Design, Synthesis, Antibacterial Activity, and Mechanisms of Novel 1,3,4-Thiadiazole Derivatives Containing an Amide Moiety

Novel trans-Resveratrol Derivatives: Design, Synthesis, Antibacterial Activity, and Mechanisms

Rice bacterial leaf blight and rice bacterial leaf streak have induced tremendous damage to production of rice worldwide. To discover an effective novel antibacterial agent, a series of novel trans-resveratrol (RSV) derivatives containing 1,3,4-oxadiazole and amide moieties were designed and synthesized for the first time. Most of them showed excellent antibacterial activities against Xanthomonas oryzae pv oryzicola and Xanthomonas oryzae pv oryzae. Especially, compound J12 had the best inhibitory with the half-maximal effective concentration values of 4.2 and 5.0 mg/L, respectively, which were better than that of RSV (63.7 and 75.4 mg/L), bismerthiazol (79.5 and 89.6 mg/L), and thiodiazole copper (105.4 and 112.8 mg/L). Furthermore, compound J12 had an excellent control effect against rice bacterial leaf streak and rice bacterial leaf blight, with protective activities of 46.2 and 42.1% and curative activities of 44.5 and 41.7%, respectively. Preliminary mechanisms indicated that compound J12 could not only remarkably decrease biofilm formation, extracellular polysaccharide production, and the synthesis of extracellular enzymes but also destroy bacterial cell surface morphology, thereby reducing the pathogenicity of bacteria. In addition, compound J12 could increase the activity of defense-related enzymes and affect the expression of multiple pathogenic-related genes including plant-pathogen interaction, the MAPK signaling pathway, and phenylpropanoid biosynthesis, and this could improve the defense of rice against rice bacterial leaf streak infection. The present work indicates that the RSV derivatives can be used as promising candidates for the development of antibacterial agents.

Synthesis and agricultural antimicrobial evaluation of new quinazoline derivatives containing both a piperazine linker and the N-acetyl moiety

BACKGROUND

To discover more efficient agricultural antimicrobial agents, a series of new quinazoline derivatives containing both a piperazine linker and the N-acetyl moiety were prepared and assessed for their antibacterial and antifungal activities.

RESULTS

All the target compounds were characterized by 1H and 13C NMR as well as high-resolution mass spectrometry (HRMS), and the chemical structure of the most potent compound E19 incorporating a 4-trifluoromethoxy substituent was clearly confirmed via single crystal X-ray diffraction measurements. The bioassay results indicated that some compounds possessed notable inhibitory effects in vitro against the bacterium Xanthomonas oryzae pv. oryzicola (Xoc). For example, compound E19 had an EC50 (effective concentration for 50% activity) value of 7.1 μg/mL towards this pathogen, approximately 15- and 10-fold more effective than the commercial bactericides thiodiazole copper and bismerthiazol (EC50 = 110.2 and 72.4 μg/mL, respectively). Subsequently, the mechanistic studies showed that compound E19 likely exerted its antibacterial efficacies by altering the cell morphology, increasing the permeability of bacterial cytoplasmic membrane, suppressing the production of bacterial extracellular polysaccharides and the extracellular enzyme activities (amylase and cellulase), and blocking the swimming motility of Xoc. Moreover, the proteomic analysis revealed that compound E19 could reduce the bacterial flagellar biosynthesis and decrease the flagellar motility by down-regulating the expression of the related differential proteins.

CONCLUSION

Compound E19 exhibited good potential for further development as a bactericide candidate for control of Xoc. © 2024 Society of Chemical Industry.

Recent Advances and Outlook of Benzopyran Derivatives in the Discovery of Agricultural Chemicals

Scaffold structures, new mechanisms of action, and targets present enormous challenges in the discovery of novel pesticides. The discovery of new scaffolds is the basis for the continuous development of modern agrochemicals. Identification of a good scaffold such as triazole, carbamate, methoxy acrylate, pyrazolamide, pyrido-pyrimidinone mesoionic, and bisamide often leads to the development of a new series of pesticides. In addition, pesticides with the same target, including the inhibitors of succinate dehydrogenase (SDH), oxysterol-binding-protein, and p-hydroxyphenyl pyruvate dioxygenase (HPPD), may have the same or similar scaffold structure. Recent years have witnessed significant progress in the discovery of new pesticides using natural products as scaffolds or bridges. In recent years, there have been increasing reports on the application of natural benzopyran compounds in the discovery of new pesticides, especially osthole and coumarin. A systematic and comprehensive review of benzopyran active compounds in the discovery of new agricultural chemicals is helpful to promote the discussion and development of benzopyran active compounds. Therefore, this work systematically reviewed the research and application of benzopyran derivatives in the discovery of agricultural chemicals, summarized the antiviral, herbicidal, antibacterial, fungicidal, insecticidal, nematicidal and acaricidal activities of benzopyran active compounds, and discussed the structural-activity relationship and mechanism of action. In addition, some active fragments were recommended to further optimize the chemical structure of benzopyran active compounds based on reference information.

Synthesis, Structural Characterization, and Biological Activities of 1,3,4- Thiadiazole Derivatives Containing Sulfonylpiperazine Structures

To develop novel bacterial biofilm inhibiting agents, a series of 1,3,4-thiadiazole derivatives containing sulfonylpiperazine structures were designed, synthesized, and characterized using 1H nuclear magnetic resonance (1H NMR), 13C nuclear magnetic resonance (13C NMR), and high-resolution mass spectrometry. Meanwhile, their biological activities were evaluated, and the ensuing structure-activity relationships were discussed. The bioassay results showed the substantial antimicrobial efficacy exhibited by most of the compounds. Among them, compound A24 demonstrated a strong efficacy with an EC50 value of 7.8 μg/mL in vitro against the Xanthomonas oryzae pv. oryzicola (Xoc) pathogen, surpassing commercial agents thiodiazole copper (31.8 μg/mL) and bismerthiazol (43.3 μg/mL). Mechanistic investigations into its anti-Xoc properties revealed that compound A24 operates by increasing the permeability of bacterial cell membranes, inhibiting biofilm formation and cell motility, and inducing morphological changes in bacterial cells. Importantly, in vivo tests showed its excellent protective and curative effects on rice bacterial leaf streak. Besides, molecular docking showed that the hydrophobic effect and hydrogen-bond interactions are key factors between the binding of A24 and AvrRxo1-ORF1. Therefore, these results suggest the utilization of 1,3,4-thiadiazole derivatives containing sulfonylpiperazine structures as a bacterial biofilm inhibiting agent, warranting further exploration in the realm of agrochemical development.

New Antibacterial 1,3,4-Thiadiazole Derivatives With Pyridine Moiety

1,3,4-Thiadiazole compounds were synthesized using pyridine carboxylic acid derivatives and thiosemicarbazide derivatives. The molecular structures of the resulting compounds were characterized by spectroscopic methods such as ATR-FTIR, 1H-NMR, and elemental analysis. Its compounds were also examined for their antibacterial properties against some strains of bacteria. Five synthesized compounds showed varying antibacterial effects on Escherichia coli, Salmonella kentucky, Bacillus substilis and Klebsiella pneumoniae. This result revealed that some of the resulting compounds could be antibacterial agents.

Synthesis and Antifungal Activity of Chalcone Derivatives Containing 1,3,4-Thiadiazole

24 chalcone derivatives containing 1,3,4-thiadiazole were synthesized. The results of bioactivity tests indicated that some of the target compounds exhibited superior antifungal activities in vitro. Notably, the EC50 value of D4 was 14.4 μg/mL against Phomopsis sp, which was significantly better than that of azoxystrobin (32.2 μg/mL) and fluopyram (54.2 μg/mL). The in vivo protective activity of D4 against Phomopsis sp on kiwifruit (71.2 %) was significantly superior to azoxystrobin (62.8 %) at 200 μg/mL. The in vivo protective activities of D4 were 74.4 and 57.6 % against Rhizoctonia solani on rice leaf sheaths and rice leaves, respectively, which were slightly better than those of azoxystrobin (72.1 and 49.2 %) at 200 μg/mL. Scanning electron microscopy (SEM) results showed that the mycelial surface collapsed, contracted and grew abnormally after D4 treatment. Finally, the results were further verified by in vivo antifungal assay, fluorescence microscopy (FM) observation, determination of relative conductivity, membrane lipid peroxidation degree assay, and determination of cytoplasmic content leakage. Molecular docking results suggested that D4 could be a potential SDHI.

Design, Synthesis, Antibacterial Activity, and Mechanisms of Novel Benzofuran Derivatives Containing Disulfide Moieties

The unsatisfactory effects of conventional bactericides and antimicrobial resistance have increased the challenges in managing plant diseases caused by bacterial pests. Here, we report the successful design and synthesis of benzofuran derivatives using benzofuran as the core skeleton and splicing the disulfide moieties commonly seen in natural substances with antibacterial properties. Most of our developed benzofurans displayed remarkable antibacterial activities to frequently encountered pathogens, including Xanthomonas oryzae pv oryzae (Xoo), Xanthomonas oryzae pv oryzicola (Xoc), and Xanthomonas axonopodis pv citri (Xac). With the assistance of the three-dimensional quantitative constitutive relationship (3D-QSAR) model, the optimal compound V40 was obtained, which has better in vitro antibacterial activity with EC50 values of 0.28, 0.56, and 10.43 μg/mL against Xoo, Xoc, and Xac, respectively, than those of positive control, TC (66.41, 78.49, and 120.36 μg/mL) and allicin (8.40, 28.22, and 88.04 μg/mL). Combining the results of proteomic analysis and enzyme activity assay allows the antibacterial mechanism of V40 to be preliminarily revealed, suggesting its potential as a versatile bactericide in combating bacterial pests in the future.

Antifungal Activity of Novel Indole Derivatives Containing 1,3,4-Thiadiazole

In this study, 24 indole derivatives containing 1,3,4-thiadiazole were discovered and synthesized. The target compounds' antifungal efficacy against 14 plant pathogenic fungal pathogens was then determined in vitro. With an EC50 value of 2.7 μg/mL, Z2 demonstrated the highest level of bioactivity among them against Botrytis cinerea (B.c.), exceeding the concentrations of the control prescription drugs azoxystrobin (Az) (EC50 = 14.5 μg/mL) and fluopyram (Fl) (EC50 = 10.1 μg/mL). Z2 underwent in vivo testing on blueberry leaves in order to evaluate its usefulness in real-world settings. A reasonable protective effect was obtained with a control effectiveness of 93.0% at 200 μg/mL, which was superior to those of Az (83.0%) and Fl (52.0%). At 200 μg/mL, this chemical had an efficacy of 84.0% in terms of curative efficacy. These figures outperformed those of Az (69.0%) and Fl (48.0%). Scanning electron microscopy (SEM) experiments and light microscopy experiments showed that Z2 altered the integrity of the cell wall and cell membrane of the pathogenic fungus B.c., which led to an increase in the content of malondialdehyde (MDA), cellular leakage, and cellular permeability. Enzyme activity assays and molecular docking studies indicated that Z2 could act as a potential succinate dehydrogenase inhibitor (SDHI). It was hypothesized that Z2 could cause disruption of mycelial cell membranes, which in turn leads to mycelial death. According to the research, indole derivatives containing 1,3,4-thiadiazole were expected to evolve into new fungicides due to their significant antifungal effects on plant fungi.

Novel Flavonol Derivatives Containing 1,3,4-Thiadiazole as Potential Antifungal Agents: Design, Synthesis, and Biological Evaluation

In order to discover novel compounds with excellent agricultural activities, novel flavonol derivatives containing 1,3,4-thiadiazole were synthesized and evaluated for their antifungal activities. The bioassay results showed that some of the target compounds had good antifungal activities against Botrytis cinerea, Phomopsis sp. and Sclerotinia sclerotiorum in vitro. It is worth noting that the half-effective concentration (EC50) value of Y18 against B. cinerea was 2.4 μg/mL, which was obviously superior to that of azoxystrobin (21.7 μg/mL). The curative activity of Y18 at 200 μg/mL (79.9%) was better than that of azoxystrobin (59.1%), and its protective activity (90.9%) was better than that of azoxystrobin (83.9%). Morphological studies by using scanning electron microscopy and fluorescence microscopy revealed that Y18 could affect the normal growth of B. cinerea mycelium. In addition, the mechanism of action studies indicated that Y18 could affect the integrity of cell membranes by inducing the production of endogenous reactive oxygen species and the release of the malondialdehyde content, leading to membrane lipid peroxidation and the release of cell contents. The inhibitory activity of flavonol derivatives containing 1,3,4-thiadiazole on plant fungi is notable, offering significant potential for the development of new antifungal agents.

Synthesis, antifungal activity and mechanism of action of novel chalcone derivatives containing 1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazole

A series of chalcone derivatives containing 1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazole was designed and synthesized. Structures of all compounds were characterized by 1H NMR, 13C NMR, 19F NMR, and HRMS. The biological activities of the compounds were determined with the mycelial growth rate method, and further studies showed that some compounds had good antifungal activities at the concentration of 100 μg/mL. The EC50 value of compound L31 was 15.9 μg/mL against Phomopsis sp., which were better than that of azoxystrobin (EC50 value was 69.4 μg/mL). In addition, the mechanism of action of compound L31 shown that compound can affect mycelial growth by disrupting membrane integrity against Phomopsis sp., and that the higher the concentration of the compound is, the greater the disruption of membrane integrity is.

Novel 5-Sulfonyl-1,3,4-thiadiazole-Substituted Flavonoids as Potential Bactericides and Fungicides: Design, Synthesis, Three-Dimensional Quantitative Structure-Activity Relationship Studies

Flavonoids, ubiquitous natural products, provide sources for drug discovery owing to their structural diversity, broad-spectrum pharmacological activity, and excellent environmental compatibility. To develop antibacterial and antifungal agents with novel mechanisms of action and innovative structures, a series of novel 5-sulfonyl-1,3,4-thiadiazole-substituted flavonoids were designed and synthesized, and their biological activities against seven agriculturally common phytopathogenic microorganisms were evaluated. The results of the antimicrobial bioassay showed that most of the target compounds displayed excellent inhibitory effects against Xanthomonas oryzae, Rhizoctonia solani, and Colletotrichum orbiculare. Compounds 1, 3, 7, 9, 13, and 14 exhibited remarkable antibacterial activity against X. oryzae pv. oryzae with EC50 values below 10 μg/mL, which were superior to bismerthiazol (70.89 μg/mL). Compound 2 (EC50 = 0.41 μg/mL) displayed the most effective inhibitory potency against R. solani in vivo, comparable protective effects with the positive control carbendizam. Preliminary mechanistic studies indicated that compound 2 induced disordered entanglement of hyphae, shrinkage of hyphal surfaces, extravasation of cellular contents, and vacuole swelling and rupture, which disrupted normal hyphal growth. Subsequently, compounds 35-53 with good antifungal activity were designed and synthesized based on reliable three-dimensional quantitative structure-activity relationship (3D-QSAR) models. Compound 49 showed high efficacy and superior antifungal activity against R. solani, with an EC50 value of 0.28 μg/mL and a half-maximal effective concentration of 0.46 μg/mL.

New N-(1,3,4-thiadiazole-2-yl)acetamide derivatives as human carbonic anhydrase I and II and acetylcholinesterase inhibitors

Various carbonic anhydrase (CA) enzyme isoforms are known today. In addition to the use of CA inhibitors as diuretics, antiepileptics and antiglaucoma agents, the inhibition of other specific isoforms of CA was reported to have clinical benefits in cancers. In this study, two groups of 1,3,4-thiadiazole derivatives were designed and synthesized to act as human CA I and II (hCA I and hCA II) inhibitors. The activities of these compounds were tested in vitro and evaluated in silico studies. The activity of the synthesized compounds was also tested against acetylcholinesterase (AChE) to evaluate the relation of the newly designed structures to the activity against AChE. The synthesized compounds were analyzed by 1H NMR,13C NMR and high-resolution mass spectroscopy (HRMS). The results displayed a better activity of all the synthesized compounds against hCA I than that of the commonly used standard drug, Acetazolamide (AAZ). The compounds also showed better activity against hCA II, except for compounds 5b and 6b. Only compounds 6a and 6c showed superior activity against AChE compared to the standard agent, tacrine (THA). In silico studies, including absorption, distribution, metabolism and excretion (ADME) and drug-likeness evaluation, molecular docking, molecular dynamic simulations (MDSs) and density functional theory (DFT) calculations, were compatible with the in vitro results and presented details regarding the structure-activity relationship.Communicated by Ramaswamy H. Sarma.

Synthesis, Bioactivities, and Antibacterial Mechanism of 5-(Thioether)-N-phenyl/benzyl-1,3,4-oxadiazole-2-carboxamide/amine Derivatives

1,3,4-Oxadiazole thioethers have shown exciting antibacterial activities; however, the current mechanism of action involving such substances against bacteria is limited to proteomics-mediated protein pathways and differentially expressed gene analysis. Herein, we report a series of novel 1,3,4-oxadiazole thioethers containing a carboxamide/amine moiety, most of which show good in vitro and in vivo bacteriostatic activities. Compounds A10 and A18 were screened through CoMFA models as optimums against Xanthomonas oryzae pv. oryzae (Xoo, EC50 values of 5.32 and 4.63 mg/L, respectively) and Xanthomonas oryzae pv. oryzicola (Xoc, EC50 values of 7.58 and 7.65 mg/L, respectively). Compound A10 was implemented in proteomic techniques and activity-based protein profiling (ABPP) analysis to elucidate the antibacterial mechanism and biochemical targets. The results indicate that A10 disrupts the growth and pathogenicity of Xoc by interfering with pathways associated with bacterial virulence, including the two-component regulation system, flagellar assembly, bacterial secretion system, quorum sensing, ABC transporters, and bacterial chemotaxis. Specifically, the translational regulator (CsrA) and the virulence regulator (Xoc3530) are two effective target proteins of A10. Knocking out the CsrA or Xoc3530 gene in Xoc results in a significant reduction in the motility and pathogenicity of the mutant strains. This study contributes available molecular entities, effective targets, and mechanism basis for the management of rice bacterial diseases.

Design, synthesis, and bioactivity studies of chalcone derivatives containing [1,2,4]-triazole-[4,3-a]-pyridine

In this study, 30 chalcone derivatives containing [1,2,4]-triazole-[4,3-a]-pyridine were designed and synthesized. The results of antibacterial activity showed that EC50 values of N26 against Xoo, Pcb was 36.41, 38.53 μg/mL, respectively, which were better than those of thiodiazole copper, whose EC50 values were 60.62, 106.75 μg/mL, respectively. The bacterial inhibitory activity of N26 against Xoo was verified by SEM. Antibacterial mechanism between N26 and Xoo was preliminarily explored, the experimental results showed that when the drug concentration was 100 mg/L, N26 had a good cell membrane permeability of Xoo, and it can inhibit the production of EPS content and extracellular enzyme content to disrupt the integrity of the Xoo biofilms achieving the effect of inhibiting Xoo. At 200 mg/L, N26 can protect and inhibit the lesions of post-harvested potatoes in vivo. The activities of N1-N30 against TMV were determined with half leaf dry spot method. The EC50 values of the curative and protective activity of N22 was 77.64 and 81.55 μg/mL, respectively, which were superior to those of NNM (294.27, 175.88 μg/mL, respectively). MST experiments demonstrated that N22 (Kd = 0.0076 ± 0.0007 μmol/L) had a stronger binding ability with TMV-CP, which was much higher than that of NNM (Kd = 0.7372 ± 0.2138 μmol/L). Molecular docking results showed that N22 had a significantly higher affinity with TMV-CP than NNM.

Synthesis, antibacterial and antifungal activity of myricetin derivatives containing piperidine and amide fragments

BACKGROUND

Continuous use of synthetic bactericides and fungicides is causing pathogens to develop resistance, resulting in increased use of pesticides and affecting food security. The green pesticides derived from natural products could reduce or avoid 'pesticide hazards' caused by synthetic pesticides as a result of their unique mechanism of action. Therefore, it is of great significance to create green pesticides with novel structures.

RESULTS

Herein, 30 novel myricetin derivatives containing piperidine and amide fragments were designed and synthesized using active group splicing. Among them, compound Z30 had excellent inhibitory effect against Xanthomonas oryzae pv. Oryzae (Xoo) with the half effective concentration (EC50 ) of 2.7 μg mL-1 . Compound Z26 not only exhibited better antibacterial activity against Xaxonopodis pv. Citri (Xac) with EC50 of 3.9 μg mL-1 , but also displayed higher antifungal activity against Rhizoctonia solani (Rs) with EC50 of 8.3 μg mL-1 . In vivo experiments proved that Z30 against bacterial blight of rice and Z26 against rice blast exhibits significant protective and curative effect. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that Z26 and Z30 could change the integrity of cell wall and membrane of pathogen Xoo, Xac and Rs, resulting in cytoplasmic leakage and eventually death. Enzymatic assay, molecular docking and molecular dynamics simulations (MDs) indicated that Z26 could be used as a potential succinate dehydrogenase inhibitor (SDHI).

CONCLUSION

Z26 and Z30 significantly reduced the pathogenicity of the pathogens, which provided a new idea and direction for the development of green pesticides. © 2023 Society of Chemical Industry.

Design, synthesis, and antimicrobial evaluation of 2-aminothiazole derivatives bearing the 4-aminoquinazoline moiety against plant pathogenic bacteria and fungi

BACKGROUND

To find more effective agricultural antibiotics, a class of new 2-aminothiazole derivatives containing the 4-aminoquinazoline moiety were synthesized and evaluated for their antimicrobial properties against phytopathogenic bacteria and fungi of agricultural importance.

RESULTS

All the target compounds were fully characterized by 1 H NMR, 13 C NMR, and high-resolution mass spectrometry. The bioassay results showed that compound F29 with a 2-pyridinyl substituent exhibited an outstanding antibacterial effect against Xanthomonas oryzae pv. oryzicola (Xoc) in vitro, having an half-maximal effective concentration (EC50 ) value as low as 2.0 μg/mL (over 30-fold more effective than the commercialized agrobactericide bismerthiazol, with an EC50 value of 64.3 μg/mL). In addition, compound F8 with a 2-fluorophenyl group demonstrated a good inhibitory activity toward the bacterium Xanthomonas axonopodis pv. citri (Xac), around twofold more active than bismerthiazol in terms of their EC50 values (22.8 versus 71.5 μg/mL). Interestingly, this compound also demonstrated a notable fungicidal effect against Phytophthora parasitica var. nicotianae, with an EC50 value largely comparable with that of the commercialized fungicide carbendazim. Finally, mechanistic studies revealed that compound F29 exerted its antibacterial effects by increasing the permeability of bacterial membranes, reducing the release of extracellular polysaccharides, and triggering morphological changes of bacterial cells.

CONCLUSION

Compound F29 has promising potential as a lead compound for developing more efficient bactericides to fight against Xoc. © 2023 Society of Chemical Industry.

Design, synthesis and antifungal evaluation of phenylthiazole-1,3,4-oxadiazole thione (ketone) derivatives inspired by natural thiasporine A

BACKGROUND

Plant pathogenic fungal infections have become a severe threat to the yield and quality of agricultural products, and new green antifungal agents with high efficiency and low toxicity are needed. In this study, a series of thiasporine A derivatives containing phenylthiazole-1,3,4-oxadiazole thione (ketone) structures were designed and synthesized, and their antifungal activities against six invasive and highly destructive phytopathogenic fungi were evaluated.

RESULTS

The results found that all compounds showed moderate to potent antifungal activity against six phytopathogenic fungi, and most of the E series compounds showed remarkable antifungal activity against Sclerotinia sclerotiorum and Colletotrichum camelliaet. In particular, compounds E1-E5, E7, E8, E13, E14, E17, and E22 showed more significant antifungal activity against S. sclerotiorum, with half-maximal effective concentration (EC50 ) values of 0.22, 0.48, 0.56, 0.65, 0.51, 0.39, 0.60, 0.56, 0.60, 0.63, and 0.45 μg mL-1 , respectively, which were superior to that of carbendazim (0.70 μg mL-1 ). Further activity studies showed that compound E1 possessed superior curative activities against S. sclerotiorum in vivo and better inhibitory effects on sclerotia germination and the formation of S. sclerotiorum compared with those of carbendazim.

CONCLUSIONS

This study indicates that these thiasporine A derivatives containing phenylthiazole-1,3,4-oxadiazole thione structures might be used as antifungal agents against S. sclerotiorum. © 2023 Society of Chemical Industry.

Design, synthesis, antibacterial activity, and mechanism of novel resveratrol derivatives containing an 1,3,4-oxadiazole moiety

Rice bacterial diseases seriously threaten the development of rice industry in the world, and chemical control is still one of the effective means to control it. To find novel antibacterial agents, 42 resveratrol derivatives were designed and synthesized based on natural product resveratrol as lead structure, and their antibacterial activities were evaluated. Most compounds have excellent antibacterial activities. Among them, the EC₅₀ values of compound B1 against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc) were 4.76 and 8.85 mg/L, respectively. The curative activities of compound B1 against bacterial leaf blight and bacterial leaf streak were 45.57 and 38.40%, and the protective activities were 49.41 and 35.93%, respectively. In addition, compound B1 could change bacterial cell surface morphology by inhibiting biofilm formation and exopolysaccharide production, and increasing membrane permeability, thereby affecting the normal growth of bacteria. Furthermore, transcriptome analysis showed that differential expressed genes were mainly enriched in plant-pathogen interaction pathway and MAPK signaling pathway-plant after compound B1 treated susceptible rice. We will further optimize the structure of compound B1 in future work to find more efficient antibacterial agents.

Design, synthesis and mechanism research of novel algicide based on bioactive fragments synthesis strategy

The frequency and intensity of harmful cyanobacterial blooms (HCBs) are increasing all over the world, their prevention and control have become a great challenge. In this paper, a series of 1,3,4-thiadiazole thioacetamides (T series) were designed and synthesized as potential algaecides. Among them, the compound T3 showed its best algacidal activity against Synechocystis sp. PCC 6803 (PCC 6803, EC₅₀ = 1.51 μM) and Microcystis aeruginosa FACHB 905 (FACHB905, EC₅₀ = 4.88 μM), which was more effective than the lead compound L1 (PCC6803, EC₅₀ = 7.7 μM; FACHB905, EC₅₀ = 8.8 μM) and the commercially available herbicide prometryn (PCC6803, EC₅₀ = 4.64 μM；FACHB905, EC₅₀ = 6.52 μM). Meanwhile, T3 showed a lower inhibitory activity (EC₅₀ = 12.76 μM) than prometryn (EC₅₀ = 7.98 μM) to Chlorella FACHB1227, indicating that T3 had selective inhibition to prokaryotic algae (PCC6803, FACHB905) and eukaryotic algae (FACHB1227). Furthermore, the algacidal and anti-algae activities of T3 were significantly better than those of prometryn, while the toxicity of zebrafish and human cells was less than prometryn. Electron microscope, physiological, biochemical and metabonomic analysis showed that T3 interfered with light absorption and light conversion during photosynthesis by significantly reducing chlorophyll content, thus inhibited metabolic pathways such as the Calvin cycle and TCA cycle, and eventually led to the cell rupture of cyanobacteria. These results afforded further development of effective and safe algaecides.

Design, synthesis, crystal structure, and antimicrobial activities of new quinazoline derivatives containing both the sulfonate ester and piperidinylamide moieties

BACKGROUND

To discover more efficient antimicrobial agents in agriculture, a series of new quinazoline derivatives bearing both sulfonate ester and piperidine-4-carboxamide moieties were synthesized and assessed for their antimicrobial effects.

RESULTS

All of the target compounds were fully characterized by proton (¹ H) nuclear magnetic resonance (NMR), carbon-13 (¹³ C) NMR, and high-resolution mass spectroscopy (HRMS), and compound III-6 containing a 3-bromophenyl substituent was clearly confirmed via single-crystal X-ray diffraction analysis. The bioassay results indicated that some compounds displayed noticeable inhibitory effects in vitro against Xanthomonas oryzae pv. oryzicola (Xoc). Further measurements of median effective concentration (EC₅₀ ) values showed that compound III-17 bearing a 4-methoxyphenyl group had the best anti-Xoc efficacy (EC₅₀  = 12.4 μg mL^-1 ), far better than the commercialized bismerthiazol (77.5 μg mL^-1 ). Moreover, this compound also demonstrated good protection and curative activities in vivo against rice bacterial leaf streak caused by Xoc.

CONCLUSION

Compound III-17 had a good potential for further development as a new bactericide for controlling Xoc. © 2023 Society of Chemical Industry.

Design, Synthesis, Antibacterial Evaluation, Three-Dimensional Quantitative Structure-Activity Relationship, and Mechanism of Novel Quinazolinone Derivatives

Plant bacterial illnesses are common and cause dramatic damage to agricultural goods all over the world, yet there are few efficient bactericides to alleviate them at present. To discover novel antibacterial agents, two series of quinazolinone derivatives with novel structures were synthesized and their bioactivity against plant bacteria was tested. Combining CoMFA model search and the antibacterial bioactivity assay, D32 was identified as a potent antibacterial inhibitor against Xanthomonas oryzae pv. Oryzae (Xoo), with an EC₅₀ value of 1.5 μg/mL, much better in inhibitory capacity compared to bismerthiazol (BT) and thiodiazole copper (TC) (31.9 and 74.2 μg/mL). The activities of compound D32 against rice bacterial leaf blight in vivo were 46.7% (protective activities) and 43.9% (curative activities), better than commercial drug thiodiazole copper (29.3% protective activities and 30.6% curative activities). Flow cytometry, proteomics, reactive oxygen species, and key defense enzymes were used to further investigate the relevant mechanisms of action of D32. The identification of D32 as an antibacterial inhibitor and revelation of its recognition mechanism not only open the possibility of developing new therapeutic strategies for treatment of Xoo but also provide clues for elucidation of the acting mechanism of quinazolinone derivative D32, which is a possible clinical candidate worth in-depth study.

Design, Synthesis and Bioactivity of Novel Pyrimidine Sulfonate Esters Containing Thioether Moiety

Pesticides play an important role in crop disease and pest control. However, their irrational use leads to the emergence of drug resistance. Therefore, it is necessary to search for new pesticide-lead compounds with new structures. We designed and synthesized 33 novel pyrimidine derivatives containing sulfonate groups and evaluated their antibacterial and insecticidal activities. Results: Most of the synthesized compounds showed good antibacterial activity against Xanthomonas oryzae pv. Oryzae (Xoo), Xanthomonas axonopodis pv. Citri (Xac), Pseudomonas syringae pv. actinidiae (Psa) and Ralstonia solanacearum (Rs), and certain insecticidal activity. A₅, A₃₁ and A₃₃ showed strong antibacterial activity against Xoo, with EC₅₀ values of 4.24, 6.77 and 9.35 μg/mL, respectively. Compounds A₁, A₃, A₅ and A₃₃ showed remarkable activity against Xac (EC₅₀ was 79.02, 82.28, 70.80 and 44.11 μg/mL, respectively). In addition, A₅ could significantly improve the defense enzyme (superoxide dismutase, peroxidase, phenylalanine ammonia-lyase and catalase) activity of plants against pathogens and thus improve the disease resistance of plants. Moreover, a few compounds also showed good insecticidal activity against Plutella xylostella and Myzus persicae. The results of this study provide insight into the development of new broad-spectrum pesticides.

Comprehensive Overview of β-Methoxyacrylate Derivatives as Cytochrome bc1 Inhibitors for Novel Pesticide Discovery

β-Methoxyacrylate derivatives represent a new class of pesticides, which have attracted increasing attention owing to their unique structure, broad biological activity, and unique mechanisms of action. They inhibit mitochondrial respiration via preventing electron transfer at the Qo site of the cytochrome bc₁ complex and thus are identified as cyt bc₁ inhibitors. A variety of β-methoxyacrylate derivatives have been reported by many research groups for discovery of novel pesticides with improved expected activities. This review focuses on development of β-methoxyacrylate derivatives with great significance as pesticides such as fungicides, acaricides, insecticides, herbicides, and antiviral agents. In addition, the structure-activity relationships (SARs) of β-methoxyacrylate derivatives are summarized. Moreover, the cause of resistance to β-methoxyacrylate fungicides and some solutions are also introduced. Finally, the development trend of β-methoxyacrylate derivatives as pesticides is explored. We hope the review will give a guide to develop novel β-methoxyacrylate pesticides in the future.

Synthesis and Antibacterial Activities of 2-Oxo-N-phenylacetamide Derivatives Containing a Dissulfone Moiety Target on Clp

Rice bacterial blight and rice bacterial streak are two serious rice diseases and have caused great harm to the production of rice all over the world. To develop an efficient antibacterial agent with a novel target, a series of novel 2-oxo-N-phenylacetamide derivatives containing a dissulfone moiety were synthesized, and their antibacterial activities were evaluated. Among them, compound D₁₄ exhibited the best antibacterial activities, especially against Xoo and Xoc with EC₅₀ values of 0.63 and 0.79 mg/L, respectively, which were much better than the commercial control of bismerthiazol (BT) (76.59 and 83.35 mg/L, respectively) and thiodiazole copper (TC) (91.72 and 114.00 mg/L, respectively). Meanwhile, compound D₁₄ can interact with a CRP-like protein (Clp) of Pxo99^A and show strong binding activity with Xoo-Clp with a K_d value of 0.52 μM, which was far superior to the corresponding K_d values of BT (183.94 μM) and TC (222.58 μM). Treatment of D₁₄ and deletion of the clp gene could significantly reduce the expression of the clp gene and attenuate the virulence of pathogenic bacteria. These results indicated that compound D₁₄ could be used as a potential novel agricultural bactericide and Clp can be used as a target protein for the control of plant bacterial diseases. This work provided reliable support for developing novel antibacterial agents based on Clp as a target protein.

Discovery of novel rost-4-ene derivatives as potential plant activators for preventing phytopathogenic bacterial infection: Design, synthesis and biological studies

BACKGROUND

Gradually aggravated disease caused by phytopathogenic bacteria severely restricts food security and crop yield, and few pesticides can relieve this severe situation. Thus, development and excavation of new agrochemicals with high bioactivity and novel action mechanism may be a feasible strategy to control intractable bacterial diseases. As a privileged molecular framework, steroid molecules exhibit diversiform bioactivities. Herein, a series of novel androst-4-ene derivatives were designed, synthesised and investigated for their antibacterial behaviour to excavate novel agrochemicals on the base of steroid molecules.

RESULTS

Bioassay results indicated that target compounds displayed high bioactivities toward three destructive phytopathogenic bacteria, including Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas axonopodis pv. citri (Xac) and Pseudomonas syringae pv. actinidiae (Psa). Compound III₁₉ displayed excellent in vitro antibacterial profiling (EC₅₀  = 2.37 mg L^-1 towards Xoo, EC₅₀  = 2.10 mg L^-1 towards Xac, EC₅₀  = 9.50 mg L^-1 towards Psa). Furthermore, compound III₁₉ showed outstanding in vivo protective activities, with values of 81.81% and 58.75% towards kiwifruit bacterial canker and rice bacterial leaf blight, respectively. Analysis of the antibacterial mechanism disclosed that compound III₁₉ enhanced host defence enzyme activities superoxide dismutase (SOD), peroxidase (POD), phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and catalase (CAT) and increased the salicylate synthase content to induce host resistance. In addition, compound III₁₉ increased the membrane permeability, destroyed the cell membrane and killed the bacteria.

CONCLUSION

Given these profiles of target compounds, we highlight a new strategy for controlling intractable plant bacterial diseases by inducing plant resistance and targeting the bacterial cell membrane. © 2022 Society of Chemical Industry.

Design, synthesis, antiviral activity, and mechanisms of novel ferulic acid derivatives containing amide moiety

To explore the novel compounds with high antiviral activity, three series ferulic acid derivatives containing amide moiety were gradually designed and synthesized based on antiviral activity tracking. The bioassay results exhibited that some target compounds had notable antiviral activities against tomato spotted wilt virus (TSWV) and cucumber mosaic virus (CMV). Compounds Y1, Y2, Y8, Z1 and Z2 presented splendid curative, protective, and inactivating activities to TSWV and CMV at 500 μg/mL. Especially, these compounds displayed outstanding inactivating effects on TSWV with the EC₅₀ values of 225.9, 126.1, 224.6, 216.1, and 147.3 μg/mL, which were superior to ningnanmycin (249.1 μg/mL) and ribavirin (315.7 μg/mL). Furthermore, the antiviral mechanisms of compound Y2 were investigated by conducting microscale thermophoresis experiment and molecular docking experiment. The results suggested that compound Y2 performed excellent binding affinity to TSWV coat protein (TSWV CP) with the binding constant of 2.14 μM, which due to two strong hydrogen bonds of compound Y2 to the key amino acids ARG94 of TSWV CP. Therefore, compound Y2 can be regarded as a leading structure for development of the potential antiviral agent.

Novel Pyrimidine Derivatives Bearing a 1,3,4-Thiadiazole Skeleton: Design, Synthesis, and Antifungal Activity

In this study, twenty novel pyrimidine derivatives bearing a 1,3,4-thiadiazole skeleton were designed and synthesized. Then their antifungal activity against Botrytis cinereal (B. cinereal), Botryosphaeria dothidea (B. dothidea), and Phomopsis sp. were determined using the poison plate technique. Biological test results showed that compound 6h revealed lower EC₅₀ values (25.9 and 50.8 μg/ml) on Phompsis sp. than those of pyrimethanil (32.1 and 62.8 μg/ml).

Discovery of Novel Dihydrolipoamide S-Succinyltransferase Inhibitors Based on Fragment Virtual Screening

A series of new oxadiazole sulfone derivatives containing an amide moiety was synthesized based on fragment virtual screening to screen high-efficiency antibacterial agents for rice bacterial diseases. All target compounds showed greater bactericidal activity than commercial bactericides. 3-(4-fluorophenyl)-N-((5-(methylsulfonyl)-1,3,4-oxadiazol-2-yl)methyl)acrylamide (10) showed excellent antibacterial activity against Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola, with EC₅₀ values of 0.36 and 0.53 mg/L, respectively, which were superior to thiodiazole copper (113.38 and 131.54 mg/L) and bismerthiazol (83.07 and 105.90 mg/L). The protective activity of compound 10 against rice bacterial leaf blight and rice bacterial leaf streak was 43.2% and 53.6%, respectively, which was superior to that of JHXJZ (34.1% and 26.4%) and thiodiazole copper (33.0% and 30.2%). The curative activity of compound 10 against rice bacterial leaf blight and rice bacterial leaf streak was 44.5% and 51.7%, respectively, which was superior to that of JHXJZ (32.6% and 24.4%) and thiodiazole copper (27.1% and 28.6%). Moreover, compound 10 might inhibit the growth of Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola by affecting the extracellular polysaccharides, destroying cell membranes, and inhibiting the enzyme activity of dihydrolipoamide S-succinyltransferase.