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.

Scaffold-Hopping Approach To Identify New Chemotypes of Dimpropyridaz

Dimpropyridaz is a pyrazole carboxamide insecticide with a novel mode of action, currently under worldwide development by BASF, providing excellent activity against sucking pests. A series of dimpropyridaz analogues were designed to investigate the impact of bioisosteric heterocyclic replacements on the biological activity and molecular properties. Focus was given to prepare analogues where the 4-pyridazinyl moiety was replaced by 5-pyrimidinyl, 2-pyrimidinyl, 3-pyridazinyl, and 2-pyrazinyl groups. Five different synthetic routes were developed for the preparation of these analogues, delivering the target compounds in moderate to good yields. We explained some aspects of the observed structure-activity relationship by a density functional theory (DFT) calculation and DFT-derived Multiwfn and VMD program models. These findings provide first insights into the important role of the 4-pyridazinyl heterocyclic moiety in the pyrazole carboxamide insecticide chemical class and the mechanism of action of dimpropyridaz.

Bioisosteric-Replacement-Driven Lead Optimization of Tyclopyrazoflor

A heterocyclic replacement strategy has been applied attempting to further optimize the biological properties of the new insecticide tyclopyrazoflor, a pyridinyl-pyrazole compound with excellent activity against sap-feeding insects recently discovered by Corteva. Our research program on this novel chemical class of insecticide was targeted to evaluate the importance of both the pyridyl and pyrazole moieties on the biological activity, properties, and structure-activity. Synthetic methodologies have been developed delivering our designed target compounds in moderate to good yields. In our attempt to rationalize the biological activity differences of tyclopyrazoflor analogues, a potential surface analysis based on a density functional theory (DFT) calculation and DFT-derived Multiwfn and VMD program model was performed. Furthermore, the SwissBioisostere online database was applied as a great source for inspiration for bioisosteric replacements.

Chemical profile and antifungal activity of plant extracts on Colletotrichum spp. isolated from fruits of Pimenta dioica (L.) Merr

Pimenta dioica (L.) Merr. is a popular seasoning species. During its production, there are losses of up to 50% due to anthracnose caused by fungi of the genus Colletotrichum. In this study, we evaluated the effect of ethanolic extracts on the in vitro and in vivo control of isolated Colletotrichum spp. Allspice. Extracts of leaves of P. dioica, Piper auritum, Plectranthus amboinicus and Psidium guajava were chemically characterized by gas chromatography and high performance liquid chromatography. Several monoterpenes, sesquiterpenes, flavonoids, organic acids, alkaloids and monoterpenoid phenols were identified among other organic compounds. Alpha-ocimene in P. dioica; alpha-thujene and isosafrole in P. auritum; kumatakenin, cirsilineol, taxifolin and retusin in P. amboinicus are reported for the first time. The extracts of P. amboinicus and P. dioica inhibited mycelial growth, spore germination in Colletotrichum spp. at concentrations of 5, 10 and 20 mg/mL, while the extracts of P. guajava and P. auritum did so at concentrations of 30 and 40 mg/mL. The extracts of P. amboinicus, P. dioica and P. auritum modified the size of the spores, caused degradation and formation of vacuoles in the spores of C. acutatum and C. gloeosporioides. The incidences in fruit inoculated with C. boninense and treated with the extracts of P. amboinicus and P. dioica were of 12% and 4% respectively. The severity was 1.5% with the extract of P. amboinicus and 0% with P. dioica. The results show the richness of bioactive compounds present in the extracts and their possible application to develop biotechnological products against phytopathogenic fungi.

Design, Synthesis, Antibacterial, Antifungal and Anticancer Evaluations of Novel β-Pinene Quaternary Ammonium Salts

β-pinene is a monoterpene isolated from turpentine oil and numerous other plants' essential oils, which has a broad spectrum of biological activities. In the current work, six novel β-pinene quaternary ammonium (β-PQA) salts were synthesized and evaluated in vitro for their antifungal, antibacterial and anticancer activities. The in vitro assay results revealed that compounds 4a and 4b presented remarkable antimicrobial activity against the tested fungi and bacteria. In particular, compound 4a showed excellent activities against F. oxysporum f.sp. niveum, P. nicotianae var.nicotianae, R. solani, D. pinea and Fusicoccumaesculi, with EC50 values of 4.50, 10.92, 9.45, 10.82 and 6.34 μg/mL, respectively. Moreover, compound 4a showed the best antibacterial action against E. coli, P. aeruginosa, S. aureus and B. subtilis, with MIC at 2.5, 0.625, 1.25 and 1.25 μg/mL, respectively. The anticancer activity results demonstrated that compounds 4a, 4b, 4c and 4f exhibited remarkable activity against HCT-116 and MCF-7 cell lines, with IC50 values ranged from 1.10 to 25.54 μM. Notably, the compound 4c displayed the strongest cytotoxicity against HCT-116 and MCF-7 cell lines, with the IC50 values of 1.10 and 2.46 μM, respectively. Furthermore, preliminary antimicrobial mechanistic studies revealed that compound 4a might cause mycelium abnormalities of microbial, cell membrane permeability changes and inhibition of the activity of ATP. Altogether, these findings open interesting perspectives to the application of β-PQA salts as a novel leading structure for the development of effective antimicrobial and anticancer agents.

β-Pinene Derived Products With Enhanced In Vitro Antimicrobial Activity

The development of new antimicrobials has always been a research hotspot. In this study, β-pinene-based derivatives were synthesized, and their antimicrobial activity was evaluated. The purpose was to develop some novel, promising new fungicides. Three β-pinene derivatives containing bis-hydronopyl were prepared, and their antifungal and antibacterial activities were evaluated against 6 plant pathogenic fungi and 4 bacterial species; a preliminary structure-activity relationship is discussed. The results indicated that the derivatives containing the blend of alkyl group and bis-hydronopyl had potent inhibitory activities against plant fungal pathogens and bacteria. Among these molecules, bis-hydronopyl dimethyl ammonium bromide showed excellent effects on Colletotrichum acutatum with a half-maximal effective concentration of 0.538 µg/mL, which was lower than that of carbendazim. Scanning electron microscope showed that after administration of bis-hydronopyl dimethyl ammonium bromide (compound 3a), the C. acutatum mycelia were sunken and deformed in comparison with the control group. Furthermore, the inhibitory activities of the methyl derivatives against the plant pathogens were better than those of the ethyl derivatives. These results provide new insights into the inhibition of fungi and bacteria by β-pinene derivatives, which may lead them to be used as precursor molecules for novel pesticides and antimicrobials in further research.

Antifungal Activity of β-Pinene-Based Hydronopyl Quaternary Ammonium Salts Against Phytopathogenic Fungi

β-Pinene can be used as a cheap source to synthesize a large number of high value-added derivatives. In this study, a series of β-pinene derivatives was prepared, and the antifungal activities of the compounds were assessed against phytopathogenic fungi. Eight N-alkyl hydronopyl diethyl ammonium halide salts were synthesized by the reaction of hydronopyl diethyl ammonium halide with 8 halogenated alkanes. The structures of the synthesized products were characterized by Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy and mass spectrometry. The antifungal activities of these derivatives were tested against 11 plant pathogens, and the preliminary structure-activity relationship is discussed. Some derivatives exhibited moderate to significant antifungal activity due to the fusion of the hydronopyl, a long-chain alkyl, bromine, and iodine anionic groups. In contrast to the structure-activity relationship of compounds 2a, 2b, and 2c, iodine ions in 2f, 2g, and 2f had a significant effect on enhancing the antifungal activity against Colletotrichum gloeosporioides, S clerotinia sclerotiorum, Phytophthora capsici, Phomopsis, Sphaeropsis sapinea, Glomerella cingulata, and Fusicoccum aesculi. A higher molecular weight could increase the antifungal activity against Fusarium proliferatum, Alternaria kikuchiana, Sclerotinia sclerotiorum, P. capsici, Phomopsis, and S. sapinea. Compounds 2d and 2e exhibited broad-spectrum antifungal activity against the tested strains. These derivatives are expected to be used as precursor molecules for novel pesticide development in further research.

Derivatization of Natural Compound β-Pinene Enhances Its In Vitro Antifungal Activity against Plant Pathogens

Background: The development of new antifungal agents has always been a hot research topic in pesticide development. In this study, a series of derivatives of natural compound β-pinene were prepared, and the antifungal activities of these derivatives were evaluated. The purpose of this work is to develop some novel molecules as promising new fungicides. Methods: Through a variety of chemical reactions, β-pinene was transformed into a series of β-pinene-based derivatives containing amide moieties and acylthiourea moieties. The antifungal activities of these derivatives against five plant pathogens including Colletotrichum gloeosporioides, Fusarium proliferatum, Alternaria kikuchiana, Phomopsis sp. and Phytophthora capsici were tested; preliminary structure–activity relationship was discussed. Results: Some derivatives exhibited moderate or significant antifungal activity due to the fusion of the amide moiety or the acylthiourea moiety with the pinane skeleton. The structure–activity relationship analysis showed that the fluorine atom and the strong electron withdrawing nitro group, or trifluoromethyl group on the benzene ring of the derivatives had a significant effect on the improvement of the antifungal activity against Colletotrichum gloeosporioides, Fusarium proliferatum, Alternaria kikuchiana and Phomopsis sp. Meanwhile, the introduction of an ethyl group at the meta-position on the benzene ring of the derivatives could improve the antifungal activity against Phytophthora capsici. Compounds 4e, 4h, 4q, 4r exhibited broad-spectrum antifungal activity against the tested strains. Compound 4o had significant antifungal activity against Phytophthora capsici (IC₅₀ = 0.18 μmol/L). These derivatives were expected to be used as precursor molecules for novel pesticide development in further research.

High Add Valued Application of Turpentine in Crop Production through Structural Modification and QSAR Analysis

Turpentine is a volatile component of resin, which is an abundant forest resource in Southern China. As one of the most important components, the integrated application of β-pinene has been studied. The broad-spectrum evaluation of β-pinene and its analogues has, therefore, been necessary. In an attempt to expand the scope of agro-activity trials, the preparation and the evaluation of the herbicidal activity of a series of β-pinene analogues against three agricultural herbs were carried out. In accordance with the overall herbicidal activity, it is noteworthy that compounds 6k, 6l, and 6m demonstrated extreme activity with IC₅₀ values of 0.065, 0.065, and 0.052 mol active ingredients/hectare against E. crus-galli. The preliminary structure-activity relationship (SAR) was analyzed and the compounds with the appropriate volatility and substituent type that had beneficial herbicidal activity were analyzed. Simultaneously, the quantitative structure-activity relationship (QSAR) model was built and the most important structural features were indicated, which was, to a certain extent, in line with the SAR study. The study aimed to study the application of the forest resource turpentine in agriculture as a potential and alternative approach for comprehensive utilization.

Bioactivity-guided mixed synthesis and evaluation of α-alkenyl-γ and δ-lactone derivatives as potential fungicidal agents

In view of the great antifungal activities of sesquiterpene lactones and natural product Tulipalin A, 52 derivatives derived from α-methylene-γ-butyrolactone substructures were synthesized to study antifungal activities.

New α-Methylene-γ-Butyrolactone Derivatives as Potential Fungicidal Agents: Design, Synthesis and Antifungal Activities

In consideration of the fact that the α-methylene-γ-butyrolactone moiety is a major bio-functional group in the structure of carabrone and possesses some agricultural biological activity, forty-six new ester and six new ether derivatives containing α-methylene-γ-butyrolactone moieties were synthesized, and their fungicidal activities against Colletotrichum lagenarium and Botrytis cinerea were investigated. Most of the synthesized compounds showed moderate to significant fungicidal activity. Among them, halogen atom-containing derivatives showed better activity than others, especially compounds 6a,d which exhibited excellent fungicidal activity against C. lagenarium, with IC₅₀ values of 7.68 and 8.17 μM. The structure-activity relationship (SAR) analysis indicated that ester derivatives with electron-withdrawing groups on the benzene ring showed better fungicidal activity than those with electron-donating groups. A quantitative structure-activity relationship (QSAR) model (R² = 0.9824, F = 203.01, S² = 0.0083) was obtained through the heuristic method. The built model revealed a strong correlation of fungicidal activity against C. lagenarium with the molecular structures of these compounds. These results are expected to prove helpful in the design and exploration of low toxicity and high efficiency α-methylene-γ-butyrolactone-based fungicides.