Discovery of Terpene-Derived Quaternary Ring Compounds Containing an Oxime Moiety as Potential Fungicides

Design, synthesis and antifungal evaluation of low bee-toxicity coumarin oxime derivatives

BACKGROUND

Structural modification of natural products is one of the most effective approaches for discovering new agrochemical compounds. Coumarin, a natural product, is widely found in higher plants from the Brassicaceae, Umbelliferae, Leguminosae, and Orchidaceae families. Coumarin and its derivatives exhibit a wide range of biological activities. Based on our previous research, a series of novel coumarin oxime derivatives were designed and synthesized. The preliminary mechanism of action and bee toxicity of the highly active compound were also investigated.

RESULTS

Most of the target compounds exhibited good antifungal activities. Compound 5k demonstrated moderate to strong broad-spectrum antifungal activities against all seven tested pathogenic fungi. Notably, it showed satisfactory antifungal activity against Rhizoctonia solani (median effective concentration = 3.29 μg/mL), surpassing the performance of the commercial coumarin fungicide osthole. In addition, the protective and curative effects of compound 5k against rice sheath blight at 200 μg/mL were 82.1% and 91.4% on detached rice leaves, and 82.5% and 72.5% on potted rice plants, respectively, outperforming osthole. Preliminary mechanistic studies suggested that compound 5k could alter mycelial morphology and increase catalase activity, promoting antioxidant and free radical scavenging functions to activate the plant's defense system. Furthermore, the median lethal dose of compound 5k was found to exceed 200 μg/bee based on an acute contact toxicity test conducted on honeybees.

CONCLUSION

This study demonstrates that coumarin oxime derivatives, with their novel structures, simple synthesis, excellent activity, and low bee toxicity, have the potential to become practical fungicides for plant protection, offering broad application prospects. © 2025 Society of Chemical Industry.

Design, synthesis, antifungal evaluation and mechanism study of myrtenal derivatives as potential laccase inhibitors

BACKGROUND

To develop novel natural product-derived fungicides, four series of myrtenal oxadiazole/thiadiazole-hydrazide/amide derivatives were designed, synthesized and evaluated for their inhibitions toward several crop pathogenic fungi/oomycetes.

RESULTS

In the in vitro antifungal experiments, some myrtenal derivatives showed good antifungal activity against Botryosphaeria dothidea, Sclerotinia sclerotiorum and Fusarium graminearum. Among them, compound 6d exhibited the best antifungal activity against B. dothidea, with EC50 value of 0.052 mg/L, which was significantly stronger than carbendazim (EC50 = 0.40 mg/L). In vivo antifungal activity assay on apple fruits and branches showed that 6d displayed significant protective and curative effects, both superior to carbendazim. In the preliminary antifungal mechanism study, 6d can damage the surface morphology of mycelia, destroy the integrity and permeability of cell membrane, increase intracellular ROS content, thereby inhibiting the growth of B. dothidea. Compound 6d also significantly inhibited laccase with IC50 value of 8.45 μM, much stronger than cysteine and PMDD-5Y. Molecular docking also confirmed the binding affinity and interaction mode of 6d with laccase.

CONCLUSION

This study presented a promising lead compound for the study on novel laccase inhibitors as fungicidal agrochemicals, which demonstrated significant anti-B. dothidea activity and laccase inhibitory activity. © 2025 Society of Chemical Industry.

Design, synthesis, X-ray crystal structure, and antifungal evaluation of new acetohydrazide derivatives containing a 4-thioquinazoline moiety

BACKGROUND

To find efficient agricultural fungicides, 29 new 4-thioquinazoline-containing acetohydrazide derivatives were prepared and tested for their fungicidal properties.

RESULTS

All of the target compounds were characterized by 1H and 13C nuclear magnetic resonance and high-resolution mass spectrometry techniques, and the molecular structure of compound A2 was verified by single-crystal X-ray diffraction measurement. The experimental results revealed that many compounds from this series had impressive inhibition efficacies in vitro against the tested fungi. For example, compound A25 was identified as the best fungicidal agent against Rhizoctonia solani with an EC50 (half-maximal effective concentration) value of 0.66 μg mL-1, superior to those of the commercial fungicides chlorothalonil, carbendazim and boscalid. Additionally, this compound displayed favorable protection and curative activities in vivo against rice sheath blight caused by R. solani. Antifungal mechanistic studies on compound A25 indicated that this compound exerted its strong anti-R. solani effects probably through an effective inhibition of fungal succinate dehydrogenase activity [half-maximal inhibitory concentration (IC50) = 4.88 μm] and the impairment of cell membrane integrity, based on the results from enzymatic bioassays, molecular docking studies, and scanning and transmission electron microscopy observations.

CONCLUSION

Acetohydrazide derivatives containing the 4-thioquinazoline moiety had the potential to be employed as lead compounds for developing more efficient agricultural fungicides in the near future. © 2024 Society of Chemical Industry.

Design, synthesis and antifungal activity of novel pyrazole-amide-isothiazole derivatives as succinate dehydrogenase inhibitors

To discover new fungicides to protect food safety and quality, thirty-four novel pyrazole-amide-isothiazole compounds were designed, synthesised by using scaffold hopping theory for the first time. The bioactivity of all the target compounds against five plant pathogens (Including Penicillium digitatum, Physalospora piricola, Helminthosporium maydis, Sclerotinia sclerotiorum and Botrytis cinerea) were determined, the results showed that most of the compounds exhibited certain biological activities against B. cinerea in vitro. Compounds 7-XHU-6 had better antifungal activities than fluopyram with the EC50 values were 1.02, 1.78 mg/L, respectively. Moreover, the SDH inhibiting activities results indicated that 7-XHU-6 possessed outstanding activities with an IC50 value of 0.47 mg/L which better than fluopyram (IC50 = 0.88 mg/L). Besides, the in vivo experiments indicated that compound 7-XHU-6 had excellent protection efficiency and therapeutic efficiency. In addition, molecular docking studies demonstrated that compound 7-XHU-6 (-10 kcal/mol) has superior binding energy compared to fluopyram (-8.6 kcal/mol).

Design, Synthesis and Bioactivity of Benzyl Propiolates with Broad-Spectrum Inhibition Activity on Phytopathogenic Fungi

As part of our continuing research on propiolic acid derivatives, a series of benzyl propiolate derivatives and analogues were designed, synthesized, and investigated for inhibition activity in vitro and in vivo on phytopathogenic fungi, structure-activity relationship (SAR) and action mechanism. The results showed that most of the compounds had potent and broad-spectrum antifungal activity in vitro at 50 μg/mL. Among the compounds, 2-bromobenzyl propiolate (3h) displayed the highest comprehensive activity with total activity index (TAI) of 4.57 against all the eight test fungi followed by 3-fluorobenzyl propiolate (3c) (TAI = 4.53), superior to positive fungicides thiabendazole (TAI < 4.12) and/or azoxystrobin (TAI < 2.90). Relative to the other fungi, Fusarium solani and Fusarium graminearum revealed higher total susceptibility indexes (TSI) of 11.1 and 8.98, respectively, for all compounds. 3h and 3g (4-chlorobenzyl propiolate) gave the smallest EC50 values of 0.86 and 0.67 μg/mL against F. solani and F. graminearum, respectively, superior or comparable with thiabendazole and azoxystrobin. As a representative, 3h at 200 μg/mL displayed 100% protection on F. solani infections on potatoes over 7 days and high safety for plant growth. In antifungal mechanism, 3h was able to change mycelial morphology, destroy the structures of both hypha and cell membrane, increase the intracellular ROS level, decrease the intracellular mitochondrial membrane potential level, and change the permeability of the cell membrane. The SAR showed that ethynyl is a key group for the activity, and the presence of halogen atoms at the 2-site of the benzene ring can significantly improve the activity in most cases. Thus, benzyl propiolate can be considered a novel antifungal lead compound, while 3h can be considered a promising fungicide candidate to develop new agricultural fungicides.

Discovery of Novel Cyclobutyl Oxime Ester Derivatives Containing an α,β-Unsaturated Carbonyl Moiety as Potential Mitochondrial Toxins

As part of continuous work to explore novel and efficient fungicides originating from natural products, a series of cyclobutyl oxime ester derivatives containing an α,β-unsaturated carbonyl moiety were designed and synthesized. In line with the primary evaluation of the inhibitory effect on common pathogenic fungi causing crop failure, a systematic study on the antifungal activity of target compounds against Rhizoctonia solani was carried out. Most target compounds exhibited satisfactory antifungal activity, and 10 of them were superior to the positive control trifloxystrobin. The most notable median effective concentration (EC50) of compound 6b was 1.70 μg/mL, which was considerable for an intensive study. The control efficacy of compound 6b on potted rice against R. solani was superior to trifloxystrobin at identical concentration. The mycelial morphology and cell membrane permeability of the treated fungi were disrupted, and the meaningful enzyme activities of SDH and POD were also restrained. The reactive oxygen species, nuclear morphology, and mitochondrial membrane potential of the treated hypha reflected an apparent difference compared with the normal morphology, which represented mitochondrial function damage. In addition, chemical features essential for the activity and docking mode within the compound and cytochrome bc1 complex were accessed by computer-aided technology. This study provided insights into the development of new green and efficient fungicides targeting the mitochondria.

Pinonic Acid Derivatives Containing Thiourea Motif: Promising Antifungal Lead Compound Targeting Cellular Barrier of Colletotrichum fructicola

In order to explore novel antifungal lead compounds from plant essential oil, thirty-two pinonic acid derivatives containing thiourea groups were designed and synthesized using α-pinene as a raw material. One of these pinonic acid derivatives compound 3a exhibited noteworthy in vitro antifungal activity against Colletotrichum fructicola (EC50 = 9.22 mg/L), which was comparable to that of the positive control kresoxim-methyl (EC50 = 9.69 mg/L). Structure-activity relationship (SAR) studies demonstrated that the introduction of thiourea groups, F atoms, and Cl atoms into the structure of pinonic acid derivatives significantly improved their antifungal activity. The in vivo antifungal test revealed that compound 3a could effectively control pear anthracnose. It also proved that compound 3a showed low acute oral toxicity to honeybees (LD50 > 100 μg/bee) and low or no cytotoxicity to LO2 and HEK293 cell lines. The preliminary mechanism of action studies revealed that compound 3a caused mycelium deformity, increased cell membrane permeability, blocked the normal process of phospholipase C on the cell membrane, and reduced mycelium protein content. The results of molecular docking studies demonstrated the stable binding of compound 3a to phospholipase C and chitin synthetase. This study suggested that compound 3a could be used as a promising lead compound for the development of novel antifungal agents targeting the cellular barrier of C. fructicola.

Synthesis and Evaluation of Novel 1-Methyl-1H-pyrazol-5-amine Derivatives with Disulfide Moieties as Potential Antimicrobial Agents

Sulfur-containing compounds have diverse biological functions and are crucial in crop protection chemistry. In this study, a series of novel 1-methyl-1H-pyrazol-5-amine derivatives incorporating disulfide moieties were synthesized and evaluated for their antimicrobial properties. In vitro bioassays demonstrated that compound 7f displayed potent antifungal activity against Valsa mali, with an EC50 value of 0.64 mg/L, outperforming allicin (EC50 = 26.0 mg/L) but lower than tebuconazole (EC50 = 0.33 mg/L). In vivo experiments confirmed that compound 7f could effectively inhibit V. mali infection on apples at a concentration of 100 mg/L, similar to the positive control tebuconazole. Mechanistic studies revealed that compound 7f could induce hyphal shrinkage and collapse, trigger intracellular reactive oxygen species accumulation, modulate antioxidant enzyme activities, initiate lipid peroxidation, and ultimately cause irreversible oxidative damage to the cells of V. mali. Additionally, compound 7b exhibited notable antibacterial activity, particularly against Pseudomonas syringae pv. actinidiae, with a MIC90 value of 1.56 mg/L, surpassing the positive controls allicin, bismerthiazol, and streptomycin sulfate. These findings suggest that 1-methyl-1H-pyrazol-5-amine derivatives containing disulfide moieties hold promise as potent candidates for the development of novel antimicrobial agents.

Design, synthesis and antifungal activity of novel α-methylene-γ-butyrolactone derivatives containing benzothiophene moiety

BACKGROUND

The discovery of agricultural fungicide candidates from natural products is one of the key strategies for developing environment friendly agricultural fungicides with high efficiency, high selectivity and unique modes-of-action. Based on previous work, a series of novel α-methylene-γ-butyrolactone (MBL) derivatives containing benzothiophene moiety were designed and synthesized.

RESULTS

The majority of the proposed compounds displayed moderate to considerable antifungal efficacy against the tested pathogenic fungi and oomycetes, some exhibiting broad spectrum antifungal activity. Notably, compounds 2 (3-F-Ph) and 7 (4-Cl-Ph) showed excellent antifungal activity against Rhizoctonia with half maximal effective concentration (EC50) values of 0.94 and 0.99 mg L-1, respectively, comparable to the commercial fungicide tebuconazole (EC50 = 0.96 mg L-1), and also displayed significant inhibitory effects against V alsa mali with EC50 values of 2.26 and 1.67 mg L-1, respectively - better than famoxadone and carabrone. The in vivo protective and curative effects against R. solani of compound 2 were 57.2% and 53.7% at 100 mg L-1, respectively, which were equivalent to tebuconazole (51.6% and 52.4%). Further investigations found that compound 2 altered the ultrastructure of R. solani cell, significantly increased the relative conductivity of the cells, and reduced the activity of complex III in a dose-dependent manner. Molecular docking results showed that compound 2 matched well with the Qo pocket.

CONCLUSION

The results revealed that MBL derivatives containing benzothiophene moiety are promising antifungal candidates and provide a new backbone structure for further optimization of novel fungicides. © 2024 Society of Chemical Industry.

Design, Synthesis and Antifungal Activity of Nootkatone Derivatives Containing Acylhydrazone and Oxime Ester

In an attempt to search for new natural products-based antifungal agents, fifty-three nootkatone derivatives were designed, synthesized, and evaluated for their antifungal activity against Phytophthora parasitica var nicotianae, Fusarium oxysporum, Fusarium graminearum and Phomopsis sp. by the mycelium growth rate method. Nootkatone derivatives N17 exhibited good inhibitory activity against Phomopsis. sp. with EC50 values of 2.02 μM. The control effect of N17 against Phomopsis. sp. on kiwifruit showed that N17 exhibited a good curative effect in reducing kiwifruit rot at the concentration of 202 μM(100×EC50 ), with the curative effect of 41.11 %, which was better than commercial control of pyrimethanil at the concentration of 13437 μM(100×EC50 ) with the curative effect of 38.65 %. Phomopsis. sp. mycelium treated with N17 showed irregular surface collapse and shrinkage, and the cell membrane crinkled irregularly, vacuoles expanded significantly, mitochondria contracted, and organelles partially swollen by the SEM and TEM detected. Preliminary pharmacological experiments show that N17 exerted antifungal effects by altering release of cellular contents, and altering cell membrane permeability and integrity. The cytotoxicity test demonstrated that N17 showed almost no toxicity to K562 cells. The presented results implied that N17 may be as a potential antifungal agents for developing more efficient fungicides to control Phomopsis sp.

Aloperine-Type Alkaloids with Antiviral and Antifungal Activities from the Seeds of Sophora alopecuroides L

As a continuous flow investigation of novel pesticides from natural quinolizidine alkaloids, the chemical compositions of the seeds of Sophora alopecuroides were thoroughly researched. Fifteen new aloperine-type alkaloids (1-15) as well as six known aloperine-type alkaloids (16-21) were obtained from the extract of S. alopecuroides. The structures of 1-21 were confirmed via HRESIMS, NMR, UV, IR, ECD calculations, and X-ray diffraction. The antiviral activities of 1-21 against tobacco mosaic virus (TMV) were detected following the improved method of half-leaf. Compared with ningnanmycin (protective: 69.7% and curative: 64.3%), 15 exhibited excellent protective (71.7%) and curative (64.6%) activities against TMV. Further biological studies illustrated that 15 significantly inhibited the transcription of the TMV-CP gene and increased the activities of polyphenol oxidase (PPO), peroxidase (POD), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL). The antifungal activities of 1-21 against Phytophythora capsica, Botrytis cinerea, Alternaria alternata, and Gibberella zeae were screened according to a mycelial inhibition test. Compound 13 displayed excellent antifungal activity against B. cinerea (EC50: 7.38 μg/mL). Moreover, in vitro antifungal mechanism studies displayed that 13 causes accumulation of reactive oxygen species and finally leads to mycelia cell membrane damage and cell death in vitro.

Isolating Antipathogenic Fungal Coumarins from Coriaria nepalensis and Determining Their Primary Mechanism In Vitro

Through bioassay-guided isolation, eight undescribed coumarins (1-8), along with six reported coumarins (9-14), were obtained from Coriaria nepalensis. The new structures were determined by using IR, UV, NMR, HRESIMS, and ECD calculations. The results of the biological activity assays showed that compound 9 exhibited broad spectrum antifungal activities against all tested fungi in vitro and a significant inhibitory effect on Phytophthora nicotianae with an EC50 value of 3.00 μg/mL. Notably, compound 9 demonstrated greater curative and protective effects against tobacco balack shank than those of osthol in vivo. Thus, 9 was structurally modified to obtain new promising antifungal agents, and the novel derivatives (17b, 17j, and 17k) exhibited better effects on Sclerotinia sclerotiorum than did lead compound 9. Preliminary mechanistic exploration illustrated that 9 could enhance cell membrane permeability, destroy the morphology and ultrastructure of cells, and reduce the exopolysaccharide content of P. nicotianae mycelia. Furthermore, the cytotoxicity results revealed that compound 9 exhibited relatively low cytotoxicity against HEK293 cell lines with an inhibition rate of 33.54% at 30 μg/mL. This research is promising for the discovery of new fungicides from natural coumarins with satisfactory ecological compatibility.

Design of a delivery vehicle chitosan-based self-assembling: controlled release, high hydrophobicity, and safe treatment of plant fungal diseases

BACKGROUND

Traditional pesticides are poorly water-soluble and suffer from low bioavailability. N-succinyl chitosan (NSCS) is a water-soluble chitosan derivative, has been recently used to encapsulate hydrophobic drugs to improve their bioavailability. However, it remains challenging to synthesize pesticides of a wide variety of water-soluble drugs and to scale up the production in a continuous manner.

RESULTS

A synthetic method for preparing water-soluble nanopesticides with a polymer carrier was applied. The bioactive molecule BTL-11 was loaded into hollow NSCS to promote drug delivery, improve solubility and anti-fungal activity. The synthesized nanopesticides had well controlled sizes of 606 nm and the encapsulation rate was 80%. The release kinetics, drug toxicity and drug activity were further evaluated. The inhibitory activity of nanopesticides against Rhizoctonia solani (R. solani) was tested in vivo and in vitro. In vivo against R. solani trials revealed that BTL-11 has excellent control efficiency for cultivated rice leaf and sheath was 79.6 and 76.5%, respectively. By contrast, for BTL-11@NSCS NPs, the anti-fungal ability was strongly released and afforded significant control efficiencies of 85.9 and 81.1%. Those effects were significantly better than that of the agricultural fungicide azoxystrobin (51.5 and 66.5%). The proposed mechanism was validated by successfully predicting the synthesis outcomes.

CONCLUSIONS

This study demonstrates that NSCS is a promising biocompatible carrier, which can enhance the efficacy of pesticides, synergistically improve plant disease resistance, protect crop growth, and can be used for the delivery of more insoluble pesticides.

Quinolizidine Alkaloids and Isoflavones from the Herb of Thermopsis lupinoides and Their Antiviral, Antifungal, and Insecticidal Activities

As part of our ongoing investigation of natural bioactive substances from the genus Thermopsis of the tribe Fabaceae for agricultural protection, the chemical constituents of the herb Thermopsis lupinoides were systematically investigated, which led to the isolation of 39 quinolizidine alkaloids (QAs) (1-39), including 14 new QAs (1-14) and 14 isoflavones (40-53). Their structures were elucidated through comprehensive spectroscopic data analysis (IR, UV, NMR, HRESIMS), ECD calculations, and X-ray crystallography. The antitomato spotted wilt virus (TSWV) and antifungal (against Botrytis cinerea, Gibberella zeae, Phytophythora capsica, and Alternaria alternata) and insecticidal (against Aphis fabae and Tetranychus urticae) activities of the isolated compounds were screened using the lesion counting method, mycelial inhibition assay, and spray method, respectively. The bioassay results showed that 34 exhibited excellent protective activity against TSWV, with an EC50 value of 36.04 μg/mL, which was better than that of the positive control, ningnanmycin (86.03 μg/mL). The preliminary mechanistic exploration illustrated that 34 induced systemic acquired resistance in the host plant by acting on the salicylic acid signaling pathway. Moreover, 1 showed significant antifungal activity against B. cinerea (EC50 value of 20.83 μg/mL), while 2 exhibited good insecticidal activity against A. fabae (LC50 value of 24.97 μg/mL). This research is promising for the invention of novel pesticides from QAs with high efficiency and satisfactory ecological compatibility.

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.

Natural terpene-based derivatives to control postharvest sclerotinia rot and the involved potential mechanism

In an effort to develop novel postharvest preservatives of satisfactory environmental compatibility from natural monoterpene, a series of terpene-based derivatives containing oxime ester were designed and prepared. In this research, the inhibitory effect of target compounds against S. sclerotiorum were evaluated though in vitro and in vivo tests. It was investigated that most compounds exhibited promising antifungal activity, especially compound 4k with EC50 value of 3.02 μg/mL, which was significantly superior to commercial fungicide trifloxystrobin. Notably, compound 4k improved the physicochemical quality of carrot including weight loss, contents of titratable acidity, ascorbic acid, carotenoid, malondialdehyde, and enzymes activities, ensuring post-harvest preservation. Simultaneously, the mycelial morphology, ultrastructure, cell wall permeability, and defense/respiration-related enzymes of S. sclerotiorum were destructed. The preliminary toxicity evaluation of target compounds indicated that the prepared target compounds possessed safety and low toxicity. Additionally, the essential chemical features for activity and interaction mode between molecule and cytochrome bc1 complex were inquired by computer-aid technology. The study provided meaningful insight into formulation of natural terpene-based fresh-keeping agent to resist postharvest decay infected by S. sclerotiorum.

Synthesis and Fabrication of Betulin-Derived Polysulfide and Polysulfoxide Electrospun Fibers for Fruit Preservation

Plant-derived biocompounds play a crucial role in the field of renewable materials due to their sustainability as they can be converted into monomers for polymerization, comparable to numerous monomers obtained from petroleum. In this work, betulin, a triterpene derivative with antibacterial properties obtained from birch tree bark, was esterified to produce two varieties of α,ω-diene derivatives with different lengths of methylene spacers. These derivatives were then copolymerized with 2,2'-(ethylenedioxy)diethanethiol using thiol-ene photopolymerization. We optimized and confirmed the polymerization parameters such as solvents, catalysts, and monomer concentrations. These analyses allowed for the obtainment of polysulfides with a high molar mass of up to 38.9 kg/mol under the optimized conditions. Furthermore, the polysulfides were converted into polysulfoxides by using a dilute hydrogen peroxide solution. Thermal analysis of the obtained polymers revealed excellent thermal stability (up to 300 °C) and tunable glass transition temperatures depending on their molar mass and composition. We successfully produced fibers with a diameter of approximately 3.9 μm by using the electrospinning technique. The morphology and hydrophobicity of the fibers were analyzed by using scanning electron microscopy and water contact angle analysis. Plant-derived polymeric fibers exhibited good cellular biocompatibility and broad-spectrum antibacterial activity, making them promising candidates for applications in fruit preservation.

Discovery of Pyrazole-5-yl-amide Derivatives Containing Cinnamamide Structural Fragments as Potential Succinate Dehydrogenase Inhibitors

To promote the development of novel agricultural succinate dehydrogenase inhibitor (SDHI) fungicides, we introduced cinnamamide and nicotinamide structural fragments into the structure of pyrazol-5-yl-amide by carbon chain extension and scaffold hopping, respectively, and synthesized a series of derivatives. The results of the biological activity assays indicated that most of the target compounds exhibited varying degrees of inhibitory activity against the tested fungi. Notably, compounds G22, G28, G34, G38, and G39 exhibited excellent in vitro antifungal activities against Valsa mali with EC50 values of 0.48, 0.86, 0.57, 0.73, and 0.87 mg/L, respectively, and this result was significantly more potent than boscalid (EC50 = 2.80 mg/L) and closer to the specialty control drug tebuconazole (EC50 = 0.30 mg/L). Compounds G22 and G34 also exhibited excellent in vivo protective and curative effects against V. mali at 40 mg/L. The SEM and TEM observations indicated that compounds G22 and G34 may affect normal V. mali mycelial morphology as well as the cellular ultrastructure. Molecular docking analysis results indicated that G22 and boscalid possessed a similar binding mode to that of SDH, and detailed SDH inhibition assays validated the feasibility of the designed compounds as potential SDH inhibitors. Compounds G22 and G3 were selected for theoretical calculations, and the terminal carboxylic acid group of this series of compounds may be a key region influencing the antifungal activity. Furthermore, toxicity tests on Apis mellifera l. revealed that compounds G22 and G34 exhibited low toxicity to A. mellifera l. populations. The above results demonstrated that these series of pyrazole-5-yl-amide derivatives are promising for development as potential low-risk drug-resistance agricultural SDHI fungicides.