Antimicrobial evaluation and action mechanism of pyridinium-decorated 1,4-pentadien-3-one derivatives

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.

Investigation of the antibacterial mechanism of the novel bactericide dioctyldiethylenetriamine (Xinjunan)

BACKGROUND

Chemical control is an important method for tackling crop diseases. Clarifying the antibacterial mechanisms of bactericides is useful for developing new bactericides and for continuous plant disease control. In this study, the antibacterial mechanism of a novel bactericide, dioctyldiethylenetriamine (Xinjunan), which affects adenosine triphosphate (ATP) synthesis, was investigated.

RESULTS

The results of an in vitro inhibition activity assay showed that dioctyldiethylenetriamine inhibited the growth of a variety of plant pathogenic bacteria, especially that of Xanthomonas spp. Scanning electron microscopy demonstrated that dioctyldiethylenetriamine caused cell distortion and rupture. To investigate the molecular mechanism underlying the antibacterial effect of dioctyldiethylenetriamine, transcriptome sequencing (RNA-seq) was performed for Xanthomonas oryzae pv. oryzae (Xoo, PXO99A) treated with dioctyldiethylenetriamine, which has strong antibacterial effects against xanthomonads. The results showed that differentially expressed genes were enriched mainly in the oxidative phosphorylation and tricarboxylic acid (TCA) cycle pathways after treatment. Moreover, the dioctyldiethylenetriamine treatment exhibited reduction in enzyme activities in the TCA cycle, decreased intracellular nicotinamide adenine dinucleotide and ATP contents, and increased accumulation of reactive oxygen species. In addition, dioctyldiethylenetriamine exhibited an inhibitory effect on the growth of other bacterial pathogens by reducing ATP synthesis.

CONCLUSION

This is the first report of the mechanism by which dioctyldiethylenetriamine inhibits ATP synthesis by affecting oxidative phosphorylation and TCA cycle pathways in bacteria. © 2023 Society of Chemical Industry.

Novel cinnamic acid derivatives as a versatile tool for developing agrochemicals for controlling plant virus and bacterial diseases by enhancing plant defense responses

BACKGROUND

Plant pathogens have led to large yield and quality losses in crops worldwide. The discovery and study of novel agrochemical alternatives based on the chemical modification of bioactive natural products is a highly efficient approach. Here, two series of novel cinnamic acid derivatives incorporating diverse building blocks with alternative linking patterns were designed and synthesized to identify their antiviral capacity and antibacterial activity.

RESULTS

The bioassay results demonstrated that most cinnamic acid derivatives had excellent antiviral competence toward tobacco mosaic virus (TMV) in vivo, especially compound A₅ (median effective concentration [EC₅₀ ] = 287.7 μg mL^-1 ), which had a notable protective effect against TMV when compared with the commercial virucide ribavirin (EC₅₀  = 622.0 μg mL^-1 ). In addition, compound A₁₇ had a protective efficiency of 84.3% at 200 μg mL^-1 against Xac in plants. Given these outstanding results, the engineered title compounds could be regarded as promising leads for controlling plant virus and bacterial diseases. Preliminary mechanistic studies suggest that compound A₅ could enhance the host's defense responses by increasing the activity of defense enzymes and upregulating defense genes, thereby suppressing phytopathogen invasion.

CONCLUSION

This research lays a foundation for the practical application of cinnamic acid derivatives containing diverse building blocks with alternative linking patterns in pesticide exploration. © 2023 Society of Chemical Industry.

Ethylicin Inhibition of Xanthomonas oryzae pv. oryzicola In Vitro and In Vivo

Infestation of rice with the bacterium Xanthomonas oryzae pv. oryzicola (Xoc) causes the serious disease bacterial leaf streak (BLS). We studied the effect of ethylicin, a broad-spectrum bactericide, on Xoc both in vivo and in vitro. Ethylicin increases the defensive enzyme activities and defensive genes expression of rice. Ethylicin also significantly inhibited Xoc activity in vitro compared with other commercial bactericides. The half-maximal effective concentration (EC₅₀) of ethylicin was 2.12 μg/mL. It has been shown that ethylicin can inhibit Xoc quorum sensing through the production of extracellular polysaccharides and enzymes, which disrupt the Xoc cell membrane. We used proteomic analysis to identify two oxidative phosphorylation pathway proteins (ACU12_RS13405 and ACU12_RS13355) which affected the virulence of Xoc and validated them using quantitative real-time polymerase chain reaction (qRT-PCR). The results indicate that ethylicin can increase the defense responses of rice and control Xoc proliferation.

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.

Discovery of Novel Benzo[4,5]thiazolo(oxazolo)[3,2-a]pyrimidinone Mesoionic Derivatives as Potential Antibacterial Agents and Mechanism Research

A series of benzo[4,5]thiazole(oxazole)[3,2-a]pyrimidine mesoionic compounds were designed and synthesized. Antibacterial activity tests revealed that compound A23 showed good in vitro activities against Xanthomonas oryzae pv. Oryzicola (Xoc) and Xanthomonas oryzae pv. oryzae (Xoo), with half-maximal effective concentration (EC₅₀) values of 47.6 and 36.8 μM, respectively, which were better than positive control agents thiodiazole copper (281 and 259 μM) and bismerthiazol (245 and 220 μM). The protective activities of compound A23 anti-Xoc and anti-Xoo were 39.7% and 49.2%, respectively, which were better than those of bismerthiazol (31.5% and 40.7%). Compound A23 improved defensive enzyme activities in rice. In addition, compound A23 could upregulate the expression of succinate dehydrogenase (SDH) in the oxidative phosphorylation (OXPHOS) pathway through proteomics analysis, which was consistent with the result of the SDH activity test. Thus, compound A23 is a novel potential antibacterial agent that can be further developed.

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.

Synthesis, antibacterial activity and mechanism of new butenolides derivatives containing an amide moiety

A series of novel butenolide derivatives containing an amide were designed and synthesized with flupyradifurone as the lead compound. The biological activities test found that this series of compounds did not exhibit insecticidal activity, but had good antibacterial activities. Among all target compounds, compound 19 showed good antibacterial activity in vitro against Xanthomonas oryzae pv. oryzae (Xoo), with an EC₅₀ value of 35.8 mg/L, which was superior to that of bismerthiazol (73.5 mg/L). Under greenhouse conditions, the curative and protective activities of compound 19 against bacterial leaf blight were 40.9% and 48.9% at 100 mg/L, respectively, which were superior to those of bismerthiazol (31.2% and 31.4%). In addition, compound 19 can not only cause changes in the cell surface morphology of Xoo, but also increase the activity of rice defense enzymes. The mechanism of action studies showed that the protective activity of compound 19 against rice bacterial leaf blight is closely related to the improvement of defense-related enzyme activities and the upregulation of proteins involved in oxidative phosphorylation.

Synthesis of osthol-based botanical fungicides and their antifungal application in crop protection

Plant pathogenic fungi decrease the quality and productivity of plant production. The botanical fungicides have better biocompatibility and rapid biodegradation, little or no cross resistance, and the structural diversity, and thus are beneficial to deal with plant fungal diseases. Osthole has been widely used as the commercial botanical fungicide against powdery mildew in China. In this article, a series of osthole derivatives were synthesized, which respectively contain different substituents on the benzene ring, at the C8-position and pyrone ring. All the target compounds were evaluated in vitro for their antifungal activity against resistant phytopathogenic fungi. Colletotrichum fragariae, Strawberry Botrytis Cinerea, Kiwifruit Botrytis Cinerea, Kiwifruit brown Rots, which are common in fruit fungal diseases. The compound C₄ was identified as the most promising candidate with the EC₅₀ values at 38.7 µg/mL against Colletotrichum Fragariae, 14.5 µg/mL against Strawberry Botrytis Cinerea and 24.3 µg/mL against Kiwifruit Botrytis Cinerea, respectively, whereas the antifungal activity against resistant phytopathogenic fungi. of osthole is too low to be used (EC₅₀ > 400 ppm). The results of mycelial relative conductivity determination, PI uptake and fluorescence spectroscopy indicated that the cell membrane of fungi is the key action site of C₄. Besides, C₄ has the potent inhibitory activity against both of plant and human pathogenic bacteria. Our studies showed that C₄ was worthy for further attention as a promising botanical fungicide candidate in crop protection.

Novel penta-1,4-diene-3-one derivatives containing quinazoline and oxime ether fragments: Design, synthesis and bioactivity

A series of novel penta-1,4-diene-3-one derivatives containing quinazoline and oxime ether moieties were designed and synthesized. Their anticancer activities were evaluated by MTT assay, the results showed that most compounds exhibited extremely inhibitory effects against hepatoma SMMC-7721 cells. In particular, compounds Q2 and Q8 displayed the more potent inhibitory activity with IC₅₀ values of 0.64 and 0.63 μM, which were better than that of gemcitabine (1.40 μM). Further mechanism studies indicated that compounds Q2, Q8, Q13 and Q19 could control the migration of SMMC-7721 cells effectively, and inhibit the proliferation of cancer cells by inhibiting the DNA replication. Western-blot results showed that compounds Q2 and Q8 induced irreversible apoptosis of SMMC-7721 cells by regulating the expression level of apoptose-related proteins. Those studies demonstrated that the penta-1,4-diene-3-one derivatives containing quinazoline and oxime ether fragments merited further research as potential anticancer agents.

Antibacterial activity of a new monocarbonyl analog of curcumin MAC 4 is associated with divisome disruption

Curcumin (CUR) is a symmetrical dicarbonyl compound with antibacterial activity. On the other hand, pharmacokinetic and chemical stability limitations hinder its therapeutic application. Monocarbonyl analogs of curcumin (MACs) have been shown to overcome these barriers. We synthesized and investigated the antibacterial activity of a series of unsymmetrical MACs derived from acetone against Mycobacterium tuberculosis and Gram-negative and Gram-positive species. Phenolic MACs 4, 6 and 8 showed a broad spectrum and potent activity, mainly against M. tuberculosis, Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus (MRSA), with MIC (minimum inhibitory concentration) values ranging from 0.9 to 15.6 µg/mL. The investigation regarding toxicity on human lung cells (MRC-5 and A549 lines) revealed MAC 4 was more selective than MACs 6 and 8, with SI (selectivity index) values ranging from 5.4 to 15.6. In addition, MAC 4 did not demonstrate genotoxic effects on A549 cells and it was more stable than CUR in phosphate buffer (pH 7.4) for 24 h at 37 °C. Fluorescence and phase contrast microscopies indicated that MAC 4 has the ability to disrupt the divisome of Bacillus subtilis without damaging its cytoplasmic membrane. However, biochemical investigations demonstrated that MAC 4 did not affect the GTPase activity of B. subtilis FtsZ, which is the main constituent of the bacterial divisome. These results corroborated that MAC 4 is a promising antitubercular and antibacterial agent.

Anti-biofouling microfiltration membranes based on 1-vinyl-3-butylimidazolium chloride grafted PVDF with improved bactericidal properties and vitro biocompatibility

Polyvinylidene fluoride (PVDF) porous membranes have been widely used as the filtration and separation industry. Herein, novel microfiltration membranes based on 1-vinyl-3-butylimidazolium chloride ([VBIm][Cl]) grafted PVDF (PVDF-g-[VBIm][Cl]) were prepared via the non-solvent induced phase separation method. The chemical composition and microstructure of PVDF-g-[VBIm][Cl] membranes were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Scanning electron microscopy and Water contact angle measurements. The results showed that an increasing in [VBIm][Cl] grafting content leads to the increasing hydrophilicity and wetting capacity of the PVDF-g-[VBIm][Cl] porous membranes. The anti-biofouling properties of membranes were evaluated by measuring the water flux before and after Bovine serum albumin solution treatment. It was found that the modified membranes presented a good anti-biofouling property. The degree of irreversible flux loss caused by protein adsorption dramatically reduced from 42.1% to 2.9% compared with the pristine hydrophobic PVDF membranes. Meanwhile, these PVDF-g-[VBIm][Cl] membranes also exhibited excellent bactericidal properties against both gram-positive bacteria Staphylococcus saureus and gram-negative bacteria Escherichia coli, while PVDF membranes did not show any antibacterial activity. The vitro biocompatibility of the modified membranes was studied by hemolysis analysis, the platelet adhesion observation, thromboelastography assay and cytotoxicity assay. It was found that the incorporation of [VBIm][Cl] into PVDF membranes has less effect on the hemolysis and cytotoxicity of PVDF membranes. Furthermore, both hydrophilicity and charges of the membrane surface played important role in the adhesion and activation of platelet cells, which consequently affected the clotting process of whole blood. The membrane with appropriate [VBIm][Cl] grafting ratio (2.94 wt.%) exhibited good hemocompatibility with less blood coagulation effect. As an ultrafiltration membrane, PVDF-g-[VBIm][Cl] membranes have potential applications in the biomedical field due to the improved antibacterial property and biocompatibility.

Design and synthesis of novel 1,3,4-oxadiazole sulfone compounds containing 3,4-dichloroisothiazolylamide moiety and evaluation of rice bacterial activity

In this study, thirty 1,3,4-oxadiazole sulfone derivatives containing 3,4-dichloroisothiazolamide moiety were designed and synthesized, and their antibacterial activities were evaluated. Bioassay results showed that some compounds exhibited excellent antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc) in vitro and in vivo. Notably, the EC₅₀ values of compounds 2 and 3 against Xoo were 0.79 and 0.85 μg/mL, respectively, which were superior to those of the control agents isotianil, bismerthiazol, and thiodiazole copper. In addition, in vivo antibacterial activities revealed that the compound 2 at 50 μg/mL possessed protective and curative activities of 43.99% and 41.06% against Xoo, respectively, which were better than positive controls. Furthermore, the preliminary mechanism study disclosed that compound 2 exhibited effective antibacterial activity against Xoo by inhibiting the formation of extracellular polysaccharides from Xoo, increasing cell permeability, and changing the shape of cells. This study suggested that 1,3,4-oxadiazole sulfone derivatives containing 3,4-dichloroisothiazolamide moiety displayed excellent antibacterial activity and could be further explored and developed as commercial pesticides.

First report about the screening, characterization, and fosmid library construction of Xanthomonas oryzae pv. oryzae strain with resistance to Fubianezuofeng

Bacterial blight (BB), which is caused by Xanthomonas oryzae pv. oryzae (Xoo), is a common bacterial disease that seriously harms rice production in major rice-growing areas worldwide. Fubianezuofeng (FBEZF), a sulfone bactericide that contains an oxadiazole moiety, exerts good control effect on BB. In this study, FBEZF-resistant strains of Xoo were screened for the first time in the laboratory to evaluate the risk of Xoo developing resistance to FBEZF. Three strains with moderate resistance to FBEZF, were obtained and named as F1, F2, and F3, which have resistance factors (RF) of 14.69, 15.72, and 11.12, respectively. FBEZF lacked positive cross-resistance to bismerthiazol, thiodiazole copper, zhongshengmycin and phenazino-1-carboxylic acid. The growth rates of the resistant strains F1 and F2 were similar to those of the wild-type strain in nutrient broth medium, but differed in nutrient agar medium. The extracellular polysaccharide production and pathogenicity of F1, F2, and F3 were reduced relative to those of the wild-type strain. A fosmid library containing 2304 transformants was constructed based on the genome of F2, and transformants 2193 and 2202 exhibited FBEZF resistance. The results are helpful for further study on the molecular mechanism of resistance to FBEZF in Xoo.

Novel sulfone derivatives containing a 1,3,4-oxadiazole moiety: design and synthesis based on the 3D-QSAR model as potential antibacterial agent

BACKGROUND

The rice bacterial leaf blight (BLB) is one of the most serious bacterial diseases caused by Xanthomonas oryzae pv. oryzae (Xoo), which can cause yield loss of rice up to 50%. The three-dimensional quantitative structure-activity relationship (3D-QSAR) is an important auxiliary method to find potential high-efficient pesticides active structures.

RESULTS

A series of novel 1,3,4-oxadiazole compounds were designed and synthesized based on the 3D-QSAR model, and their antibacterial activities in vitro against Xoo were evaluated. The results indicated that all the target compounds showed excellent in vitro antibacterial activities. For example, the compounds 6, 12, 13, 20, 21, and 23 exhibited excellent antibacterial activities against Xoo, with half-maximal effective concentration (EC₅₀ ) values of 0.24, 0.31, 0.36, 0.29, 0.19, and 0.31 mg/L, respectively, which were superior to the antibacterial agents thiodiazole copper (127.44 mg/L) and bismerthiazol (91.08 mg/L). Meanwhile, compound 21 showed good antibacterial activity in vivo against BLB, with curative and protective activities of 46.7% and 56.4%, respectively, which were superior to thiodiazole copper (28.5% and 32.5%) and bismerthiazol (37.6% and 38.4%). Compound 21 can significantly reduce the extracellular polysaccharides production of Xoo, increase the permeability of the cell membranes, and also can cause cell surface wrinkles, deformation and dryness.

CONCLUSION

The 3D-QSAR model can be used to find sulfone compounds containing a 1,3,4-oxadiazole moiety with higher antibacterial activity, and compound 21 can be used as a potential antibacterial agent in the future. © 2020 Society of Chemical Industry.

Discovery of 1,4-pentadien-3-one derivatives containing quinoxaline scaffolds as potential apoptosis inducers

Aim: To synthesize novel antiproliferative agents. Results & methodology: A variety of 1,4-pentadien-3-one derivatives bearing quinoxaline scaffolds was designed and synthesized and their antiproliferative activities were evaluated. Notably, compounds N3 and N4 exhibited markedly greater antiproliferative activities against SMMC-7721 cells in vitro compared with the well-known antitumor drug gemcitabine. The mechanistic investigation showed that compounds N3 and N4 induced SMMC-7721 cell apoptosis by regulating the expression levels of apoptosis-related proteins. In addition, the molecular docking model further revealed that compound N3 could be a potential peroxisome proliferator-activated receptor inhibitor. Conclusion: These compounds might serve as bioactive fragments and lead compounds for developing more potent apoptosis inducers.

Design, synthesis, and antimicrobial behavior of novel oxadiazoles containing various N-containing heterocyclic pendants

BACKGROUND

The gradually elevated outbreak of plant bacterial diseases severely limits agricultural products and small amounts of pesticides can manage them. Our group has previously synthesized and screened the antimicrobial activity of diverse 1,3,4-oxadiazole thioether/sulfone compounds bridged by a sulfur atom at the 2-position of 1,3,4-oxadiazole. However, few studies have evaluated the effect of eliminating the sulfur atom on bioactivity. Herein, a novel type of N-containing heterocyclic pendants-tagged 1,3,4-oxadiazoles bridged by alkyl chains only was systematically synthesized and evaluated for their antimicrobial activities.

RESULTS

Bioassay results revealed that antibacterial efficacy increased by 551- and 314-fold against the corresponding phytopathogens Xanthomonas oryzae pv. oryzae and X. axonopodis pv. citri compared to commercial agents bismerthiazol and thiodiazole copper. In vivo trials showed that C ₁ exerted remarkable curative activity against rice bacterial blight with a control effectiveness of 52.9% at 200 μg mL^-1 . Antibacterial mechanism research found that C ₁ could reduce the hypersensitive response behavior and pathogenicity of Xoo through targeting the type III secretion system (T3SS) at a lower drug dose. This outcome was verified by observing the significantly down-regulated proteins and representative genes from the related quantitative proteomics and qRT-PCR assays.

CONCLUSION

This study can inspire the design of innovative molecular frameworks targeting the T3SS of phytopathogens for controlling bacterial infections. © 2020 Society of Chemical Industry.

Discovery of novel bis-sulfoxide derivatives bearing acylhydrazone and benzothiazole moieties as potential antibacterial agents

On the basis of the active substructure combination principle, 24 novel synthesis of novel bis-sulfoxide derivatives bearing acylhydrazone and benzothiazole moieties as potential antibacterial agents were designed and synthesized. The bioactivity assay results showed that many compounds had significant in vitro inhibitory effects against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas citri pv. citri (Xac). Notably, compound 4b had the best in vitro antibacterial activity against Xoo at an half-maximal effective concentration value of 11.4 μg/mL, which was superior to those of thiodiazole copper (TDC) and bismerthiazol (BMT). Compared with TDC and BMT, compound 4b was more effective in vivo controlling rice bacterial leaf blight with curative and protection activities of 42.5% and 40.3%, respectively. In addition, compound 4b can influence biofilm formation, inhibit extracellular polysaccharide production, and ultimately reduce the pathogenicity of Xoo. All the results indicated that bis-sulfoxide derivatives bearing acylhydrazone and benzothiazole moieties can be used for the development of small-molecule pesticides with high antibacterial activity.

Synthesis and Antibacterial Evaluation of N-phenylacetamide Derivatives Containing 4-arylthiazole Moieties

A series of new N-phenylacetamide derivatives containing 4-arylthiazole moieties was designed and synthesized by introducing the thiazole moiety into the amide scaffold. The structures of the target compounds were confirmed by ¹H-NMR, ¹³C-NMR and HRMS. Their in vitro antibacterial activities were evaluated against three kinds of bacteria-Xanthomonas oryzae pv. Oryzae (Xoo), Xanthomonas axonopodis pv. Citri (Xac) and X.oryzae pv. oryzicola (Xoc)-showing promising results. The minimum 50% effective concentration (EC₅₀) value of N-(4-((4-(4-fluoro-phenyl)thiazol-2-yl)amino)phenyl)acetamide (A₁) is 156.7 µM, which is superior to bismerthiazol (230.5 µM) and thiodiazole copper (545.2 µM). A scanning electron microscopy (SEM) investigation has confirmed that compound A₁ could cause cell membrane rupture of Xoo. In addition, the nematicidal activity of the compounds against Meloidogyne incognita (M. incognita) was also tested, and compound A₂₃ displayed excellent nematicidal activity, with mortality of 100% and 53.2% at 500 μg/mL and 100 μg/mL after 24 h of treatment, respectively. The preliminary structure-activity relationship (SAR) studies of these compounds are also briefly described. These results demonstrated that phenylacetamide derivatives may be considered as potential leads in the design of antibacterial agents.

Synthesis of Thiazolium-Labeled 1,3,4-Oxadiazole Thioethers as Prospective Antimicrobials: In Vitro and in Vivo Bioactivity and Mechanism of Action

In this study, a type of thiazolium-labeled 1,3,4-oxadiazole thioether bridged by diverse alkyl chain lengths was constructed. The antimicrobial activity of the fabricated thioether toward plant pathogenic bacteria and fungi was then screened. Antibacterial evaluation indicated that title compounds possess specific characteristics that enable them to severely attack three phytopathogens, namely, Xanthomonas oryzae pv. oryzae, Ralstonia solanacearum, and Xanthomonas axonopodis pv. citri with minimal EC₅₀ values of 0.10, 3.27, and 3.50 μg/mL, respectively. Three-dimensional quantitative structure-activity relationship models were established to direct the following excogitation for exploring higher active drugs. The in vivo study against plant bacterial diseases further identified the prospective application of title compounds as alternative antibacterial agents. The proteomic technique, scanning electron microscopy patterns, and fluorescence spectrometry were exploited to investigate the antibacterial mechanism. Additionally, some target compounds performed superior inhibitory actions against three tested fungal strains. In view of their simple molecular architecture and highly efficient bioactivity, these substrates could be further explored as promising surrogates for fighting against plant microbial infections.

Synthesis and bioactivity evaluation of penta-1,4-diene-3-one oxime ether derivatives

A series of penta-1,4-diene-3-one oxime ether derivatives were synthesized, and their antiviral and antifungal activities were evaluated. Bioactivity evaluations showed that most target compounds had significant antiviral effects against tobacco mosaic virus (TMV). Among them, (1E,3Z,4E)-1-(4-(benzyloxy)phenyl)-5-(furan-2-yl)penta-1,4-dien-3-one O-(3-fluorobenzyl) oxime (5e) was found to have good curative activity against TMV, with an inhibition rate of 64.6%, which was better than that of ribavirin (45.2%). (1E,3Z,4E)-1-(4-(benzyloxy) phenyl)-5-(furan-2-yl)penta-1,4-dien-3-one O-((6-chloropyridin-3-yl)methyl) oxime (5d) had a remarkable protective effect against TMV, with an inhibitory rate of 66.9%, which was better than that of ribavirin (61.8%). The inhibitory rate of (1E,3Z,4E)-1-(2-(benzyloxy)phenyl)-5-(furan-2-yl)penta-1,4-dien-3-one O-(4-chlorobenzyl) oxime(5m) in inactivation activity against TMV was 87.0%, which was better than that of ribavirin (77.9%). Further molecular docking studies indicated that compound 5m shows strong binding affinities toward the coat protein of tobacco mosaic virus. This result indicates that penta-1,4-diene-3-one oxime ether derivatives can play a significant role in discovering new antiviral agents.

Fabrication of Furan-Functionalized Quinazoline Hybrids: Their Antibacterial Evaluation, Quantitative Proteomics, and Induced Phytopathogen Morphological Variation Studies

The limited number of agrochemicals targeting plant bacterial diseases has driven us to develop highly efficient, low-cost, and versatile antibacterial alternatives. Herein, a novel type of simple furan-functionalized quinazolin-4-amines was systematically fabricated and screened for their antibacterial activity. Bioassay results revealed that compounds C₁ and E₄ could substantially block the growth of two frequently mentioned pathogens Xanthomonas oryzae pv oryzae and X. axonopodis pv citri in vitro, displaying appreciable EC₅₀ values of 7.13 and 10.3 mg/L, respectively. This effect was prominently improved by comparing those of mainly used agrochemicals. An in vivo experiment against bacterial blight further illustrated their viable applications as antimicrobial ingredients. Quantitative proteomics demonstrated that C₁ possessed a remarkable ability to manipulate the upregulation and downregulation of expressed proteins, which probably involved d-glucose and biotin metabolic pathways. This finding was substantially verified by parallel reaction monitoring analysis. Scanning electron microscopy images and fluorescence spectra also indicated that the designed compounds had versatile capacities for destroying the integrity of bacteria. Given these remarkable characteristics, furan-functionalized quinazoline hybrids can serve as a viable platform for developing innovative antibiotic alternatives against bacterial infections.

Identification of Racemic and Chiral Carbazole Derivatives Containing an Isopropanolamine Linker as Prospective Surrogates against Plant Pathogenic Bacteria: In Vitro and In Vivo Assays and Quantitative Proteomics

Recent observations on the emergence of drug-resistant plant pathogenic bacteria have highlighted and elicited an acute campaign to develop novel, highly efficient antibiotic surrogates for managing bacterial diseases in agriculture. Thus, a type of racemic and chiral carbazole derivative containing an isopropanolamine pattern was systematically synthesized to discover low-cost and efficient antibacterial candidates. Screening results showed that compounds 2f, 6c, and 2j could significantly suppress the growth of tested plant pathogens, namely Xanthomonas oryzae pv oryzae, X. axonopodis pv citri, and Pseudomonas syringae pv actinidiae, and provided the corresponding EC₅₀ values of 1.27, 0.993, and 0.603 μg/mL, which were significantly better than those of existing commercial drugs. In vivo studies confirmed their prospective applications for controlling plant bacterial diseases. Label-free quantitative proteomics analysis indicated that compound 2f could dramatically induce the up- and down-regulation of a total of 247 differentially expressed proteins, which was further validated by the parallel reaction monitoring technique. Moreover, fluorescence spectra and SEM images were obtained to further explore the antibacterial mechanism.

Rational Optimization and Action Mechanism of Novel Imidazole (or Imidazolium)-Labeled 1,3,4-Oxadiazole Thioethers as Promising Antibacterial Agents against Plant Bacterial Diseases

The emergence and widespread occurrence of plant bacterial diseases that cause global production constraints have become major challenges to agriculture worldwide. To promote the discovery and development of new bactericides, imidazole-labeled 1,3,4-oxadiazole thioethers were first fabricated by integrating the crucially bioactive scaffolds of the imidazole motif and 1,3,4-oxadiazole skeleton in a single molecular architecture. Subsequently, a superior antibacterial compound A₆ was gradually discovered possessing excellent competence against plant pathogens Xanthomonas oryzae pv oryzae and Xanthomonas axonopodis pv citri with EC₅₀ values of 0.734 and 1.79 μg/mL, respectively. These values were better than those of commercial agents bismerthiazol (92.6 μg/mL) and thiodiazole copper (77.0 μg/mL). Further modifying the imidazole moiety into the imidazolium scaffold led to the discovery of an array of potent antibacterial compounds providing the corresponding minimum EC₅₀ values of 0.295 and 0.607 μg/mL against the two strains. Moreover, a plausible action mechanism for attacking pathogens was proposed based on the concentration dependence of scanning electron microscopy, transmission electron microscopy, and fluorescence microscopy images. Given the simple molecular structures, easy synthetic procedure, and highly efficient bioactivity, imidazole (or imidazolium)-labeled 1,3,4-oxadiazole thioethers can be further explored and developed as promising indicators for the development of commercial drugs.

Biological activity evaluation and action mechanism of chalcone derivatives containing thiophene sulfonate

A series of novel chalcone derivatives containing a thiophene sulfonate group were designed and synthesized. The structures of all title compounds were determined by ¹H-NMR, ¹³C-NMR and HRMS. Antibacterial bioassays indicated that, compound 2l demonstrated excellent antibacterial activities against Xanthomonas axonopodis pv. citri (Xac), with an EC₅₀ value of 11.4 μg mL⁻¹, which is significantly superior to those of bismerthiazol (BT) (51.6 μg mL⁻¹) and thiodiazole-copper (TC) (94.7 μg mL⁻¹). Meanwhile, the mechanism of action of compound 2l was confirmed by using scanning electron microscopy (SEM). In addition, compound 2e showed remarkable inactivation activity against Tobacco mosaic virus (TMV), with an EC₅₀ value of 44.3 μg mL⁻¹, which was superior to that of ningnanmycin (120.6 μg mL⁻¹). Microscale thermophoresis (MST) also showed that the binding of compounds 2e and 2h to Tobacco mosaic virus coat protein (TMV-CP) yielded K_d values of 0.270 and 0.301 μmol L⁻¹, which are better than that of ningnanmycin (0.596 μmol L⁻¹). At the same time, molecular docking studies for 2e and 2h with TMV-CP (PDB code: 1EI7) showed that the compound was embedded well in the pocket between the two subunits of TMV-CP in each case. These results suggested that chalcone derivatives containing a thiophene sulfonate group may be considered as activators in the design of antibacterial and antiviral agents.

Synthesis, antibacterial, antiviral activities and action mechanism of chalcone derivatives containing thiophene sulfonate.

Synthesis, antiviral and antibacterial activities and action mechanism of penta-1,4-dien-3-one oxime ether derivatives containing a quinoxaline moiety

A series of penta-1,4-dien-3-one oxime ether derivatives containing a quinoxaline moiety were synthesized, and their bioactivities and action mechanism were evaluated.