Design, synthesis, antiviral activity and three-dimensional quantitative structure-activity relationship study of novel 1,4-pentadien-3-one derivatives containing the 1,3,4-oxadiazole moiety

Anti-TMV activity based flavonol derivatives containing piperazine sulfonyl: Design, synthesis and mechanism study

A series of flavonoid derivatives containing piperazine sulfonate were designed and synthesized. The results of antiviral experiments in vivo showed that some target compounds had good inhibitory effect on tobacco mosaic virus (TMV). The EC50 values of S15 and S19 curative activity were 174.5 and 110.4 μg/mL, respectively, which were better than 253.7 μg/mL of Ningnanmycin (NNM). The EC50 values of S4 and S19 protection activity were 140.3 and 116.1 μg/mL, respectively, better than that of NNM (247.1 μg/mL). Microscale thermophoresis (MST) and molecular docking experiments showed that S19 had a good molecular binding force with TMV. Transmission electron microscopy (TEM) results show that S19 can fracture TMV particles and affect self-assembly. S19 treatment had almost no effect on the growth of seeds and seedlings, and can change the content of chlorophyll malondialdehyde (MDA) and superoxide dismutase (SOD) in tobacco to a certain extent, and improve the disease resistance of tobacco.

Discovery of New 1,2,4-Triazole/1,3,4-Oxadiazole-Decorated Quinolinones as Agrochemical Alternatives for Controlling Viral Infection by Inhibiting the Viral Replication and Self-Assembly Process

Tobacco mosaic virus (TMV), a representative plant virus, is widely known and causes severe crop losses worldwide. In order to ensure the demand for crop and food security, the exploration of novel antiviral agents with outstanding activity and unique mechanisms of action is necessary. Herein, 40 new azole-quinolinone molecules were elaborately designed and systematically evaluated for their anti-TMV activity. Notably, compound A21 had significant therapeutic activity against TMV (EC50 value = 200 μg/mL), which was superior to commercial ningnanmycin (280 μg/mL). Studies on the anti-TMV mechanism showed that compound A21 could suppress the expression level of important TMV genes and affect the assembly of TMV viral particles by disrupting the self-assembly process of TMV coat protein (TMV-CP). In-depth antiviral behaviors were verified by molecular docking, fluorescence titration analysis, and TMV assembly assays, suggesting that compound A21 strongly interacted with TMV coat protein through various interactions. Overall, this promising work discloses a new paradigm for the exploitation of 2-quinolinone-based virucidal agents for hindering plant viral infection through triggering versatile antiviral behavior.

Novel flavonol derivatives containing benzoxazole as potential antiviral agents: design, synthesis, and biological evaluation

A series of flavonol derivatives containing benzoxazole were designed and synthesized, and the structures of all the target compounds were determined by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). The structure of X2 was further confirmed by single crystal X-ray diffraction analysis. The results of the bioactivity tests showed that some of the target compounds possessed excellent antiviral activity against tobacco mosaic virus (TMV) in vivo. In particular, the median effective concentration (EC50) values for the curative and protective activities of X17 against TMV were 127.6 and 101.2 μg/mL, respectively, which were superior to those of ningnanmycin (320.0 and 234.6 μg/mL). The results of preliminary mechanism study indicated that X17 had a strong binding affinity for TMV coat protein (TMV-CP), which might hinder the self-assembly and replication of TMV particles. In addition, X17 was able to effectively inhibit tobacco leaf membrane lipid peroxidation and facilitate the removal of O2- from the body, thereby improving the disease resistance of tobacco plants. Therefore, the design and synthesis of flavonol derivatives containing benzoxazole provides value for the development of new antiviral drugs.

Design, Synthesis, Antifungal Evaluation, and Three-Dimensional Quantitative Structure-Activity Relationship of Novel 5-Sulfonyl-1,3,4-thiadiazole Flavonoids

Plant pathogenic fungi frequently disrupt the normal physiological and biochemical functions of plants, leading to diseases, compromising plant health, and ultimately reducing crop yield. This study aimed to address this challenge by identifying antifungal agents with innovative structures and novel mechanisms of action. We designed and synthesized a series of flavonoid derivatives substituted with 5-sulfonyl-1,3,4-thiadiazole and evaluated their antifungal activity against five phytopathogenic fungi. Most flavonoid derivatives demonstrated excellent antifungal activity against Botrytis cinerea (B. cinerea), Alternaria solani (A. solani), Rhizoctorzia solani (R. solani), Fusarium graminearum (F. graminearum), and Colletotrichum orbiculare (C. orbiculare). Specifically, the EC50 values of 38 target compounds against R. solani were below 4 μg/mL, among which the compounds C13 (EC50 = 0.49 μg/mL), C15 (EC50 = 0.37 μg/mL), and C19 (EC50 = 0.37 μg/mL) had the most prominent antifungal activity, superior to that of the control drug carbendazim (EC50 = 0.52 μg/mL). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the cellular ultrastructures of R. solani mycelia and cells after treatment with the compound C19 revealed sprawling growth of hyphae, a distorted outline of their cell walls, and reduced mitochondrial numbers. Studying the 3D-QSAR between the molecular structure and antifungal activity of 5-sulfonyl-1,3,4-thiadiazole-substituted flavonoid derivatives could significantly improve conventional drug molecular design pathways and facilitate the development of novel antifungal leads.

Design, Synthesis, and Antiviral and Fungicidal Activities of 4-Oxo-4H-quinolin-1-yl Acylhydrazone Derivatives

To discover novel antiviral agents, based on the high antiviral activity of (4-oxo-4H-quinolin-1-yl)-acetic acid hydrazide (C), a series of 4-oxo-4H-quinoline acylhydrazone derivatives were designed, synthesized, and first evaluated for their antiviral and fungicidal activities. Most acylhydrazone derivatives exhibited moderate to good antiviral activities in vivo. The inactive, curative, and protective activities of compounds 4 (51.2, 47.6, and 46.3%), 11 (49.6, 43.0, and 45.2% at 500 mg/L), and 17 (47.1, 49.2, and 44.1%) were higher than those of ribavirin (39.2, 38.0, and 40.8%) at 500 mg/L. Molecular docking showed that compound 4 exhibited a stronger affinity to TMV coat protein (TMV-CP) than ribavirin, with a binding energy (-6.89 kcal/mol) slightly lower than that of ribavirin (-6.08 kcal/mol). Microscale thermophoresis showed that compound 4 (K d = 0.142 ± 0.060 μM) exhibited a strong binding ability to TMV-CP, superior to that of ribavirin (K d = 0.512 ± 0.257 μM). The results of transmission electron microscopy showed that compound 4 hindered the self-assembly and growth of TMV. The antifungal activities of most compounds were moderate at 50 mg/L, among which compounds 12 and 21 exhibited a 72.1 and 76.5% inhibitory rate against Physalospora piricola, respectively. Meanwhile, compound 16 exhibited a 60% inhibitory rate against Cercospora arachidicola Hori at 50 mg/L.

Design, synthesis and antiviral activity of indole derivatives containing quinoline moiety

A series of indole derivatives containing quinoline structures were designed and synthesized. The synthesized compounds were characterized by NMR and HRMS. And W14 was performed by single crystal X-ray diffraction experiments. The antiviral activity studies showed that some of the target compounds possessed significant activity against tobacco mosaic virus (TMV). In particular, W20 had significant activity. The results of in vivo anti-TMV activity assay showed that W20 possessed the best curative and protective activities with EC50 values of 84.4 and 65.7 μg/mL, which were better than ningnanmycin (NNM) 205.1 and 162.0 μg/mL, respectively. The results of Microscale thermophoresis (MST) showed that W20 had a strong binding affinity for the tobacco mosaic virus coat protein (TMV-CP) with a dissociation constant (Kd) of 0.00519 μmol/L, which was superior to that of NNM (1. 65320 μmol/L). The molecular docking studies were in accordance with the experimental results. In addition, the determination of malondialdehyde (MDA) content in tobacco leaves showed that W20 improved the disease resistance of tobacco. Overall, this study shows that indole derivatives containing quinoline can be used as new antiviral agents for plant viruses for further research.

Substrate-based synthetic strategies and biological activities of 1,3,4-oxadiazole: A review

The five-membered 1,3,4-oxadiazole heterocyclic ring has received considerable attention because of its unique bio-isosteric properties and an unusually wide spectrum of biological activities. After a century since 1,3,4-oxadiazole was discovered, its uncommon potential attracted medicinal chemist's attention, leading to the discovery of a few presently accessible drugs containing 1,3,4-oxadiazole units, and a large number of patents have been granted on research related to 1,3,4-oxadiazole. It is worth noting that interest in 1,3,4-oxadiazoles' biological applications has doubled in the last few years. Herein, this review presents a comprehensive overview of the recent achievements in the synthesis of 1,3,4-oxadiazole-based compounds and highlights the major advances in their biological applications in the last 10 years, as well as brief remarks on prospects for further development. We hope that researchers across the scientific streams will benefit from the presented review articles for designing their work related to 1,3,4-oxadiazoles.

Antiviral activity evaluation and action mechanism of myricetin derivatives containing thioether quinoline moiety

A variety of myricetin derivatives containing thioether quinoline moiety were designed and synthesized. Their structures of title compounds were determined by 1H NMR, 13C NMR, 19F NMR, and HRMS. Single-crystal X-ray diffraction experiments were carried out with B4. Antiviral activity indicated that some of the target compounds exhibited remarkable anti-tobacco mosaic virus (TMV) activity. In particular, compound B6 possessed significant activity. The half maximal effective concentration (EC50) value of the curative activity of compound B6 was 169.0 μg/mL, which was superior to the control agent ningnanmycin (227.2 μg/mL). Meanwhile, the EC50 value of the protective activity of compound B6 was 86.5 μg/mL, which was better than ningnanmycin (179.2 μg/mL). Microscale thermophoresis (MST) indicated that compound B6 had a strong binding capability to the tobacco mosaic virus coat protein (TMV-CP) with a dissociation constant (Kd) value of 0.013 μmol/L, which was superior to that of myricitrin (61.447 μmol/L) and ningnanmycin (3.215 μmol/L). And the molecular docking studies were consistent with the experimental results. Therefore, these novel myricetin derivatives containing thioether quinoline moiety could become potential alternative templates for novel antiviral agents.

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.

In silico and in vitro prediction of new synthesized N-heterocyclic compounds as anti-SARS-CoV-2

Computer-aided drug design has been employed to get the medicinal effects against Corona virus from different pyridine derivatives after synthesizing the new compounds. Additionally, various computational studies are also employed between the newly prepared pyridine derivatives and three controls against three proteins (6Y2E, 6M71 and 6M3M). Different methods were employed to synthesize new pyridine derivatives according to the literature using different reaction mediums. MTT was performed for cytotoxicity study and IC50 for inhibitory concentration. Additionally, in-silico studies including DFT, molecular docking, molecular dynamics, MMPBSA, ADME, pharmacokinetics and Lipinski rules were evaluated. The chemical structures of all new compounds were elucidated based on spectroscopic investigation. A molecular docking study demonstrated that compounds 5, 11, and 12 have the best binders of the SARS-CoV-2 main protease enzyme, with energy scores of - 7.5 kcal/mol, - 7.2 kcal/mol, and - 7.9 kcal/mol, respectively. The net binding energy values of the 11-Mpro, 12-Mpro, and 5-Mpro complexes revealed their highly stable nature in terms of both intermolecular interactions and docked conformation across the simulation time. ADME properties, besides the pharmacokinetics and Lipinski rules, showed that all seven newly synthesized compounds follow Lipinski rules with high GI absorption. The In Vitro antiviral study against SARS-CoV-2 using MTT methods confirms that compound 5 has more potential and is safer than other tested compounds. The study shows that the newly synthesized pyridine derivatives have medicinal properties against SARS-CoV-2 without violating Lipinski rules. Compounds 5, 11, and 12, particularly compound 5, may serve as promising potential candidate for COVID-19.

A Review on the Mechanism and Structure-activity Relationship of Resveratrol Heteroaryl Analogues

Resveratrol is one of the most interesting naturally-occurring nonflavonoid phenolic compounds with various biological activities, such as anticancer, neuroprotection, antibacterial, and anti-inflammatory. However, there is no clinical usage of resveratrol due to either its poor activity or poor pharmacokinetic properties. Heteroarenes-modified resveratrol is one pathway to improve its biological activities and bioavailability, and form more modification sites. In this review, we present the progress of heteroaryl analogues of resveratrol with promising biological activities in the latest five years, ranging from the synthesis to the structure-activity relationship and mechanism of actions. Finally, introducing heteroarenes into resveratrol is an effective strategy, which focuses on the selectivity of structure-activity relationship in vivo.

Discovery of novel phenothiazine derivatives as new agrochemical alternatives for treating plant viral diseases

BACKGROUND

Plant viral diseases, namely 'plant cancer', are extremely difficult to control. Even worse, few antiviral agents can effectively control and totally block viral infection. There is an urgent need to explore and discover novel agrochemicals with high activity and a unique mode of action to manage these refractory diseases.

RESULTS

Forty-one new phenothiazine derivatives were prepared and their inhibitory activity against tobacco mosaic virus (TMV) was assessed. Compound A8 had the highest protective activity against TMV, with a half-maximal effective concentration (EC50 ) of 115.67 μg/mL, which was significantly better than that of the positive controls ningnanmycin (271.28 μg/mL) and ribavirin (557.47 μg/mL). Biochemical assays demonstrated that compound A8 could inhibit TMV replication by disrupting TMV self-assembly, but also enabled the tobacco plant to enhance its defense potency by increasing the activities of various defense enzymes.

CONCLUSION

In this study, novel phenothiazine derivatives were elaborately fabricated and showed remarkable anti-TMV behavior that possessed the dual-action mechanisms of inhibiting TMV assembly and invoking the defense responses of tobacco plants. Moreover, new agrochemical alternatives based on phenothiazine were assessed for their antiviral activities and showed extended agricultural application. © 2023 Society of Chemical Industry.

Design, Synthesis, In Vitro Antifungal Activity and Mechanism Study of the Novel 4-Substituted Mandelic Acid Derivatives

Plant diseases caused by phytopathogenic fungi are a serious threat in the process of crop production and cause large economic losses to global agriculture. To obtain high-antifungal-activity compounds with novel action mechanisms, a series of 4-substituted mandelic acid derivatives containing a 1,3,4-oxadiazole moiety were designed and synthesized. In vitro bioassay results revealed that some compounds exhibited excellent activity against the tested fungi. Among them, the EC₅₀ values of E₁₃ against Gibberella saubinetii (G. saubinetii), E₆ against Verticillium dahlia (V. dahlia), and E₁₈ against Sclerotinia sclerotiorum (S. sclerotiorum) were 20.4, 12.7, and 8.0 mg/L, respectively, which were highly superior to that of the commercialized fungicide mandipropamid. The morphological studies of G. saubinetii with a fluorescence microscope (FM) and scanning electron microscope (SEM) indicated that E₁₃ broke the surface of the hyphae and destroyed cell membrane integrity with increased concentration, thereby inhibiting fungal reproduction. Further cytoplasmic content leakage determination results showed a dramatic increase of the nucleic acid and protein concentrations in mycelia with E₁₃ treatment, which also indicated that the title compound E₁₃ could destroy cell membrane integrity and affect the growth of fungi. These results provide important information for further study of the mechanism of action of mandelic acid derivatives and their structural derivatization.

Novel 1-Indanone derivatives containing oxime and oxime ether moieties as immune activator to resist plant virus

BACKGROUND

Vegetable viruses are difficult to prevent and control in the field, causing massive economic losses of agricultural production in the world. A new natural product-based antiviral agent would be an effective means to control viral diseases. As a class of natural products, 1-indanones present various pharmacologically actives, while their application in agriculture remains to be found.

RESULTS

A series of novel 1-indanone derivatives were designed and synthesized and the antiviral activities were systematically evaluated. Bioassays showed that most compounds exhibited good protective activities against cucumber mosaic virus (CMV), tomato spotted wilt virus (TSWV), and pepper mild mottle virus (PMMoV). Notably, compound 27 exhibited the best protective effects against PMMoV with EC₅₀ values of 140.5 mg L^-1 , superior to ninanmycin (245.6 mg L^-1 ). Compound 27 induced immunity responses through multilayered regulation on mitogen-activated protein kinase, plant hormone signal transduction and phenylpropanoid biosynthesis pathways.

CONCLUSION

These 1-indanone derivatives especially compound 27 can be considered as potential immune activators to resist plant virus. © 2023 Society of Chemical Industry.

Synthesis and Evaluation of Novel S-alkyl Phthalimide- and S-benzyl-oxadiazole-quinoline Hybrids as Inhibitors of Monoamine Oxidase and Acetylcholinesterase

New S-alkyl phthalimide 5a-f and S-benzyl 6a-d analogs of 5-(2-phenylquinolin-4-yl)-1,3,4-oxadiazole-2-thiol (4) were prepared by reacting 4 with N-bromoalkylphthalimide and CF₃-substituted benzyl bromides in excellent yields. Spectroscopic techniques were employed to elucidate the structures of the synthesized molecules. The inhibition activity of newly synthesized molecules toward MAO-A, MAO-B, and AChE enzymes, was also assessed. All these compounds showed activity in the submicromolar range against all enzymes. Compounds 5a and 5f were found to be the most potent compounds against MAO-A (IC₅₀ = 0.91 ± 0.15 nM) and MAO-B (IC₅₀ = 0.84 ± 0.06 nM), while compound 5c showed the most efficient acetylcholinesterase inhibition (IC₅₀ = 1.02± 0.65 μM). Docking predictions disclosed the docking poses of the synthesized molecules with all enzymes and demonstrated the outstanding potency of compounds 5a, 5f, and 5c (docking scores = -11.6, -15.3, and -14.0 kcal/mol against MAO-A, MAO-B, and AChE, respectively). These newly synthesized analogs act as up-and-coming candidates for the creation of safer curative use against Alzheimer's illness.

Chloramine Trihydrate-mediated Tandem Synthesis of New Pyrrole and/or Arene-linked Mono- and Bis(1,3,4-oxadiazole) Hybrids as Potential Bacterial Biofilm and MRSA Inhibitors

A two-step tandem protocol was used to prepare new pyrrole and/or arene-linked bis(1,3,4-oxadiazoles) as well as their mono-analogues. The appropriate aldehydes and benzohydrazides were first condensed in ethanol at 80 °C to yield the corresponding N-benzoylhydrazones. Without isolation, the previous intermediates were subjected to a chloramine trihydrate-mediated oxidative cyclization in DMSO at 180 °C to yield the target molecules. The antibacterial potency of the (pyrrole-arene)-linked hybrids exceeded the arene-linked hybrids, and the bis(1,3,4-oxadiazoles) exceeded their mono-analogues against six different ATCC strains. Furthermore, the antibacterial efficacy of bis(1,3,4-oxadiazoles) 11c, and 11f, which are linked to pyrrole, and (p-tolylthio)methyl units, was highest against S. aureus, E. coli, and P. aeruginosa strains. Their MIC ranged between 3.8 and 3.9 µM, while their MBC values ranged between 7.7 and 15.8 µM. Additionally, they showed promising bacterial biofilm inhibitory activity against the same strains tested, with IC50 values ranging from 4.7 to 5.3 μM. They were also effective against MRSA ATCC:33591, and ATCC:43300 strains, with MIC, and MBC values ranging from 3.8-7.9 and 7.7-15.8 μM, respectively. When tested against the MCF-10A cell line, hybrids 11c, and 11f are cytotoxic at concentrations that are more than 6 and 13-fold higher than their MIC values against the S. aureus, E. coli, and P. aeruginosa strains, respectively. This lends support to both hybrids' potential as safe antibacterial agents.

1,3,4-Oxadiazole Derivatives as Plant Activators for Controlling Plant Viral Diseases: Preparation and Assessment of the Effect of Auxiliaries

Plant viral diseases cause the loss of millions of dollars to agriculture around the world annually. Therefore, the development of highly efficient, ultra-low-dosage agrochemicals is desirable for protecting the health of crops and ensuring food security. Herein, a series of 1,3,4-oxadiazole derivatives bearing an isopropanol amine moiety was prepared, and the inhibitory activity against tobacco mosaic virus (TMV) was assessed. Notably, compound A₁₄ exhibited excellent anti-TMV protective activity with an EC₅₀ value of 137.7 mg L^-1, which was superior to that of ribavirin (590.0 mg L^-1) and ningnanmycin (248.2 mg L^-1). Moreover, the anti-TMV activity of some compounds could be further enhanced (by up to 5-30%) through supplementation with 0.1% auxiliaries. Biochemical assays suggested that compound A₁₄ could suppress the biosynthesis of TMV and induce the plant's defense response. Given these merits, designed compounds had outstanding bioactivities and unusual action mechanisms and were promising candidates for controlling plant viral diseases.

Design, Synthesis and in Vitro Antifungal Mechanism of Novel Phenylalanine Derivatives

To explore novel molecules with unique mechanisms against plant pathogenic fungi, a series of phenylalanine derivatives containing a 1,3,4-oxadiazothioether moiety were designed and synthesized. Bioassays revealed that some target compounds at 100 μg/mL exhibited excellent antifungal activities against Thanatephorus cucumeris, such as G₆ (92.1 %), G₁₀ (94.3 %), G₁₈ (99.1 %), and G₁₉ (98.7 %), better than that of the commercial fungicide azoxystrobin (90.6 %), and the EC₅₀ value of G₁₀ against T. cucumeris was 31.9 μg/mL. Further mechanism studies of T. cucumeris treated with G₁₀ demonstrated that this compound can affect the growth of mycelia by disrupting the integrity of the membrane, and the higher the concentration of the compound is, the greater the degree of membrane integrity damage, similar to the commercial fungicide azoxystrobin. These conclusions provide important information for further mechanism studies of this series of phenylalanine derivatives.

Design, synthesis and biological activities of echinopsine derivatives containing acylhydrazone moiety

Based on the broad-spectrum biological activities of echinopsine and acylhydrazones, a series of echinopsine derivatives containing acylhydrazone moieties have been designed, synthesized and their biological activities were evaluated for the first time. The bioassay results indicated that most of the compounds showed moderate to good antiviral activities against tobacco mosaic virus (TMV), among which echinopsine (I) (inactivation activity, 49.5 ± 4.4%; curative activity, 46.1 ± 1.5%; protection activity, 42.6 ± 2.3%) and its derivatives 1 (inactivation activity, 44.9 ± 4.6%; curative activity, 39.8 ± 2.6%; protection activity, 47.3 ± 4.3%), 3 (inactivation activity, 47.9 ± 0.9%; curative activity, 43.7 ± 3.1%; protection activity, 44.6 ± 3.3%), 7 (inactivation activity, 46.2 ± 1.6%; curative activity, 45.0 ± 3.7%; protection activity, 41.7 ± 0.9%) showed higher anti-TMV activity in vivo at 500 mg/L than commercial ribavirin (inactivation activity, 38.9 ± 1.4%; curative activity, 39.2 ± 1.8%; protection activity, 36.4 ± 3.4%). Some compounds exhibited insecticidal activities against Plutella xylostella, Mythimna separate and Spodoptera frugiperda. Especially, compounds 7 and 27 displayed excellent insecticidal activities against Plutella xylostell (mortality 67 ± 6% and 53 ± 6%) even at 0.1 mg/L. Additionally, most echinopsine derivatives exhibited high fungicidal activities against Physalospora piricola and Sclerotinia sclerotiorum.

Trifluoromethylpyridine 1,3,4-Oxadiazole Derivatives: Emerging Scaffolds as Bacterial Agents

A new class of trifluoromethylpyridine 1,3,4-oxadiazole derivatives (6a-6v) was obtained, and their antibacterial activities were evaluated. Some of them exhibited good activity, particularly 6a, which had the highest in vitro activity against Ralstonia solanacearum (R. solanacearum) and Xanthomonas axonopodis pv. citri (Xac). The half-maximal effective concentrations (EC50) were 26.2 and 10.11 μg/mL, respectively, which were lower than those of commercial thiodiazole copper (97.2 and 35.3 μg/mL, respectively). Furthermore, 6q showed much higher activity against Xanthomonas oryzae pv. oryzae (Xoo) with an EC50 value of 7.2 μg/mL; this was superior to bismerthiazol (57.2 μg/mL). Collectively, our findings provide a foundation for the development of trifluoromethylpyridine 1,3,4-oxadiazole derivatives.

Novel Cinnamic Acid Derivatives Containing the 1,3,4-Oxadiazole Moiety: Design, Synthesis, Antibacterial Activities, and Mechanisms

There is a lack of effective antibacterial agents against rice bacterial leaf streak and leaf blight. Cinnamic acid derivatives containing the 1,3,4-oxadiazole moiety were synthesized, and their antibacterial activities against Xanthomonas oryzae pv. oryzicola (Xoc) and X. oryzae pv. oryzae (Xoo) were evaluated. Based on the three-dimensional quantitative structure-activity relationship (3D-QSAR) model, compound 31 with better antibacterial activity against Xoc was designed and synthesized, and the 50% effective concentration (EC₅₀) value was 0.2 mg/L. The curative and protective activities of compound 31 against rice bacterial leaf streak at 100 mg/L were 39.5 and 35.4%, respectively, which were higher than those of thiodiazole copper (28.4 and 20.7%, respectively). The antibacterial activity of compound 31 against rice bacterial leaf streak is closely associated with the activity of related defensive enzymes and the increase in glutathione metabolism.

Novel Pyrazole-4-acetohydrazide Derivatives Potentially Targeting Fungal Succinate Dehydrogenase: Design, Synthesis, Three-Dimensional Quantitative Structure-Activity Relationship, and Molecular Docking

Succinate dehydrogenase inhibitors (SDHIs) have emerged in fungicide markets as one of the fastest-growing categories that are widely applied in agricultural production for crop protection. Currently, the structural modification focusing on the flexible amide link of SDHI molecules is being gradually identified as one of the innovative strategies for developing novel highly efficient and broad-spectrum fungicides. Based on the above structural features, a series of pyrazole-4-acetohydrazide derivatives potentially targeting fungal SDH were constructed and evaluated for their antifungal effects against Rhizoctonia solani, Fusarium graminearum, and Botrytis cinerea. Strikingly, the in vitro EC₅₀ values of constructed pyrazole-4-acetohydrazides 6w against R. solani, 6c against F. graminearum, and 6f against B. cinerea were, respectively, determined as 0.27, 1.94, and 1.93 μg/mL, which were obviously superior to that of boscalid against R. solani (0.94 μg/mL), fluopyram against F. graminearum (9.37 μg/mL), and B. cinerea (1.94 μg/mL). Concurrently, the effects of the substituent steric, electrostatic, hydrophobic, and hydrogen-bond fields on structure-activity relationships were elaborated by the reliable comparative molecular field analysis and comparative molecular similarity index analysis models. Subsequently, the practical value of pyrazole-4-acetohydrazide derivative 6w as a potential SDHI was ascertained by the relative surveys on the in vivo anti-R. solani preventative efficacy, inhibitory effects against fungal SDH, and molecular docking studies. The present results provide an indispensable complement for the structural optimization of antifungal leads potentially targeting SDH.

Purine Nucleoside Derivatives Containing a Sulfa Ethylamine Moiety: Design, Synthesis, Antiviral Activity, and Mechanism

To find efficient and broad-spectrum viral agents, a series of purine nucleoside derivatives containing sulfa ethylamine moieties was designed and synthesized, and their antiviral activities against tobacco mosaic virus (TMV), cucumber mosaic virus (CMV), and potato virus Y (PVY) were evaluated. Some target compounds displayed good antiviral activities. Among them, compound 3 showed excellent protective activity against CMV and PVY with 50% effective concentration values (EC₅₀) of 137 and 209 μg/mL, respectively, which were better than that of the control agent ningnanmycin (508 and 431 μg/mL). Moreover, the EC₅₀ value of compound 3 for the inactivating activity against TMV was 48 μg/mL, which was better than that of ningnanmycin (88 μg/mL). In addition, compound 3 not only destroyed the structure of the TMV virus but also had a good interaction with the coat protein of the TMV virus. Therefore, compound 3 may further destroy the structure of the virus by binding to the coat protein of the TMV virus, thereby weakening the infectivity of the virus.

In vivo antiviral activity and disassembly mechanism of novel 1-phenyl-5-amine-4-pyrazole thioether derivatives against Tobacco mosaic virus

A series of novel 1-phenyl-5-amine-4-pyrazole thioether derivatives containing a 1,3,4-oxadiazole moiety was designed and synthesised. In vivo antiviral bioassay results showed that most of the target compounds exhibited excellent inactivation activity against Tobacco mosaic virus (TMV). The EC₅₀ values of the inactivation activities for T₂, T₇, T₉, T₂₄, T₂₅ and T₂₇ were 15.7, 15.7, 15.5, 11.9, 12.5 and 16.5 μg/mL, respectively, which were remarkably superior over that of the commercialised antiviral agent ningnanmycin (40.3 μg/mL). Morphological study using AFM and TEM of TMV treated with T₂₄ showed that T₂₄ could significantly shorten the polymerization length of TMV particles and formed a distinct break on the rod-shaped TMV. Investigations for virus infection efficiency on tobacco leaves demonstrated that infectivity of virion had been reduced obviously upon T₂₄ treatment. Subsequently, a strong interaction between T₂₄ and TMV-CP (K_d = 3.8 μM, score 6.11) was observed through MST experiments. Molecular docking study further revealed that target compounds interact with amino acid residue Glu50 in TMV CP, causing disassembly of virion, shorting the length of the virion and reducing the infectivity of virion, and resulting in high inactivating activity of target compounds. This study provides a new insight for discovery of antiviral compounds through a new action mechanism with a new binding site.

Study of the in vivo antiviral activity against TMV treated with novel 1-(t-butyl)-5-amino-4-pyrazole derivatives containing a 1,3,4-oxadiazole sulfide moiety

A series of new 1-tert-butyl-5-amino-4-pyrazole bioxadiazole sulfide derivatives containing a 1,3,4-oxadiazole moiety were designed and synthesized. The bioactivity results showed that some title compounds exhibited excellent protective activity against TMV and certain insecticidal activity. Among the tested compounds, the EC₅₀ values of 5d, 5j, 5k and 5l were 165.8, 163.2, 159.7 and 193.1 mg/L, respectively, which are better than the EC₅₀ value of ningnanmycin (271.3 mg/L). The chlorophyll contents and the defense enzyme activities of the tobacco leaves after treatment with 5j were significantly increased, which indicated that this series of title compounds may induce the systemic acquired resistance of host to defend against diseases. Further in vivo protective activity research on 5j using TMV with a GFP gene tag found that it can effectively inhibit the spread of TMV in inoculated tobacco. A morphological study with TEM revealed that title compound 5h can cause a distinct break of the rod-shaped TMV. Moreover, the insecticidal activity revealed that the fatality rates of 5a, 5b and 5m against aphidoidea were 85%, 83% and 87%, respectively, which indicated that the title compounds can effectively block the common carrier of plant viruses, thereby effectively reducing the TMV infection risk of tobacco. This series of synergistic effects provide key information for the research and development of antiviral agents.

Therapeutic potential of oxadiazole or furadiazole containing compounds

As we know that, Oxadiazole or furadi azole ring containing derivatives are an important class of heterocyclic compounds. A heterocyclic five-membered ring that possesses two carbons, one oxygen atom, two nitrogen atoms, and two double bonds is known as oxadiazole. They are derived from furan by the replacement of two methylene groups (= CH) with two nitrogen (-N =) atoms. The aromaticity was reduced with the replacement of these groups in the furan ring to such an extent that it shows conjugated diene character. Four different known isomers of oxadiazole were existed such as 1,2,4-oxadiazole, 1,2,3-oxadiazole, 1,2,5-oxadiazole & 1,3,4-oxadiazole. Among them, 1,3,4-oxadiazoles & 1,2,4-oxadiazoles are better known and more widely studied by the researchers due to their broad range of chemical and biological properties. 1,3,4-oxadiazoles have become important synthons in the development of new drugs. The derivatives of the oxadiazole nucleus (1,3,4-oxadiazoles) show various biological activities such as antibacterial, anti-mycobacterial, antitumor, anti-viral and antioxidant activity, etc. as reported in the literature. There are different examples of commercially available drugs which consist of 1,3,4-oxadiazole ring such as nitrofuran derivative (Furamizole) which has strong antibacterial activity, Raltegravir as an antiviral drug and Nesapidil drug is used in anti-arrhythmic therapy. This present review summarized some pharmacological activities and various kinds of synthetic routes for 2, 5-disubstituted 1,3,4-oxadiazole, and their derived products.

Marine-natural-products for biocides development: first discovery of meridianin alkaloids as antiviral and anti-phytopathogenic-fungus agents

BACKGROUND

Food is an important strategic material related to national economy and people's livelihood. Plant diseases seriously affect crop yield and quality. Marine natural products are an important source for novel drugs discovery. In this work, meridianin alkaloids were selected as the parent structure. A series of meridianin alkaloid analogues were rationally designed, synthesized and evaluated for their antiviral activities and fungicidal activities.

RESULT

These compounds were found to have good antiviral and fungicidal activities for the first time. The structure-activity relationship (SAR) research revealed that introducing bromine atom at the 5-position of indole ring is beneficial to antiviral activity, but introducing methoxy group is not conducive. Introducing bromine atom at the 6-position of indole ring or nitrogen atom at the 7-position of the indole ring resulted in lower antiviral activity. Most of the meridianin derivatives showed higher anti-TMV activities at 500 μg mL^-1 than Ribavirin, especially for compounds 6c, 8a and 10a. All of the compounds also displayed broad spectrum fungicidal activities against 14 kinds of phytopathogenic fungi at 50 μg mL^-1 .

CONCLUSION

Compound 6c with relatively simple structure and excellent antiviral activity, which is similar to that of Ningnanmycin, emerged as novel anti-TMV lead compound. Compound 5d with broad spectrum and high effect fungicidal activity emerged as a new fungicidal lead compound. Current research lays a solid foundation for the application of meridianin alkaloids in crop protection. © 2019 Society of Chemical Industry.

3D-QSAR and Docking Studies on Pyrimidine Derivatives as CSF-1R Inhibitors

Background:

Colony Stimulating Factor-1 Receptor (CSF-1R) is associated with malignancy, invasiveness and poor prognosis of tumors, and pyrimidine derivatives are considered as a novel class of CSF-1R inhibitor.

Methods:

To explore the relationship between the structures of substituted pyrimidine derivatives and their inhibitory activities against CSF-1R, CoMFA and CoMSIA analyses, and molecular docking studies were performed on a dataset of forty-four compounds.

Results:

We found in CoMFA model including steric and electrostatic fields for the training set, the cross-validated q2 value was 0.617 and the non-cross-validated r2 value was 0.983. While, the crossvalidated q2 value was 0.637 and the non-cross-validated r2 value was 0.984 in CoMSIA Model which include steric, electrostatic and hydrophobic fields. 3D equipotential maps generated from CoMFA and CoMSIA along with the docking binding structures provided enough information about the structural requirements for better activity.

Conclusion:

The data generated from the present study helped us to predict the activity of new inhibitors and further design some novel and potent CSF-1R inhibitors.

Tomato Chlorosis Virus Minor Coat Protein as a Novel Target To Screen Antiviral Drugs

Minor coat protein (mCP), an important component of tomato chlorosis virus (ToCV), plays a significant role in the process of virus assembly and movement and is directly related to the virus-insect transmission. Therefore, ToCV mCP could be considered as a potent target for anti-ToCV drugs. In this study, ToCV mCP was first cloned, expressed, purified, and a novel target to screen the antiviral agents. The results showed that some antiviral compounds bound to ToCV mCP with strongly affinities in vitro, including quinazoline derivatives 4a and 4b, Ningnanmycin, and Ribavirin. Subsequently, three-dimensional-quantitative structure-activity relationship (3D-QSAR) analysis was performed based on the binding affinities, and the model indicated that 4a and 4b had indeed stronger binding effects on ToCV mCP than other quinazoline derivatives. Finally, the anti-ToCV activities of compounds 4a and 4b were evaluated by quantitative real-time polymerase chain reaction in vivo. Compounds 4a and 4b inhibited infection of ToCV in the host and as well as reduced the level of ToCV mCP gene expression. Thus, ToCV mCP can be used as a novel drug target for screening anti-ToCV agents, and the ligand-based 3D-QSAR analysis of quinazoline derivatives provided new insights into the design and optimization of novel anti-ToCV drug molecules based on ToCV mCP.

Synthesis and antiviral activity of novel myricetin derivatives containing ferulic acid amide scaffolds

A variety of myricetin derivatives bearing ferulic acid amide scaffolds were designed and synthesized.

Design, Synthesis, and Bioactivity Evaluation of Novel Isoxazole-Amide Derivatives Containing an Acylhydrazone Moiety as New Active Antiviral Agents

As a continuation of our efforts to discover and develop "me-better" active molecules, in this study, a series of novel isoxazole-amide derivatives containing an acylhydrazone moiety were synthesized and evaluated for their antiviral activities against tobacco mosaic virus (TMV) and cucumber mosaic virus (CMV). Antiviral bioassays indicated that some of the target compounds exhibited better in vivo antiviral activities against TMV and CMV than those of Ningnanmycin (NNM). Especially, the compound 7t exhibited the best curative, protection, and inactivation activities against TMV and CMV which were superior to those of NNM. Meanwhile, our present work also revealed that compound 7t could enhance the defense-related enzyme activity and increase the chlorophyll content in tobacco leaves to induce resistance and enhance plant tolerance to TMV infection.

Synthesis, Antiviral Activity, and Mechanisms of Purine Nucleoside Derivatives Containing a Sulfonamide Moiety

Novel purine nucleoside derivatives containing a sulfonamide moiety were prepared, as well as their antiviral activities against potato virus Y (PVY), cucumber mosaic virus (CMV), and tobacco mosaic virus (TMV) were evaluated. The antiviral mechanisms of the compounds were investigated. Results showed that most of the compounds had good antiviral activities. Compound 5 at 500 μg/mL exhibited excellent curative and protective activities of 52.5% and 60.0% and of 52.0% and 60.2% for PVY and CMV, respectively, which are higher than those of ningnanmycin (48.1%, 49.6%; 45.3%, 47.7%), ribavirin (38.3%, 48.2%; 40.8%, 45.5%), and chitosan oligosaccharide (32.5%, 33.8%; 35.1%, 34.6%). Moreover, compound 5 displayed good inactivating activity against TMV, with an EC₅₀ value of 48.8 μg/mL, which is better than that of ningnanmycin (84.7 μg/mL), ribavirin (150.4 μg/mL), and chitosan oligosaccharide (521.3 μg/mL). The excellent antiviral activity of compound 5 is related to its immune induction effect which can regulate the physiological and biochemical processes in plants, including defense-related enzyme activities, defense-related genes, and photosynthesis-related proteins. These results indicate that purine nucleoside derivatives containing a sulfonamide moiety are worthy of further research and development as new antiviral agents.

A Review Exploring Therapeutic Worth of 1,3,4-Oxadiazole Tailored Compounds

1,3,4-Oxadiazole, a five-membered aromatic ring can be seen in a number of synthetic molecules. The peculiar structural feature of 1,3,4-oxadiazole ring with pyridine type of nitrogen atom is beneficial for 1,3,4-oxadiazole derivatives to have effective binding with different enzymes and receptors in biological systems through numerous weak interactions, thereby eliciting an array of bioactivities. Research in the area of development of 1,3,4-oxadiazole-based derivatives has become an interesting topic for the scientists. A number of 1,3,4-oxadiazole based compounds with high therapeutic potency are being extensively used for the treatment of different ailments, contributing to enormous development value. This work provides a systematic and comprehensive review highlighting current developments of 1,3,4-oxadiazole based compounds in the entire range of medicinal chemistry such as anticancer, antifungal, antibacterial, antitubercular, anti-inflammatory, antineuropathic, antihypertensive, antihistaminic, antiparasitic, antiobesity, antiviral, and other medicinal agents. It is believed that this review will be of great help for new thoughts in the pursuit for rational designs for the development of more active and less toxic 1,3,4-oxadiazole based medicinal agents.

Design, synthesis, antiviral bioactivities and interaction mechanisms of penta-1,4-diene-3-one oxime ether derivatives containing a quinazolin-4(3H)-one scaffold

Background

penta-1,4-diene-3-one oxime ether and quinazolin-4(3H)-one derivatives possess favorable agricultural activities. Aiming to discover novel molecules with highly-efficient agricultural activities, a series of penta-1,4-diene-3-one oxime ether derivatives containing a quinazolin-4(3H)-one scaffold were synthesized and evaluated for their antiviral activities.

Result

Antiviral bioassays indicated that some title compounds exhibited significant antiviral activity against tobacco mosaic virus (TMV). In particular, compounds 8c, 8j and 8k possessed appreciable curative activities against TMV in vivo, with half-maximal effective concentration (EC₅₀) values of 138.5, 132.9 and 125.6 μg/mL, respectively, which are better than that of ningnanmycin (207.3 μg/mL). Furthermore, the microscale thermophoresis experiments (MST) on the interaction of compound 8k with TMV coat protein (TMV CP) showed 8k bound to TMV CP with a dissociation constant of 0.97 mmol/L. Docking studies provided further insights into the interaction of 8k with the Arg90 of TMV CP.

Conclusions

Sixteen penta-1,4-diene-3-one oxime ether derivatives containing a quinazolin-4(3H)-one scaffold were designed, synthesized, and their antiviral activities against TMV were evaluated. Antiviral bioassays indicated that some target compounds exhibited remarkable antiviral activities against TMV. Furthermore, through the MST and docking studies, we can speculate that 8k inhibited the virulence of TMV by binding Arg90 in TMV CP. These results indicated that this kind of penta-1,4-diene-3-one oxime ether derivatives containing a quinazolin-4(3H)-one scaffold could be further studied as potential alternative templates in the search for novel antiviral agents.

Electronic supplementary material

The online version of this article (10.1186/s13065-019-0547-1) contains supplementary material, which is available to authorized users.

Novel Phosphorylated Penta-1,4-dien-3-one Derivatives: Design, Synthesis, and Biological Activity

A series of novel phosphorylated penta-1,4-dien-3-one derivatives were designed and synthesized. The structures of all title compounds were determined by ¹H-NMR, ¹³C-NMR, ³¹P-NMR, and high-resolution mass spectrometry (HRMS). Bioassay results showed that several of the title compounds exhibited remarkable antibacterial and antiviral activities. Among these, compound 3g exhibited substantial antibacterial activity against Xanthomonas oryzae pv. Oryzae (Xoo), with a 50% effective concentration (EC₅₀) value of 8.6 μg/mL, which was significantly superior to bismerthiazol (BT) (58.8 µg/mL) and thiodiazole-copper (TC) (78.7 μg/mL). In addition, compound 3h showed remarkable protective activity against tobacco mosaic virus (TMV), with an EC₅₀ value of 104.2 μg/mL, which was superior to that of ningnanmycin (386.2 μg/mL). Furthermore, the microscale thermophoresis and molecular docking experiments on the interaction of compounds 3h and 3j with TMV coat protein (TMV CP) were also investigated. Compounds 3h and 3j bound to TMV CP with dissociation constants of 0.028 and 0.23 μmol/L, which were better than that of ningnanmycin (0.52 μmol/L). These results suggest that novel phosphorylated penta-1,4-dien-3-one derivatives may be considered as an activator for antibacterial and antiviral agents.

Cucumber mosaic virus coat protein: The potential target of 1, 4-pentadien-3-one derivatives

Cucumber mosaic virus coat protein (CMV CP) plays a key role in cell-to-cell movement in host organisms. 1,4-Pentadien-3-one derivatives have excellent antiviral activities. In this study, we cloned, expressed and purified a CP recombinant protein. Then, we studied the binding interactions of CMV CP and 1, 4-pentadien-3-one derivatives N1-N20. Microscale thermophoresis experiments showed that N12 and N16 bound to CMV CP with dissociation constants of 0.071 and 0.11 μM, respectively. Docking and site-directed mutagenesis studies provided further insights into the interactions of N12 and N16 with Ile210, Thr69 and Ser213of CMV CP. Thus, these CMV CP residues may be important binding sites for the 1,4-pentadien-3-one derivatives N12 and N16. The data are important for designing and synthesizing new pentadienone derivatives.

Novel 1,3,4-Oxadiazole Derivatives Containing a Cinnamic Acid Moiety as Potential Bactericide for Rice Bacterial Diseases

Rice bacterial leaf blight and leaf streak are two important bacterial diseases of rice, which can result in yield loss. Currently, effective antimicrobials for rice bacterial diseases are still lacking. Thus, to develop highly effective and low-risk bactericides, 31 novel 1,3,4-oxadiazole derivatives containing a cinnamic acid moiety were designed and synthesized. Bioassay results demonstrated that all compounds exhibited good antibacterial activities in vitro. Significantly, compounds 5r and 5t showed excellent antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), with the 50% effective concentration (EC₅₀) values of 0.58 and 0.34, and 0.44 and 0.20 μg/mL, respectively. These compounds were much better than thiodiazole copper (123.10 and 161.52 μg/mL) and bismerthiazol (85.66 and 110.96 μg/mL). Moreover, compound 5t had better protective and curative activities against rice bacterial leaf blight and leaf streak than thiodiazole copper and bismerthiazol in vivo. Simultaneously, the in vivo efficacy of the compounds was demonstrated by real-time quantitative PCR to quantify bacterial titers. In addition, a three-dimensional quantitative structure⁻activity relationship model was created and presented good predictive ability. This work provides support for 1,3,4-oxadiazole derivatives containing a cinnamic acid moiety as a potential new bactericide for rice bacterial diseases.