactants were developed. The physical and morphological properties of the most lethal formulations were also determined. PREO and its major components, i.e. citronellol (21.34%), L-menthone (6.41%), linalool (4.214%), and geraniol (2.19%), showed potent larvicidal activity against the studied mosquitoes. The LC50/90 values for mysorensis and intermediate forms were computed as 11.44/42.42 ppm and 12.55/47.69 ppm, respectively. The F48/F44 nanoformulations with 94% and 88% lethality for the mysorensis and intermediate forms were designated as optimized formulations. The droplet size, polydispersity index, and zeta-potential for F48/F44 were determined as 172.8/90.95 nm, 0.123/0.183, and -1.08/-2.08 mV, respectively. These results were also confirmed by TEM analysis. Prepared formulations displayed antibacterial activity against larval gut bacteria in the following order of decreasing inhibitory: LC90, optimized nanoemulsions, and LC50. PREO-based formulations were more effective against mysorensis than intermediate. Compared to the crude PREO, the overall larvicidal activity of all nanoformulations boosted by 20% and the optimized formulations by 50%. The sensitivity of insect gut bacteria may be a crucial factor in determining the outcome of the effect of toxins on target insects. The formulations designed in the present study may be a good option as a potent and selective larvicide for An. stephensi.

Insecticidal Activity and Free Radical Scavenging Properties of Isolated Phytoconstituents from the Saudi Plant Nuxia oppositifolia (Hochst.).

Chromatographic purification of the alcoholic extract from the aerial parts of the Saudi plant Nuxia oppositifolia (Hochst.), Benth., resulted in five isolated phenolic compounds. Two flavones, hispidulin (1) and jaceosidin (2), and the phenylethanoid glycosides, verbascoside (3), isoverbascoside (4), and conandroside (5), were identified and their chemical structures were determined by spectroscopic analyses. The insecticidal activity of compounds 1 and 2, in addition to 11 compounds isolated in a previous research (6-16), was evaluated against the Yellow Fever mosquito, Aedes aegypti. Four compounds displayed adulticidal activity with LD50 values of 2-2.3 µg/mosquito. Free radical scavenging properties of the plant extracts and compounds (1-5) were evaluated by measuring the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonate radical cation (ABTS•+) scavenging activity. All compounds exhibited notable activity, compared with the positive control, l-Ascorbic acid. This study suggests that N. oppositifolia could be a promising source of secondary metabolites, some with lethal adulticidal effect against Ae. aegypti.

Antiviral Compounds for Blocking Arboviral Transmission in Mosquitoes.

Mosquito-borne arthropod-borne viruses (arboviruses) such as the dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) are important human pathogens that are responsible for significant global morbidity and mortality. The recent emergence and re-emergence of mosquito-borne viral diseases (MBVDs) highlight the urgent need for safe and effective vaccines, therapeutics, and vector-control approaches to prevent MBVD outbreaks. In nature, arboviruses circulate between vertebrate hosts and arthropod vectors; therefore, disrupting the virus lifecycle in mosquitoes is a major approach for combating MBVDs. Several strategies were proposed to render mosquitoes that are refractory to arboviral infection, for example, those involving the generation of genetically modified mosquitoes or infection with the symbiotic bacterium Wolbachia. Due to the recent development of high-throughput screening methods, an increasing number of drugs with inhibitory effects on mosquito-borne arboviruses in mammalian cells were identified. These antivirals are useful resources that can impede the circulation of arboviruses between arthropods and humans by either rendering viruses more vulnerable in humans or suppressing viral infection by reducing the expression of host factors in mosquitoes. In this review, we summarize recent advances in small-molecule antiarboviral drugs in mammalian and mosquito cells, and discuss how to use these antivirals to block the transmission of MBVDs.

Molecular characterization, gas chromatography mass spectrometry analysis, phytochemical screening and insecticidal activities of ethanol extract of Lentinus squarrosulus against Aedes aegypti (Linnaeus).

Mosquito-transmitted diseases like zika, dengue, chikungunya, and yellow fever are known to affect human health worldwide. Numerous synthetic insecticides have been used as vector control for these diseases, but there is the challenge of environmental toxicity and vector resistance. This study investigated the medicinal and insecticidal potential of Lentinus squarrosulus against Aedes aegypti. The fruiting bodies were identified morphologically as well as using internal transcribed spacer (ITS) sequences for its molecular characterization. Genomic deoxyribonucleic acid (DNA) yield was confirmed with NanoDrop Spectrophotometer ND-1000 and amplified with ITSl and ITS4 primers. The amplicons were sequenced and the National Center for Biotechnology Information (NCBI) database identified the nucleotides. Its ethanol extract was subjected to phytochemical screening and gas chromatography mass spectrometry (GC-MS) analysis and tested against the pupa and fourth instar larva of Aedes aegypti with percentage mortality monitored. The Macrofungus was identified morphologically and confirmed with molecular characterization as Lentinus squarrosulus (LS). The gene sequence was deposited in GenBank (Accession number MK629662.1). GC-MS analysis showed that its ethanol extract has 25 bioactive compounds with 9,12-Octadecadienoic acid, ethyl ester having the highest percentage of 43.32% as well as methyl-2-oxo-1-pyrrolidine acetate and 17-octadecynoic acid having the lowest percentage (0.09%). The macrofungus contained varied concentrations of phytochemicals including phenols (159 mg/g GAE), tannins (1.6 mg/g TAE), and flavonoids (31.4 mg/g QE). The ethanol extract had significant potent effects on Aedes aegypti larva and pupa which could be due to the occurrence and abundance of 9,12-octadecadienoic acid in LS. The LC50 of the extract for larvicidal and pupicidal activities were 2.95 mg/mL and 3.55 mg/mL, respectively, while its LC90 were 6.31 mg/mL and 5.75 mg/mL respectively. Lentinus squarrosulus had insecticidal effects against the Aedes aegypti larva and pupa and possessed great potential as a source of alternative medicine and eco-friendly insecticides.