Acetylcholinesterase inhibition by biofumigant (Coumaran) from leaves of Lantana camara in stored grain and household insect pests

Extraction, Chemical Composition and Insecticidal Activities of Lantana camara Linn. Leaf Essential Oils against Tribolium castaneum, Lasioderma serricorne and Callosobruchus chinensis

Storage pests and the food spoilage they cause are problems of great concern. Using essential oil obtained from different plants as an insecticide against these storage pests can be considered an environmentally friendly pest management option. Lantana camara Linn. (family Verbenaceae) is a flowering species, and is also a noxious weed that can proliferate well in nearly all geographical habitats. A biopesticide derived from the essential oil extracted from this plant can offer an effective solution for controlling storage pests. The goal of this study is to extract and analyse the chemical composition of essential oil obtained from L. camara leaves, and assess its effectiveness as a bioactive substance against three storage pests: Tribolium castaneum, Lasioderma serricorne, and Callosobruchus chinensis. The yield of essential oil extracted from L. camara leaves was about 0.24 ± 0.014%. By employing the GC-MS technique, the major phytochemicals contained in L. camara leaf essential oil were identified as caryophyllene (69.96%), isoledene (12%), and ɑ-copaene (4.11%). The essential oil exhibited excellent fumigant toxicity (LC50 of 16.70 mg/L air for T. castaneum, 4.141 mg/L air for L. serricorne and 6.245 mg/L air for C. chinensis at 24 h), contact toxicity (LC50 of 8.93 mg/cm2 for T. castaneum, 4.82 mg/cm2 for L. serricorne and 6.24 mg/cm2 for C. chinensis after 24 h) along with effective repellent activity towards the test insects. In addition, the oil showed no significant phytotoxicity on the germination of paddy seeds. This presents the potential to utilize a weed in developing a biopesticide for effectively managing stored product insects because of its strong bioactivity.

Toxicity and Repellency Efficacy of Benzyl Alcohol and Benzyl Benzoate as Eco-Friendly Choices to Control the Red Flour Beetle Tribolium castaneum (Herbst. 1797)

Tribolium castaneum is a damaging pest of stored grains, causing significant losses and secreting lethal quinones, which render the grains unfit for human consumption. Chemical insecticides are the most commonly used approach for control; however, they create insecticide resistance and affect the health of humans, animals, and the environment. As a result, it is critical to find an environmentally friendly pest-management strategy. In this study, two naturally occurring chemicals, benzyl alcohol (BA) and benzoyl benzoate (BB), were investigated for insecticidal activity against T. castaneum using different assays (impregnated-paper, contact toxicity, fumigant, and repellency assays). The results showed that BA had a significant insecticidal effect, with the LC50 achieved at a lower concentration in the direct-contact toxicity test (1.77%) than in the impregnated-paper assay (2.63%). BB showed significant effects in the direct-contact toxicity test, with an LC50 of 3.114%, and a lower toxicity in the impregnated-paper assay, with an LC50 of 11.75%. Furthermore, BA exhibited significant fumigant toxicity against T. castaneum, with an LC50 of 6.72 µL/L, whereas BB exhibited modest fumigant toxicity, with an LC50 of 464 µL/L. Additionally, at different concentrations (0.18, 0.09, 0.045, and 0.0225 µL/cm2), BA and BB both showed a notable and potent repelling effect. BA and BB significantly inhibited acetylcholinesterase, reduced glutathione (GSH), and increased malondialdehyde (MDA) in treated T. castaneum. This is the first report of BA insecticidal activity against the red flour beetle. Also, the outcomes of various assays demonstrated that the application of BA induces a potent bio-insecticidal effect. BA may be a promising eco-friendly alternative to control T. castaneum due to its safety and authorization by the EFSA (European Food Safety Authority).

Medicinal Plants as a Natural Greener Biocontrol Approach to "The Grain Destructor" Maize Weevil (Sitophilus zeamais) Motschulsky

According to the United Nations (UN), the global population may skyrocket to 9.8 billion people in 2050 and 11.2 billion in 2100, placing an overwhelming burden on food security as the world will have to meet this growing demand. Maize is the largest staple grain crop produced in developing countries. The maize weevil, Sitophilus zeamais, is one of the most destructive post-harvest pests of stored cereals and grains. The maize weevil contributes up to 40% of total food-grain losses during storage, mainly in developing countries. Current synthetic pesticides are ineffective, and, moreover, they raise serious environmental safety concerns as well as consumer health hazards. Drawing from past oversights and current environmental realities and projections, the global population has been switching to green living by developing sustainable strategies. In our context, these new greener strategies include the utilization of medicinal plants to control maize weevil infestation, which unlocks unlimited innovative possibilities, and, thus, improves the yield, quality, and safety of maize. Medicinal plants are less toxic, easily biodegradable, and capable of protecting grain from pests. This paper systematically outlines the literature on host plants as well as the feeding and associated diseases of the maize weevil. In light of this, we cement medicinal plants as excellent candidates in the pursuit of greener, sustainable, more potent, and cost-effective pesticides.

Insecticidal and biochemical effects of Dillenia indica L. leaves against three major stored grain insect pests

The Last four decades have witnessed the banning of several synthetic insecticides mainly due to the development of resistance to the target pests and due to hazardous effects on humans and the environment. Hence, the development of a potent insecticide with biodegradable and eco-friendly nature is the need of the hour. In the present study, the fumigant property, and biochemical effects of Dillenia indica L. (Dilleniaceae) were studied against three coleopterans stored-products insects. The bioactive enriched fraction (sub-fraction-III) was isolated from ethyl acetate extracts of D. indica leaves and found toxic to rice weevil, Sitophilus oryzae (L.) (Coleoptera); lesser grain borer Rhyzopertha dominica (L.) (Coleoptera) and red flour beetle, Tribolium castaneum (Herbst.) (Coleoptera) with the LC₅₀ values of 101.887, 189.908 and 115.1 µg/L respectively after 24 h exposure. The enriched fraction was found to inhibit the function of acetylcholinesterase (AChE) enzyme when tested against S. oryzae, T. castaneum, and R. dominica with LC₅₀ value of 88.57 µg/ml, 97.07 µg/ml, and 66.31 µg/ml respectively, in in-vitro condition. It was also found that the enriched fraction caused a significant oxidative imbalance in the antioxidative enzyme system such as superoxide dismutase, catalase, DPPH (2,2-diphenyl-1-picrylhydrazyl), and glutathione-S-transferase (GST). GCMS analysis of the enriched fraction indicates three major compounds namely, 6-Hydroxy-4,4,7a-trimethyl-5,6,7,7a-tetrahydrobenzofuran-2(4H)-one, 1,2-Benzisothiazol-3(2H)-one, and Benzothiazole, 2-(2-hydroxyethylthio)-. Finally, we concluded that the enriched fraction of D. indica has insecticidal properties and the toxicity may be due to the inhibition of the AChE enzyme in association with oxidative imbalance created on the insect's antioxidant enzyme systems.

Acetylcholinesterase inhibitory activity of sesquiterpenoids isolated from Laggera pterodonta

Plant-derived natural products are important resources for pesticide discovery. Acetylcholinesterase (AChE) is a well-validated pesticide target, and inhibiting AChE proves fatal for insects. Recent studies have shown that the potential of various sesquiterpenoids as AChE inhibitors. However, few studies have been conducted with eudesmane-type sesquiterpenes with AChE inhibitory effects. Therefore, in this research, we isolated two new sesquiterpenes, laggeranines A (1) and B (2), along with six known eudesmane-type sesquiterpenes (3-8) from Laggera pterodonta, and characterized their structures and the inhibitory effect they exerted on AChE. The results showed that these compounds had certain inhibitory effects on AChE in a dose-dependent manner, of which compound 5 had the best inhibitory effect with IC50 of 437.33 ± 8.33 mM. As revealed by the Lineweaver-Burk and Dixon plots, compound 5 was observed to suppress AChE activity reversibly and competitively. Furthermore, all compounds exhibited certain toxicity levels on C. elegans. Meanwhile, these compounds had good ADMET properties. These results are significant for the discovery of new AChE targeting compounds, and also enrich the bioactivity activity repertoire of L. pterodonta.

Phytochemical Investigation of Three Cystoseira Species and Their Larvicidal Activity Supported with In Silico Studies

Culex pipiens mosquitoes are transmitters of many viruses and are associated with the transmission of many diseases, such as filariasis and avian malaria, that have a high rate of mortality. The current study draws attention to the larvicidal efficacy of three methanolic algal extracts, Cystoseira myrica, C. trinodis, and C. tamariscifolia, against the third larval instar of Cx. pipiens. The UPLC-ESI-MS analysis of three methanol fractions of algal samples led to the tentative characterization of twelve compounds with different percentages among the three samples belonging to phenolics and terpenoids. Probit analysis was used to calculate the lethal concentrations (LC₅₀ and LC₉₀). The highest level of toxicity was attained after treatment with C. myrica extract using a lethal concentration 50 (LC₅₀) of 105.06 ppm, followed by C. trinodis (135.08 ppm), and the lowest level of toxicity was achieved by C. tamariscifolia (138.71 ppm) after 24 h. The elevation of glutathione-S-transferase (GST) and reduction of acetylcholine esterase (AChE) enzymes confirm the larvicidal activity of the three algal extracts. When compared to untreated larvae, all evaluated extracts revealed a significant reduction in protein, lipid, and carbohydrate contents, verifying their larvicidal effectiveness. To further support the observed activity, an in silico study for the identified compounds was carried out on the two tested enzymes. Results showed that the identified compounds and the tested enzymes had excellent binding affinities for each other. Overall, the current work suggests that the three algal extractions are a prospective source for the development of innovative, environmentally friendly larvicides.

Consolidation of temperature-dependent toxicity and thermoregulatory behavior into risk assessments of insecticides under thermal scenarios: A prospective study on Eremias argus

In this study, the temperature-dependent chemical toxicity of three insecticides and the resulting thermoregulatory (TR) behavior of the lizard Eremias argus have been consolidated into the current risk assessment framework. According to acute dermal toxicity assays, an increase of ambient temperature from 15 °C to 35 °C decreased the acute dermal toxicity of beta-cyfluthrin (BC) but increased the toxicity of chlorpyrifos (CPF). The toxicity of avermectin (AVM) did not show significant temperature-dependent responses. Based on thermal preference trials, lizards changed their body temperature via TR behavior to adaptively reduce toxicity under sub-lethal doses, which can be understood as a "self-rescue" behavior attenuating lethal effects. However, the risk quotient indicated that the effectiveness of this "self-rescue" behavior is limited. Metabolomics analysis showed that six different metabolites (i.e., creatine, glutamate, succinate, N-acetylaspartate, acetylcholine, and lactate) contributed to TR behavior changes. Biochemical assays and insecticide residue results demonstrated that the temperature-dependent toxicity of BC, CPF, and AVM affected lizards in the three aspects of biotransformation, oxidative stress, and neurometabolic interference. This work clarifies the ecotoxicological impacts of representative insecticides on reptiles from toxicological understanding to risk relevance. This knowledge may improve ecological predictions of agrochemical applications in the context of global climate change.

Larvicidal and repellent potential of Ageratum houstonianum against Culex pipiens

Mosquitoes are unquestionably the most medic arthropod vectors of disease. Culex pipiens, usually defined as a common house mosquito, is a well-known carrier of several virus diseases. Crude ethanol extracts of different organs of Agratum houstonianum are tested with Culex pipiens Linnaeus (Diptera: Culicidae) to determine their larvicidal, antifeedant, and repellency effects. Alongside biochemical analysis, the activity of the AChE, ATPase, CarE, and CYP-450 is detected in the total hemolymph of the C. pipiens larvae to examine the enzymatic action on the way to explain their neurotoxic effect and mode of action. Through HPLC and GC-MS analysis of the phytochemical profile of A. houstonianum aerial parts is identified. The larvicidal activity of aerial parts; flower (AF), leaf (AL), and stem (AS) of A. houstonianum extracts are evaluated against the 3rd instar larvae of C. pipiens at 24-, 48- and 72-post-treatment. A. houstonianium AF, AL, and AS extracts influenced the mortality of larvae with LC50 values 259.79, 266.85, and 306.86 ppm, respectively after 24 h of application. The potency of AF and AL extracts was 1.69- and 1.25-folds than that of AS extract, respectively. A high repellency percentage was obtained by AF extract 89.10% at a dose of 3.60 mg/cm². A. houstonianium AF prevailed inhibition on acetylcholinesterase and decrease in carboxylesterase activity. Moreover, a significant increase in the ATPase levels and a decrease in cytochrome P-450 monooxegenase activity (- 36.60%) are detected. HPLC analysis prevailed chlorogenic and rosmarinic acid as the major phenolic acids in AL and AF, respectively. GC-MS analysis of A. houstonianum results in the identification of phytol as the major makeup. Precocene I and II were detected in AF. Linoleic, linolenic, and oleic acid were detected in comparable amounts in the studied organs. Overall, results suggest that the A. houstonianum flower extract (AF) exhibits significant repellent, antifeedant, and larvicidal activities.

Insecticidal Activity of a Component, (-)-4-Terpineol, Isolated from the Essential Oil of Artemisia lavandulaefolia DC. against Plutella xylostella (L.)

Plutella xylostella (L.) is one of the most serious pests of cruciferous vegetables. Our previous work demonstrated that the essential oil of Artemisia lavandulaefolia DC. exhibits promising insecticidal activities against P. xylostella. This study further characterizes the key components that are responsible for the insecticidal effect. In total, 47 compounds (96.52% of the total compounds) were identified from the total oil using GC-MS, and the major compounds were eucalyptol (21.57%), D(+)-camphor (17.33%), (-)-4-terpineol (9.96%) and caryophyllene oxide (10.96%). Among them, (-)-4-terpineol showed significantly larvicidal and fumigant activities against P. xylostella. The LD₅₀ of (-)-4-terpineol was 43.15 mg/mL at 12 h and 31.22 mg/mL at 24 h for 3rd instar larvae, and the LC₅₀ for adults was 8.34 mg/mL at 12 h and 7.35 mg/mL at 24 h. In addition, the adults treated with (-)-4-terpineol showed varying degrees of inhibitory activity toward glutathione S-transferase, catalase, acetylcholinesterase and Na⁺/K⁺-ATPase at different post-treatment intervals and concentrations. The results indicate that (-)-4-terpineol has promising insecticidal activities against P. xylostella, and it has good inhibitory effects on the four enzymes of P. xylostella adults.

Phospholipids modifications, genotoxic and anticholinesterase effects of pepper fruit (Dennettia tripetala G. Baker) extract in Swiss mice

The toxicity of D. tripetala fruit extract to mice was investigated using data obtained from lipidomic analyses, comet and Acetylcholinesterase (AChE) assays. Mice (n = 8) were exposed for 30 days via oral gavage to vehicle (5% Tween 80) (negative control), D. tripetala extract (100, 200 and 400 mg/kg) and 40 mg/kg methyl methanesulfonate (MMS) (positive control). The profile of compounds in the fruit extract was analyzed using gas chromatography-mass spectrometry. Out of the total of 32 compounds identified, considerable amount of established insecticidal compounds such as 2-phenylnitroethane, cis-vaccenic acid, linalool and linoleic acid were detected. Fruit extract did not induce DNA damage relative to negative control. Percentage gain in body weights differed significantly across the four weeks. Significantly highest and lowest brain AChE activity was observed in animals exposed to 200 and 400 mg/kg D. tripetala, respectively. Fruit extract modulated the brain phospholipid profile due to significant fold changes of 48 lipid species out of the total of 280 lipid species. High number of differentially expressed phosphatidylcholine (PC) species and significant levels of phosphatidylethanolamine (PE) at 400 mg/kg suggests that activation of inflammation and methylation pathways are the most plausible mechanisms of D. tripetala toxicity to mouse brain tissue.

Eugenia uniflora, Melaleuca armillaris, and Schinus molle essential oils to manage larvae of the filarial vector Culex quinquefasciatus (Diptera: Culicidae)

Populations of Culex quinquefasciatus Say, 1823 (Diptera: Culicidae) have shown resistance to insecticides of the carbamate and organophosphate classes. The objective of this study was to assess the susceptibility of C. quinquefasciatus larvae to essential oils from leaves of Eugenia uniflora L., Melaleuca armillaris (Sol. ex Gaertn.) Sm., and Schinus molle L and C. quinquefasciatus larvae's biochemical responses after their exposure to these leaves. The essential oils were chemically analyzed by GC and GC/MS. First, the lethal concentration for 50% (LC₅₀) values was estimated using different concentrations of essential oils and probit analysis. The larvae were exposed for 1 h at the LC₅₀ estimated for each essential oil. The susceptibility of the larvae to essential oils was evaluated using the following biochemical parameters: concentrations of total protein and reduced glutathione; levels of production of hydrogen peroxide and lipid peroxidation; and the activity of the enzyme acetylcholinesterase (AChE). The main chemical constituents in E. uniflora were E-β-ocimene, curzerene, germacrene B, and germacrone; in M. armillaris were 1,8-cineole and terpinolene; and in S. molle were sabinene, myrcene, and sylvestrene. The essential oils had LC₅₀ values between 31.52 and 60.08 mg/L, all of which were considered effective. All of them also promoted changes in biochemical parameters when compared to the control treatment. The essential oils of S. molle and E. uniflora inhibited the activity of the AChE enzyme, and the essential oil of M. armillaris increased it. All essential oils had larvicidal activity against C. quinquefasciatus, but the essential oil of E. uniflora was the most efficient. Thus, the findings of the present study suggest that the essential oil of E. uniflora can be considered promising for the development of botanical larvicides.

In Vitro and In Vivo Anti-Inflammatory Effects of Cannabis sativa Stem Extract

With growing scientific interest in cannabinoids, a number of studies have focused on biological activities of cannabidiol and its major source, inflorescence and leaf of Cannabis sativa plant. However, recent analytical chemistry studies have reported the pharmacological significance of non-cannabinoid phytochemicals that are rich in other parts of the plant. Thus, the objective of this study was to investigate the anti-inflammatory effects of Cannabis extracts from plant parts of shelled seeds, roots, and stems containing no or trace amounts of cannabinoids. Among water and ethanol extracts from three plant parts, Cannabis stem ethanol extract (CSE) had the most potent free radical scavenging activities and suppressive effects on the production of nitric oxide from macrophages. In further studies using macrophages, CSE effectively inhibited lipopolysaccharide (LPS)-induced inflammatory responses by suppressing proinflammatory cytokines, nuclear factor-κB and mitogen-activated protein kinase phosphorylations, and cellular accumulation of reactive oxygen species. Moreover, in mice exposed to LPS, CSE reduced tumor necrosis factor-α production and normalized activations of proapoptotic proteins in the liver, kidney, and spleen. Gas chromatography/mass spectrometry analyses of CSE showed several active compounds that might be associated with its antioxidant and anti-inflammatory effects. Collectively, these findings indicate that CSE counteracts LPS-induced acute inflammation and apoptosis, suggesting pharmaceutical applications for the stem part of C. sativa.

Analysis of the insect-repelling mechanism of star anise extract and its major active compounds against Plodia interpunctella

One of the major stored product pests, Indian meal moth causes the loss on the agriculture and food industries. This study was conducted to screen the insecticidal activity of ethanolic extracts and fractions partitioned by four different solvents [(1) n-hexane; (2) ether; (3) ethyl acetate; (4) water] from star anise (Illicium verum Hook. f.) against Plodia interpunctella larvae. Among all solvent-partitioned fractions, the strongest repellency was found for the n-hexane fraction of star anise extract. Solvent-solvent partitioning and chromatographic methods were further used to isolate and identify major anti-insect compounds from star anise extract. The results showed that trans-anethole (94.24%) was the major active compound showing an insect-repelling activity against P. interpunctella. Consequently, trans-anethole can be utilized as a main natural insect-repelling agent for controlling the P. interpunctella infestation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01053-8.

Nematicidal activity of tirotundin and parthenolide isolated from Tithonia diversifolia and Chrysanthemum parthenium

Acetylcholinesterase (AChE) is an enzyme that catalyzes acetylcholine into choline and acetic acid. Conventional pesticides, including organophosphates and carbamates target and inhibit the activity of AChE. To obtain more pesticide precursors that meet the safety requirements, more than 200 compounds were screened. Tirotundin and parthenolide identified as potential neurotoxins to nematodes were isolated from Tithonia diversifolia and Chrysanthemum parthenium, respectively. Their IC₅₀ values were 6.89 ± 0.30 and 5.51 ± 0.23 μg/mL, respectively against the AChE isolated from Caenorhabditis elegans. AChE was inhibited in a dose-dependent manner using the two compounds. And the Lineweaver-Burk and Dixon plots indicated that tirotundin and parthenolide were reversible inhibitors against AChE, both inhibiting AChE in a mixed-type competitive manner and demonstrating these compounds may possess dual binding site AChE inhibitors. LC₅₀ values of tirotundin and parthenolide against C. elegans were 9.16 ± 0.21 and 7.23 ± 0.48 μg/mL, respectively. These results provide a certain theoretical basis for the development and utilization of novel pesticides.

Metabolomic Response of the Creeping Wood Sorrel Oxalis corniculata to Low-Dose Radiation Exposure from Fukushima's Contaminated Soil

The biological consequences of the Fukushima nuclear accident have been intensively studied using the pale grass blue butterfly Zizeeria maha and its host plant, the creeping wood sorrel Oxalis corniculata. Here, we performed metabolomic analyses of Oxalis leaves from Okinawa to examine the plant metabolites that were upregulated or downregulated in response to low-dose radiation exposure from Fukushima's contaminated soil. The cumulative dose of radiation to the plants was 5.7 mGy (34 μGy/h for 7 days). The GC-MS analysis revealed a systematic tendency of downregulation among the metabolites, some of which were annotated as caproic acid, nonanoic acid, azelaic acid, and oleic acid. Others were annotated as fructose, glucose, and citric acid, involved in the carbohydrate metabolic pathways. Notably, the peak annotated as lauric acid was upregulated. In contrast, the LC-MS analysis detected many upregulated metabolites, some of which were annotated as either antioxidants or stress-related chemicals involved in defense pathways. Among them, only three metabolite peaks had a single annotation, one of which was alfuzosin, an antagonist of the α1-adrenergic receptor. We conclude that this Oxalis plant responded metabolically to low-dose radiation exposure from Fukushima's contaminated soil, which may mediate the ecological "field effects" of the developmental deterioration of butterflies in Fukushima.

Plant-Derived Pesticides as an Alternative to Pest Management and Sustainable Agricultural Production: Prospects, Applications and Challenges

Pests and diseases are responsible for most of the losses related to agricultural crops, either in the field or in storage. Moreover, due to indiscriminate use of synthetic pesticides over the years, several issues have come along, such as pest resistance and contamination of important planet sources, such as water, air and soil. Therefore, in order to improve efficiency of crop production and reduce food crisis in a sustainable manner, while preserving consumer's health, plant-derived pesticides may be a green alternative to synthetic ones. They are cheap, biodegradable, ecofriendly and act by several mechanisms of action in a more specific way, suggesting that they are less of a hazard to humans and the environment. Natural plant products with bioactivity toward insects include several classes of molecules, for example: terpenes, flavonoids, alkaloids, polyphenols, cyanogenic glucosides, quinones, amides, aldehydes, thiophenes, amino acids, saccharides and polyketides (which is not an exhaustive list of insecticidal substances). In general, those compounds have important ecological activities in nature, such as: antifeedant, attractant, nematicide, fungicide, repellent, insecticide, insect growth regulator and allelopathic agents, acting as a promising source for novel pest control agents or biopesticides. However, several factors appear to limit their commercialization. In this critical review, a compilation of plant-derived metabolites, along with their corresponding toxicology and mechanisms of action, will be approached, as well as the different strategies developed in order to meet the required commercial standards through more efficient methods.

Acute aluminum phosphide poisoning: The menace of phosphine exposure

Aluminum phosphide (AlP) is a popular fumigant used widely for the safe storage of food grain. Although A1P is free from toxic residues, it releases phosphine which acts on mitochondrial components of almost all types of pests. Unfortunately A1P is also a common suicidal agent in developing countries with no known antidote. In addition, accidental exposure to phosphine may also occur. AlP poisoning affects cardiac and vascular tissue directly and can result in multiorgan system failure leading to death in severe cases. There is no specific biomarker for diagnosing AlP poisoning and management depends on a high level of clinical suspicion. Although acetylcholinesterase has been suggested as a surrogate biomarker of AlP exposure, there are opposing views. In this review, we analyzed the relevant published material with emphasis on the need to recognize and explore the use of plasma mitochondrial enzyme activity as a potential biomarker for AlP exposure.

In silico annotation of unreviewed acetylcholinesterase (AChE) in some lepidopteran insect pest species reveals the causes of insecticide resistance

Lepidoptera is the second most diverse insect order outnumbered only by the Coeleptera. Acetylcholinesterase (AChE) is the major target site for insecticides. Extensive use of insecticides, to inhibit the function of this enzyme, have resulted in the development of insecticide resistance. Complete knowledge of the target proteins is very important to know the cause of resistance. Computational annotation of insect acetylcholinesterase can be helpful for the characterization of this important protein. Acetylcholinesterase of fourteen lepidopteran insect pest species was annotated by using different bioinformatics tools. AChE in all the species was hydrophilic and thermostable. All the species showed lower values for instability index except L. orbonalis, S. exigua and T. absoluta. Highest percentage of Arg, Asp, Asn, Gln and Cys were recorded in P. rapae. High percentage of Cys and Gln might be reason for insecticide resistance development in P. rapae. Phylogenetic analysis revealed the AChE in T. absoluta, L. orbonalis and S. exigua are closely related and emerged from same primary branch. Three functional motifs were predicted in eleven species while only two were found in L. orbonalis, S. exigua and T. absoluta. AChE in eleven species followed secretory pathway and have signal peptides. No signal peptides were predicted for S. exigua, L. orbonalis and T. absoluta and follow non secretory pathway. Arginine methylation and cysteine palmotylation was found in all species except S. exigua, L. orbonalis and T. absoluta. Glycosylphosphatidylinositol (GPI) anchor was predicted in only nine species.

Micronutrient Fertilization of Greenhouse Cucumbers Mitigates Pirimicarb Resistance in Aphis gossypii (Hemiptera: Aphididae)

The nutritional status of host plants can have direct impacts on herbivore physiology and insect-plant interactions. We investigated the effect of micronutrients, including manganese, iron, zinc, and copper, on cucumber plant physiology, and on the biology and physiology of a strain of Aphis gossypii Glover selected over 12 generations to be resistant to pirimicarb. The micronutrient treatment increased the activity of superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase in cucumber plants, and also increased levels of total phenolics, hydrogen peroxide, salicylic acid, and total chlorophyl, whereas malondialdehyde levels were unaffected. Pirimicarb-resistant cotton aphids that fed on micronutritient-amended cucumber plants expressed significantly decreased levels of acetylcholinesterase and detoxifying enzymes, specifically glutathione S-transferase, and carboxylesterase. Analysis of energy reserves in resistant A. gossypii fed on micronutritient-amended plants revealed decreases in the lipid and protein contents of aphids, whereas glycogen and carbohydrate contents showed no response. Resistant cotton aphids fed on micronutritient-amended plants showed significantly reduced fecundity, longevity, and reproductive periods, and a 1.7-fold reduction in pirimicarb LC50 compared with those fed on control plants. We conclude that micronutrient amendment negatively impacts the biological performance of insecticide-resistant cotton aphids, and diminishes their resistance to pirimicarb. Both direct effects on plant health, such as enhanced inducible defenses, and indirect effects on aphid fitness, such as reduced biological performance and detoxification abilities, were implicated. Therefore, optimization of micronutrient amendments could be a useful complement to other tactics for managing insecticide-resistant A. gossypii on cucumbers, and warrants exploration in other contexts.

Anti-Termitic Activity of Three Plant Extracts, Chlorpyrifos, and a Bioagent Compound (Protecto) against Termite Microcerotermes eugnathus Silvestri (Blattodea: Termitidae) in Egypt

A trend towards environmentally friendly chemicals for use in termite management has been occurring globally. This study examined three naturally occurring plant extracts from Lavandula latifolia (Spike lavender), Origanum vulgare (Marjorum), and Syzygium aromaticum (Clove) against the termite Microcerotermes eugnathus. Plant extract results were compared to two commercially used termite pesticides, the bio-insecticide, Bacillus thuringiensis var. kurstaki (Protecto 9.4% WP) and Dursban (Chlorpyrifos 48%). Gas chromatography-mass spectrometry (GC-MS) analysis was used to identify the main compounds in the three plant extracts. The main compounds in Lavandula Latifolia were linalool (21.49%), lavandulol (12.77%), β-terpinyl acetate (10.49%), and camphor (9.30%). Origanum vulgare extract contained thymol (14.64%), m-cymene (10.63%), linalool (6.75%), and terpinen-4-ol (6.92%) as main compounds. Syzygium aromaticum contained eugenol (99.16%) as the most abundant identified compound. The extract of O. vulgare caused the highest termite death rate, with an LC50 of 770.67 mg/L. Exposure to lavender extract showed a high death rate with an LC50 of 1086.39 mg/L. Clove extract did not show significant insecticidal activity with an LC50 > 2000 mg/L. Significant termiticide effects were found, with LC50 values of 84.09 and 269.98 mg/L for soldiers and workers under the application of Dursban and Protecto, respectively. The LC50 values reported for nymphs were <120, <164.5, and 627.87 mg/L after exposure to Dursban, Protecto, and O. vulgare extract, respectively. The results of the study show that some of the extracts have low toxicity compared to the bioagent and Dursban, and may show promise as natural termiticides, particularly as extracts from O. vulgare.

Bioactivity and efficacy of essential oils extracted from Artemisia annua against Tribolium casteneum (Herbst. 1797) (Coleoptera: Tenebrionidae): An eco-friendly approach

Tribolium casteneum is a major stored grains pest causing huge loss by secreting toxic quinones' which make the grains unfit for human consumption. Increasing concern about the fast-growing resistance in T. casteneum against fumigants has evoked more intense research worldwide. Therefore, finding an eco-friendly alternative for the management of the pest is of great importance. In this study, the insecticidal activity of the essential oils (EOs) of Artemisia annua is evaluated. Chemical composition of the EOs eluted with methanol and petroleum ether was analysed through Gas chromatography-mass spectrometry (GC-MS). The result has reported a total of 13 & 16 compounds in the methanol and petroleum ether EOs respectively. In contact toxicity studies, adults were found more susceptible to the petroleum ether EOs (LD₅₀ = 0.43 mg adult-¹) than the methanolic EOs (LD₅₀ = 1.87 mg adult-¹). Petroleum ether EOs was also superior in fumigant assays against both the adults (0.81 mg L air^-1) and larvae (0.65 mg L air^-1). Moreover, the same was also recorded as a strong repellent. The bio-molecular studies conducted to gain an insight into the extent of metabolic disturbances inflicted in the treatment sets has shown a significant increase in Lipid peroxidase and decrease (p˂0.01) in protein, Acetylcholinesterase, Glutathione S Transferees, Reduced Glutathione level. This indicates the major signs of oxidative stress in the treatment sets. The Results ascertain the knowledge to develop natural insecticides from Artemisia annua using a potential solvent to be used in the future as an efficient management tool against T. casteneum.

Baccharis dracunculifolia (Asteraceae) essential oil toxicity to Culex quinquefasciatus (Culicidae)

The control of mosquitoes by means of chemical insecticides has been a problem, mainly due to the possibility of resistance developed by insects to xenobiotics. For this reason, demand for botanical insecticides has increased. In this sense, the present work aims to verify the susceptibility and morphological and biochemical alterations of Culex quinquefasciatus larvae after exposure to essential oil (EO) of leaves of Baccharis dracunculifolia. To observe the larvicidal action, larvae were exposed to EO at concentrations of 25, 50, 100, and 200 mg/L, until their emergence to adults. The control group was exposed to deionized water and dimethyl sulfoxide. Morphological analyses were also carried out using hematoxylin and eosin, mercury bromophenol blue, Nile blue, and periodic acid Schiff. Biochemical analyses of total glucose, triacylglyceride (TAG), protein, and acetylcholinesterase levels were performed. The phytochemical analysis of the EO showed (E)-nerolidol as the major compound (30.62%). Larvae susceptibility results showed a LC₅₀ of 34.45 mg/L for EO. Morphological analysis showed that there were histological changes in midgut. For biochemical analyses, the glucose level in the larvae exposed to EO for 24 h decreased significantly, unlike the TAG levels, which increased. The total protein level of the larvae also increased after exposure for 24 h, and acetylcholinesterase levels decreased significantly. Taking all our data into account, we can conclude that EO causes destabilization in larva, leading to histological changes, metabolic deregulation and, consequently, their death.

Insecticidal activity and the mechanism of action of three phenylpropanoids isolated from the roots of Piper sarmentosum Roxb

Hexane, dichloromethane and methanol extracts of the roots of Piper sarmentosum Roxb. were screened for toxicity towards Sitophilus oryzae (L.), Rhyzopertha dominica (F.), and Plodia interpunctella (Hübner) and the hexane extract exhibited the highest mortality percentage. Bioassay-guided fractionation of the hexane extract resulted in the isolation of asaricin 1, isoasarone 2, and trans-asarone 3. Asaricin 1 and isoasarone 2 were the most toxic compounds to Sitophilus oryzae, Rhyzopertha dominica, and Plodia interpunctella. Sitophilus oryzae and Rhyzopertha dominica exposed to asaricin 1 and isoasarone 2 required the lowest median lethal time. Insecticidal activity of trans-asarone 3 showed consistent toxicity throughout the 60 days towards all three insects as compared to asaricin 1 and isoasarone 2. Asaricin 1 and isoasarone 2 at different doses significantly reduced oviposition and adult emergence of the three insects in treated rice. Trans-asarone 3 had lowest toxicity with highest LC and LT values in all tested insects relative to its mild oviposition inhibition and progeny activity. Moreover, asaricin 1 and isoasarone 2 significantly inhibited acetylcholinesterase in comparison with trans-asarone 3 and the control. Acetylcholinesterase inhibition of Rhyzopertha dominica and Plodia interpunctella by asaricin 1 and isoasarone 2 were lower than that of Sitophilus oryzae, which correlated with their higher resistance.

Volatile Organic Compounds Emitted by Fungal Associates of Conifer Bark Beetles and their Potential in Bark Beetle Control

Conifer bark beetles attack and kill mature spruce and pine trees, especially during hot and dry conditions. These beetles are closely associated with ophiostomatoid fungi of the Ascomycetes, including the genera Ophiostoma, Grosmannia, and Endoconidiophora, which enhance beetle success by improving nutrition and modifying their substrate, but also have negative impacts on beetles by attracting predators and parasites. A survey of the literature and our own data revealed that ophiostomatoid fungi emit a variety of volatile organic compounds under laboratory conditions including fusel alcohols, terpenoids, aromatic compounds, and aliphatic alcohols. Many of these compounds already have been shown to elicit behavioral responses from bark beetles, functioning as attractants or repellents, often as synergists to compounds currently used in bark beetle control. Thus, these compounds could serve as valuable new agents for bark beetle management. However, bark beetle associations with fungi are very complex. Beetle behavior varies with the species of fungus, the stage of the beetle life cycle, the host tree quality, and probably with changes in the emission rate of fungal volatiles. Additional research on bark beetles and their symbiotic associates is necessary before the basic significance of ophiostomatoid fungal volatiles can be understood and their applied potential realized.

Potentiality of botanical agents for the management of post harvest insects of maize: a review

Natural products derived from plants are emerging as potent biorational alternatives to synthetic insecticides for the integrated management of post harvest insects of maize. In this paper, effectiveness of botanicals including plant extracts, essential oils, their isolated pure compounds, plant based nano formulations and their mode of action against storage insects have been reviewed with special reference to maize. Plant based insecticides found to be the most promising means of controlling storage insects of maize in an eco friendly and sustainable manner. This article also throws light on the commercialization of botanicals, their limitations, challenges and future trends of storage insect management.

In Vitro Pharmacological Activities and GC-MS Analysis of Different Solvent Extracts of Lantana camara Leaves Collected from Tropical Region of Malaysia

We investigated the effect of different solvents (ethyl acetate, methanol, acetone, and chloroform) on the extraction of phytoconstituents from Lantana camara leaves and their antioxidant and antibacterial activities. Further, GC-MS analysis was carried out to identify the bioactive chemical constituents occurring in the active extract. The results revealed the presence of various phytocompounds in the extracts. The methanol solvent recovered higher extractable compounds (14.4% of yield) and contained the highest phenolic (92.8 mg GAE/g) and flavonoid (26.5 mg RE/g) content. DPPH radical scavenging assay showed the IC₅₀ value of 165, 200, 245, and 440 μg/mL for methanol, ethyl acetate, acetone, and chloroform extracts, respectively. The hydroxyl scavenging activity test showed the IC₅₀ value of 110, 240, 300, and 510 μg/mL for methanol, ethyl acetate, acetone, and chloroform extracts, respectively. Gram negative bacterial pathogens (E. coli and K. pneumoniae) were more susceptible to all extracts compared to Gram positive bacteria (M. luteus, B. subtilis, and S. aureus). Methanol extract had the highest inhibition activity against all the tested microbes. Moreover, methanolic extract of L. camara contained 32 bioactive components as revealed by GC-MS study. The identified major compounds included hexadecanoic acid (5.197%), phytol (4.528%), caryophyllene oxide (4.605%), and 9,12,15-octadecatrienoic acid, methyl ester, (Z,Z,Z)- (3.751%).

Insecticidal and Nematicidal Activities of Novel Mimosine Derivatives

Mimosine, a non-protein amino acid, is found in several tropical and subtropical plants, which has high value for medicine and agricultural chemicals. Here, in continuation of works aimed to development of natural product-based pesticidal agents, we present the first significant findings for insecticidal and nematicidal activities of novel mimosine derivatives. Interestingly, mimosinol and deuterated mimosinol (d-mimosinol) from mimosine had strong insecticidal activity which could be a result of tyrosinase inhibition (IC₅₀ = 31.4 and 46.1 μM, respectively). Of synthesized phosphoramidothionate derivatives from two these amino alcohols, two compounds (1a and 1b) showed high insecticidal activity (LD₅₀ = 0.5 and 0.7 μg/insect, respectively) with 50%–60% mortality at 50 μg/mL which may be attributed to acetylcholinesterase inhibition. Compounds 1a and 1b also had strong nematicidal activity with IC₅₀ = 31.8 and 50.2 μM, respectively. Our results suggest that the length of the alkyl chain and the functional group at the C₅-position of phosphoramidothionates derived from mimosinol and d-mimosinol are essential for the insecticidal and nematicidal activities. These results reveal an unexplored scaffold as new insecticide and nematicide.

In vitro acaricidal activity of 1,8-cineole against Sarcoptes scabiei var. cuniculi and regulating effects on enzyme activity

1,8-Cineole found in many essential oils is a monoterpene and acts as a repellent against Sarcoptes scabiei var. cuniculi. In the present study, the acaricidal activity of 1,8-cineole against S. scabiei var. cuniculi was evaluated and the acaricidal mechanism was also investigated by assaying enzyme activities. The results showed that the lethal concentration of 50% (LC50) value (95% confidence limit (CL)) and the lethal time of 50% (LT50) value (95% CL) of 1,8-cineole were 2.77 mg/mL and 3.606 h, respectively. The pathological changes under transmission electron microscopy showed that the morphology of the mitochondria was abnormal, the cell nuclear membrane was damaged, and the nuclear chromatin was dissoluted. The activities of superoxide dismutase (SOD), glutathione-s-transferases (GSTs), monoamine oxidase (MAO), nitric oxide synthase (NOS), and acetylcholinesterase (AChE) were significantly changed after treatment with 1,8-cineole for 4, 8, 12, and 24 h. SOD and GSTs are associated with the protection mechanism of scabies mites. And, the activities of SOD and GSTs were increased as compared with the control group. MAO, AChE, and NOS are associated with the nervous system of scabies mites. The activity of MAO was increased whereas the AChE was suppressed. The activity of NOS was suppressed in the high-dose group whereas increased in the middle-dose group and low-dose group. These results indicated that the mechanism of 1,8-cineole mainly attributed to the changes of these enzyme activities related to the nervous system of scabies mites.