Novel chlorantraniliprole derivatives as potential insecticides and probe to chlorantraniliprole binding site on ryanodine receptor

Effects of Bacillus thuringiensis Treatment on Expression of Detoxification Genes in Chlorantraniliprole-Resistant Plutella xylostella

Detoxification genes are crucial to insect resistance against chemical pesticides, yet their expression may be altered by exposure to biopesticides such as spores and insecticidal proteins of Bacillus thuringiensis (Bt). Increased enzymatic levels of selected detoxification genes, including glutathione S-transferase (GST), cytochrome P450 (CYP450), and carboxylesterase (CarE), were detected in chlorantraniliprole (CAP)-resistant strains of the diamondback moth (DBM, Plutella xylostella) from China when compared to a reference susceptible strain. These CAP-resistant DBM strains displayed distinct expression patterns of GST 1, CYP6B7, and CarE-6 after treatment with CAP and a Bt pesticide (Bt-G033). In particular, the gene expression analysis demonstrated significant upregulation of the CYP6B7 gene in response to the CAP treatment, while the same gene was downregulated following the Bt-G033 treatment. Downregulation of CYP6B7 using RNAi resulted in increased susceptibility to CAP in resistant DBM strains, suggesting a role of this gene in the resistant phenotype. However, pretreatment with a sublethal dose of Bt-G033 inducing the downregulation of CYP6B7 did not significantly increase CAP potency against the resistant DBM strains. These results identify the DBM genes involved in the metabolic resistance to CAP and demonstrate how their expression is affected by exposure to Bt-G033.

Novel Nitrophenyl Substituted Anthranilic Diamide Derivatives: Design, Synthesis, Selectivity, and Antiresistance

Diamide insecticides have gained popularity due to their high efficacy and low toxicity to nontarget organisms. However, diamide-associated resistance has emerged recently, causing a significant reduction in their potency, thereby hindering sustainable agricultural development. Here, we explored novel diamide insecticide analogs and, using a structure-based approach, rationally designed and synthesized 28 nitrophenyl substituted anthranilic diamides. Most of the compounds showed moderate to good activity against Mythimna separata, Plutella xylostella, and Spodoptera frugiperda. Among them, compounds Ia and Im showed extraordinarily high activity and their mode of action was verified on isolated neurons. Additionally, Im exhibited over 10-fold greater potency than chlorantraniliprole in a HEK293 cell line stably expressing S. frugiperda ryanodine receptors (SfRyRs) containing the resistance mutations, G4891E and I4734M. The binding modes of Im in the SfRyRs were predicted using in silico molecular docking analysis. Our novel nitrophenyl substituted anthranilic diamide derivatives provide valuable insights for the design of insecticidal RyR-targeting compounds to effectively control both wild type and diamide insecticide-resistant lepidopteran pests.

Synthesis, Insecticidal Activities, and 3D-QASR of N-Pyridylpyrazole Amide Derivatives Containing a Phthalimide as Potential Ryanodine Receptor Activators

To develop potent and environment-friendly insecticides, novel N-pyridylpyrazole amide derivatives containing a phthalimide were designed and synthesized. The preliminary bioassay results showed that most of the target compounds exhibited good insecticidal activities. For oriental armyworm (Mythimna separata), compounds E₅, E₂₉, E₃₀, and E₃₃ displayed higher than 90% lethal rates at 25 mg L^-1. In particular, compound E₃₃ displayed 60% mortality at a lower concentration of 6.25 mg L^-1. Besides, compound E₃₃ also showed a 30% lethal rate at 5 mg L^-1 against diamondback moth (DBM) (Plutella xylostella). Molecular docking between the most active compound E₃₃ and DBM ryanodine receptor (RyR), comparative molecular field analysis (CoMFA), and density functional theory (DFT) calculations were conducted and discussed. Furthermore, according to vitro studies using a calcium imaging technique, compound E₃₃ was a potent novel lead targeting insect RyR.

Design, synthesis and biological activity of diamide compounds based on 3-substituent of the pyrazole ring†

BACKGROUND

Diamide insecticides have attracted significant attention due to their high efficacy and low toxicity to non-target organisms since they were introduced to the market. In order to tackle the problems of insecticide resistance and ecological safety, 16 novel nitrobenzene substituted anthranilic diamides with ester, hydroxyl or sulfonyl at the 3-position of the pyrazole ring were designed and synthesized.

RESULTS

All of these compounds possessed good activity against the ryanodine receptor (RyR) from Spodoptera frugiperda and relatively lower activity against mammalian RyR1, showing a better insect-selectivity compared to chlorantraniliprole in a cell-based assay. The molecular docking analysis predicted the binding conformations of these compounds, which showed a good correlation between the insecticidal activity and the binding scores. In vitro studies using a calcium imaging method demonstrated that the novel compounds could not only activate the RyR but may also target the dihydropyridine receptor on the plasma membrane of insect neurons, implicating a similar but not same mode of action.

CONCLUSION

Substituted anthranilic diamides with an ester at the 3-position of the pyrazole ring exhibited a promising insecticidal activity and better insect-selectivity, which provided insight into the rational design of a new generation of effective diamide insecticides.

Synthesis, insecticidal evaluation and 3D-QSAR study of novel anthranilic diamide derivatives as potential ryanodine receptor modulators

BACKGROUND

Anthranilic diamide insecticides control lepidopteran pests through selectively binding and activating insect ryanodine receptors. In order to search for potential insecticides targeting the ryanodine receptors, a series of anthranilic diamide analogs including trifluoromethyl, nitro, or chloro groups were designed and synthesized by the principle of bioisosterism and structural optimization.

RESULTS

Insecticidal data indicated that some compounds displayed good activity against oriental armyworm (Mythimna separata) and diamondback moth (Plutella xylostella). In particular, the larvicidal activity of 6p against P. xylostella was 95% at 0.01 mg L^-1 , equivalent to chlorantraniliprole (85%, 0.01 mg L^-1 ). The comparative molecular similarity index analysis model obtained indicated that hydrogen bond acceptor and electron-withdrawing groups in the R'₃ group are favourable for insecticidal activity against M. separata, which is consistent with the structure-activity relationships. Moreover, the calcium imaging experiment indicated, like chlorantraniliprole, that 6h and 6p are interacting with the ryanodine receptor.

CONCLUSION

Introducing trifluoromethyl, nitro, or chloro groups to a specific position in the N-phenylpyrazole could improve or maintain the activity against M. separata and P. xylostella. 6h and 6p could be used as potential lead compounds for ryanodine receptor modulators. © 2018 Society of Chemical Industry.

Overexpression of cytochrome P450 CYP6BG1 may contribute to chlorantraniliprole resistance in Plutella xylostella (L.)

BACKGROUND

The diamondback moth Plutella xylostella (L.) is the most widely distributed pest of cruciferous crops and has developed resistance to most commonly used insecticides, including chlorantraniliprole. Resistance to chlorantraniliprole is likely caused by mutations of the target, the ryanodine receptor, and/or mediated by an increase in detoxification enzyme activities. Although target-site resistance is documented in detail, resistance mediated by increased metabolism has rarely been reported.

RESULTS

The activity of cytochrome P450 was significantly higher in two resistant P. xylostella populations than in a susceptible one. Among ten detected cytochrome P450 genes, CYP6BG1 was significantly overexpressed (over 80-fold) in a field-resistant population compared with expression in a susceptible one. Knockdown of CYP6BG1 by RNA interference dramatically reduced the 7-ethoxycoumarin-O-deethylase (7-ECOD) activity of P450 by 45.5% and increased the toxicity of chlorantraniliprole toward P. xylostella by 26.8% at 48 h postinjection of double-stranded RNA. By contrast, overexpression of CYP6BG1 in a transgenic Drosophila melanogaster line significantly decreased the toxicity of the insecticide to the transgenic flies.

CONCLUSIONS

Overexpression of CYP6BG1 may contribute to chlorantraniliprole resistance in P. xylostella. Our findings will provide new insights into the mechanisms of resistance to diamide insecticides in other insect pests. © 2017 Society of Chemical Industry.

Anthranilic diamides derivatives as potential ryanodine receptor modulators: Synthesis, biological evaluation and structure activity relationship

A series of novel anthranilic diamides derivatives (7a-s) containing halogen, trifluoromethyl group and cyano group were designed, synthesized, and characterized by melting point, ¹H NMR, ¹³C NMR and elemental analyses. The bioactivity revealed that most of them showed moderate to excellent activities against oriental armyworm (Mythimna separata) and diamondback moth (Plutella xylostella). Above all, the larvicidal activity of 7o against oriental armyworm was 100% and 40% at 0.25 and 0.1 mg L^-1, comparable to that of the standard chlorantraniliprole (100%, 0.25 mg L^-1 and 20%, 0.1 mg L^-1). What is more, 7o against diamondback moth displayed 90% insecticidal activity at 0.01 mg L^-1, superior to chlorantraniliprole (45%, 0.01 mg L^-1). The experiments 7o on the American cockroach (Periplaneta Americana) heart beating rates (Dorsal vessel) and contractile force were compared with chlorantraniliprole. In addition, 7o could affect the calcium homeostasis in the central neurons of the third larvae of oriental armyworm, which revealed that the ryanodine receptor is the potential target of 7o. The density functional theory (DFT) calculation results revealed the amide bridge, the benzene ring of anthraniloyl moiety and pyrazole ring might play an important role in the insecticidal activity through hydrophobic interactions and π-π conjugations.

High Concentrations of Chlorantraniliprole Reduce Its Compatibility with a Key Predator, Hippodamia convergens (Coleoptera: Coccinellidae)

Diamides are a novel insecticide group that act by disrupting insect muscle contraction. Recommended field rates (FRs) vary greatly among target pests and cropping systems, leading to variable risks for non-target organisms. We evaluated the toxicity of chlorantraniliprole to the predator Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae) by exposure to residues, topical application, and consumption of contaminated food. We also estimated lethal concentrations (LCs) of chlorantraniliprole in two target pests, cotton leafworm, Alabama argillacea (Hübner) (Lepidoptera: Erebidae), and tobacco budworm, Chloridea virescens (F.) (Lepidoptera: Noctuidae), by exposing larvae to treated cotton, Gossypium hirsutum L., leaves and assessed residual activity at various intervals after application to cotton plants. Exposure to dried residues and ingestion of treated moth eggs resulted in similar toxicity to H. convergens, whereas topical application was a less toxic route of exposure. Regardless of exposure route, the LC50s and LC90s obtained for H. convergens were higher than those calculated for the pests. Residues at the upper limit of the LC90 for C. virescens remained effective against this pest for up to 16 d, while exhibiting minor impacts on H. convergens. In contrast, the FR concentration of C. virescens caused significant mortality in H. convergens. The results suggest that the current FR for C. virescens is too high to be safe for H. convergens, and given the LCs observed for this pest in the present study, trials to explore the potential efficacy of lower FRs are justified. Depending on the concentration and route of exposure, this insecticide has the potential to be compatible with H. convergens.

Over-expression of UDP-glycosyltransferase gene UGT2B17 is involved in chlorantraniliprole resistance in Plutella xylostella (L.)

BACKGROUND

UDP-glycosyltransferases (UGTs) are phase II detoxification enzymes widely distributed within living organisms. Their involvement in the biotransformation of various lipophilic endogenous compounds and phytoalexins in insects has been documented. However, the roles of this enzyme family in insecticide resistance have rarely been reported. Here, the functions of UGTs in chlorantraniliprole resistance in Plutella xylostella were investigated.

RESULTS

Treatment with sulfinpyrazone and 5-nitrouracil (both inhibitors of UGT enzymes) significantly increased the toxicity of chlorantraniliprole against the third instar larvae of P. xylostella. Among the 23 UGT transcripts examined, only UGT2B17 was found to be over-expressed (with a range from 30.7- to 77.3-fold) in all four chlorantraniliprole-resistant populations compared to the susceptible one (CHS). The knock-down of UGT2B17 by RNA interference (RNAi) dramatically increased the toxicity of chlorantraniliprole by 27.4% and 29.8% in the CHS and CHR (resistant) populations, respectively. In contrast, exposure to phenobarbital significantly increased the relative expression of UGT2B17 while decreasing the toxicity of chlorantraniliprole to the larvae by 14.0%.

CONCLUSION

UGT2B17 is involved in the detoxification of chlorantraniliprole, and its over-expression may play an important role in chlorantraniliprole resistance in P. xylostella. These results shed some light upon and further our understanding of the mechanisms of diamide insecticide resistance in insects. © 2016 Society of Chemical Industry.

Novel Anthranilic Diamide Scaffolds Containing N-Substituted Phenylpyrazole as Potential Ryanodine Receptor Activators

To discover potent insecticides targeting ryanodine receptors (RyRs), a series of novel anthranilic diamides analogues (12a-12u) containing N-substituted phenylpyrazole were designed and synthesized. These compounds were characterized by (1)H NMR, (13)C NMR, and HRMS, and the structure of compound 12u was confirmed by X-ray diffraction. Their insecticidal activities indicated that these compounds displayed moderate to excellent activities. In particular, 12i showed 100 and 37% larvicidal activities against oriental armyworm (Mythimna separata) at 0.25 and 0.05 mg L(-1), equivalent to that of chlorantraniliprole (100%, 0.25 mg L(-1); and 33%, 0.05 mg L(-1)). The activity of 12i against diamondback moth (Plutella xylostella) was 95% at 0.05 mg L(-1), whereas the control was 100% at 0.05 mg L(-1). The calcium-imaging technique experiment results showed that the effects of 12i on the intracellular calcium ion concentration ([Ca(2+)]i) in neurons were concentration-dependent. After the central neurons of Helicoverpa armigera were dyed by loading with fluo-5N and treated with 12i, the free calcium released in endoplasmic reticulum indicated the target of compound 12i is RyRs or IP3Rs. The activation of RyRs by natural ryanodine completely blocked the calcium release induced by 12i, which indicated that RyRs in the central neurons of H. armigera third-instar larvae is the possible target of compound 12i.

Design, synthesis, and insecticidal activity of some novel diacylhydrazine and acylhydrazone derivatives

In this study a series of diacylhydrazine and acylhydrazone derivatives were designed and synthesized according to the method of active group combination and the principles of aromatic group bioisosterism. The structures of the novel derivatives were determined on the basis on ¹H-NMR, IR and ESI-MS spectral data. All of the compounds were evaluated for their in vivo insecticidal activity against the third instar larvae of Spodopteraexigua Hiibner, Helicoverpaarmigera Hubner, Plutellaxyllostella Linnaeus and Pierisrapae Linne, respectively, at a concentration of 10 mg/L. The results showed that all of the derivatives displayed high insecticidal activity. Most of the compounds presented higher insecticidal activity against S. exigua than the reference compounds tebufenozide, metaflumizone and tolfenpyrad, and approximately identical insecticidal activity against H.armigera, P.xyllostella and P.rapae as the references metaflumizone and tolfenpyrad.

Synthesis, larvicidal activities and antifungal activities of novel chlorantraniliprole derivatives and their target in the ryanodine receptor

In order to identify novel chlorantraniliprole derivatives as potential insecticides or fungicides, 25 analogues of chlorantraniliprole were synthesized. The insecticidal activities against oriental armyworm and the antifungal activities against five typical fungi of these derivatives were tested. Compounds 2u, 2x and 2y exhibited good activities against oriental armyworm, especially compounds 2u and 2x which showed higher larvicidal activities than indoxacarb. Moreover, all of the tested compounds exhibited activities against five typical fungi. The Ki values of all synthesized compounds were calculated using AutoDock4. The relationship between the Ki values and the results of insecticidal activities against oriental armyworm further indicated that the membrane-spanning domain protein of the ryanodine receptor might contain chlorantraniliprole binding sites.

Design, synthesis and insecticidal activities of N-(4-cyano-1-phenyl-1H-pyrazol-5-yl)-1,3-diphenyl-1H-pyrazole-4-carboxamide derivatives

Twenty novel diphenyl-1H-pyrazole derivatives with cyano substituent were designed and synthesized, and their insecticidal activities were evaluated.

Synthesis, insecticidal activity, structure–activity relationship (SAR) and density functional theory (DFT) of novel anthranilic diamides analogs containing 1,3,4-oxadiazole rings

A series of anthranilic diamides analogs (5a–x) containing 1,3,4-oxadiazole rings were synthesized, and their insecticidal activities were evaluated. The density functional theory (DFT) studies was used to understand the various insecticidal activities.