Discovery of the Chlorinated and Ammoniated Derivatives of Vanillin as Potential Insecticidal Candidates Targeting V-ATPase: Structure-Based Virtual Screening, Synthesis, and Bioassay

Vacuolar-type H+-ATPases (V-ATPases) play a crucial role in the life cycle of agricultural pests and represent a promising target for the development of novel insecticides. In this study, S18, a derivative of vanillin acquired from Specs database using a structure-based virtual screening methodology, was first identified as a V-ATPase inhibitor. It binds to subunit A of the enzyme with a Kd of 1 nM and exhibits insecticidal activity against M. separata. Subsequently, using S18 as the lead compound, a new series of vanillin derivatives were rationally designed and efficiently synthesized. and their biological activities were assessed. Among them, compound 3b-03 showed the strongest insecticidal activity against M. separata by effectively targeting the V-ATPase subunit A with Kd of 0.803 μM. Isothermal titration calorimetric measurements and docking results provided insights into its interaction with subunit A of V-ATPase, which could facilitate future research aimed at the development of novel chemical insecticides.

Novel Pesticide Candidates Inspired by Natural Neolignan: Preparation and Insecticidal Investigation of Honokiol Analogs Containing 2-Aminobenzoxazole-Fused Core Scaffold

As a continuation of our efforts to develop new agrochemicals with typical architecture and efficient bioactivity from plant natural products, natural neolignan honokiol was used as a lead compound to prepare novel analogs bearing the core 2-aminobenzoxazole scaffold. Their insecticidal potency against two representative agricultural pests, Plutella xylostella Linnaeus and Mythimna separata (Walker), were evaluated in vivo. The pesticide bioassay results revealed that compounds 7″a, 9, 10d, and 10j exhibited prominent larvicidal activity against the larvae of P. xylostella (LC50 = 7.95, 11.85, 15.51, and 12.06 μg/mL, respectively), superior to the precursor honokiol (LC50 = 43.35 μg/mL) and two botanical insecticides, toosendanin (LC50 = 26.20 μg/mL) and rotenone (LC50 = 23.65 μg/mL). Compounds 7d, 10d, and 10j displayed a more pronounced nonchoice antifeedant effect (AFC50 = 9.48, 9.14, and 12.41 μg/mL, respectively) than honokiol (AFC50 = 54.81 μg/mL) on P. xylostella. Moreover, compounds 7b, 7″a, 9, 10d, 10f, and 10j showed better growth inhibitory activity against M. separata (LC50 = 0.36, 0.34, 0.28, 0.16, 0.26, and 0.11 mg/mL, respectively) than honokiol, toosendanin, and rotenone (LC50 = 1.48, 0.53, and 0.46 mg/mL, respectively). A potted plant assay under greenhouse conditions illustrated that compounds 10d and 10j continued to provide good control efficacy against P. xylostella and an apparent protective effect on plants. Further cytotoxicity assay revealed that the aforementioned potent compounds showed relatively moderate toxicity and a good safety profile for non-target mammalian cells. Overall, the current work provides valuable insight into the agrochemical innovation of honokiol-derived analogs for use as natural-inspired pesticides in agricultural pest management.

Pyridine Derivatives as Insecticides: Part 6. Design, Synthesis, Molecular Docking, and Insecticidal Activity of 3-(Substituted)methylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles Toward Aphis gossypii (Glover, 1887)

Three new series of 3-(substituted)methylthio-4-cyano-5,6,7,8-tetrahydroisoquinolines were designed and synthesized starting from readily available materials, 7-acetyl-4-cyano-1,6-dimethyl-6-hydroxy-8-(4-pyridyl, 3-pyridyl, phenyl, 4-methoxyphenyl, or 4-chlorophenyl)-5,6,7,8-tetrahydrosoquinoline-3(2H)-thiones 2a-e in high yields and very pure states. Thus, compounds 2a-e were reacted with some chloro reagents, namely, N-aryl-2-chloroacetamides 3a-f and N-(naphthalen-2-yl)-2-chloroacetamide (3g) under mild basic conditions to give the first two series of the target compounds, 3-(N-aryl)carbamoylmethylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles 4a-l and 5a-e, respectively. Reaction of compounds 2d,e with ethyl chloroacetate under the same conditions gave the other series, 3-ethoxycarbonyl-methylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles 6d,e. Structural formulas of all of the new compounds were elucidated and confirmed by elemental and spectral analyses. The insecticidal activity of all synthesized 5,6,7,8-tetrahydrosoquinolines toward the nymphs and adults of Aphis gossypii were screened. The results revealed the promising insecticidal activity of some tested compounds. Moreover, the structure-activity relationships as well as molecular docking of some representative compounds were evaluated.

Design, Synthesis, and Insecticidal Activity of Isoxazoline Derivatives Incorporating an Acylhydrazine Moiety

The long-term use of agricultural insecticides has led to the development of resistant strains. In this context, the isoxazoline structure has become an active area of pesticide research owing to its wide insecticidal spectrum, nontoxicity to mammals, and lack of cross-resistance with known insecticides. In the present study, based on the discovery of compound G22 in our previous work, a series of novel isoxazoline compounds containing acylhydrazine were designed and synthesized using a scaffold hopping strategy. The insecticidal activities of the target compounds were assessed, and compound L17 (LC50 = 0.489 mg/L) showed insecticidal activity against Spodoptera frugiperda superior to those of the commercial insecticides indoxacarb (LC50 = 3.14 mg/L) and fluralaner (LC50 = 0.659 mg/L). Theoretical calculations indicated that the introduction of acylhydrazine plays an important role in the biological activity of the target compounds. Furthermore, the enzyme-linked immunosorbent assay and molecular docking results indicated that L17 may act on the GABA receptor of the target insect. These results indicated that L17 is a potential candidate compound for controlling S. frugiperda populations in agriculture.

Chemical Characterization and Insecticidal Activities of the Essential Oils from the Different Parts of Ocimum gratissimum var. suave (Willd.) Hook. f

In this research, the essential oils (EOs) from different parts of Ocimum gratissimum var. suave were chemically characterized and evaluated for insecticidal activity, especially against two common storage pests of Chinese herbal medicines: Tribolium castaneum and Liposcelis bostrychophila. Ocimum gratissimum is a plant with several medicinal values in traditional Chinese medicine. In the study, EOs were successfully extracted from inflorescences (OGI) and stem-leaf (OGLS) parts of O. gratissimum by steam distillation and 16 compounds were identified by gas chromatography-mass spectrometry (GC-MS), of which eugenol was the major constituent in both extracts. In fumigation toxicity tests against both pests, the EOs showed limited toxicity against T. castaneum but showed better toxicity against L. bostrychophila. Contact toxicity tests showed that OGLS had better insecticidal potential than OGI, while the insecticidal effect of eugenol sometimes exceeded that of EOs. In addition, repellency experiments showed that O. gratissimum EOs repelled the pests to varying degrees, with the effect being influenced by concentration and exposure time. The results suggest that O. gratissimum EOs could be a promising alternative to synthetic insecticides for sustainable utilization.

Enhancing Deer Sous Vide Meat Shelf Life and Safety with Eugenia caryophyllus Essential Oil against Salmonella enterica

Modern lifestyles have increased the focus on food stability and human health due to evolving industrial goals and scientific advancements. Pathogenic microorganisms significantly challenge food quality, with Salmonella enterica and other planktonic cells capable of forming biofilms that make them more resistant to broad-spectrum antibiotics. This research examined the chemical composition and antibacterial and antibiofilm properties of the essential oil from Eugenia caryophyllus (ECEO) derived from dried fruits. GC-MS analyses identified eugenol as the dominant component at 82.7%. Additionally, the study aimed to extend the shelf life of sous vide deer meat by applying a plant essential oil and inoculating it with S. enterica for seven days at 4 °C. The essential oil demonstrated strong antibacterial activity against S. enterica. The ECEO showed significant antibiofilm activity, as indicated by the MBIC crystal violet test results. Data from MALDI-TOF MS analysis revealed that the ECEO altered the protein profiles of bacteria on glass and stainless-steel surfaces. Furthermore, the ECEO was found to have a beneficial antibacterial effect on S. enterica. In vacuum-packed sous vide red deer meat samples, the anti-Salmonella activity of the ECEO was slightly higher than that of the control samples. These findings underscore the potential of the ECEO's antibacterial and antibiofilm properties in food preservation and extending the shelf life of meat.

Chemical Composition of Five Lamiaceae Essential Oils and Their Insecticidal and Phytotoxic Activity

The Lamiaceae family is widely distributed worldwide. In this study, we investigated the insecticidal activity of five Lamiaceae essential oils against Thrips flavus Schrank and the phytotoxic activity against Glycine max (L.) Merr., Zea mays L., Portulaca oleracea L., and Echinochloa oryzoides (Ard.) Fritsch. Then, the chemical composition of the five essential oils was analyzed by using gas chromatography-mass spectrometry (GC-MS). The five Lamiaceae essential oils were melissa, basil, rosemary, negundo chastetree, and salvia. The main constituents of the five Lamiaceae essential oils were preliminarily determined to be as follows: α-pinene and 1,8-cineole in the rosemary essential oil; β-pinene, γ-terpinene, and d-limonene in the negundo chastetree essential oil; β-cadinene and isolongifolen-5-one in the melissa essential oil; 5-allylguaiacol in the basil essential oil; and isopropyl myristate, linalyl acetate, and linalool in the salvia essential oil. Using a bioassay, it was found that, among the five essential oils, the melissa essential oil exhibited the lowest LC50 value, which was 0.18 mg/mL, and the salvia essential oil exhibited the highest LC50 value, which was 0.42 mg/mL. The control efficacy of the five essential oils significantly increased with time and concentration in pot experiments. The negundo chastetree, basil, rosemary, and salvia essential oils at 900.00 g a.i.·hm-2 showed high control efficacy against T. flavus, with values higher than 90%. Female thrips were attracted to the negundo chastetree essential oil. The five essential oils were also tested for their effects on the germination rate, germination potential, germination index, and shoot length of G. max, Z. mays, P. oleracea, and E. oryzoides. The basil essential oil significantly inhibited the germination of P. oleracea, with germination at a concentration of 1.0 mg/mL being only 11.11 ± 5.09%. This study provides a reference for the development of botanical pesticides to control T. flavus, crops, and weeds.

In silico studies of benzothiazole derivatives as potential inhibitors of Anopheles funestus and Anopheles gambiae trehalase

Introduction

In malaria management, insecticides play a crucial role in targeting disease vectors. Benzothiazole derivatives have also been reported to possess insecticidal properties, among several other properties they exhibit. The female Anopheles mosquito is responsible for transmitting the malaria parasite when infected. Anopheles gambiae (Ag) and Anopheles funestus (Af) are two of the most notable Anopheles species known to spread malaria in Nigeria. Trehalase is an enzyme that breaks down trehalose. Recent research has proposed it as a viable target for inhibition since it aids in flight and stress adaptation.

Methods

This study aimed to investigate benzothiazole derivatives as potential inhibitors of trehalase of Anopheles funestus (AfTre) and Anopheles gambiae (AgTre) using toxicity profiling, molecular docking, and dynamic simulation for future insecticidal intervention. A total of 4,214 benzothiazole-based compounds were obtained from the PubChem database and subjected to screening against the 3D modelled structure of AfTre and AgTre. Compounds with some toxicity levels were optimised, and the obtained lead compounds were further investigated through molecular docking studies. Furthermore, the best hit was subjected to parameters such as RMSD, RMSF, SASA, Rg, and hydrogen bond to confirm its stability when in a complex with AfTre, and these parameters were compared to that of validamycin A (control ligand).

Results and discussion

The post-screening analysis showed binding affinities of -8.7 and -8.2 kcal/mol (compound 1), -8.2 and -7.4 kcal/mol (compound 2), compared to -6.3 and -5.1 kcal/mol (Validamycin A, a known inhibitor) against AfTre and AgTre, respectively. The molecular dynamics simulation showed that compound 1 (the best hit) had good stability when in complex with AfTre. These findings suggest that these best hits can serve as potential inhibitors for the development of novel insecticides in the control of malaria vectors.

Pyridine Derivatives as Insecticides. Part 5. New Thieno[2,3-b]pyridines and Pyrazolo[3,4-b]pyridines Containing Mainly Ethyl Nicotinate Scaffold and Their Insecticidal Activity toward Aphis gossypii (Glover,1887)

Ethyl 5-cyano-1,6-dihydro-2-methyl-4-(2'-thienyl)-6-thioxonicotinate (A) was synthesized and reacted with ethyl chloroacetate in the presence of sodium acetate or sodium carbonate to give ethyl 5-cyano-6-((2-ethoxy-2-oxoethyl)thio)-2-methyl-4-(2'-thienyl)nicotinate (1a) or its isomeric thieno[2,3-b]pyridine 2a. 3-Aminothieno[2,3-b]pyridine-2-carboxamide 2b was also synthesized by the reaction of A with 2-chloroacetamide. The reaction of 1a with hydrazine hydrate in boiling ethanol gave acethydrazide 3. Heating ester 1a with hydrazine hydrate under neat conditions afforded 3-amino-1H-pyrazolo[3,4-b]pyridine 10. Compounds 2b, 3, and 10 were used as precursors for synthesizing other new thieno[2,3-b]pyridines and pyrazolo[3,4-b]pyridines containing mainly the ethyl nicotinate scaffold. Structures of all new compounds were confirmed by elemental and spectral analyses. Most of the obtained compounds were evaluated for their insecticidal activity toward the nymphs and adults of Aphis gossypii (Glover,1887). Some compounds such as 4, 9b, and 9c showed promising results. The effect of some sublethal concentrations, less than LC50, of compounds 4, 9b, and 9c on the examined Aphis was subjected to a further study. The results demonstrated that exposure of A. gossypii nymphs to sublethal concentrations of compounds 4, 9b, and 9c had noticeable effects on their biological parameters, i.e., nymphal instar duration, generation time, and adult longevity. The highest concentration C1 of all three compounds increased the nymphal instar duration and generation time and decreased adult longevity and vice versa.

Discovery of Novel (+)-Nootkatone-Based Amine Derivatives as Potential Insecticide Candidates

To discover novel natural product-based insecticides, a series of (+)-nootkatone-based amine derivatives 3a-t were prepared and evaluated for their insecticidal activities against Mythimna separata Walker, Myzus persicae Sulzer, and Plutella xylostella Linnaeus. Insecticidal assays showed that most of the title (+)-nootkatone derivatives exhibited stronger insecticidal activities against three insect pests than the precursor (+)-nootkatone after the introduction of amine groups on the parent (+)-nootkatone. Compounds 3a, 3d, 3h, 3m, 3n, 3p, and 3r displayed more promising growth inhibitory (GI) effect against M. separata than the commercially available botanical insecticide toosendanin. Compound 3o exhibited the most potent aphicidal activity with an LD50 value of 0.011 μg/larvae, which was 2.09-fold higher than the positive control rotenone. Additionally, compounds 3g and 3n showed more promising larvicidal activity against P. xylostella with LC50 values of 260 and 230 mg/L, respectively, superior to that of rotenone (460 mg/L). Moreover, derivatives 3g and 3n exhibited better control efficacy toward P. xylostella than rotenone under greenhouse conditions. Preliminary mechanistic studies revealed that derivative 3n could inhibit the activity of glutathione S-transferase (GST) in P. xylostella and thus exerted larvicidal activity, and molecular docking further demonstrated that 3n could interact well with some amino acid residues of GST. Finally, the toxicity assay suggested that derivatives 3g and 3n were relatively less toxic to nontarget organisms. These findings will provide insights into the development of (+)-nootkatone derivatives as green pesticides.

Quantitative structure-insecticidal activity of essential oils on the human head louse (Pediculus humanus capitis)

In the search for natural and non-toxic products alternatives to synthetic pesticides, the fumigant and repellent activities of 35 essential oils are predicted in the human head louse (Pediculus humanus capitis) through the Quantitative Structure-Activity Relationships (QSAR) theory. The number of constituents of essential oils with weight percentage composition greater than 1% varies from 1 to 15, encompassing up to 213 structurally diverse compounds in the entire dataset. The 27,976 structural descriptors used to characterizing these complex mixtures are calculated as linear combinations of non-conformational descriptors for the components. This approach is considered simple enough to evaluate the effects that changes in the composition of each component could have on the studied bioactivities. The best linear regression models found, obtained through the Replacement Method variable subset selection method, are applied to predict 13 essential oils from a previous study with unknown property data. The results show that the simple methodology applied here could be useful for predicting properties of interest in complex mixtures such as essential oils.

Repellency, Toxicity, and Chemical Composition of Plant Essential Oils from Myrtaceae against Asian Citrus Psyllid, Diaphorina citri Kuwayama (Hemiptera Liviidae)

Diaphorina citri Kuwayama (D. citri) is one of the major pests in the citrus industry, which spreads Citrus Huanglongbing disease. It has developed resistance to chemical insecticides. Therefore, searching for greener solutions for pest management is critically important. The main aim of this study was to evaluate the repellent and insecticidal efficacy of essential oils (EOs) from four species of Myrtaceae plants: Psidium guajava (PG), Eucalyptus robusta (ER), Eucalyptus tereticornis (ET), and Baeckea frutescens (BF) against D. citri and to analyze their chemical compositions. GC-MS analysis was performed, and the results indicated that the EOs of PG, ER, ET, and BF were rich in terpenoids, ketones, esters, and alcohol compounds. The repellent rate of all four EOs showed that it decreased with exposure time but increased with the concentration of EOs from 80.50% to 100.00% after treating D. citri for 6 h with four EOs at 100% concentration and decreased to 67.71% to 85.49% after 24 h of exposure. Among the compounds from the EOs tested, eucalyptol had the strongest repellent activity, with a 24 h repellency rate of 100%. The contact toxicity bioassay results showed that all EOs have insecticidal toxicity to D. citri; the LC50 for nymphs was 36.47-93.15 mL/L, and for adults, it was 60.72-111.00 mL/L. These results show that when PG is used as the reference material, the ER, ET, and BF EOs have strong biological activity against D. citri, which provides a scientific basis for the further development of plant-derived agrochemicals.

Synthetic Modification and Insecticidal Activity of 4-epi-cis-Dihydroagarofuran Derivatives

To synthesize the fundamental framework of dihydroagarofuran, a novel strategy was devised for constructing the C-ring through a dearomatization reaction using 6-methoxy-1-tetralone as the initial substrate. Subsequently, the dihydroagarofuran skeleton was assembled via two consecutive Michael addition reactions. The conjugated diene and trans-dihydroagarofuran skeleton were modified. The insecticidal activities of 33 compounds against Mythimna separata were evaluated. Compounds 11-5 exhibited an LC50 value of 0.378 mg/mL. The activity exhibited a remarkable 29-fold increase compared to positive control Celangulin V, which was widely recognized as the most renowned natural dihydroagarofuran polyol ester insecticidal active compound. Docking experiments between synthetic compounds and target proteins revealed the shared binding sites with Celangulin V. Structure-activity relationship studies indicated that methyl groups at positions C4 and C10 significantly improved insecticidal activity, while ether groups with linear chains displayed enhanced activity; in particular, the allyl ether group demonstrated optimal efficacy. Furthermore, a three-dimensional quantitative structure-activity relationship model was established to investigate the correlation between the skeletal structure and activity. These research findings provide valuable insights for discovering and developing dihydroagarofuran-like compounds.

Design, Synthesis, and Acaricidal/Insecticidal Activities of New Phenylpyrazole Derivatives Comprising an Imide Moiety

Using nicofluprole as the lead compound, we designed and synthesized a series of new phenylpyrazole analogues through substituting the methyl group on the nitrogen atom of the amide with an acyl group. Bioassay results showed that compounds A12-A17 with a 1-cyanocyclopropimide group exhibited outstanding insecticidal activity. The LC50 values for compounds A12-A17 against Tetranychus cinnabarinus ranged from 0.58 to 0.91 mg/L. Compound A15 showed an LC50 value of 0.29 and 3.10 mg/L against Plutella xylostella and Myzus persicae, respectively. Molecular docking indicated the potential binding interactions of compound A15 with a gamma-aminobutyric acid receptor. Additionally, density functional theory calculations implied that the 1-cyanocyclopropimide structure might be essential for its biological activity. Phenylpyrazole derivatives, containing a 1-cyanocyclopropimide fragment, have the potential for further development as potential insecticides.

Recent Research Progress in Oxime Insecticides and Perspectives for the Future

In recent decades, the unique structural attributes and purported insecticidal properties of oximes have garnered increasing attention. A variety of insecticides, encompassing fluxametamide, fluhexafon, and lepimectin, have been synthesized, all of which incorporate oximes. This review endeavors to encapsulate the insecticidal efficacy, structure-activity correlations, and operative mechanisms of oxime-containing compounds. Furthermore, it delves into the conceptual frameworks underpinning the design of innovative oxime-based insecticides, thereby shedding light on prospective advancements in this field.

In-Depth Structural Simplification of Celangulin V: Design, Synthesis, and Biological Activity

Celangulin V is a novel botanical insecticide with significant bioactivity and a unique molecular target, but its complex polyol ester structure hinders its broader application in agriculture. To discover new analogues of celangulin V with a simpler structure and enhanced biological activities, we initiated a research project aimed at simplifying its structure and assessing insecticidal efficacy. In this study, a series of novel 1-tetralone derivatives were designed via a structure-based rational design approach and synthesized by a facile method. The biological activities of the target compounds were determined against Mythimna separata (M. separata), Plutella xylostella, and Rhopalosiphum padi. The results revealed that most of the synthesized compounds exhibited superior activities compared to celangulin V. Remarkably, the insecticidal activity of compound 6.16 demonstrated 102-fold greater stomach toxicity than celangulin V against M. separata. In addition, certain compounds showed significant contact toxicity against M. separata, a finding not reported previously in the structural optimization studies of celangulin V. Molecular docking analysis illustrated that the binding pocket of compound 6.16 with the H subunit of V-ATPase was the same as celangulin V. This study presents novel insights into the structural optimization of botanical pesticides.

Novel Insecticidal Butenolide-Containing Methylxanthine Derivatives: Synthesis, Crystal Structure, Biological Activity Evaluation, DFT Calculation and Molecular Docking

The design of novel agrochemicals starting from bioactive natural products is one of the most effective ways in the discovery and development of new pesticidal agents. In this paper, a series of novel butenolide-containing methylxanthine derivatives (Ia-Ir) were designed based on natural methylxanthine caffeine and stemofoline, and the derivatized insecticide flupyradifurone of the latter. The structures of the synthesized compounds were confirmed via 1H-NMR, 13C NMR, HRMS and X-ray single crystal diffraction analyses. The biological activities of the compounds were evaluated against a variety of agricultural pests including oriental armyworm, bean aphid, diamondback moth, fall armyworm, cotton bollworm, and corn borer; the results indicated that some of them have favorable insecticidal potentials, particularly toward diamondback moth. Among others, Ic and Iq against diamondback moth possessed LC50 values of 6.187 mg ⋅ L-1 and 3.269 mg ⋅ L-1, respectively, - 2.5- and 4.8-fold of relative insecticidal activity respectively to that of flupyradifurone (LC50=15.743 mg ⋅ L-1). Additionally, both the DFT theoretical calculation and molecular docking with acetylcholine binding protein were conducted for the highly bioactive compound (Ic). Ic and Iq derived from the integration of caffeine (natural methylxanthine) and butenolide motifs can serve as novel leading insecticidal compounds for further optimization.

Design, Synthesis and Insecticidal Activity of Novel meta-Diamide Compounds Containing Pyridine Rings

In order to discover new meta-diamide compounds with good activity and novel structure, 15 related compounds were designed and synthesized by the bioisosterism principle with cyproflanilide as the lead compound. The insecticidal activities of these compounds against Plutella xylostella and Tetranychus cinnabarinus were tested, and the results of biological activity test showed that some compounds had more than 90 % insecticidal activity against Plutella xylostella at 1 mg/L and Tetranychus cinnabarinus at 100 mg/L. Especially, N-(2-bromo-6-(difluoromethoxy)-4-(perfluoro propan-2-yl)phenyl)-6-(isonicotinamido)picolinamide against Tetranychus cinnabarinus at 10 mg/L was 100 %, which was better than that of cyproflanilide. Molecular docking studies suggested that N-(2-bromo-6-(difluoromethoxy)-4-(perfluoropropan-2-yl)phenyl)-6-(4-cyano-2-methylbenzamido)picolinamide had a closely combined with the Plutella xylostella 3RHW (a glutamate-gated chloride channel). This study provides an avenue for designing and synthesizing a new generation of more effective pesticides.

Chemical Synthesis and Insecticidal Activity Research Based on α-Conotoxins

The escalating resistance of agricultural pests to chemical insecticides necessitates the development of novel, efficient, and safe biological insecticides. Conus quercinus, a vermivorous cone snail, yields a crude venom rich in peptides for marine worm predation. This study screened six α-conotoxins with insecticidal potential from a previously constructed transcriptome database of C. quercinus, characterized by two disulfide bonds. These conotoxins were derived via solid-phase peptide synthesis (SPPS) and folded using two-step iodine oxidation for further insecticidal activity validation, such as CCK-8 assay and insect bioassay. The final results confirmed the insecticidal activities of the six α-conotoxins, with Qc1.15 and Qc1.18 exhibiting high insecticidal activity. In addition, structural analysis via homology modeling and functional insights from molecular docking offer a preliminary look into their potential insecticidal mechanisms. In summary, this study provides essential references and foundations for developing novel insecticides.

Rational Design of Triazinone Derivatives with Low Bee Toxicity Based on the Binding Mechanism of Neonicotinoids to Apis mellifera

Bees, one of the most vital pollinators in the ecosystem and agriculture, are currently threatened by neonicotinoids. To explore the molecular mechanisms of neonicotinoid toxicity to bees, the different binding modes of imidacloprid, thiacloprid, and flupyradifurone with nicotinic acetylcholine receptor (nAChR) α1β1 and cytochrome P450 9Q3 (CYP9Q3) were studied using homology modeling and molecular dynamics simulations. These mechanisms provided a basis for the design of compounds with a potential low bee toxicity. Consequently, we designed and synthesized a series of triazinone derivatives and assessed their bioassays. Among them, compound 5a not only displayed substantially insecticidal activities against Aphis glycines (LC50 = 4.40 mg/L) and Myzus persicae (LC50 = 6.44 mg/L) but also had low toxicity to Apis mellifera. Two-electrode voltage clamp recordings further confirmed that compound 5a interacted with the M. persicae nAChR α1 subunit but not with the A. mellifera nAChR α1 subunit. This work provides a paradigm for applying molecular toxic mechanisms to the design of compounds with low bee toxicity, thereby aiding the future rational design of eco-friendly nicotinic insecticides.

Essential Oils from Different Parts of Magnolia laevifolia: Chemical Constituents and Insecticidal Activities against Liposcelis bostrychophila

Many synthetic pesticides were used to control a severe storage pest, booklouse (Liposcelis bostrychophila). However, considering the environmental impact, plant secondary metabolites were acceptable alternatives. An endemic plant, Magnolia laevifolia, has a significant and unique odour, so its essential oil (EO) could be an option for bio-pesticide development. This study extracted EOs from leaves, flowers, carpels and seeds of M. laevifolia. The common and major compound of EOs was isocapnell-9-en-8-one, which was present at 17.7 to 91.6 % in these four parts. We found no regular pattern in the composition of EO in terms of parts and collection time according to principal component analysis. The contact and repellent activities of EOs against the booklouse were then conducted. Leaves and flowers' EOs collected in the flowering stage had the best contact toxicity. The percent repellency values of the EOs from different parts of M. laevifolia reached above 80 % after 2 and 4 h exposure at 63.17 nL/cm2, with the same levels as DEET (p<0.05). It was shown that parts of plants and collecting time could influence the insecticidal activities of M. laevifolia EOs against booklouse, but collecting time played a significant decisive role in the contact test.

Design, Synthesis, and Bioactivity of Trifluoroethylthio-Substituted Phenylpyrazole Derivatives

As the first marketed phenylpyrazole insecticide, fipronil exhibited remarkable broad-spectrum insecticidal activity. However, it poses a significant threat to aquatic organisms and bees due to its high toxicity. Herein, 35 phenylpyrazole derivatives containing a trifluoroethylthio group on the 4 position of the pyrazole ring were designed and synthesized. The predicted physicochemical properties of all of the compounds were within a reasonable range. The biological assay results revealed that compound 7 showed 69.7% lethality against Aedes albopictus (A. albopictus) at the concentration of 0.125 mg/L. Compounds 7, 7g, 8d, and 10j showed superior insecticidal activity for the control of Plutella xylostella (P. xylostella). Notably, compound 7 showed similar insecticidal activity against Aphis craccivora (A. craccivora) compared with fipronil. Potential surface calculation and molecular docking suggested that different lipophilicity and binding models to the Musca domestica (M. domestica) gamma-aminobutyric acid receptors may be responsible for the decreased activity of the tested derivatives. Toxicity tests indicated that compound 8d (LC50 = 14.28 mg/L) induced obviously 14-fold lower toxicity than fipronil (LC50 = 1.05 mg/L) on embryonic-juvenile zebrafish development.

Computational Modeling Oriented Substructure Splicing Application in the Identification of Thiazolidine Derivatives as Potential Low Honeybee Toxic Neonicotinoids

With the aim of identifying novel neonicotinoid insecticides with low bee toxicity, a series of compounds bearing thiazolidine moiety, which has been shown to be low bee toxic, were rationally designed through substructure splicing strategy and evaluated insecticidal activities. The optimal compounds A24 and A29 exhibited LC50 values of 30.01 and 17.08 mg/L against Aphis craccivora, respectively. Electrophysiological studies performed on Xenopus oocytes indicated that compound A29 acted on insect nAChR, with EC50 value of 50.11 μM. Docking binding mode analysis demonstrated that A29 bound to Lymnaea stagnalis acetylcholine binding protein through H-bonds with the residues of D_Arg55, D_Leu102, and D_Val114. Quantum mechanics calculation showed that A29 had a higher highest occupied molecular orbit (HOMO) energy and lower vertical ionization potential (IP) value compared to the high bee toxic imidacloprid, showing potentially low bee toxicity. Bee toxicity predictive model also indicated that A29 was nontoxic to honeybees. Our present work identified an innovative insecticidal scaffold and might facilitate the further exploration of low bee toxic neonicotinoid insecticides.

A Novel Peptidomimetic Insecticide: Dippu-AstR-Based Rational Design and Biological Activity of Allatostatin Analogs

Insect neuropeptides play an essential role in regulating growth, development, reproduction, nerve conduction, metabolism, and behavior in insects; therefore, G protein-coupled receptors of neuropeptides are considered important targets for designing green insecticides. Cockroach-type allatostatins (ASTs) (FGLamides allatostatins) are important insect neuropeptides in Diploptera punctata that inhibit juvenile hormone (JH) synthesis in the corpora allata and affect growth, development, and reproduction of insects. Therefore, the pursuit of novel insecticides targeting the allatostatin receptor (AstR) holds significant importance. Previously, we identified an AST analogue, H17, as a promising candidate for pest control. Herein, we first modeled the 3D structure of AstR in D. punctata (Dippu-AstR) and predicted the binding mode of H17 with Dippu-AstR to study the critical interactions and residues favorable to its bioactivity. Based on this binding mode, we designed and synthesized a series of H17 derivatives and assessed their insecticidal activity against D. punctata. Among them, compound Q6 showed higher insecticidal activity than H17 against D. punctata by inhibiting JH biosynthesis, indicating that Q6 is a potential candidate for a novel insect growth regulator (IGR)-based insecticide. Moreover, Q6 exhibited insecticidal activity against Plutella xylostella, indicating that these AST analogs may have a wider insecticidal spectrum. The underlying mechanisms and molecular conformations mediating the interactions of Q6 with Dippu-AstR were explored to understand its effects on the bioactivity. The present work clarifies how a target-based strategy facilitates the discovery of new peptide mimics with better bioactivity, enabling improved IGR-based insecticide potency in sustainable agriculture.

Design, Synthesis, and Insecticidal Activity of Pyridino[1,2-a]pyrimidines Containing Indole Moeites at the 1-Position

Research on mesoionic structures in pesticide design has gained significant attention in recent years. However, the 1-position of pyridino[1,2-a]pyrimidine is usually designed with 2-chlorothiazole, 2-chloropyridine, or cyano moieties commonly found in neonicotinoid insecticides. In order to enrich the available pharmacophore library, here, we disclose a series of new pyridino[1,2-a]pyrimidine mesoionics bearing indole-containing substituents at the 1-position. Most of these target compounds are confirmed to have good insecticidal activity against aphids through bioevaluation. In addition, a three-dimensional structure-activity relationship model is established to allow access to optimal compound F45 with an LC50 value of 2.97 mg/L. This value is comparable to the property achieved by the positive control triflumezopyrim (LC50 = 2.94 mg/L). Proteomics and molecular docking analysis suggest that compound F45 has the potential to modulate the functioning of the aphid nervous system through its interaction with neuronal nicotinic acetylcholine receptors. This study expands the existing pharmacophore library for the future development of new mesoionic insecticides based on 1-position modifications of the pyridino[1,2-a]pyrimidine scaffold.