Bioactivity evaluation and active compounds identification of Symphoricarpos orbiculatus as potential botanical herbicide.

BACKGROUND: Evaluation of herbicidal activity and identification of active compounds are important bases for the development of new botanical herbicides. RESULTS: This study confirmed that Symphoricarpos orbiculatus has high herbicidal activities against mono-dicotyledonous weeds, including Echinochloa crusgalli, Digitaria sanguinalis, Amaranthus retroflexus and Portulaca oleracea. By bioassay-guided isolation, 12 compounds were isolated and identified from S. orbiculatus for the first time, including iridoids: naucledal (K1), loganin (K2), loganigenin (K3), loganin acid (K4), glucologanin (K5) and vogeloside (K6), as well as flavonoids: quercetine (K7), luteolin (K8), nobiletin (K9), astragalin (K10), isorhamnetin 3-d-glucoside (K11) and rutin (K12). Biological assays showed that iridoids are the main active ingredients of S. orbiculatus. The compounds of K5 and K6 could inhibit both the root (IC50 = 37.54 and 38.91 µg mL-1, respectively) and shoot (IC50 = 42.78 and 45.72 µg mL-1, respectively) of Portulaca oleracea, which have a weeding toxicity similar to that of the commercialized plant-based herbicide pelargonic acid. In addition, the results of pot culture assay showed that S. orbiculatus ethanol extracts had high fresh weight control effect against Digitaria sanguinalis and P. oleracea at the concentration of 40 g L-1. After 7 days, both the soil treatment and the stem and leaf spray method resulted in severe leaf necrosis and significant leaf etiolation. CONCLUSION: Symphoricarpos orbiculatus and its herbicidal active compounds have the potential to develop into botanical herbicides, and are first reported in the present study. © 2024 Society of Chemical Industry.

Amphiphilic amidines as potential plasmic membrane-targeting antifungal agents: synthesis, bio-activities and QSAR.

BACKGROUND: Cationic antimicrobial peptides (AMPs) possess broad-spectrum biological activities with less inclination to inducing antibiotic resistance. Herein a battery of amphiphilic amidines were designed by mimicking the characteristics of AMPs. The antifungal activities and the effects to the hyphal morphology and membrane permeability were investigated. RESULTS: The results indicated the inhibitory rates of ten compounds were over 80% to Botrytis cinerea and ten compounds over 90% to Valsa mali Miyabe et Yamada at 50 mg L-1. The half maximal effective concentration (EC50) values of compound 5g and 6g to V. mali were 1.21 and 1.90 mg L-1 respectively. The protective rate against apple canker of compound 5g reached 93.4% at 100 mg L-1 on twigs, superior to carbendazim (53.3%). When treated with 5g, the cell membrane permeability and leakage of content of V. mali increased, accompanied with the decrease of superoxide dismutase (SOD) and catalase (CAT) level. Concurrently, the mycelial hyphae contracted, wrinkled, and collapsed, providing evidence of membrane perturbation. A three-dimensional quantitative structure-activity relationship (3D-QSAR) between the topic compounds and the EC50 to V. mali was established showing good predictability (r2 = 0.971). CONCLUSION: Amphiphilic amidines can acquire antifungal activities by acting on the plasmic membrane. Compound 5g could be a promising lead in discovering novel fungicidal candidates. © 2024 Society of Chemical Industry.

Isolation of anthraquinone derivatives from Rubia cordifolia (Rubiaceae) and their bioactivities against plant pathogenic microorganisms.

BACKGROUND: The discovery of antimicrobial ingredients from natural products could be an effective way to create novel fungicides. Rubia cordifolia L., a traditional Chinese herb, may have antimicrobial effects on plant pathogens according to our previous screening study. RESULTS: Rubia cordifolia L. extracts had moderate inhibitory effects on apple Valsa canker (Valsa mali) and tomato grey mould (Botrytis cinerea) at a concentration of 10 mg mL-1. With the use of bioguided isolation methods, eight compounds (1-8) were obtained, including the new compound 2,2,6-trimethyl-6-(4-methylphenyl)-tetrahydropyrano- 3-ol (7), and seven quinone derivatives. Two compounds, mollugin (1) and 1,3,6-trihydroxy-2-methylanthraquinone (6), were found to exhibit outstanding antifungal activities against V. mali and Phytophthora capsici Leon. The half maximal effective concentration (EC50) of compound 1 and compound 6 against V. mali were 79.08 and 81.78 µg mL-1, respectively, and the EC50 of compound 6 against P. capsici was 4.86 µg mL-1. Compound 1 also showed excellent activity against tobacco mosaic virus (TMV). The inactive, inductive, protective and curative activities against TMV were 84.29%, 83.38%, 86.81%, and 60.02%, respectively, at a concentration of 500 µg mL-1, which were all close to or greater than that of the positive control (100 µg mL-1 chitosan oligosaccharide, COS). CONCLUSION: Mollugin and 1,3,6-trihydroxy-2-methylanthraquinone are potentially valuable active compounds that lay a foundation for research on botanical fungicide products derived from R. cordifolia L. and provide lead structures for quinone derivative synthesis and structural modification. © 2024 Society of Chemical Industry.

Pd-NHC (NHC = N-Heterocyclic Carbene)-Catalyzed B-Alkyl Suzuki Cross-Coupling of 2-Pyridyl Ammonium Salts by N-C Activation: Application to the Discovery of Agrochemical Molecular Hybrids.

2-Alkylpyridines are a privileged scaffold throughout the realm of organic synthesis and play a key role in natural products, pharmaceuticals, and agrochemicals. Herein, we report the first B-alkyl Suzuki cross-coupling of 2-pyridyl ammonium salts to access functionalized 2-alkylpyridines. The use of well-defined, operationally simple Pd-NHCs permits for an exceptionally broad scope of the challenging B-alkyl C-N cross-coupling with organoboranes containing ß-hydrogen, representing a novel method for the discovery of highly sought-after molecules for plant protection.

Establishment and evaluation of targeted molecular screening model for the ryanodine receptor or sarco/endoplasmic reticulum calcium ATPase.

BACKGROUD: Endoplasmic reticulum/sarcoplasmic reticulum (ER/SR) is crucial for maintaining intracellular calcium homeostasis due to the calcium-signaling-related proteins on its membrane. While ryanodine receptors (RyR) on insect ER/SR membranes are well-known as targets for diamide insecticides, little is known about other calcium channels. Given the resistance of diamide insecticides, the establishment of molecular screening models targeting RyR or sarco/endoplasmic reticulum calcium ATPase (SERCA) is conducive to the discovery of new insecticidal molecules. RESULTS: The morphological features of Mythimna separata SR have closed vesicles with integrity and high density. The 282 proteins in the SR component contained RyR and SERCA. A measurement model for the release and uptake of calcium was successfully established by detecting calcium ions outside the SR membrane using a fluorescence spectrophotometer. In vitro testing systems using SR vesicles found that diamide insecticides could activate dose-dependently RyR, with EC50 values of 0.14 µM (Chlorantraniliprole), 0.21 µM (Flubendiamide), and 0.57 µM (Cyantraniliprole), respectively. However, dantrolene inhibited RyR-mediated calcium release with an IC50 value of 353.9 µM, suggesting that dantrolene can weakly antagonize RyR. Moreover, cyclopiazonic acid significantly reduced the enzyme activity and calcium uptake capacity of SERCA. On the contrary, CDN1163 markedly activated the enzyme activity and improved the calcium transport capacity of SERCA. CONCLUSIONS: SR vesicles can be used to study the function of unknown proteins on the SR membranes, as well as for high-throughput screening of highly active compounds targeting RyR or SERCA. © 2024 Society of Chemical Industry.

Separation of anti-TMV active components and modes of action of Omphalia lapidescens.

BACKGROUND: Omphalia lapidescens is a saprophytic and parasitic fungus belonging to the Polypora genus of Tricholomataceae. It has repellent, insecticidal, anti-inflammatory and immunomodulatory effects. RESULT: This study found that the extract of O. lapidescens had significant anti-TMV activity, and the main active component was homopolysaccharide LW-1 by Bioassay-guided fractionation. LW-1 is a glucan with ß-(1,3) glucoside bond as the main chain and ß-(1,6) glucoside bond as the branch chain, with molecular weight in the range of 172,916-338,827 Da. The protective and inactive efficacies of LW-1(100 mg/L) against TMV were 78.10% and 48.20%, but had no direct effect on the morphology of TMV particles. The results of mechanism of action showed that LW-1 induced the increase of the activity of defense enzymes such as POD, SOD and PAL in Nicotiana glutinosa. The overexpression of resistance genes such as NPR1, PR1 and PR5, and the increase of SA content. Further transcriptome sequencing showed that LW-1 activated MAPK signaling pathway, plant-pathogen interaction pathway and glucosinolide metabolic pathway in Arabidopsis thaliana. Besides, LW-1 induced crops resistance against plant pathogenic fungi. CONCLUSION: Taken together, the anti-TMV mechanism of LW-1 was to activate MAPK signaling pathway, inducing overexpression of resistance genes, activating plant immune system, and improving the synthesis and accumulation of plant defencins such as glucosinolide. LW-1-induced plant disease resistance has the advantages of broad spectrum and long duration, which has the potential to be developed as a new antiviral agent or plant immune resistance inducer.

Discovery of Novel Cinnamic Acid Derivatives as Fungicide Candidates.

Structural diversity derivatization from natural products is an important and effective method of discovering novel green pesticides. Cinnamic acids are abundant in plants, and their unparalleled structures endow them with various excellent biological activities. A series of novel cinnamic oxime esters were designed and synthesized to develop high antifungal agrochemicals. The antifungal activity, structure-activity relationship, and action mechanism were systematically studied. Compounds 7i, 7u, 7v, and 7x exhibited satisfactory activity against Gaeumannomyces graminis var. tritici, with inhibition rates of ≥90% at 50 µg/mL. Compounds 7z and 7n demonstrated excellent activities against Valsa mali and Botrytis cinerea, with median effective concentration (EC50) values of 0.71 and 1.41 µg/mL, respectively. Compound 7z exhibited 100% protective and curative activities against apple Valsa canker at 200 µg/mL. The control effects of 7n against gray mold on tomato fruits and leaves were all >96%, exhibiting superior or similar effects to those of the commercial fungicide boscalid. Furthermore, the quantitative structure-activity relationship was established to guide the further design of higher-activity compounds. The preliminary results on the action mechanism revealed that 7n treatment could disrupt the function of the nucleus and mitochondria, leading to reactive oxygen species accumulation and cell membrane damage. Its primary biochemical mechanism may be inhibiting fungal ergosterol biosynthesis. The novel structure, simple synthesis, and excellent activity of cinnamic oxime esters render them promising potential fungicides.

Efficacy and toxic action of the natural product natamycin against Sclerotinia sclerotiorum.

BACKGROUND: Sclerotinia stem rot caused by Sclerotinia sclerotiorum seriously endangers oilseed rape production worldwide, and the occurrence of fungicide-resistant mutants of S. sclerotiorum leads to control decline. Thus, it is critical to explore new green substitutes with different action mechanisms and high antifungal activity. Herein, the activity and the action mechanism of natamycin against S. sclerotiorum were evaluated. RESULTS: Natamycin showed potent inhibition on the mycelial growth of S. sclerotiorum, and half-maximal effective concentration (EC50 ) values against 103 S. sclerotiorum strains ranged from 0.53 to 4.04 µg/mL (mean 1.44 µg/mL). Natamycin also exhibited high efficacy against both carbendazim- and dimethachlone-resistant strains of S. sclerotiorum on detached oilseed rape leaves. No cross-resistance was detected between natamycin and carbendazim. Natamycin markedly disrupted hyphal form, sclerotia formation, integrity of the cell membrane, and reduced the content of oxalic acid and ergosterol, whereas it increased the reactive oxygen species (ROS) and malondialdehyde content. Interestingly, exogenous addition of ergosterol could reduce the inhibition of natamycin against S. sclerotiorum. Importantly, natamycin significantly inhibited expression of the Cyp51 gene, which is contrary to results for the triazole fungicide flusilazole, indicating a different action mechanism from triazole fungicides. CONCLUSION: Natamycin is a promising effective candidate for the resistance management of S. sclerotiorum. © 2023 Society of Chemical Industry.

Study on the Antifungal Activity and Potential Mechanism of Natamycin against Colletotrichum fructicola.

In this investigation, the antifungal activity, its influence on the quality of apples, and the molecular mechanism of natamycin against Colletotrichum fructicola were systematically explored. Our findings indicated that natamycin showed significant inhibition against C. fructicola. Moreover, it efficaciously maintained the apple quality by modulating the physicochemical index. Research on the antifungal mechanism showed that natamycin altered the mycelial microstructure, disrupted the plasma membrane integrality, and decreased the ergosterol content of C. fructicola. Interestingly, the exogenous addition of ergosterol weakened the antifungal activity of natamycin. Importantly, natamycin markedly inhibited the expression of Cyp51A and Cyp51B genes in C. fructicola, which was contrary to the results obtained after treatment with triazole fungicide flusilazole. All these results exhibited sufficient proof that natamycin had enormous potential to be conducive as a promising biopreservative against C. fructicola on apples, and these findings will advance our knowledge on the mechanism of natamycin against pathogenic fungi.

Exogenous phthalanilic acid induces resistance to drought stress in pepper seedlings (Capsicum annuum L.).

Drought stress (DS) is one of the main abiotic negative factors for plants. Phthalanilic acid (PPA), as a plant growth regulator, can promote the growth and development of crops. In order to evaluate the ideal application concentration and frequency of PPA-induced drought resistance in pepper (Capsicum annuum) seedlings, the concentration of PPA was 133.3 mg·L-1; 200.0 mg·L-1; 266.7 mg·L-1, and some key indicators were investigated, including leaf wilting index (LWI), relative water content (RWC), and malondialdehyde (MDA). We found that the LWI and RWC in the PPA-applied pepper leaves under light drought stress (LDS) and moderate drought stress (MDS) were all elevated, while MDA contents were decreased. To better understand how PPA makes pepper drought resistant, we examined the photosynthetic characteristics, growth parameters, antioxidant activities, and osmotic substances in pepper seedlings treated twice with PPA at a concentration of 133.3 mg·L-1 under LDS, MDS, and severe drought stress (SDS). Results showed that PPA increased the chlorophyll, plant height, stem diameter, root-shoot ratio, and seedling index of pepper leaves under LDS, MDS, and SDS. The net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rates (Tr), and water-use efficiency (WUE) in the PPA-treated pepper leaves under LDS and MDS were improved, while their stomatal limitation (Ls) were reduced. PPA also boosted the activities of enzymatic antioxidants (superoxide dismutase, catalase, and peroxidase), as well as enhanced the accumulation of osmotic substances such as soluble sugar, soluble protein, and free proline in pepper leaves under LDS, MDS, and SDS. Thus, PPA can alleviate the growth inhibition and damage to pepper seedlings caused by DS, and the PPA-mediated efficacy may be associated with the improvement in PPA-mediated antioxidant activities, Pn, and accumulation of osmotic substances.

Chitosan-thymol nanoparticle with pH responsiveness as a potential intelligent botanical fungicide against Botrytis cinerea.

The practical application of essential oils (EOs) as an alternative for synthetic pesticides in agricultural production is severely limited because of their instability, high volatility, and water insolubility. Nanoencapsulation of EOs is an important strategy to overcome these limitations. In view of this, this study aimed to develop chitosan-thymol nanoparticle (NCS-Thy) with pH-responsive which can be used as an intelligent botanical fungicide to control Botrytis cinerea. The NCS-Thy nanoparticle was prepared by ionic crosslinking method with the loading capacity and encapsulation efficiency of 29.87% and 41.92%, respectively. The synthesized NCS-Thy nanoparticle was further characterized by Fourier transform infrared spectroscopy analysis, transmission electron microscopy observation, and dynamic lights scattering. The results of release kinetics and antifungal activity of NCS-Thy under different pH conditions were determined. The results showed that the NCS-Thy nanoparticle had excellent pH-responsiveness and can release more thymol under acidic conditions formed by B. cinerea, thereby achieving higher antifungal effects. Therefore, compared with unencapsulated thymol, the NCS-Thy nanoparticle had higher antifungal activity against B. cinerea in vitro. In addition, both the protective and curative efficacies of detached leaf test and pot experiment were significantly higher than those of unencapsulated thymol. Among them, the protective efficacy of NCS-Thy in the pot experiment was 78.73%, which was significantly higher than that of unencapsulated thymol with 61.13%. Therefore, the pH-responsive chitosan-thymol nano-preparation had a promising prospect of application in practical management of gray mold as an intelligent botanical fungicide.

Limonene anti-TMV activity and its mode of action.

The main component of orange peel essential oil is limonene. Limonene is a natural active monoterpene with multiple functions, such as antibacterial, antiseptic and antitumor activity, and has important development value in agriculture. This study found that limonene exhibited excellent anti-tobacco mosaic virus (TMV) bioactivity, with results showing that its protection activity, inactivation activity, and curative activity at 800 µg/mL were 84.93%, 59.28%, and 58.89%, respectively-significantly higher than those of chito-oligosaccharides. A direct effect of limonene on TMV particles was not observed, but limonene triggered the hypersensitive response (HR) in tobacco. Further determination of the induction activity of limonene against TMV demonstrated that it displayed good induction activity at 800 µg/mL, with a value of 60.59%. The results of physiological and biochemical experiments showed that at different treatment days, 800 µg/mL limonene induced the enhancement of defense enzymes activity in tobacco, including of SOD, CAT, POD, and PAL, which respectively increased by 3.2, 4.67, 4.12, and 2.33 times compared with the control (POD and SOD activities reached highest on the seventh day, and PAL and CAT activities reached highest on the fifth day). Limonene also enhanced the relative expression levels of pathogenesis related (PR) genes, including NPR1, PR1, and PR5, which were upregulated 3.84-fold, 1.86-fold and 1.71-fold, respectively. Limonene induced the accumulation of salicylic acid (SA), and increased the relative expression levels of genes related to SA biosynthesis (PAL) and reactive oxygen species (ROS) burst (RBOHB), which respectively increased by 2.76 times and 4.23 times higher than the control. Systemic acquired resistance (SAR) is an important plant immune defense against pathogen infection. The observed accumulation of SA, the enhancement of defense enzymes activity and the high-level expression of defense-related genes suggested that limonene may induce resistance to TMV in tobacco by activating SAR mediated by the SA signaling pathway. Furthermore, the experimental results demonstrated that the expression level of the chlorophyll biosynthesis gene POR1 was increased 1.72-fold compared to the control in tobacco treated with 800 µg/mL limonene, indicating that limonene treatment may increase chlorophyll content in tobacco. The results of pot experiment showed that 800 µg/mL limonene induced plant resistance against Sclerotinia sclerotiorum (33.33%), Phytophthora capsici (54.55%), Botrytis cinerea (50.00%). The bioassay results indicated that limonene provided broad-spectrum and long-lasting resistance to pathogen infection. Therefore, limonene has good development and utilization value, and is expected to be developed into a new botanical-derived anti-virus agent and plant immunity activator in addition to insecticides and fungicides.

An Asymmetric Hydrogenation/N-Alkylation Sequence for a Step-Economical Route to Indolizidines and Quinolizidines.

The direct catalytic asymmetric hydrogenation of pyridines for the synthesis of piperidines remains a challenge. Herein, we report a one-pot asymmetric hydrogenation of pyridines with subsequent N-alkylation using a traceless Brønsted acid activation strategy. Catalyzed by an iridium-BINAP complex, the substrates undergo ketone reduction, cyclization and pyridine hydrogenation in sequence to form indolizidines and quinolizidines. The absolute configuration of the stereocenter of the alcohol is retained and influences the formation of the second stereocenter. Experimental and theoretical mechanistic studies reveal that the chloride anion and certain noncovalent interactions govern the stereoselectivity of the cascade reaction throughout the catalytic process.

Incorporating Portulaca oleracea extract endows the chitosan-starch film with antioxidant capacity for chilled meat preservation.

This study aimed to investigate the application potential of Portulaca oleracea extract (POE) in active packaging for the preservation of chilled meat. First, the antioxidant capacity and active ingredients of POE were systematically studied. The results demonstrated that POE has excellent antioxidant capacity and contains abundant antioxidant compounds. Subsequently, antioxidant-active packaging films based on chitosan and starch containing different concentrations of POE (CS/POE films) were successfully developed. The main physicochemical and mechanical properties of the CS/POE films were characterized and evaluated. The CS/POE films exhibited remarkable antioxidant activity and can significantly reduce lipid oxidation in meat. Compared with polyethylene film, the CS/POE films-treated meats had better preservation effects and longer shelf-life. These findings suggested that CS/POE film has the potential to become a good alternative to conventional plastics in food packaging. In conclusion, Portulaca oleracea extract is an excellent natural antioxidant with great potential in active packaging for chilled meat preservation.

Cloning and expression of the mitochondrial cytochrome c oxidase subunit II gene in Sitophilus zeamais and interaction mechanism with allyl isothiocyanate.

In the United States, allyl isothiocyanate (AITC) has been registered as an insecticide, bactericide, and nematicide. And it has been confirmed that AITC has significant insecticidal activities against four stored product pests including Sitophilus zeamais Mostchulky (Coleoptera: Curculionidae). This study aimed to verify the mechanism of action of AITC on cytochrome c oxidase core subunits II in S. zeamais. Enzyme - catalyzed reactions and Fourier transform infrared spectrometer (FTIR) analysis revealed that the expressed COX II proteins could competitively bind and inhibit the activity of COX II. Furthermore, molecular docking results showed that a sulfur atom of AITC could form a 2.9 Å hydrogen bond with Ile-30, having a binding energy of -2.46 kcal/mol.

Suzuki-Miyaura Cross-Coupling of 2-Pyridyl Trimethylammonium Salts by N-C Activation Catalyzed by Air- and Moisture-Stable Pd-NHC Precatalysts: Application to the Discovery of Agrochemicals.

We report the first Suzuki-Miyaura cross-coupling of 2-pyridyl ammonium salts by highly selective N-C activation catalyzed by air- and moisture-stable Pd(II)-NHC (NHC = N-heterocyclic carbene) precatalysts. The use of well-defined and highly reactive [Pd(IPr)(3-CF3-An)Cl2] (An = aniline) or [Pd(IPr)(cin)Cl] (cin = cinnamyl) Pd(II)-NHC catalysts permits an exceptionally broad scope of the cross-coupling to furnish valuable biaryl and heterobiarylpyridines that are ubiquitous in medicinal chemistry and agrochemistry research. The overall process leverages the Chichibabin C-H amination of pyridines with N-C activation to enable an attractive strategy to the 2-pyridyl problem. The utility of the method to the discovery of potent agrochemicals is presented. Considering the importance of 2-pyridines and the versatility of N-C activation methods, we envision that this new C-H/N-C activation strategy will find broad application.

Linalool Induces Resistance Against Tobacco Mosaic Virus in Tobacco Plants.

The essential oil of Cinnamomum camphora is the most widely consumed and used spice in the world today. It has therapeutic effects in medicine and has been shown to have good antibacterial and bacteriostatic effects in agriculture. This study found that C. camphora oil significantly induced plant disease resistance activity. Linalool, its main active component, significantly induced plant disease resistance activity (67.49% at a concentration of 800 µg/ml) over the same concentration of the chitosan oligosaccharide positive control but had no direct effect on tobacco mosaic virus (TMV). In this study of its antiviral mechanism, linalool induced hypersensitive reaction (HR); the overexpression of related defense enzymes SOD, CAT, POD, and PAL; and the accumulation of H2O2 and SA content in N. glutinosa. Besides, linalool induced crops resistance against Colletotrichum lagenarium, Botrytis cinerea, Sclerotinia sclerotiorum, and Phytophthora capsica. Taken together, the anti-TMV mechanism of linalool involved the induction of plant disease resistance through activation of a plant immune response mediated by salicylic acid. Linalool-induced plant disease resistance activity has a long duration, broad spectrum, and rich resources; linalool thus has the potential to be developed as a new plant-derived antiviral agent and plant immune activator.

Systematic Study on Turpentine-Derived Amides from Natural Plant Monoterpenes as Potential Antifungal Candidates.

To overcome the high volatility, low aqueous solubility, and few definite action sites of monoterpenoid pesticides and improve their properties and effectiveness in the control of crop pathogenic fungi, herein, a series of natural turpentine-based amide derivatives exhibiting satisfactory antifungal activity were designed and synthesized. A systematic study was conducted on antifungal activity and the physiological and biochemical response of compounds 5o (EC50 = 1.139 µg/mL) and 5j (EC50 = 1.762 µg/mL) against Rhizoctonia solani. The effect of the target compound on the potential target-site succinate dehydrogenase was evaluated. The soluble concentrates of compounds 5o and 5j possessing good performance and control effects were prepared for practical application. To conduct a comprehensive analysis of the relationship between structural descriptors and activity, four representative title compounds were selected for theoretical calculation: 5o, 5j, 5k, and 5j. The binding mode of compound 5o and boscalid with succinate dehydrogenase was analyzed via molecular docking. This study provides a reference for the development of monoterpene pesticides with high efficiency, elucidated target sites, and the appropriate formula.

Structural Diversity Design, Synthesis, and Insecticidal Activity Analysis of Ester-Containing Isoxazoline Derivatives Acting on the GABA Receptor.

To explore insecticides targeting the γ-aminobutyric acid (GABA) receptor, two series of novel isoxazoline derivatives containing sulfonic and carboxylic esters were designed and synthesized. Their insecticidal activities against Plutella xylostella, Mythimna separata, and Aedes aegypti larvae and their structure-activity relationship were investigated. The sulfonate-containing isoxazoline derivatives (10k-q) exhibited promising insecticidal activities against the three insect larvae. Compound 10o displayed excellent activities with LC50 values of 8.32, 5.23, and 0.35 µg/mL at 48 h against P. xylostella, M. separata, and A. aegypti larvae, respectively, which were better than or similar to those of avermectin. Furthermore, compound 10o exhibited a faster insecticidal effect than avermectin against M. separata. The mode of action of 10o was preliminarily verified by molecular docking, theoretical calculations, and measurement of glutamate decarboxylase and glutamic pyruvic transaminase activities. Compound 10o is a novel insecticidal candidate acting on GABA receptors, which could guide the discovery of isoxazoline insecticides.

Eukaryotic Expression of the Cytochrome c Oxidase Subunit I of Sitophilus zeamais and Its Interaction with Allyl Isothiocyanate.

Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) is a destructive pest of stored grains around the world. Allyl isothiocyanate (AITC) was shown to have good bioactivity in the control of S. zeamais. In this study, the interaction of AITC on cytochrome c oxidase core subunits I (COX I) and their binding mechanism were determined using spectroscopic, isothermal titration calorimetry and molecular docking techniques. The results indicate the binding constant (Ka) of AITC and COX I was 6.742 × 103 L/mol. Analysis of spectroscopic revealed that the binding of COX I to reduced Cyt c induced conformational changes of reduced Cyt c, while AITC could competitively bind and inhibit the activity of the COX I protein. Moreover, molecular docking results suggested a sulfur atom in the AITC structure could form a hydrogen bond having a length of 3.3 Å with the Gly- 27 of COX I.