Synthesis, Bioactivity, and QSAR Study of 3,4-Dichlorophenyl Isoxazole-Substituted Stilbene Derivatives against the Phytopathogenic Fungus Botrytis cinerea

Bioactivity of novel isoxazole-fused heterocycles: comprehensive antimicrobial, antioxidant activities, SwissADME predictions, molecular docking, and DFT analysis

Among the foremost goals for organic chemists is to discover novel approaches for the synthesis of a particular heterocyclic and its design. Our approach focused on the vital precursor 4-acetyl-3-phenylisoxazol-5(4H)-one 3, as this molecule has an endocyclic carbonyl function in position 5 adjacent to the substituted acetyl function at site 4. Therefore, compound 3 was a crucial component of many types of fused isoxazole. The investigators provide a straightforward synthesis of fused isoxazole from the following categories: pyrano[3,2-d]isoxazole 4 & 6, isochromeno[4,3-d]isoxazole 5, isoxazolo[4',5':5,6]pyrano[3,4-c]pyridine 7, thieno[3',4':4,5]pyrano [3,2-d]isoxazole 8, pyrazolo[4,3-d]isoxazole 10a,b and 11a,b, and isoxazolo[4,5-c]pyridazine derivatives 14a,b. The target compounds and their structures were supported by the results of 1H-NMR, IR and mass spectroscopy. Molecular docking studies highlighted strong binding affinities to bacterial enzymes crucial for cell wall synthesis, while DFT calculations provided deep insights into their electronic properties and stability. Additionally, the antioxidant potential of compounds 11a,b was assessed using DPPH and ABTS assays, showing impressive concentration-dependent activity. Addressing the critical issue of antibiotic resistance, especially due to β-lactamases, molecular docking affirmed the high binding propensity of these derivatives with essential β-lactamase proteins (PDB: 1CK3, 6MU9, and 6W2Z). These findings underscore the promise of isoxazoline derivatives as powerful antimicrobial and antioxidant agents, paving the way for further development in combating bacterial resistance and oxidative stress.

Identification of a novel Src inhibitor K882 derived from quinazoline-based stilbenes with anti-NSCLC effect

The growing concern about drug resistance to KRAS G12C inhibitors emphasizes the urgent need for effective therapies targeting NSCLC with KRAS G12C mutation. In this research, a series of quinazoline-based stilbene derivatives were designed, synthesized and assayed for cytotoxic activities against human KRAS G12C mutant NSCLC NCI-H358 cells. Among them, K882 (4e) exhibited remarkable inhibitory activities on tumor cell proliferation, migration and invasion, as well as tumor organoids growth in vitro. Subsequent study revealed that K882 arrested NCI-H358 cell cycle in G2/M phase and induced apoptosis. In a NCI-H358 xenograft tumor model, K882 showed potential tumor inhibition effect in vivo without causing obvious organ damage. Mechanistically, K882 bound to ATP binding hydrophobic pocket of Src and inhibited its downstream signaling pathways including Jak/Stat, PI3K/Akt and RAS/MAPK activation, thereby exerting its anti-tumor effect. These findings highlight the promising potential of K882 as a therapeutic targeting agent for the treatment of KRAS mutant NSCLC while also providing novel insights into targeted therapy strategies for this type of malignancy. Furthermore, the information of structure-activity relationship presents valuable molecular design blueprints for the development of novel and highly potent compounds targeting Src.

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

BACKGROUND

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

RESULTS

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

CONCLUSION

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

Alanazi M, El Yazidi M. Efficient Synthesis, Structural Characterization, Antibacterial Assessment, ADME-Tox Analysis, Molecular Docking and Molecular Dynamics Simulations of New Functionalized Isoxazoles

This work describes the synthesis, characterization, and in vitro and in silico evaluation of the biological activity of new functionalized isoxazole derivatives. The structures of all new compounds were analyzed by IR and NMR spectroscopy. The structures of 4c and 4f were further confirmed by single crystal X-ray and their compositions unambiguously determined by mass spectrometry (MS). The antibacterial effect of the isoxazoles was assessed in vitro against Escherichia coli, Bacillus subtilis, and Staphylococcusaureus bacterial strains. Isoxazole 4a showed significant activity against E. coli and B. subtilis compared to the reference antibiotic drugs while 4d and 4f also exhibited some antibacterial effects. The molecular docking results indicate that the synthesized compounds exhibit strong interactions with the target proteins. Specifically, 4a displayed a better affinity for E. coli, S. aureus, and B. subtilis in comparison to the reference drugs. The molecular dynamics simulations performed on 4a strongly support the stability of the ligand-receptor complex when interacting with the active sites of proteins from E. coli, S. aureus, and B. subtilis. Lastly, the results of the Absorption, Distribution, Metabolism, Excretion and Toxicity Analysis (ADME-Tox) reveal that the molecules have promising pharmacokinetic properties, suggesting favorable druglike properties and potential therapeutic agents.

Design, synthesis, and cytotoxic activity of pyridine-based stilbenes

In the present study, three series of 35 pyridine-based stilbenes include 10 new compounds prepared by Horner-Wadsworth-Emmons (HWE) reaction were assayed for cytotoxic activities toward two tumoral cell lines (K562 and MDA-MB-231) and one non-tumoral cell line (L-02). The bioassay results indicated that hybrid stilbenes formed at the C-3 position of pyridine displayed stronger antiproliferative activities against K562 cells and C-4 pyridine-based stilbenes showed broad-spectrum cytotoxic effects. Among them, C-3 pyridine-based stilbene PS2g bearing 2,6-dimethoxy possessed extremely potent antiproliferative activity with IC50 values 1.46 µM against K562 cells, along with excellent selectivity towards normal L-02 cells. In summary, the present study contributes to the development of natural stilbene-based derivatives as antitumor agents and PS2g may serve as a promising lead for the treatment of chronic myeloid leukemia (CML) worthy further investigation.

Dibenzylideneacetone Overcomes Botrytis cinerea Infection in Cherry Tomatoes by Inhibiting Chitinase Activity

Chitinase, a crucial component of the fungal cell wall and septa, plays an important role in fungal germination by hydrolyzing chitin to provide carbon and energy for fungal growth and reproduction. In this study, we initially screened dibenzylideneacetone (DBA), a small molecule with inhibitory activity against Botrytis cinerea Chitinase, exhibiting an IC50 of 13.10 μg/mL. By constructing a three-dimensional (3D) model of the B. cinerea Chitinase and utilizing computational biology approaches, we found DBA bound to the active site pocket and formed strong π-π interactions and hydrophobic interactions with Chitinase, indicative of its competitive inhibitory mode. Site-directed mutagenesis also revealed that TRP-382, TRP-135, and ALA-215 were key amino acid residues involved in DBA binding. Subsequent antifungal assays showed that DBA had an MIC of 32 μg/mL against B. cinerea and EC50 values of 16.29 and 14.64 μg/mL in inhibiting mycelial growth and spore germination, respectively. Importantly, in vivo experiments demonstrated that DBA treatment significantly extended the shelf life of cherry tomatoes by 2-fold. Therefore, DBA represents a promising antifungal agent for fruit preservation applications.

Synthesis and Biological Activity Evaluation of Novel Chalcone Analogues Containing a Methylxanthine Moiety and Their N-Acyl Pyrazoline Derivatives

On the basis of the structures of natural methylxanthines and chalcone, a series of novel chalcone analogues containing a methylxanthine moiety, Ia-Ig, and their N-acyl pyrazoline derivatives IIa-IIz and IIaa-IIaf were synthesized and identified through melting points, 1H NMR, 13C NMR, and HRMS. The single crystal of compound IId was obtained, which further illustrated the structural characteristics of the methylxanthine-acylpyrazoline compounds. The biological tests showed that some of them displayed favorable insecticidal activities toward Plutella xylostella L. and were superior to the natural methylxanthine compound caffeine while being comparable with the insecticide triflumuron (e.g., compound Ic: LC50 = 16.8508 mg/L, IIf: LC50 = 1.5721 mg/L, against P. xylostella). Of these compounds, Ic, IIf, and IIu could serve as novel insecticidal leading structures for further study. Some of the compounds showed good fungicidal activities (e.g., compound Ig: EC50 = 14.74 μg/mL, against Rhizoctonia cerealis; IIf: EC50 = 7.06 μg/mL, against Physalospora piricola; IIac: EC50 = 5.37 and 8.19 μg/mL, against Phytophthora capsici and Sclerotinia sclerotiorum, respectively); Ic, Ig, IIa, IIf, IIr, IIs, IIv, IIac, and IIaf could be novel fungicidal leading compounds for further exploration. Furthermore, most of the tested compounds exhibited apparent herbicidal activities against Brassica campestris at a concentration of 100 μg/mL; among others, compound IIa was the best one both toward Brassica campestris and Echinochloa crusgalli and deserves further investigation. The structure-activity relationships of these compounds were also summarized and discussed in detail. The contrast experiment results of compounds C-1 and C-2 showed a positive effect on the biological activity enhancement from the combination of the methylxanthine moiety with the N-dichloroacetyl phenylpyrazoline skeleton. In addition, two 3D-QSAR models with predictive capability were constructed based on the insecticidal and fungicidal activities to afford deep insight into the bioactivity profiles of these compounds. This research provides useful guidance and reference for the discovery and development of novel xanthine natural product-based pesticides.

Discovery of Novel Carboxamide Derivatives Containing Biphenyl Pharmacophore as Potential Fungicidal Agents Used for Resistance Management

Natural products are one of the main sources of drug and agrochemicals discovery. Biphenyls skeleton are ubiquitous structures in many classes of natural products, which indicate extensive biological activities. So, in order to investigate the potential applications for natural biphenyl derivatives, a series of novel carboxamide derivatives with diverse substituent patterns were designed and synthesized based on active pharmacophore from natural biphenyl lignans, and their in vitro antifungal activities against several typical plant pathogens belonging to oomycetes, ascomycete, deuteromycetes, and basidiomycetes were fully investigated. The highly potential compounds were further tested in vivo assay against Botrytis cinerea Pers. of cucumber to demonstrate a practical application for controlling common plant diseases, which indicated four compounds could effectively control the resistant strains of carbendazim, rutamycin, and pyrazolidide. The potential modes of action for compound B12 against B. cinerea were also explored using molecular docking, microscopic technology, and label-free quantitative proteomics analysis. The results show that compound B12 may be a potential novel fungicidal agent used for gray mold resistance control, which can influence the protein synthesis of B. cinerea. These findings can provide a certain theoretical basis for the development of novel biphenyl derivatives as potential green antifungal agents.

The Effect of Terbinafine and Its Ionic Salts on Certain Fungal Plant Pathogens

Terbinafine, an inhibitor of squalene epoxidase in ergosterol biosynthesis, is chiefly utilized as an antifungal medication with potential uses in pesticide applications. This study explores the fungicidal efficacy of terbinafine against prevalent plant pathogens and confirms its effectiveness. To augment its water solubility, five ionic salts of terbinafine were synthesized by pairing them with organic acids. Among these salts, TIS 5 delivered the most impressive results, amplifying the water solubility of terbinafine by three orders of magnitude and lessening its surface tension to facilitate better dispersion during spraying. The in vivo experiments on cherry tomatoes showed that TIS 5 had a superior therapeutic activity compared to its parent compound and two commonly used broad-spectrum fungicides, pyraclostrobin and carbendazim. The results highlight the potential of terbinafine and its ionic salts, particularly TIS 5, for use as fungicides in agriculture due to their synergistic effects with furan-2-carboxylate.

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.

A green protocol for the one-pot synthesis of 3,4-disubstituted isoxazole-5(4H)-ones using modified β-cyclodextrin as a catalyst

This manuscript reports an impressive and facile strategy for synthesizing isoxazole derivatives using immobilized Cu (I) in metformin-functionalized β-cyclodextrin as a catalyst. The architecture of this catalyst was characterized by different analytical techniques such as Fourier transform infrared spectroscopy, Thermogravimetric analysis, X-ray diffraction, Field emission scanning electron microscopy, and Energy-dispersive X-ray spectroscopy. The catalyst showed remarkable reusability even after 7 consecutive runs.

Insecticidal Triterpenes in Meliaceae: Plant Species, Molecules, and Activities: Part II (Cipadessa, Melia)

Plant-originated triterpenes are important insecticidal molecules. Research on the insecticidal activity of molecules from Meliaceae plants has always been a hotspot due to the molecules from this family showing a variety of insecticidal activities with diverse mechanisms of action. In this paper, we discussed 116 triterpenoid molecules with insecticidal activity from 22 plant species of five genera (Cipadessa, Entandrophragma, Guarea, Khaya, and Melia) in Meliaceae. In these genera, the insecticidal activities of plants from Entandrophragma and Melia have attracted substantial research attention in recent years. Specifically, the insecticidal activities of plants from Melia have been systemically studied for several decades. In total, the 116 insecticidal chemicals consisted of 34 ring-intact limonoids, 31 ring-seco limonoids, 48 rearranged limonoids, and 3 tetracyclic triterpenes. Furthermore, the 34 ring-intact limonoids included 29 trichilin-class chemicals, 3 azadirone-class chemicals, and 1 cedrelone-class and 1 havanensin-class limonoid. The 31 ring-seco limonoids consisted of 16 C-seco group chemicals, 8 B,D-seco group chemicals, 4 A,B-seco group chemicals, and 3 D-seco group chemicals. Furthermore, among the 48 rearranged limonoids, 46 were 2,30-linkage group chemicals and 2 were 10,11-linkage group chemicals. Specifically, the 46 chemicals belonging to the 2,30-linkage group could be subdivided into 24 mexicanolide-class chemicals and 22 phragmalin-class chemicals. Additionally, the three tetracyclic triterpenes were three protolimonoids. To sum up, 80 chemicals isolated from 19 plant species exhibited antifeedant activity toward 14 insect species; 18 chemicals isolated from 17 plant species exhibited poisonous activity toward 10 insect species; 16 chemicals isolated from 11 plant species possessed growth-regulatory activity toward 8 insect species. In particular, toosendanin was the most effective antifeedant and insect growth-regulatory agent. The antifeedant activity of toosendanin was significant. Owing to its high effect, toosendanin has been commercially applied. Three other molecules, 1,3-dicinnamoyl-11-hydroxymeliacarpin, 1-cinnamoyl-3-methacryl-11-hydroxymeliacarpin, and 1-cinnamoyl-3-acetyl-11-hydroxymeliacarpin, isolated from Meliaazedarach, exhibited a highly poisonous effect on Spodoptera littoralis; thus, they deserve further attention.

Indole/Tetrahydroquinoline as Renewable Natural Resource-Inspired Scaffolds in the Devising and Preparation of Potential Fungicide Candidates

As a continuous effort toward developing novel and highly efficient agrochemicals for integrated management of crop pathogens, two series of oxime ester derivatives from indole and tetrahydroquinoline natural scaffolds were prepared. Guided by the preliminary inhibition rates against ubiquitous and representative fungi, the antifungal profile of the target compounds against Valsa mali was intensively and extensively studied. The tetrahydroquinoline-based derivatives 12a-12r exerted a promising inhibition effect, especially against V. mali. The remarkable compounds 12p (R = 4-OCF₃) and 12r (R = 4-OBn) with EC₅₀ values of 0.81 and 0.47 μg/mL, respectively, have a far more prominent activity than commercial fungicide trifloxystrobin. The biochemistry and physiology responses of V. mali after treatment with target compound 12p was examined, and the fruit body production, hyphae morphology, and organelles were profoundly affected. Moreover, the curative effects of compound 12p on apple detached branches and leaves were 57.69 and 64.84% at 100 μg/mL, respectively, which were even superior to that of trifloxystrobin. Meanwhile, the three-dimensional quantitative structure-activity relationship model [comparative molecular field analysis (CoMFA): q² = 0.823, r² = 0.924, F = 189.781, and standard error of estimation (SEE) = 0.138 and comparative molecular similarity index analysis (CoMSIA): q² = 0.795, r² = 0.904, F = 145.644, and SEE = 0.156] indicated that the antifungal activity of target compounds was facilitated by crucial structural factors, which would render inspiration for further design and discovery of novel fungicidal candidates.

Design, Synthesis, Herbicidal Activity, and Molecular Docking Study of 2-Thioether-5-(Thienyl/Pyridyl)-1,3,4-Oxadiazoles as Potent Transketolase Inhibitors

Transketolase (TK) has been regarded as a new target for the development of novel herbicides. In this study, a series of 2-thioether-5-(thienyl/pyridyl)-1,3,4-oxadiazoles were designed and synthesized based on TK as the new target. The preliminary bioassay results indicated that compounds 4l and 4m displayed the best herbicidal activities against Amaranthus retroflexus (AR) and Digitaria sanguinalis (DS), with the inhibition exceeding 90% at 100-200 mg/L in vitro. Moreover, they also displayed higher postemergence herbicidal activities (90% control) against AR and DS than all of the positive controls at 45-90 g [active ingredient (ai)]/ha in a greenhouse. Notably, compounds 4l and 4m showed a broad spectrum of weed control at 90 g ai/ha. More significantly, compound 4l exhibited good crop selectivity against maize at 90 g ai/ha. Both fluorescent binding experiments and molecular docking analyses indicated that compounds 4l and 4m exhibited strong TK inhibitory activities with superior binding affinities than the others. Preliminary mechanism studies suggested that they might exert their TK inhibitory effects by occupying the active cavity of At TK and forming more strong interactions with amino acids in the active site. Taken together, these results suggested that compound 4l was a potential herbicide candidate for weed control in maize fields targeting TK.