Development of novel 2-substituted acylaminoethylsulfonamide derivatives as fungicides against Botrytis cinerea

Discovery of novel piperidine-containing thymol derivatives as potent antifungal agents for crop protection

BACKGROUND

Plant fungal diseases pose a significant threat to crop production. The extensive use of chemical pesticides has led to growing environmental safety risks and pesticide resistance of various plant pathogens. Therefore, it is an urgent task to explore novel eco-friendly fungicidal agents with high efficacy to combat fungal infection.

RESULTS

In this study, we rationally designed a series of novel thymol derivatives by incorporation of the sulfonamide moiety and evaluated their biological activities against plant pathogenic fungi. The bioassay results underscored the remarkable in vitro antifungal activity of compounds 5m and 5t against Phytophthora capsici (P. capsici), with EC50 values of 8.420 and 8.414 μg/mL, respectively. Their efficacies were superior to that of widely used commercial fungicides azoxystrobin (AZO, 20.649 μg/mL) and cabendazim (CAB, 251.625 μg/mL). Furthermore, compound 5v exhibited excellent in vitro antifungal activity against Sclerotinia sclerotiorum (S. sclerotiorum), with an EC50 value of 12.829 μg/mL, significantly outperforming AZO (63.629 μg/mL). In vivo bioassays demonstrated the impactful activity of compound 5v against S. sclerotiorum, achieving over 98% curative and protective efficacies at the concentration of 200 μg/mL. Further mechanistic investigations unveiled that compound 5v induced mycelial shrinkage and collapse in S. sclerotiorum, resulting in organelle damage and the accumulation of antioxidant enzyme activity.

CONCLUSION

The significant antifungal efficacy of the prepared thymol derivatives shall encourage further exploration of compound 5v as a promising candidate to develop novel fungicides for crop protection. © 2024 Society of Chemical Industry.

A Lesion Microenvironment-Responsive Fungicide Nanoplatform for Crop Disease Prevention and Control

Controlled fungicide delivery in response to the specific microenvironment produced by fungal pathogens is an advisable strategy to improve the efficacy of fungicides. Herein, the authors construct a smart fungicide nanoplatform, using mesoporous silica nanoparticles (MSNs) as nanocarriers loaded with eugenol (EU) and Ag⁺ coordinated polydopamine (Ag⁺ -PDA) as a coating to form Ag⁺ -PDA@MSNs-EU NPs for Botrytis cinerea (B. cinerea) control. As a botanical fungicide, EU offers an eco-friendly alternative to synthetic fungicides and can upregulate several defense-related genes in the tomato plant. The Ag⁺ -PDA coating can lock the EU inside the nanocarriers and respond to the oxalic acid produced by B. cinerea to corelease the loaded EU and Ag⁺ . The results demonstrate that Ag⁺ -PDA@MSNs-EU NPs can effectively inhibit the mycelial growth of B. cinerea on detached and potted tomato leaves. The construction of such a smart fungicide nanoplatform provides new guidance to design controlled fungicides release systems, which can respond to the microenvironment associated with plant pathogen to realize fungus control.

Mulberrin inhibits Botrytis cinerea for strawberry storage by interfering with the bioactivity of 14α-demethylase (CYP51)

Currently, chemical agents hold great promise in preventing and combating Botrytis cinerea. However, the antifungal mechanism of some agents for B. cinerea remains rather vague, imposing restrictions on the research and development of novel antifungal inhibitors. In this work, we discovered that mulberrin (MBN), a natural compound from the root bark of Ramulus Mori, with an IC₅₀ of 1.38 μM together, demonstrated marked anti-14α-demethylase (CYP51) activity through high throughput virtual screening and in vitro bioactivity assay. The computational biology results demonstrated that MBN and its derivatives were bound to the catalytic activity region of CYP51, but only MBN could form a strong π-cation interaction with the Fe ion of heme in CYP51 via the 2-methylpent-2-ene moiety at atom C9. MBN had a stronger binding free energy than the other three compounds with CYP51, implying that the 2-methylpent-2-ene moiety at atom C9 is a critical pharmacophore for CYP51 inhibitors. Subsequently, through an antifungal test, MBN demonstrated excellent anti-B. cinerea activity by inhibiting CYP51 activity. The EC₅₀ values of MBN toward hyphal growth and spore germination in B. cinerea were 17.27 and 9.56 μg mL^-1, respectively. The bioactivity loss of CYP51 by direct interaction with MBN induced the increase of cell membrane permeability, membrane destruction, and cell death. Meanwhile, in the B. cinerea infection model, MBN significantly prolonged the preservation of strawberries by preventing B. cinerea from infecting strawberries and could be used as a potential natural preserving agent for storing fruits.

Primary Mode of Action of the Novel Sulfonamide Fungicide against Botrytis cinerea and Field Control Effect on Tomato Gray Mold

Botrytis cinerea is considered an important plant pathogen and is responsible for significant crop yield losses. With the frequent application of commercial fungicides, B. cinerea has developed resistance to many frequently used fungicides. Therefore, it is necessary to develop new kinds of fungicides with high activity and new modes of action to solve the increasingly serious problem of resistance. During our screening of fungicide candidates, one novel sulfonamide compound, N-(2-trifluoromethyl-4-chlorphenyl)-2-oxocyclohexyl sulfonamide (L13), has been found to exhibit good fungicidal activity against B. cinerea. In this work, the mode of action of L13 against B. cinerea and the field control effect on tomato gray mold was studied. L13 had good control against B. cinerea resistant to carbendazim, diethofencarb, and iprodione commercial fungicides in the pot culture experiments. SEM and TEM observations revealed that L13 could cause obvious morphological and cytological changes to B. cinerea, including excessive branching, irregular ramification or abnormal configuration, and the decomposition of cell wall and vacuole. L13 induced more significant electrolyte leakage from hyphae than procymidone as a positive control. L13 had only a minor effect on the oxygen consumption of intact mycelia, with 2.15% inhibition at 50 μg/mL. In two locations over 2 years, the field control effect of L13 against tomato gray mold reached 83% at a rate of 450 g ai ha⁻¹, better than the commercial fungicide of iprodione. Moreover, toxicological tests demonstrated the low toxicological effect of L13. This research seeks to provide technical support and theoretical guidance for L13 to become a real commercial fungicide.

Design, Synthesis, and Antifungal Evaluation of Luotonin A Derivatives against Phytopathogenic Fungi

Crop diseases caused by fungi threaten food security and exacerbate the food crisis. Inspired by the application of fungicide candidates from natural products in agrochemical discovery, a series of luotonin A derivatives were designed, synthesized, and evaluated for their antifungal activities against five plant fungi. Most of these compounds exhibited significant fungicidal activity against Botrytis cinerea in vitro with EC₅₀ values less than 1 μg/mL. Among them, compounds w7, w8, w12, and w15 showed superior antifungal activity against B. cinerea with EC₅₀ values of 0.036, 0.050, 0.042, and 0.048 μg/mL, respectively, which were more potent than boscalid (EC₅₀ = 1.790 μg/mL). Preliminary mechanism studies revealed that compound w7 might pursue its antifungal activity by disrupting the fungal cell membrane and cell wall. Moreover, in vivo bioassay also indicated that compound w7 could be effective for the control of B. cinerea. The above results evidenced the potential of luotonin A derivatives as novel and promising candidate fungicides.

Design, synthesis and antifungal/anti-oomycete activity of pyrazolyl oxime ethers as novel potential succinate dehydrogenase inhibitors

BACKGROUND

Succinate dehydrogenase inhibitors (SDHIs) play an increasingly important role in controlling plant diseases. However, the similar structures of SDHIs result in rapid development of cross-resistance development and a clear bottleneck of poor activity against oomycetes, therefore the need to seek new SDHI fungicides with novel structures is urgent.

RESULTS

Innovative pyrazolyl oxime ethers were designed by replacing amide with oxime ether based on the succinate dehydrogenase (SDH) structure, and 19 pairs of Z- and E-isomers were efficiently prepared for the discovery of SDHI compounds with a novel bridge. Their biological activities against four fungi and two oomycetes were evaluated, and substantial differences were observed between the Z- and E- isomers of the title compounds. Furthermore, most of these compounds exhibited remarkable activities against Rhizoctonia solani with EC₅₀ values of less than 10 mg L^-1 in vitro, and bioassay in vivo further confirmed that E-I-6 exhibited good protective efficacy (76.12%) at 200 mg L^-1 . In addition, Z-I-12 provided better activity against the oomycetes Pythium aphanidermatum and Phytophthora capsici (EC₅₀  = 1.56 and 0.93 mg L^-1 ) than those of boscalid. Moreover, E-I-12 exhibited excellent SDH inhibition (IC₅₀  = 0.21 mg L^-1 ) thanks to its good binding ability to the SDH by hydrogen-bonding interactions, π-cation interaction and hydrophobic interactions.

CONCLUSION

Novel pyrazolyl oxime ethers have the potential as SDHI compounds for future development, and the strategy of replacing an amide bond with oxime ether may offer an alternative option in SDHI fungicide discovery.

Synthesis, Fungicidal Activity and SAR of 2-Thiazolamide/Pyrazolamide-Cyclohexylsulfonamides against Botrytis cinerea

In order to explore more efficient sulfonamides against Botrytis cinereal, 36 novel cyclohexylsulfonamides were synthesized by N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDCI) and 1-hydroxybenzotriazole (HOBt) condensation reaction using chesulfamide as a lead compound, introducing thiazole and pyrazole active groups. Their structures were characterized by ¹H-NMR, ¹³C-NMR, mass spectrum (MS), and elemental analysis. Compound III -31 was further confirmed by X-ray single crystal diffraction. The in vitro and in vivo fungicidal activities against B. cinerea were evaluated by three bioassay methods. The results of mycelial growth demonstrated that median effective concentration (EC₅₀) values of nine compounds were close to boscalid (EC₅₀ = 1.72 µg/mL) and procymidone (EC₅₀ = 1.79 µg/mL) against B. cinerea (KZ-9). In the spore germination experiment, it was found that compounds III-19 and III-31 inhibited germination 93.89 and 98.00%, respectively; at 10 µg/mL, they approached boscalid (95.97%). In the tomato pot experiment, the control effects of two compounds (III-21 and III-27) were 89.80 and 87.90%, respectively, at 200 µg/mL which were significantly higher than boscalid (81.99%). The structure–activity relationship (SAR) was also discussed, which provided a valuable idea for developing new fungicides.