Synthesis of Novel Antiviral Ferulic Acid-Eugenol and Isoeugenol Hybrids Using Various Link Reactions

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.

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.

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.

Insights into a class of natural eugenol and its optimized derivatives as potential tobacco mosaic virus helicase inhibitors by structure-based virtual screening

Plant diseases caused by malignant and refractory phytopathogenic viruses have considerably restricted crop yields and quality. To date, drug design targeting functional proteins or enzymes of viruses is an efficient and viable strategy to guide the development of new pesticides. Herein, a series of novel eugenol derivatives targeting the tobacco mosaic virus (TMV) helicase have been designed using structure-based virtual screening (SBVS). Structure-activity relationship indicated that 2 t displayed the most powerful bonding capability (Kd = 0.2 μM) along with brilliant TMV helicase ATPase inhibitory potency (IC50 = 141.9 μM) and applausive anti-TMV capability (EC50 = 315.7 μg/mL), ostentatiously outperforming that of commercial Acyclovir (Kd = 23.0 μM, IC50 = 183.7 μM) and Ribavirin (EC50 = 624.3 μg/mL). Molecular dynamics simulations and docking suggested ligand 2 t was stable and bound in the active pocket of the TMV helicase by multiple interactions. Given these superior properties, eugenol-based derivatives could be considered as the novel potential plant viral helicase inhibitors. Furthermore, this effective and feasible SBVS strategy established a valuable screening platform for helicase-targeted drug development.

Synthesis, anti-amoebic activity and molecular docking simulation of eugenol derivatives against Acanthamoeba sp

Amoebae of the genus Acanthamoeba can cause diseases such as amoebic keratitis and granulomatous amoebic encephalitis. Until now, treatment options for these diseases have not been fully effective and have several drawbacks. Therefore, research into new drugs is needed for more effective treatment of Acanthamoeba infections. Eugenol, a phenolic aromatic compound mainly derived from cloves, has a variety of pharmaceutical properties. In this study, nine eugenol derivatives (K1-K9), consisting of five new and four known compounds, were synthesized and screened for their antiamoebic properties against Acanthamoeba sp. The structure of these compounds was characterized spectroscopically by Fourier transform infrared (FTIR), Ultraviolet-Visible (UV-Vis), 1H and 13C Nuclear Magnetic Resonance (NMR) and mass spectrometer (MS). The derived molecules were screened for antiamoebic activity by determining IC50 values based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and observation of amoeba morphological changes by light and fluorescence microscopy. Most of the tested compounds possessed strong to moderate cytotoxic effects against trophozoite cells with IC50 values ranging from 0.61 to 24.83 μg/mL. Observation of amoebae morphology by light microscopy showed that the compounds caused the transformed cells to be roundish and reduced in size. Furthermore, fluorescence microscopy observation using acridine orange (AO) and propidium iodide (PI) (AO/PI) staining showed that the cells have damaged membranes by displaying a green cytoplasm with orange-stained lysosomes. Acidification of the lysosomal structure indicated disruption of the internal structure of Acanthamoeba cells when treated with eugenol derivatives. The observed biological results were also confirmed by interaction simulations based on molecular docking between eugenol derivatives and Acanthamoeba profilin. These interactions could affect the actin-binding ability of the protein, disrupting the shape and mobility of Acanthamoeba. The overall results of this study demonstrate that eugenol derivatives can be considered as potential drugs against infections caused by Acanthamoeba.

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

BACKGROUND

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

RESULTS

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

CONCLUSION

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

Design, synthesis, and antifungal activities of novel sulfoximine derivatives for plant protection

BACKGROUND

Fungicides play a significant role in the integrated management of plant pathogens. However, the irrational application of fungicides with similar structures has led to development of cross-resistance, therefore there is a need to seek novel fungicides with new structures.

RESULTS

Twenty-eight novel sulfoximine derivatives incorporating nitroguanidine moieties were designed, synthesized, and evaluated as antifungal agents. The bioassay results indicated that most of the synthesized compounds displayed excellent fungicidal activities against Sclerotinia sclerotiorum, Rhizoctonia solani, Fusarium graminearum, and Pyricularia grisea. Among these, compounds 6c₄ , 6c₅ , and 6c₆ exhibited remarkable fungicidal activities against P. grisea, with EC₅₀ values of 1.28, 1.17, and 1.68 μg mL^-1 , respectively. In addition, compound 6c₂ displayed the most potent activity against S. sclerotiorum (EC₅₀  = 3.64 μg mL^-1 ). Further in vivo fungicidal activity screening against S. sclerotiorum demonstrated that the protective and curative effects of compound 6c₂ were 98.1% and 91.3% at 25 μg mL^-1 , respectively, comparable to that of boscalid (94.4%, 89.6%). The preliminary mechanism study found that the hyphae of S. sclerotiorum treated with compound 6c₂ was abnormal with mycelial collapse and membrane permeability increase. The present findings can help to develop new fungicides for crop protection.

CONCLUSION

Novel sulfoximine derivatives containing nitroguanidine possess potential antifungal activity, and the unique structure may offer an alternative option for fungicide development in the future. © 2022 Society of Chemical Industry.

Synthesis and biological activities of novel chalcone derivatives containing pyrazole oxime ethers

A series of novel chalcone derivatives containing pyrazole oxime ethers were designed and synthesized. The structures of all the target compounds were determined by NMR and HRMS. The structure of H5 was further confirmed via single-crystal X-ray diffraction analysis. The results of biological activity test showed that some of the target compounds exhibited significant antiviral and antibacterial activities. The test results of EC₅₀ value against tobacco mosaic virus showed that H9 had the best curative and protective effect, and the EC₅₀ value of curative activity of H9 was 166.9 μg/mL, which was superior to ningnanmycin (NNM) 280.4 μg/mL, the EC₅₀ value of protective activity of H9 was 126.5 μg/mL, which was superior to ningnanmycin 227.7 μg/mL. Microscale thermophoresis (MST) experiments demonstrated that H9 (K_d = 0.0096 ± 0.0045 μmol/L) exhibited a strong binding ability with tobacco mosaic virus capsid protein (TMV-CP), which was far superior to ningnanmycin (K_d = 1.2987 ± 0.4577 μmol/L). In addition, molecular docking results showed that the affinity of H9 to TMV protein was significantly higher than ningnanmycin. The results of against bacterial activity showed that H17 has a good inhibiting effect against Xanthomonas oryzae pv. oryzae (Xoo), the EC₅₀ value of H17 was 33.0 μg/mL, which was superior to the commercial drugs thiodiazole copper (68.1 μg/mL) and bismerthiazol (81.6 μg/mL), and the antibacterial activity of H17 was verified by scanning electron microscopy (SEM).

Recent Achievements in Antiviral Agent Development for Plant Protection

Plant virus disease is the second most prevalent plant diseases and can cause extensive loss in global agricultural economy. Extensive work has been carried out on the development of novel antiplant virus agents for preventing and treating plant virus diseases. In this review, we summarize the achievements of the research and development of new antiviral agents in the recent five years and provide our own perspective on the future development in this highly active research field.

Hydrazone modification of non-food natural product sclareolide as potential agents for plant disease

Plant diseases and their drug resistance pose a serious threat to agricultural production. One way to solve this problem is to discover new and efficient botanical pesticides. Herein, a series of novel hydrazide-hydrazone-containing sesquiterpenoid derivatives were synthesized by simply modifying the structure of the non-food natural product sclareolide. The biological activity results illustrated that compared to ningnanmycin (39.2 μg/mL), compound Z28 had the highest antiviral activity against tobacco mosaic virus (TMV), and the concentration for 50% of maximal effect (EC₅₀) of its inactivation activity was 38.7 μg/mL, followed by compound Z14 (40.6 μg/mL). Transmission electron microscopy (TEM) demonstrated that TMVs treated with compounds Z14 and Z28 were broken into rods of different lengths, and their external morphology was fragmented or even severely fragmented. Autodocking and molecular dynamics (MD) simulations indicated that compound Z28 had a strong affinity for tobacco mosaic virus coat protein (TMV-CP), with a higher binding energy of -8.25 kcal/mol compared to ningnanmycin (-6.79 kcal/mol). The preliminary mechanism revealed that compound Z28 can achieve an antiviral effect by targeting TMV-CP, rendering TMV unable to self-assemble and replicate, and might be a candidate for a novel plant antiviral agent. Furthermore, the curative and protective activities of compound Z22 (EC₅₀ = 16.1 μg/mL) against rice bacterial blight were 51.3% and 50.8%, respectively. Its control effect was better than that of bismerthiazol (BT) and thiadiazole copper (TC), compound Z22 that can be optimized as an active molecule.

The Discovery of Novel Ferulic Acid Derivatives Incorporating Substituted Isopropanolamine Moieties as Potential Tobacco Mosaic Virus Helicase Inhibitors

Target-based drug design, a high-efficiency strategy used to guide the development of novel pesticide candidates, has attracted widespread attention. Herein, various natural-derived ferulic acid derivatives incorporating substituted isopropanolamine moieties were designed to target the tobacco mosaic virus (TMV) helicase. Bioassays demonstrating the optimized A₁₉, A₂₀, A₂₉, and A₃₁ displayed excellent in vivo antiviral curative abilities, affording corresponding EC₅₀ values of 251.1, 336.2, 347.1, and 385.5 μg/mL, which visibly surpassed those of commercial ribavirin (655.0 μg/mL). Moreover, configurational analysis shows that the R-forms of target compounds were more beneficial to aggrandize antiviral profiles. Mechanism studies indicate that R-A₁₉ had a strong affinity (K_d = 5.4 μM) to the TMV helicase and inhibited its ability to hydrolyze ATP (50.61% at 200 μM). Meanwhile, A₁₉ could down-regulate the expression of the TMV helicase gene in the host to attenuate viral replication. These results illustrate the excellent inhibitory activity of A₁₉ towards the TMV helicase. Additionally, docking simulations uncovered that R-A₁₉ formed more hydrogen bonds with the TMV helicase in the binding pocket. Recent studies have unambiguously manifested that these designed derivatives could be considered as promising potential helicase-based inhibitors for plant disease control.

Design, Synthesis, and Bioactivities of Novel Tryptophan Derivatives Containing 2,5-Diketopiperazine and Acyl Hydrazine Moieties

Based on the scaffolds widely used in drug design, a series of novel tryptophan derivatives containing 2,5-diketopiperazine and acyl hydrazine moieties have been designed, synthesized, characterized, and evaluated for their biological activities. The bioassay results showed that the target compounds possessed moderate to good antiviral activities against tobacco mosaic virus (TMV), among which compounds 4, 9, 14, 19, and 24 showed higher inactivation, curative, and protection activities in vivo than that of ribavirin (39 ± 1, 37 ± 1, 39 ± 1 at 500 mg/L) and comparable to that of ningnanmycin (58 ± 1, 55 ± 1, 57 ± 1% at 500 mg/L). Thus, these compounds are a promising candidate for anti-TMV development. Most of these compounds showed broad-spectrum fungicidal activities against 13 kinds of phytopathogenic fungi and selective fungicidal activities against Alternaria solani, Phytophthora capsica, and Sclerotinia sclerotiorum. Additionally, some of these compounds exhibited larvicidal activities against Tetranychus cinnabarinus, Plutella xylostella, Culex pipiens pallens, Mythimna separata, Helicoverpa armigera, and Pyrausta nubilalis.

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

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

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.

Coumarin Derivatives Containing Sulfonamide and Dithioacetal Moieties: Design, Synthesis, Antiviral Activity, and Mechanism

Cucumber mosaic virus (CMV) is currently a known plant virus with the most hosts, broadest distribution, and economic hazard. To develop new antiviral drugs against this serious virus, a new range of coumarin derivatives containing sulfonamide and dithioacetal structures were designed and synthesized, and their anti-CMV activities were detected by the half-leaf dead spot method. The results of the biological activity assay showed that most of the compounds exhibited outstanding anti-CMV activity. Especially, compound C23 displayed the optimal in vivo anti-CMV activity, with an EC50 value of 128 μg/mL, which was remarkably better than that of COS (781 μg/mL) and ningnanmycin (436 μg/mL). Excitingly, we found that compound C23 could be a promising plant activator that significantly increased defense-related enzyme activities and the tobacco chlorophyll content. Furthermore, compound C23 enhanced defense responses against viral infection by inducing the abscisic acid (ABA) pathway in tobacco. This work established a basis for multifunction pesticide discovery involving mechanism of action study and structure optimization.

Ferulic acid derivatives with piperazine moiety as potential antiviral agents

BACKGROUND

Plant virus diseases are difficult to control and severely threaten the productivity of crops, which leads to huge financial losses. To discover the new antiviral drugs, 34 novel ferulic acid derivatives with piperazine moiety were synthesized, and the antiviral activities were systematically screened as well.

RESULTS

Bioassay results indicated that most of the target compounds had outstanding antiviral activities against tobacco mosaic virus (TMV) and cucumber mosaic virus (CMV) in vivo. In particular, compound E2 exhibited remarkable curative activities to TMV and CMV with EC₅₀ values of 189.0 and 401.7 μg/mL compared to those for ningnanmycin (387.0, 519.3 μg/mL) and ribavirin (542.1, 721.5 μg/mL). And then the mechanisms of compound E2 were studied by chlorophyll content, differentially expressed proteins and genes tests.

CONCLUSION

The excellent antiviral activity of compound E2 was closely associated with the increase in host photosynthesis, which was confirmed by chlorophyll content, differentially expressed proteins and genes assays. Compound E2 can be considered as a lead structure for the discovery of new antiviral agents. © 2022 Society of Chemical Industry.