Discovery of Dithioacetal Derivatives Containing Sulfonamide Moiety of Novel Antiviral Agents by TMV Coat Protein as a Potential Target

Chemical and Biological Investigations of Antiviral Agents Against Plant Viruses Conducted in China in the 21st Century

Research into the biology of plant viruses, their mechanisms of pathogenicity, and the induction of host resistance has laid a solid foundation for the discovery of antiviral agents and their targets and the development of effective control technologies. Additionally, recent advancements in fields such as chemical biology, cheminformatics, bioinformatics, and synthetic biology have provided valuable methods and tools for the design of antiviral drugs, the synthesis of drug molecules, assessment of their activity, and investigation of their modes of action. Compared with drug development for human viral diseases, the control of plant viral diseases presents greater challenges, including the cost-benefit of agents, simplification of control technologies, and the effectiveness of treatments. Therefore, in the current context of complex outbreaks and severe damage caused by plant viral diseases, it is crucial to delve deeper into the research and development of antiviral agents. This review provides a detailed overview of the biological characteristics of current targets for antiviral agents, the mode of interaction between plant virus targets and antivirals, and insights for future drug development. We believe this review will not only facilitate the in-depth analysis of the development of antivirals for crops but also offer valuable perspectives for the development of antiviral agents for use in human and veterinary medicine.

Corrolato(oxo)antimony(V) Dimer with Hydrogen-Bond Donor Groups in Secondary Coordination Sphere as a Catalyst for Hydrogen Evolution Reaction

The focus is on developing alternative molecular catalysts using main-group elements and implementing strategic improvements for sustainable hydrogen production. For this purpose, a FB corrole with a (2-(2-((4-methylphenyl)sulfonamido)ethoxy)phenyl) group inserted into the meso position (C-10) of the corrole, along with its high-valent (corrolato)(oxo)antimony(V) dimer, was synthesized. In the crystal structure analysis of the FB corrole and the (corrolato)(oxo)antimony(V) dimer complex, it was noted that the sulfonamido group in the ligand periphery sits atop the corrole ring. The electrochemical hydrogen evolution reaction (HER) of the (corrolato)(oxo)antimony(V) dimer was studied and compared with a previously reported (corrolato)(oxo)antimony(V) complex, which lacks hydrogen-bond donor groups in the secondary coordination sphere. The newly designed molecules, featuring hydrogen-bond donor groups in the secondary coordination sphere, demonstrated clear superiority in the electrochemical HER. Controlled potential electrolysis was employed to evaluate the charge accumulation associated with hydrogen generation in a homogeneous three-electrode system in the presence of 50 mM TFA. The produced hydrogen exhibits a Faradaic efficiency of approximately 80.96%, a turnover frequency (TOF) of 0.44 h-1, and a production rate of 52.83 μL h-1, highlighting the effective catalytic activity of the (corrolato)(oxo)antimony(V) dimer in hydrogen evolution.

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.

Ferulic Acid Dimers as Potential Antiviral Agents by Inhibiting TMV Self-Assembly

A series of ferulic acid dimers were designed, synthesized, and evaluated for anti-TMV activity. Biological assays demonstrated that compounds A6, E3, and E5 displayed excellent inactivating against tobacco mosaic virus (TMV) with EC50 values of 62.8, 94.4, and 85.2 μg mL-1, respectively, which were superior to that of ningnanmycin (108.1 μg mL-1). Microscale thermophoresis indicated that compounds A6, E3, and E5 showed strong binding capacity to TMV coat protein with binding affinity values of 1.862, 3.439, and 2.926 μM, respectively. Molecular docking and molecular dynamics simulation revealed that compound A6 could firmly bind to the TMV coat protein through hydrogen and hydrophobic bonds. Transmission electron microscopy and self-assembly experiments indicated that compound A6 obviously destroyed the integrity of the TMV particles and blocked the virus from infecting the host. This study revealed that A6 can be used as a promising leading structure for the development of antiviral agents by inhibiting TMV self-assembly.

Antiviral Mechanisms of Anisomycin Produced by Streptomyces albulus SN40 on Potato Virus Y

Microbial secondary metabolites produced by Streptomyces have diverse application prospects in the control of plant diseases. Herein, the fermentation filtrate of Streptomyces SN40 effectively inhibited the infection of tobacco mosaic virus (TMV) in Nicotiana glutinosa and systemic infection of potato virus Y (PVY) in Nicotiana benthamiana. Additionally, metabolomic analysis indicated that anisomycin (C14H19NO4) and trans-3-indoleacrylic acid (C11H9NO2) were highly abundant in the crude extract and that anisomycin effectively suppressed the infection of TMV as well as PVY. Subsequently, transcriptomic analysis was conducted to elucidate its mechanisms on the induction of host defense responses. Furthermore, the results of molecular docking suggested that anisomycin can potentially bind with the helicase domain (Hel) of TMV replicase, TMV coat protein (CP), and PVY helper component proteinase (HC-Pro). This study demonstrates new functions of anisomycin in virus inhibition and provides important theoretical significance for the development of new biological pesticides to control diverse plant viruses.

Eco-Friendly Cinnamic Acid Derivatives Containing Glycoside Scaffolds as Potential Antiviral Agents

Natural products are a crucial source in the development of new eco-friendly antiviral agents to control plant viral diseases. In our previous studies, some ferulic acid derivatives with good antiviral activity were obtained as an immune activator. To continue the discovery of eco-friendly antiviral agents, different monosaccharides were introduced into cinnamic acid skeletons by an activity-based strategy to obtain a series of cinnamic acid derivatives containing glycoside scaffolds, and their antiviral activities against tobacco mosaic virus (TMV) and tomato spotted wilt virus (TSWV) were evaluated. Among them, compound 8d showed the greatest protective activities against TMV and TSWV, with the EC50 values of 128.5 and 236.8 μg mL-1, respectively, which were superior to those of ningnanmycin (238.5 and 315.7 μg mL-1, respectively). Moreover, compound 8d could significantly improve the defense enzyme activities of peroxidase, chitinase, and β-1,3-glucanase. Proteomic and transcriptome analyses indicated that compound 8d regulated gene transcription and protein expression levels involved in the defense response to resist virus infection. The present study revealed that compound 8d is a potential lead candidate for the development of novel, eco-friendly, and natural-product-based antiviral agents.

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.

3-Hydroxy-2-oxindole Derivatives Containing Sulfonamide Motif: Synthesis, Antiviral Activity, and Modes of Action

3-Hydroxy-2-oxindole motif constitutes a core structure in numerous natural products and imparts notable biological activities. Here, we describe the design and synthesis of four series of novel 3-substituted-3-hydroxy-2-oxindole derivatives containing sulfonamide moiety along with their antiviral activities against potato virus Y (PVY). Compound 10b displayed optimal antiviral activity and superior anti-PVY activity compared with the lead compound and commercial Ningnanmycin in terms of curative and protective effects. Additionally, 10b considerably inhibited PVY systemic infection in Nicotiana benthamiana. Physiological and biochemical analyses revealed that the activities of the four crucial defense-related enzymes increased in the tobacco plant following treatment with 10b. RNA-sequencing analysis revealed that 10b substantially induced the upregulation of 38 differentially expressed genes, which were enriched in the photosynthesis pathway. These findings suggest that 10b is a promising antiviral agrochemical that can effectively control PVY infection and trigger plant host immunity to develop virus resistance. This study provides novel molecular entities and ideas for developing new pesticides.

Design, Synthesis, and Bioactivity of Spiro Derivatives Containing a Pyridine Moiety

We designed and synthesized a series of pyridine spiro derivatives and evaluated their insecticidal and antiviral activities. Some compounds exhibited good insecticidal and antiviral activities. Notably, the E series of compounds displayed good insecticidal activity against Tetranychus urticae. Compounds E20 (EC₅₀ = 63.68 mg/L) and F4 (EC₅₀ = 47.81 mg/L) exhibited inactivation activities against the tobacco mosaic virus (TMV), which were similar to that of Ningnanmycin (EC₅₀ = 58.01 mg/L). Molecular docking showed that compounds E20 and F4 exhibited satisfactory affinities for the TMV coat protein (TMV-CP), with binding energies (-6.7 and -6.4 kcal/mol, respectively) slightly lower than that of Ningnanmycin (-6.3 kcal/mol). Further, molecular dynamics analysis revealed that compounds E20 and F4 exhibited better binding stability values than Ningnanmycin. Microscale thermophoresis showed that compounds E20 (K_d = 0.053 ± 0.016 μM) and F4 (K_d = 0.045 ± 0.022 μM) bound more strongly to TMV-CP than Ningnanmycin (K_d = 0.10 ± 0.029 μM). The results of transmission electron microscopy showed that these two compounds hindered the self-assembly and growth of TMV. In summary, we showed that these pyridine spiro derivatives could be used as a basis for the research and development of novel pesticides.

Synthesis and biological evaluation of N-alkyl sulfonamides derived from polycyclic hydrocarbon scaffolds using a nitrogen-centered radical approach

Polycyclic hydrocarbons (PH) provide intriguing potential as lipophilic scaffolds within medicinal chemistry, but are currently limited by the availability of synthetic tools for predictable modification of the PH unit. Herein we report the development of new methods for installation of a sulfonamide unit to PH cores. In the first method, a xanthate ester serves as reagent for aminosulfonation using pre-formed imidoiodinane as N-source. An investigation of the reaction mechanism was performed to implicate a process involving a N-centered radical. An additional method for sulfonamide installation is described that involves the use of commercially available reagents and operationally convenient conditions. Using the new synthetic methods, 22 compounds were prepared and screened for biological activity against 6 mammalian cell lines along with Gram-positive and Gram-negative bacterial strains. Results of the viability assays have identified compounds that exhibit higher potency than other known anticancer agents such as indisulam and ABT-751. Additionally, the physicochemical and drug-likeness properties of the synthesized compounds have been determined experimentally and using in silico predictive tools. The initial exploration into sulfonamide insertion into PH cores has resulted in a number of compounds that warrant further development to produce molecules with therapeutic value.

Plant Viral Coat Proteins as Biochemical Targets for Antiviral Compounds

Coat proteins (CPs) of RNA plant viruses play a pivotal role in virus particle assembly, vector transmission, host identification, RNA replication, and intracellular and intercellular movement. Numerous compounds targeting CPs have been designed, synthesized, and screened for their antiviral activities. This review is intended to fill a knowledge gap where a comprehensive summary is needed for antiviral agent discovery based on plant viral CPs. In this review, major achievements are summarized with emphasis on plant viral CPs as biochemical targets and action mechanisms of antiviral agents. This review hopefully provides new insights and references for the further development of new safe and effective antiviral pesticides.

First Discovery of Imidazo[1,2-a]pyridine Mesoionic Compounds Incorporating a Sulfonamide Moiety as Antiviral Agents

The applications of mesoionic compounds and their analogues as agents against plant viruses remain unexplored. This was the first evaluation of the antiviral activities of mesoionic compounds on this issue. Our study involved the design and synthesis of a series of novel imidazo[1,2-a]pyridine mesoionic compounds containing a sulfonamide moiety and the assessment of their antiviral activities against potato virus Y (PVY). Compound A33 was assessed on the basis of three-dimensional quantitative structure-activity relationship (3D-QSAR) model analysis and displayed good curative, protective, and inactivating activity effects against PVY at 500 mg/L, up to 51.0, 62.0, and 82.1%, respectively, which were higher than those of commercial ningnanmycin (NNM, at 47.2, 50.1, and 81.4%). Significantly, defensive enzyme activities and proteomics results showed that compound A33 could enhance the defense response by activating the activity of defense enzymes, inducing the glycolysis/gluconeogenesis pathway of tobacco to resist PVY infection. Therefore, our study indicates that compound A33 could be applied as a potential viral inhibitor.

Anti-TMV activity and effects of three prieurianin-type limonoids from Munronia henryi

Three prieurianin-type limonoids (1-3), including two new compounds (1 and 2) and one known compound (3) were isolated from Munronia henryi. These compounds were tested for their activities against tobacco mosaic virus (TMV) by the conventional half-leaf method and the outcomes were analyzed by western blotting and RT-PCR assays. The three tested compounds, at 100 μg/mL, showed strong antiviral activities in the pretreated tobacco plants with inhibition rates ranging from 70.5% to 81.3%, which were significantly higher than that of the positive control, ningnanmycin (55.6%). Their potential of inducing systemic acquired resistance (SAR) was also evaluated, in which compound 1 showed excellent induction activities. Furthermore, it was found that potentiation of defense-related enzyme activity and the contents of SA was increased. Compound 1 could also inhibit the expression of TMV CP and up-regulate the expression of defense-related genes. This work revealed that these limonoids, especially compound 1 could induce resistance in tobacco plants against the viral pathogen TMV. Meanwhile, compounds 1-3 could down-regulate the expression of NtHsp70-1 and Nthsp70-261 genes, indicating that these limonoids possibly inhibit TMV infection by suppressing NtHsp70-1 and Nthsp70-261 expression. This study is the first to report antiviral compounds with two different mechanisms of action.

Anti-TMV effects of seco-pregnane C21 steroidal glycosides isolated from the roots of Cynanchum paniculatum

Tobacco mosaic virus (TMV) is known to infect a wide range of plants, resulting in reduced yield and productivity. Novel, effective, and plant-based pesticides are required to protect plants against TMV infection. To identify novel anti-TMV agents from natural sources, we systematically studied the roots of Cynanchum paniculatum and isolated six new seco-pregnane C₂₁ steroidal glycosides, along with 14 known compounds. Their structures were elucidated by comprehensive spectroscopic data analysis. The anti-TMV activity of compounds were screened using the half-leaf method. Biological tests revealed that compounds 1, 2, 5, 9, 10, 15, and 16 displayed significant anti-TMV activities compared with the positive control ningnanmycin. In addition, reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis confirmed the antiviral activity of these compounds, as evident from reduced TMV coat protein (TMV-CP) gene replication and TMV-CP protein expression. These compounds downregulated the expression of NtHsp70-1 and NtHsp70-261, indicating that these steroidal glycosides possibly inhibit the TMV infection by suppressing the expression of NtHsp70-1 and NtHsp70-061 expression.

Recent Research Progress: Discovery of Anti-Plant Virus Agents Based on Natural Scaffold

Plant virus diseases, also known as “plant cancers”, cause serious harm to the agriculture of the world and huge economic losses every year. Antiviral agents are one of the most effective ways to control plant virus diseases. Ningnanmycin is currently the most successful anti-plant virus agent, but its field control effect is not ideal due to its instability. In recent years, great progress has been made in the research and development of antiviral agents, the mainstream research direction is to obtain antiviral agents or lead compounds based on structural modification of natural products. However, no antiviral agent has been able to completely inhibit plant viruses. Therefore, the development of highly effective antiviral agents still faces enormous challenges. Therefore, we reviewed the recent research progress of anti-plant virus agents based on natural products in the past decade, and discussed their structure-activity relationship (SAR) and mechanism of action. It is hoped that this review can provide new inspiration for the discovery and mechanism of action of novel antiviral agents.

First Discovery of Novel Cytosine Derivatives Containing a Sulfonamide Moiety as Potential Antiviral Agents

A series of cytosine derivatives containing a sulfonamide moiety were designed and synthesized, and their antiviral activities against pepper mild mottle virus (PMMoV) were systematically evaluated. Then, a three-dimensional quantitative structure-activity relationship (3D-QSAR) model was constructed to study the structure-activity relationship according to the pEC₅₀ of the compounds' protective activities. Next, compound A32 with preferable antiviral activity on PMMoV was obtained based on the CoMSIA and CoMFA models, with an EC₅₀ of 19.5 μg/mL, which was superior to the template molecule A25 (21.3 μg/mL) and ningnanmycin (214.0 μg/mL). In addition, further studies showed that the antiviral activity of compound A32 against PMMoV was in accord with the up-regulation of proteins expressed in the defense response and carbon fixation in photosynthetic organisms. These results indicated that cytosine derivatives containing a sulfonamide moiety could be used as novel potential antiviral agents for further research and development.

Discovery of novel chromone derivatives containing a sulfonamide moiety as potential anti-TSWV agents

A number of chromone derivatives containing sulfonamide structure were designed and synthesized. Firstly, the target compounds were evaluated for anti-TSWV activities in vivo by the half-leaf method. We found that most of the compounds had good anti-TSWV activities. Among them, compound 12B had excellent anti-TSWV inactivating activity with an EC₅₀ of 80.5 μg/mL, which was significantly better than xiangcaoliusuobingmi (765.7 μg/mL). Secondly, TSWV nucleocapsid protein (N) was expressed and purified, and the affinity between the compounds and TSWV N was tested by microscale thermophoresis (MST). Compound 12B had a good affinity for TSWV N with a K_d value of 5.02 μM, which was superior to xiangcaoliusuobingmi (29.83 μM). Finally, in order to study the mode of interaction between the compound 12B and TSWV N, we carried out molecular docking. The results indicated that compound 12B might inactivate the virus by destroying the TSWV N oligomer structure. These results lay a solid foundation for the further discovery of chromone derivatives containing sulfonamide structure with high anti-TSWV activities.

Discovery of Novel Chromone Derivatives Containing a Sulfonamide Moiety as Anti-ToCV Agents through the Tomato Chlorosis Virus Coat Protein-Oriented Screening Method

A number of novel chromone derivatives containing sulfonamide moieties were designed and synthesized, and the activity of compounds against tomato chlorosis virus (ToCV) was assessed using the ToCVCP-oriented screening method. Comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) models were established based on the dissociation constant (K_d) values of the target compounds, and compound 35 was designed and synthesized with the aid of CoMFA and CoMSIA models. The study of affinity interaction indicated that compound 35 exhibited excellent affinity with ToCVCP with a K_d value of 0.11 μM, which was better than that of the positive control agents xiangcaoliusuobingmi (0.44 μM) and ningnanmycin (0.79 μM). In addition, the in vivo inhibitory effect of compound 35 on the ToCVCP gene was evaluated by the quantitative real-time polymerase chain reaction. ToCVCP gene expression levels of the compound 35 treatment group were reduced by 67.2%, which was better than that of the positive control agent ningnanmycin (59.5%). Therefore, compound 35 can be used as a potential anti-ToCV drug in the future.