Project description:Unrestricted reproduction and spread of pest had caused great damage to the quality and yield of crops in recent years. Besides the use of traditional chemical pesticides, natural products also make a huge contribution against pests. Chasmanthinine, a diterpenoid alkaloid isolated from Aconitum franchetii var. villosulum, shown extremely antifeedant activity against Spodoptera exigua. Therefore, a series of novel Chasmanthinine derivatives were synthesized and their biological activity was studied in this work. Compound 33 showed the strongest antifeedant activity (EC50 = 0.10 mg/cm2) among all the test compounds. The mechanism research of 33 revealed that its antifeedant effect was related to the inhibition of carboxylesterase (CES), and proved the thiophene acyl group could form a strong binding effect with CES by molecular docking. Moreover, compound 10 exhibited the strongest cytotoxicity (IC50 = 12.87 μM) against Sf9 cell line and moderate contact toxicity. The mechanism research indicated that compound 10 could induce Sf9 cells apoptosis. In summary, the results lay a foundation for the application of diterpene alkaloids in plant protection.
Project description:?-Conotoxins are small disulfide-constrained peptides that act as potent and selective antagonists on specific subtypes of nicotinic acetylcholine receptors (nAChRs). We previously cloned two ?-conotoxins, Mr1.1 from the molluscivorous Conus marmoreus and Lp1.4 from the vermivorous Conus leopardus. Both of them have the typical 4/7-type framework of the subfamily of ?-conotoxins that act on neuronal nAChRs. In this work, we chemically synthesized these two toxins and characterized their functional properties. The synthetic Mr1.1 could primarily inhibit acetylcholine (ACh)-evoked currents reversibly in the oocyte-expressed rat ?7 nAChR, whereas Lp1.4 was an unexpected specific blocker of the mouse fetal muscle ?1?1?? receptor. Although their inhibition affinities were relatively low, their unique receptor recognition profiles make them valuable tools for toxin-receptor interaction studies. Mr1.1 could also suppress the inflammatory response to pain in vivo, suggesting that it should be further investigated with respect to its molecular role in analgesia and its mechanism or therapeutic target for the treatment of pain.
Project description:Mesoionic pyrido[1,2-α]pyrimidinone derivatives containing a neonicotinoid moiety were designed, synthesized, and evaluated for their insecticidal activity. Some of the title compounds showed remarkable insecticidal properties against Aphis craccivora. Compound I13 exhibited satisfactory insecticidal activity against A. craccivora. Meanwhile, label-free proteomics analysis of compound I13 treatment identified a total of 821 proteins. Of these, 35 proteins were up-regulated, whereas 108 proteins were down-regulated. Differential expressions of these proteins reflected a change in cellular structure and metabolism.
Project description:Building bridges: The use of diselenide and selectively ((15)N/(13)C)-labeled disulfide bridges is combined to give improvements in oxidative folding and disulfide mapping. Conotoxin analogues, each with a pair of selenocysteines (Sec) and labeled cysteines (see scheme, red), exhibited significantly improved folding and the labeled cysteines allow correctly folded species to be rapidly identified by NMR spectroscopy.
Project description:Cone snails produce a fast-acting and often paralyzing venom that is usually injected into their prey or predator through a hypodermic needle-like modified radula tooth. Many diverse compounds are found in their venom including small molecules, peptides and enzymes. However, peptidic toxins called conotoxins (10⁻40 residues and 2⁻4 disulfide bonds) largely dominate these cocktails. These disulfide rich toxins are very valuable pharmacological tools for investigating the function of ions channels, G-protein coupled receptors, transporters and enzymes. Here, we report on the synthesis, structure determination and biological activities of two α-conotoxins, CIA and CIB, found in the predatory venom of the piscivorous species Conus catus. CIA is a typical 3/5 α-conotoxin that blocks the rat muscle type nAChR with an IC50 of 5.7 nM. Interestingly, CIA also inhibits the neuronal rat nAChR subtype α3β2 with an IC50 of 2.06 μM. CIB is a 4/7 α-conotoxin that blocks rat neuronal nAChR subtypes, including α3β2 (IC50 = 128.9 nM) and α7 (IC50 = 1.51 μM). High resolution NMR structures revealed typical α-conotoxin folds for both peptides. We also investigated the in vivo effects of these toxins on fish, since both peptides were identified in the predatory venom of C. catus. Consistent with their pharmacology, CIA was highly paralytic to zebrafish (ED50 = 110 μg/kg), whereas CIB did not affect the mobility of the fish. In conclusion, CIA likely participates in prey capture through muscle paralysis, while the putative ecological role of CIB remains to be elucidated.
Project description:Most previous studies have focused on analgesic and anti-cancer activities for the conotoxins identified from piscivorous and molluscivorous cone snails, but little attention has been devoted to insecticidal activity of conotoxins from the dominant vermivorous species. As a representative vermivorous cone snail, the Chinese tubular cone snail (Conus betulinus) is the dominant Conus species inhabiting the South China Sea. We sequenced related venom transcriptomes from C. betulinus using both the next-generation sequencing and traditional Sanger sequencing technologies, and a comprehensive library of 215 conotoxin transcripts was constructed. In our current study, six conotoxins with potential insecticidal activity were screened out from our conotoxin library by homologous search with a reported positive control (alpha-conotoxin ImI from C. imperialis) as the query. Subsequently, these conotoxins were synthesized by chemical solid-phase and oxidative folding for further insecticidal activity validation, such as MTT assay, insect bioassay and homology modeling. The final results proved insecticidal activities of our achieved six conotoxins from the transcriptome-based dataset. Interestingly, two of them presented a lot of high insecticidal activity, which supports their usefulness for a trial as insecticides in field investigations. In summary, our present work provides a good example for high throughput development of biological insecticides on basis of the accumulated genomic resources.
Project description:Nicotinic acetylcholine receptors (nAChRs) are found throughout the mammalian body and have been studied extensively because of their implication in a myriad of diseases. α-Conotoxins (α-CTxs) are peptide neurotoxins found in the venom of marine snails of genus Conus. α-CTxs are potent and selective antagonists for a variety of nAChR isoforms. Over the past 40 years, α-CTxs have proven to be valuable molecular probes capable of differentiating between closely related nAChR subtypes and have contributed greatly to understanding the physiological role of nAChRs in the mammalian nervous system. Here, we review the amino acid composition and structure of several α-CTxs that selectively target nAChR isoforms and explore strategies and outcomes for introducing mutations in native α-CTxs to direct selectivity and enhance binding affinity for specific nAChRs. This review will focus on structure-activity relationship studies involving native α-CTxs that have been rationally mutated and molecular interactions that underlie binding between ligand and nAChR isoform.
Project description:A series of novel phenylurea derivatives were designed and synthesized according to the method of active groups linkage and the principle of aromatic groups bioisosterism in this study. The structures of the novel phenylurea derivatives were confirmed based on ESI-MS, IR and 1H-NMR spectral data. All of the compounds were evaluated for the insecticidal activity against the third instars larvae of Spodoptera exigua Hiibner, Plutella xyllostella Linnaeus, Helicoverpa armigera Hubner and Pieris rapae Linne respectively, at the concentration of 10 mg/L. The results showed that all of the derivatives displayed strong insecticidal activity. Most of the compounds presented higher insecticidal activity against S. exigua than the reference compounds tebufenozide, chlorbenzuron and metaflumizone. Among the synthesized compounds, 3b, 3d, 3f, 4b and 4g displayed broad spectrum insecticidal activity.
Project description:Structural optimization of natural products has become one of the most effective ways to develop novel pesticides. In this study, 30 novel pesticide derivatives containing a linear bisamide were synthesized. Then, their insecticidal activities against P. xylostella were evaluated. Results indicate that different bisamide substitutes show different larvicidal structure-activity relationships. At the same time, 2-trifluoroethyl is the most efficient substituent. The bioactivity results showed that most of the desired compounds exhibited better insecticidal activity against P. xylostella than piperine. Among them, compound D28 resulted in 90% mortality at 1 mg/ml concentration. This study provides a novel protocol for the discovery of new insecticides. The molecular docking results indicated that compound D28 could act on γ-aminobutyric acid receptors.