Physiological response of Metarhizium rileyi with linoleic acid supplementation.

Metarhizium rileyi has a broad biocontrol spectrum but is highly sensitive to abiotic factors. A Colombian isolate M. rileyi Nm017 has shown notorious potential against Helicoverpa zea. However, it has a loss of up to 22 % of its conidial germination after drying, which limits its potential as a biocontrol agent and further commercialization. Conidial desiccation resistance can be enhanced by nutritional supplements, which promotes field adaptability and facilitates technological development as a biopesticide. In this study, the effect of culture medium supplemented with linoleic acid on desiccation tolerance in Nm017 conidia was evaluated. Results showed that using a 2 % linoleic acid-supplemented medium increased the relative germination after drying by 41 % compared to the control treatment, without affecting insecticidal activity on H. zea. Also, the fungus increased the synthesis of trehalose, glucose, and erythritol during drying, independently of linoleic acid use. Ultrastructural analyses of the cell wall-membrane showed a loss of thickness by 22 % and 25 %, in samples obtained from 2 % linoleic acid supplementation and the control, respectively. Regarding its morphological characteristics, conidia inner area from both treatments did not change after drying. However, conidia from the control had a 24 % decrease in length/width ratio, whereas there was no alteration in conidia from acid linoleic. The average value of dry conidia elasticity coefficient from linoleic acid treatment was 200 % above the control. Medium supplementation with linoleic acid is a promising fermentation strategy for obtaining more tolerant conidia without affecting production and biocontrol parameters, compatible solutes synthesis, or modifying its cell configuration.

Insecticidal, antifeedant and acetylcholinesterase inhibitory activity of sesquiterpenoids derived from eudesmane, their molecular docking and QSAR.

This work evaluated the insecticidal, antifeedant and AChE inhibitory activity of compounds with eudesmane skeleton. The insecticidal activity was tested against larvae of Drosophila melanogaster and Cydia pomonella, the compounds 3 and 4 were the most active (LC50 of 104.2 and 106.7 µM; 82.0 and 84.4 µM, respectively). Likewise, the mentioned compounds were those that showed the highest acetylcholinesterase inhibitory activity, with IC50 of 0.26 ± 0.016 and 0.77 ± 0.016 µM, respectively. Enzyme kinetic studies, as well as molecular docking, show that the compounds would be non-competitive inhibitors of the enzyme. The antifeedant activity on Plodia interpunctella larvae showed an antifeedant index (AI) of 99% at 72 h for compounds 16, 27 and 20. The QSAR studies show that the properties associated with the polarity of the compounds would be responsible for the biological activities found.

Insecticidal effect of metabolites identified in edible mushrooms against Rhyssomatus nigerrimus Fahraeus / Efeito inseticida dos metabólitos identificados nos cogumelos comestíveis contra Rhyssomatus nigerrimus Fahraeus

Excessive use of insecticides has led to resistance of some pathogenic organisms (nematodes, bacteria and fungi), environmental contamination, and the presence of hazardous residues. Therefore, the aim of the present study was to evaluate synthetic metabolites derived from previous studies with edible mushrooms against the soybean weevil Rhyssomatus nigerrimus Fahraeus (Curculonidae) because of the relevance of pest control in an economically important crop. Furthermore, this is one of the first studies where edible fungal molecules are evaluated for the control of these insects. Initially, two in vitro tests (toxic effect and immersion) were evaluated against R. nigerrimus. In these tests, sensitivity and viability were determined in the 2% Tween control in water. For these two tests, the synthetic metabolites pentadecanoic acid (PNA), palmitic acid (PMA), stearic acid (STA), linoleic acid (LNA), ß-sitosterol (ßT) were evaluated individually as well as in combinations, "the fraction of standards (E1)". Based on the results obtained, the dip test was selected to evaluate the mixtures of two standards (1. PMA + ßT, 2. PMA + PNA, 3. PMA + LNA, 4. PMA + STA, 5. STA + ßT, 6. STA + PNA, 7. STA + LNA, 8. PNA + ßT, 9. PNA + LNA, 10. LNA + ßT), three (1. PNA + ßT + LNA, 2. PNA + ßT + STA, 3. STA + LNA + PNA and 4. STA + LNA + ßT) and four (PNA, ßT, LNA and STA). The results showed that the mixture of three standards caused a higher percentage of mortality relative to the control group: l. PNA + ßT + LNA and 2. PNA + ßT + STA with 54.44 and 48% mortality of R. nigerrimus insects exposed for 15 days. These results show the importance of evaluating mixtures of molecules against R. nigerrimus.

O uso excessivo de inseticidas levou à resistência de alguns organismos patogênicos (nematódeos, bactérias e fungos), à contaminação ambiental e à presença de resíduos perigosos. Portanto, o objetivo do presente estudo foi avaliar a mortalidade de metabólitos sintéticos derivados de estudos anteriores com cogumelos comestíveis contra o gorgulho-da-soja Rhyssomatus nigerrimus Fahraeus (Curculonidae) por causa da relevância do controle de pragas em uma cultura economicamente importante. Além disso, este é um dos primeiros estudos em que as moléculas fúngicas comestíveis são avaliadas para o controle desses insetos. Inicialmente, dois testes in vitro (efeito tóxico e imersão) foram avaliados contra R. nigerrimus. Nesses testes, a sensibilidade e a viabilidade foram determinadas no controle de 2% de Tween na água. Para esses dois testes, os metabólitos sintéticos ­ ácido pentadecanoico (PNA), ácido palmítico (PMA), ácido esteárico (STA), ácido linoleico (LNA) e ß-sitosterol (ßT) ­ foram avaliados individualmente, bem como a combinação dos 5, "a fração de padrões (E1)". Com base nos resultados obtidos, o teste de imersão foi selecionado para avaliar as misturas de dois padrões (1. PMA + ßT, 2. PMA + PNA, 3. PMA + LNA, 4. PMA + STA, 5. STA + ßT, 6. STA + PNA, 7. STA + LNA, 8. PNA + ßT, 9. PNA + LNA, 10. LNA + ßT), três (1. PNA + ßT + LNA, 2. PNA + ßT + STA, 3. STA + LNA + PNA e 4. STA + LNA + ßT) e quatro (PNA, ßT, LNA e STA). Os resultados mostraram que a mistura de três padrões foi a com maior porcentagem de mortalidade em relação ao grupo controle, quais sejam, l. PNA + ßT + LNA e 2. PNA + ßT + STA, com 54,44% e 48% de mortalidade, respectivamente, em uma exposição de 15 dias contra R. nigerrimus. Estes resultados mostram a importância de avaliar as misturas entre moléculas contra R. nigerrimus.

Cytotoxic, phytotoxic and insecticidal potential of Achillea millefolium L. and Chaerophyllum villosum wall. ex dc / Potencial citotóxico, fitotóxico e insecticida de Achillea millefolium L. e Chaerophyllum villosum

The methanolic, chloroformic and aqueous extract of Achillea millefolium and Chaerophyllum villosum were investigated for cytotoxicity, phytotoxic and insecticidal activities. Cytotoxicity was investigated by brine shrimp lethality assay indicating that the crude methanolic extract of A.millefolium and chloroformic extract of C.villosum revealed highest mortality of brine shrimps with (LD50 of 52.60 µg/ml) and (14.81 µg/ml). Phytotoxicity was evaluated using the Lemna minor bioassay which revealed that the crude methanolic extract of A.millefolium and C.villosum extract has maximum inhibition of Lemna minor with (Fl50 6.60 µg/ml) and (0.67 µg/ml).The insecticidal activity showed that among all the insects studied it was observed that methanolic extract of A. millefoliumand C. villosum was highly toxic to Sphenoptera dadkhani with (LD50=4.17 µg/ml) and (0.34 µg/ml). From the present study it can be concluded that different extracts from A. millefolium and C. villosum showed good cytotoxic, phytotoxic and insecticidal activity in a dose dependent manner.

Neste estudo, os extratos metanólico, clorofórmico e aquoso de Achillea millefolium e Chaerophyllum villosum foram analisados em relação à citotoxicidade, atividade fitotóxica e inseticida. A citotoxicidade foi analisada através do ensaio de letalidade de artémia, indicando que o extrato metanólico bruto de A. millefolium e o extrato clorofórmico de C. villosum revelaram maior mortalidade de artêmias com DL50 de 52,60 µg/ml e 14,81 µg/ml. A fitotoxicidade foi avaliada utilizando o bioensaio de Lemna minor que revelou que o extrato metanólico bruto de A. millefolium e extrato de C. villosum têm inibição máxima de Lemna minor com Fl50 6,60 µg/ml e 0,67 µg/ml. A atividade inseticida mostrou que dentre todos os insetos estudados, o extrato metanólico de A. millefolium e de C. villosum foi altamente tóxico para Sphenoptera dadkhanicom DL50 = 4,17 µg/ml e 0,34 µg/ml . Por outro lado, diferentes extratos, como A. millefolium e C. villosum apresentaram boa atividade citotóxica, fitotóxica e inseticida de forma dose-dependente.

Synergism in Two-Component Insecticides with Dillapiole against Fall Armyworm.

The fall armyworm (Spodoptera frugiperda), a polyphagous insect pest, is a major threat to food production, rapidly spreading through all the tropical areas in the world. Resistance has developed to the control protocols used so far (pyrethroids, organophosphorus, and genetically modified plants), and alternative strategies must be found. The bioactivity in essential oils is usually associated with the major constituents, but synergistic interactions among the constituents (even minor ones) can improve the levels of activity considerably. Herein, we tested the insecticidal activity of several constituents of the essential oil from Piper aduncum, an Amazonian Piperaceae, both separately and as binary mixtures, through their application on the dorsal side of the larva pronotum. Dillapiole proved to be, isolated, the most active compound in this oil (LD50 = 0.35 ppm). In binary mixtures, a strong synergistic effect was observed for the pairs of dillapiole with ß-caryophyllene (LD50 = 0.03 ppm), methyl eugenol (LD50 = 0.05 ppm), and α-humulene (LD50 = 0.05 ppm). In some cases, however, antagonism was recorded, as for dillapiole + ß-pinene (LD50 = 0.44 ppm). The use of binary mixtures of essential oil constituents as low-environmental-toxicity insecticides allows a fine tuning of the insecticidal activity, and the exploitation of synergy effects.

Insecticidal activity of extracts of handroanthus impetiginosus on Plutella xylostella (Lepidoptera: plutellidae) larvae.

Plutella xylostella is considered the main pest of cabbage in Brazil and the world, causing damage of up to 100%. Thus, this study evaluated the insecticidal activity of extracts obtained from the fruits, seeds, bark, leaves, and flowers of Handroanthus impetiginosus against the diamondback moth, P. xylostella larvae. The seed extract showed the highest mortality (97.0%) compared to the control treatment. The LC50 values indicated that the seed and flower extracts (0.01003 and 0.01288 mg/L respectively) assumed the highest toxicity to P. xylostella larvae after 24 h of exposure. The results of this study indicated that the seeds extract is the most promising toxic extract, with measured mortality of approximately 97.0% for P. xylostella larvae after 144 h of exposure in kale plants. Seed extract showed the best insecticidal activity. Thus, this extract can be applied to develop an insecticide based on H. impetiginosus seed.

Development and characterization of nanoemulsions loaded with essential oil and ß-cypermethrin and their bioefficacy on insect pest of economic and medical importance.

BACKGROUND: The development of novel and ecofriendly tools plays an important role in insect pest management. Nanoemulsions (NEs) based on essential oils (EOs) offer a safer alternative for human health and the environment. This study aimed to elaborate and evaluate the toxicological effects of NEs containing peppermint or palmarosa EOs combined with ß-cypermethrin (ß-CP) using ultrasound technique. RESULTS: The optimized ratio of active ingredients to surfactant was 1:2. The NEs containing peppermint EO combined with ß-CP (NEs peppermint/ß-CP) were polydisperse with two peaks at 12.77 nm (33.4% intensity) and 299.1 nm (66.6% intensity). However, the NEs containing palmarosa EO combined with ß-CP (NEs palmarosa/ß-CP) were monodisperse with a size of 104.5 nm. Both NEs were transparent and stable for 2 months. The insecticidal effect of NEs was evaluated against Tribolium castaneum and Sitophilus oryzae adults, as well as Culex pipiens pipiens larvae. On all these insects, NEs peppermint/ß-CP enhanced pyrethroid bioactivity from 4.22- to 16-folds while NEs palmarosa/ß-CP, from 3.90- to 10.6-folds. Moreover, both NEs maintained high insecticidal activities against all insects for 2 months, although a slight increase of the particle size was detected. CONCLUSION: The NEs elaborated in this work can be considered as highly promising formulations for the development of new insecticides. © 2023 Society of Chemical Industry.

Synthesis, insecticidal activity, and ensembled docking of nitroguanidines bearing S- and R-proline.

BACKGROUND: The amino acids R- and S-proline were used to synthesize novel neonicotinoid derivatives that, after being characterized by 1 H, DEPTQ 135, and HRMS-QTOF, were evaluated for use as insecticides against Galleria mellonella (caterpillar), Sitophilus zeamais, Xylosandrus morigerus, Xyleborus affinis, and Xyleborus ferrugineus. RESULTS: Comparisons of biological activity and absolute configuration showed that the R enantiomer had excellent and outstanding insecticidal activity against the insects tested, with up to 100% mortality after 12 h compared with dinotefuran at the same concentration. CONCLUSIONS: The results suggest that compound R6 is an excellent lead enantiopure insecticide for future development in the field of crop protection. Furthermore, intermolecular interactions between nicotinic acetylcholine receptors and the R enantiomer displays a lower score which mean a higher affinity to the nAChR receptor and the π-π interactions are more stable than the S derivative. © 2023 Society of Chemical Industry.

Insecticidal activity of the essential oil of Schinus areira against Rhipibruchus picturatus (F.) (Coleoptera: Bruchinae), and its inhibitory effects on acetylcholinesterase.

During the storage of Prosopis alba pods, substantial quantitative and qualitative losses were observed. One of the main factors is the seed beetle Rhipibruchus picturatus. A key strategy to develop new pest control management is the use of essential oils (EOs) due they are efficient, less toxic, and less persistent in the environment compared to synthetic pesticides. In this context, seeds and leaves of Schinus areira L. (Anacardiaceae) EOs and Citrus spp. EO were studied in the present work. In the leaves of S. areira EO, 1-epi-cadinol, sesquiterpenoid alcohol, was the major compound. On the other hand, the main compounds of the EO extracted from S. areira seeds are the monoterpenes sabinene, and α-pinene. Finally, in the Citrus EO, limonene is the principal component. The three EOs obtained exhibited insecticidal activity against R. picturatus, being the first report of the use of EOs against this insect pest. The best insecticidal results were obtained with the leaves of S. areira EO. Moreover, this EO inhibits the acetylcholinesterase enzyme in vitro assays. Molecular docking studies on acetylcholinesterase (AChE) suggest that the main components of the leaves of S, areira EOs, bind to the active site of the enzyme, in good agreement with in vitro competitive inhibition against AChE observed for this EO. The data obtained demonstrate the potential use of Schinus areira EOs in the development of new storage pest control strategies.

Chemical Composition and Insecticidal Properties of Moroccan Lavandula dentata and Lavandula stoechas Essential Oils Against Mediterranean Fruit Fly, Ceratitis capitata.

The current study describes the chemical composition and insecticidal activities of the essential oils (EOs) extracted from Lavandula dentata L. and Lavandula stoechas L. against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), a worldwide fruit pest. Gas chromatography (GC) and GC-mass spectrophotometry (GC-MS) analyses revealed that L. dentata oil contained camphor (50.8%), 1,8-cineole (6.6%), ß-selinene (5%), and borneol (3.2%) as major components. On the other hand, L. stoechas EO was characterized by high contents of camphor (44%), camphene (14.8%), fenchone (9.1%), and 1-10-diepi-cubenol (4.6%). The toxic impact of EOs against C. capitata was evaluated through ingestion and contact methods. All of the EOs were toxic to C. capitata, and insect mortality was dose and time-dependent. In ingestion toxicity assays, L. dentata was the most toxic oil with an LC50 (lethal concentration for 50% mortality) of 6.54% for males and 10.21% for females. Topical applications revealed that all the EOs had a good insecticidal activity at 24 h. The results of this study show that L. dentata and L. stoechas EOs may reduce the risks associated with the use of synthetic insecticides and may also be considered as a potent source for the production of botanical insecticides against C. capitata.

Genomic and Experimental Analysis of the Insecticidal Factors Secreted by the Entomopathogenic Fungus Beauveria pseudobassiana RGM 2184.

The entomopathogenic fungus Beauveria pseudobassiana strain RGM 2184 can reach a maximum efficacy of 80% against the quarantine pest Lobesia botrana in field assays. In this study, the RGM 2184 genome was sequenced, and genome mining analyses were performed to predict the factors involved in its insecticidal activity. Additionally, the metabolic profiling of the RMG 2184 culture's supernatants was analyzed by mass spectrometry, and the insecticidal activity from one of these extracts was evaluated in Galleria mellonella larvae. The genome analysis resulted in 114 genes encoding for extracellular enzymes, four biosynthetic gene clusters reported as producers of insecticidal and bactericidal factors (oosporein, beauvericin, desmethylbassianin, and beauveriolide), 20 toxins, and at least 40 undescribed potential biocontrol factors (polyketides and nonribosomal peptides). Comparative genomic analysis revealed that 65-95% of these genes are Beauveria genus-specific. Metabolic profiling of supernatant extracts from RGM 2184 cultures exhibited secondary metabolites such as beauveriolide, oosporein, inflatin C, and bassiatin. However, a number of detected metabolites still remain undescribed. The metabolite extract caused 79% mortality of Galleria mellonella larvae at 28 days. The results of this research lay the groundwork for the study of new insecticidal molecules.

Biocontrol potential of Beauveria bassiana and Metarhizium anisopliae isolates from Turkey against Hyphantria cunea (Drury) (Lepidoptera: arctiidae) Larvae under laboratory and field conditions

Hyphantria cunea is one of the most important pest insects causing significant damage in many plant species. The present study aimed to evaluate the insecticidal activity of Turkey isolates of Beauveria bassiana and Metarhizium anisopliae against H. cunea larvae under laboratory and field conditions. B. bassiana isolates YK16, YK23 and YK26, and M. anisopliae isolates YK41 and YK45 were sprayed onto the larvae of H. cunea at the respective doses of 1x105 and 1x106 conidia mL-1 and monitored for seven days. Fungal isolates, bio-insecticide Bacillus thuringiensis and chemical insecticide diflubenzuron were used in field studies. Trials were carried out in five replications. All B. bassiana isolates caused 100% mortality on first instar larvae in laboratory trials. Mortality ratios ranged from 100 to 96% on second instar larvae. M. anisopliae isolates YK45 and YK41 caused 88 and 84%, and 81.33 and 77.11% mortalities for the first and second instar larvae, respectively. The mortality rates fluctuated between 91.78-72.89% for B. bassiana on third instar larvae in laboratory conditions. However, M. anisopliae isolates YK45 and YK41 caused 77.11 and 60.22% mortality on third instar larvae, respectively. In the field trials, B. bassiana YK23 displayed promising insecticidal activity with 80.60% mortality on second instar larvae of H. cunea. Other isolates as well caused mortalities ranging from 60.77 to 49.55%. The results revealed that some isolates of B. bassiana and M. anisopliae have potential to control H. cunea larvae. However, additional detailed studies need to be carried out to increase their effectiveness in field conditions.

Machaerium opacum Vogel (Fabaceae): phytochemical study and toxicity to Atta sexdens Linnaeus (Hymenoptera: Formicidae).

In this work was described the phytochemical investigation of Machaerium opacum Vogel (Fabaceae) leaves as well as the insecticidal activity of its crude extract and fractions against Atta sexdens Linnaeus (Hymenoptera: Formicidae). The phytochemical study led to the identification of α-amyrin, ß-amyrin, lupeol, phytol, isomucronulatol and rutin, described for the first time in M. opacum and mucronulatol. Insecticidal activity was assessed by the ingestion of the crude extract and fractions incorporated into an artificial diet at three different concentrations (0.2, 1.0 and 2.0 mg mL-1). Statistical analysis revealed that all the samples of M. opacum at all concentrations tested showed significant results when compared to the pure diet control.

Synthesis and Insecticidal Evaluation of Chiral Neonicotinoids Analogs: The Laurel Wilt Case.

Xyleborus sp beetles are types of ambrosia beetles invasive to the United States and recently also to Mexico. The beetle can carry a fungus responsible for the Laurel Wilt, a vascular lethal disease that can host over 300 tree species, including redbay and avocado. This problem has a great economic and environmental impact. Indeed, synthetic chemists have recently attempted to develop new neonicotinoids. This is also due to severe drug resistance to "classic" insecticides. In this research, a series of neonicotinoids analogs were synthesized, characterized, and evaluated against Xyleborus sp. Most of the target compounds showed good to excellent insecticidal activity. Generally, the cyclic compounds also showed better activity in comparison with open-chain compounds. Compounds R-13, 23, S-29, and 43 showed a mortality percent of up to 73% after 12 h of exposure. These results highlight the enantioenriched compounds with absolute R configuration. The docking results correlated with experimental data which showed both cation-π interactions in relation to the aromatic ring and hydrogen bonds between the search cavity 3C79 and the novel molecules. The results suggest that these sorts of interactions are responsible for high insecticidal activity.

QSAR models for insecticidal properties of plant essential oils on the housefly (Musca domestica L.).

The fumigant and topical activities exhibited by 27 plant-derived essentials oils (EOs) on adult M. domestica housefly are predicted through the Quantitative Structure-Activity Relationship (QSAR) theory. These molecular structure based calculations are performed on 253 structurally diverse compounds from the EOs, where the number of constituents in each essential oil mixture varies between 2 to 24. A large number of 86,048 non-conformational mixture descriptors are derived as linear combinations of the molecular descriptors of the EO components. Two strategies are compared for the mixture descriptor formulation, which consider or avoid the use of the chemical composition. The multivariable linear regression QSAR models of the present work are useful for fumigant and topical applications, describing predictive parallelisms for the insecticidal activity of the analysed complex mixtures.

Computer-assisted discovery of compounds with insecticidal activity against Musca domestica and Mythimna separata.

Pesticides are used to control and combat insects and pests in the agricultural sector, households, and public health programs. The frequent and disorderly use of these pesticides may lead to variety of undesired effects. Therefore, natural products have many advantages over to synthetic compounds to be used as insecticides. The goal of this study was to find natural products with insecticidal potential against Musca domestica and Mythimna separata. To achieve this goal, we developed predictive QSAR models using MuDRA, PLS, and RF approaches and performed virtual screening of 117 natural products. As a result of QSAR modeling, we formulated the recommendations regarding physico-chemical characteristics for promising compounds active against Musca domestica and Mythimna separata. Homology models were successfully built for both species and molecular docking of QSAR hits vs known insecticides allowed us to prioritize twenty-two compounds against Musca domestica and six against Mythimna separata. Our results suggest that pimarane diterpenes, abietanes diterpenes, dimeric diterpenes and scopadulane diterpenes obtained from aerial parts of species of the genus Calceolaria (Calceolariaceae: Scrophulariaceae) can be considered as potential insecticidal.

Synergistic effects of binary mixtures of linalool with pyrethroids against fall armyworm / Efeitos sinérgicos de misturas binárias de linalol com piretroides contra lagarta-do-cartucho

The present work aimed to determine the toxicity of linalool and evaluate the lethal and toxic effects of linalool associated with pyrethroids in binary mixtures to fall armyworm (Spodoptera frugiperda). The insects used in the experiment were obtained from stock breeding initiated from larvae collected from conventional corn plants, grown in an experimental area, in the city of Uberlândia, Minas Gerais. Also, it was obtained essential oil from a variety of Ocimum basilicum, with a high content of linalool (80%), found naturally, as a measure of comparison of different linalool (97.5%) assays. Dose-response bioassays with 3rd instar larvae were performed to determine lethal dose for 50% mortality (LD50) of linalool. Toxicity tests were also performed with O. basilicum essential oil and with pyrethroid insecticides: deltamethrin and its commercial product (Decis 25 EC, Bayer®). After this, combinations between different doses of these products were made and applied on 3rd instar larvae of Spodoptera frugiperda (Smith). Linalool presented high toxicity to S. frugiperda (LD50 = 0.177 µL a.i. µL-1). It was observed neurotoxic effects after the linalool application since the insects presented an aspect of confusion, followed by extreme agitation and finally death. All binary mixtures caused mortality higher than the products applied alone (deltamethrin and linalool) used at 100% LD50, except to 75% LD50 deltamethrin added to 25% LD50 linalool, whose mortality did not differ the products alone, in 24 hours. It was obtained over 90% larval mortality when linalool was combined with 25% LD50 of deltamethrin, in 24 and 48 hours after application, and over 80% of mortality when linalool was combined with 25% LD50 of Decis, only in 48 hours after application. We conclude that linalool is a potential insecticidal and can be associated with pyrethroids to control of S. frugiperda. Further studies are required in order to evaluate the synergistic combinations against field populations of S. frugiperda.

O objetivo deste trabalho foi determinar a toxicidade do linalol e avaliar os efeitos tóxicos e letais do linalol associado a piretroides em misturas binárias para lagarta do cartucho do milho (Spodoptera frugiperda). Os insetos utilizados no experimento foram obtidos de criação estoque iniciada a partir de larvas coletadas em plantas de milho convencional, cultivado em área experimental, no município de Uberlândia, Minas Gerais. Também foi obtido óleo essencial de uma variedade de Ocimum basilicum, com alto teor de linalol (80%), encontrado naturalmente, como medida de comparação para ensaios com linalol (97.5%). Os bioensaios do tipo dose-resposta com larvas de 3º instar foram realizados para determinar a dose letal do linalol para 50% de mortalidade da população (DL50). Também foram realizados testes de toxicidade com óleo essencial de Ocimum basilicum e com inseticidas piretroides: deltametrina e seu produto comercial (Decis 25 EC, Bayer®). Em seguida, foram realizadas combinações entre diferentes doses desses produtos e aplicadas em larvas de 3º instar de Spodoptera frugiperda (Smith). De acordo com os resultados, observou-se que o linalol apresentou alta toxicidade para S. frugiperda (DL50 = 0,177 µL a. i. µL-1). Foram observados efeitos neurotóxicos após a aplicação do linalol, uma vez que os insetos apresentaram um aspecto de confusão, seguido de extrema agitação e, por fim, morte. Todas as combinações binárias causaram mortalidade maior que os produtos aplicados isoladamente (deltametrina e linalol) utilizando-se 100% da DL50, exceto para 75% DL50 de deltametrina somada a 25% DL50 de linalol, cuja mortalidade não diferiu dos produtos isolados, em 24 horas após a aplicação. Foi obtida mais de 90% de mortalidade de larvas quando se combinou linalol com 25% da DL50 de deltametrina, em 24 e 48 horas após a aplicação, e mais de 80% de mortalidade quando se combinou linalol com 25% da DL50 do produto comercial, somente 48 horas após a aplicação. Concluímos que o linalol é um potencial inseticida e pode ser associado a piretroides no controle de S. frugiperda. Mais estudos são necessários em vista de avaliar as combinações sinérgicas contra populações de campo de S. frugiperda.

Structure-Function Insights of Jaburetox and Soyuretox: Novel Intrinsically Disordered Polypeptides Derived from Plant Ureases.

Intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) do not have a stable 3D structure but still have important biological activities. Jaburetox is a recombinant peptide derived from the jack bean (Canavalia ensiformis) urease and presents entomotoxic and antimicrobial actions. The structure of Jaburetox was elucidated using nuclear magnetic resonance which reveals it is an IDP with small amounts of secondary structure. Different approaches have demonstrated that Jaburetox acquires certain folding upon interaction with lipid membranes, a characteristic commonly found in other IDPs and usually important for their biological functions. Soyuretox, a recombinant peptide derived from the soybean (Glycine max) ubiquitous urease and homologous to Jaburetox, was also characterized for its biological activities and structural properties. Soyuretox is also an IDP, presenting more secondary structure in comparison with Jaburetox and similar entomotoxic and fungitoxic effects. Moreover, Soyuretox was found to be nontoxic to zebra fish, while Jaburetox was innocuous to mice and rats. This profile of toxicity affecting detrimental species without damaging mammals or the environment qualified them to be used in biotechnological applications. Both peptides were employed to develop transgenic crops and these plants were active against insects and nematodes, unveiling their immense potentiality for field applications.

The Cytocidal Spectrum of Bacillus thuringiensis Toxins: From Insects to Human Cancer Cells.

Bacillus thuringiensis (Bt) is a ubiquitous bacterium in soils, insect cadavers, phylloplane, water, and stored grain, that produces several proteins, each one toxic to different biological targets such as insects, nematodes, mites, protozoa, and mammalian cells. Most Bt toxins identify their particular target through the recognition of specific cell membrane receptors. Cry proteins are the best-known toxins from Bt and a great amount of research has been published. Cry are cytotoxic to insect larvae that affect important crops recognizing specific cell membrane receptors such as cadherin, aminopeptidase-N, and alkaline phosphatase. Furthermore, some Cry toxins such as Cry4A, Cry4B, and Cry11A act synergistically with Cyt toxins against dipteran larvae vectors of human disease. Research developed with Cry proteins revealed that these toxins also could kill human cancer cells through the interaction with specific receptors. Parasporins are a small group of patented toxins that may or may not have insecticidal activity. These proteins could kill a wide variety of mammalian cancer cells by recognizing specific membrane receptors, just like Cry toxins do. Surface layer proteins (SLP), unlike the other proteins produced by Bt, are also produced by most bacteria and archaebacteria. It was recently demonstrated that SLP produced by Bt could interact with membrane receptors of insect and human cancer cells to kill them. Cyt toxins have a structure that is mostly unrelated to Cry toxins; thereby, other mechanisms of action have been reported to them. These toxins affect mainly mosquitoes that are vectors of human diseases like Anopheles spp (malaria), Aedes spp (dengue, zika, and chikungunya), and Culex spp (Nile fever and Rift Valley fever), respectively. In addition to the Cry, Cyt, and parasporins toxins produced during spore formation as inclusion bodies, Bt strains also produce Vip (Vegetative insecticidal toxins) and Sip (Secreted insecticidal proteins) toxins with insecticidal activity during their vegetative growth phase.

Quantitative Structure-Activity Relationship Modeling and Docking of Monoterpenes with Insecticidal Activity Against Reticulitermes chinensis Snyder and Drosophila melanogaster.

The goal of this study was to perform in silico identification of bioinsecticidal potential of 42 monoterpenes against Drosophila melanogaster and Reticulitermes chinensis Snyder. Quantitative structure-activity relationship (QSAR) modeling was performed for both organisms, while docking and molecular dynamics were used only for Drosophila melanogaster. Neryl acetate has the lowest interaction energy (-87 kcal/mol) against active site of acetylcholinesterase, which is comparable to the ones of methiocarb and pirimicarb (-90 kcal/mol) and reported PDB binder 9-(3-iodobenzylamino)-1,2,3,4-tetrahydroacridine (-112.67 kcal/mol). Interaction stability was verified by molecular dynamics simulations and showed that the stability of ACHE active site complexes with three selected terpenes is comparable to the one of the pirimicarb and methiocarb. Overall, our results suggest that pulegone, citronellal, carvacrol, linalyl acetate, neryl acetate, citronellyl acetate, and geranyl acetate may be considered as a potential pesticide candidates.