Discovery of 1,2,4-Oxadiazole Derivatives Containing Haloalkyl as Potential Acetylcholine Receptor Nematicides.

Plant-parasitic nematodes pose a serious threat to crops and cause substantial financial losses due to control difficulties. Tioxazafen (3-phenyl-5-thiophen-2-yl-1,2,4-oxadiazole) is a novel broad-spectrum nematicide developed by the Monsanto Company, which shows good prevention effects on many kinds of nematodes. To discover compounds with high nematocidal activities, 48 derivatives of 1,2,4-oxadiazole were obtained by introducing haloalkyl at the 5-position of tioxazafen, and their nematocidal activities were systematically evaluated. The bioassays revealed that most of 1,2,4-oxadiazole derivatives showed remarkable nematocidal activities against Bursaphelenchus xylophilus, Aphelenchoides besseyi, and Ditylenchus dipsaci. Notably, compound A1 showed excellent nematocidal activity against B. xylophilus with LC50 values of 2.4 µg/mL, which was superior to that of avermectin (335.5 µg/mL), tioxazafen (>300 µg/mL), and fosthiazate (436.9 µg/mL). The transcriptome and enzyme activity results indicate that the nematocidal activity of compound A1 was mainly related to the compound which affected the acetylcholine receptor of B. xylophilus.

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.

Design, Synthesis and Antifungal/Nematicidal Activity of Novel 1,2,4-Oxadiazole Derivatives Containing Amide Fragments.

Plant diseases that are caused by fungi and nematodes have become increasingly serious in recent years. However, there are few pesticide chemicals that can be used for the joint control of fungi and nematodes on the market. To solve this problem, a series of novel 1,2,4-oxadiazole derivatives containing amide fragments were designed and synthesized. Additionally, the bioassays revealed that the compound F15 demonstrated excellent antifungal activity against Sclerotinia sclerotiorum (S. sclerotiorum) in vitro, and the EC50 value of that was 2.9 µg/mL, which is comparable with commonly used fungicides thifluzamide and fluopyram. Meanwhile, F15 demonstrated excellent curative and protective activity against S. sclerotiorum-infected cole in vivo. The scanning electron microscopy results showed that the hyphae of S. sclerotiorum treated with F15 became abnormally collapsed and shriveled, thereby inhibiting the growth of the hyphae. Furthermore, F15 exhibited favorable inhibition against the succinate dehydrogenase (SDH) of the S. sclerotiorum (IC50 = 12.5 µg/mL), and the combination mode and binding ability between compound F15 and SDH were confirmed by molecular docking. In addition, compound F11 showed excellent nematicidal activity against Meloidogyne incognita at 200 µg/mL, the corrected mortality rate was 93.2%, which is higher than that of tioxazafen.

A new strain of Volutella citrinella with nematode predation and nematicidal activity, isolated from the cysts of potato cyst nematodes in China.

BACKGROUND: Plant parasitic nematodes (PPNs) are responsible for causing many plant diseases and are extremely difficult to control at present. Currently, due to the negative effects of chemical agents on the environment and human health, the development of new biological pesticides has become an important part of plant nematode control. Nematophagous fungi refers to a class of fungi that kill plant nematodes. Notably, a large number of nematophagous fungi resources remain to be studied. The objective of our study was to use in vitro screening to identify nematophagous fungi and select strains that were highly active against nematodes, providing a primary research for the development and utilization of new nematophagous fungi. RESULTS: A new nematophagous fungal strain (GUCC2219) was isolated from cysts of possibly Globodera spp. and Heterodera spp., identified as Volutella citrinella. The hyphae of V. citrinella produced ring structures of variable size and exhibited predatory and nematicidal activity. The hyphal predation rates (in vitro) against three species of nematodes, Aphelenchoides besseyi, Bursaphelenchus xylophilus, and Ditylenchus destructor, averaged 59.45, 33.35, and 50.95%, respectively, while the fermentation broth produced by the fungus exhibited mortality rates of 100, 100, and 55.63%, respectively, after 72 h. CONCLUSION: V. citrinella is a new strain with nematophagous properties, which are a novel discovery. At the same time, this is the first report of nematicidal and nematode predation activity in the genus Volutella.

Novel vanillin derivatives containing a 1,3,4-thiadiazole moiety as potential antibacterial agents.

In this study, thirty-four novel vanillin derivatives containing a 1,3,4-thiadiazole structure were obtained and their antibacterial activities were evaluated. The results indicate that most of the title compounds displayed inhibitory effects on Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc). Among them, compound 29 exhibited excellent antibacterial activities against Xoo and Xoc in vitro, with the EC50 values of 3.14 and 8.83 µg/mL, respectively, much superior to thiodiazole copper (87.03 and 108.99 µg/mL) and bismerthiazol (67.64 and 79.26 µg/mL). Under greenhouse condition, the protective efficiency of compound 29 against rice bacterial leaf blight was 49.34%, and curative efficiency was 40.96%. In addition, compound 29 can reduce the exopolysaccharides production of Xoo, increase the permeability of cell membrane and damage cell membrane.

Design, synthesis, bioactivity and mechanism of dithioacetal derivatives containing dioxyether moiety.

The present work designed and synthesized a series of dithioacetal derivatives containing dioxyether, as well as evaluated their antiviral activities against tobacco mosaic virus (TMV). Bioassays demonstrated that the target compounds showed excellent anti-TMV activities in vivo and in vitro. Compound 24c has excellent anti-TMV activities, and its curative, protective and inactivating activities for TMV were 50.9%, 58.9% and 81.8%, respectively, which are obviously superior to those of ribavirin (50.2%, 41.3% and 69.5%, respectively). Moreover, the EC50 of the inactivating activities of the anti-TMV of compound 24c is 67.9 mg/L, which is superior to that of ribavirin (149.5 mg/L). Transmission electron microscopy showed that compound 24c caused great damage to the morphology of TMV particles, causing fracture and bending. Molecule docking model revealed that this compound formed five conventional hydrogen bonds with the active sites of amino acids GLN57, ASN73, TYR139, and SER138. Furthermore, the test results of Fluorescence titration and microscale thermophoresis showed that compound 24c has a strong binding force with TMV coat protein (TMV CP), with an association constant (Ka) of 1.04 × 105 L/mol and dissociation constant (Kd) of 1.6 ±â€¯0.6 µM. These results indicate that the dithioacetal derivatives containing dioxyether are worthy of further research and development as novel antiviral agents.

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.

Syntheses, antiviral activities and induced resistance mechanisms of novel quinazoline derivatives containing a dithioacetal moiety.

A series of novel quinazoline derivatives containing a dithioacetal moiety were designed and synthesized, and their structures were characterized by 1H nuclear magnetic resonance, 13C nuclear magnetic resonance, and high-resolution mass spectrometry. Bioassay results indicated that compound 4b exhibited remarkable protective activity against cucumber mosaic virus (CMV, EC50 = 248.6 µg/mL) and curative activity against potato virus Y (EC50 = 350.5 µg/mL), which were better than those of ningnanmycin (357.7 µg/mL and 493.7 µg/mL, respectively). Moreover, compound 4b could increase the chlorophyll content in plants, improve photosynthesis, and effectively induce tobacco anti-CMV activity.

Induced Resistance Mechanism of Novel Curcumin Analogs Bearing a Quinazoline Moiety to Plant Virus.

Plant immune activators can protect crops from plant virus pathogens by activating intrinsic immune mechanisms in plants and are widely used in agricultural production. In our previous work, we found that curcumin analogs exhibit excellent biological activity against plant viruses, especially protective activity. Inspired by these results, the active substructure of pentadienone and quinazoline were spliced to obtain curcumin analogs as potential exogenously induced resistant molecule. Bioassay results showed that compound A13 exhibited excellent protective activity for tobacco to against Tobacco mosaic virus (TMV) at 500 µg/mL, with a value of 70.4 ± 2.6% compared with control treatments, which was better than that of the plant immune activator chitosan oligosaccharide (49.0 ± 5.9%). The protective activity is due to compound A13 inducing tobacco resistance to TMV, which was related to defense-related enzymes, defense-related genes, and photosynthesis. This was confirmed by the up-regulated expression of proteins that mediate stress responses and oxidative phosphorylation.

Novel Pyrazole-Hydrazone Derivatives Containing an Isoxazole Moiety: Design, Synthesis, and Antiviral Activity.

In this study, a series of novel pyrazole-hydrazone derivatives containing an isoxazole moiety were synthesized. Antiviral bioassays indicated that some of the title compounds exhibited better in vivo antiviral activities against tobacco mosaic virus (TMV). In particular, compounds 6a, 6c and 6q exhibited the best curative activity, protection activity, and inactivation activity against TMV, respectively, which were superior to those of Ningnanmycin. This study demonstrated that this series of novel pyrazole-hydrazone derivatives containing an isoxazole amide moiety could effectively control TMV.

Synthesis and antiviral evaluation of novel 1,3,4-oxadiazole/thiadiazole-chalcone conjugates.

A series of novel 1,3,4-oxadiazole/thiadiazole-chalcone conjugates were synthesized and their in vitro and in vivo antiviral activities were evaluated via microscale thermophoresis method and half-leaf method, respectively. The in vitro results indicated that compounds 7g, 7l, 8h, and 8l displayed good antiviral activity against TMV, with the binding constant values of 5.93, 6.15, 6.02, and 5.04µM, respectively, which were comparable to that of Ninnanmycin (6.78µM) and even better than that of Ribavirin (99.25µM). The in vivo results demonstrated that compounds 7g, 7l, 8h, and 8l exhibited remarkable anti-TMV activity with the EC50 values of 33.66, 33.97, 33.87 and 30.57µg/mL, respectively, which were comparable to that of Ningnanmycin (36.85µg/mL) and superior to that of Ribavirin (88.52µg/mL). Interestingly, the trend of antiviral activity in vivo was consistent with the in vitro results.

Synthesis, antiviral activity, and molecular docking study of trans-ferulic acid derivatives containing acylhydrazone moiety.

In this study, we report the synthesis and antiviral activity of trans-ferulic acid derivatives containing acylhydrazone moiety. Biological tests demonstrated that most target compounds showed potent antiviral activity against tobacco mosaic virus (TMV). Compound D4 showed remarkable inactivating activity with EC50 value of 36.59µg/mL, which was obviously superior to ribavirin (126.05µg/mL). Molecular docking results revealed that compound D4 exhibited the optimal combining capacity with five hydrogen bonds to different amino-acid residues of TMV coat protein (TMV-CP). Docking results were consistent with the inactivating activity of target compounds against TMV.

Synthesis and Antiviral Activity of Novel 1,4-Pentadien-3-one Derivatives Containing a 1,3,4-Thiadiazole Moiety.

1,4-Pentadien-3-one derivatives derived from curcumin possess excellent inhibitory activity against plant viruses. On the basis of this finding, a series of novel 1,4-pentadien-3-one derivatives containing a 1,3,4-thiadiazole moiety were designed and synthesized, and their structures confirmed by IR, ¹H-NMR, and 13C-NMR spectroscopy and elemental analysis. The antiviral activities of the title compounds were evaluated against tobacco mosaic virus (TMV) and cucumber mosaic virus (CMV) in vivo. The assay results showed that most of compounds had remarkable antiviral activities against TMV and CMV, among which compounds 4b, 4h, 4i, 4k, 4o, and 4q exhibited good curative, protection, and inactivation activity against TMV. Compounds 4h, 4i, 4k, 4l, 4o, and 4q exhibited excellent protection activity against TMV, with EC50 values of 105.01, 254.77, 135.38, 297.40, 248.18, and 129.87 µg/mL, respectively, which were superior to that of ribavirin (457.25 µg/mL). In addition, preliminary SARs indicated that small electron-withdrawing groups on the aromatic ring were favorable for anti-TMV activity. This finding suggests that 1,4-pentadien-3-one derivatives containing a 1,3,4-thiadiazole moiety may be considered as potential lead structures for discovering new antiviral agents.

Synthesis, Antiviral Bioactivity of Novel 4-Thioquinazoline Derivatives Containing Chalcone Moiety.

A series of novel 4-thioquinazoline derivatives containing chalcone moiety were designed, synthesized and systematically evaluated for their antiviral activity against TMV. The bioassay results showed that most of these compounds exhibited moderate to good anti-TMV activity. In particular, compounds M2 and M6 possessed appreciable protection activities against TMV in vivo, with 50% effective concentration (EC50) values of 138.1 and 154.8 µg/mL, respectively, which were superior to that of Ribavirin (436.0 µg/mL). The results indicated that chalcone derivatives containing 4-thioquinazoline moiety could effectively control TMV. Meanwhile, the structure-activity relationship (SAR) of the target compounds, studied using the three-dimensional quantitative structure-activity relationship (3D-QSAR) method of comparative molecular field analysis (CoMFA) based on the protection activities against TMV, demonstrated that the CoMFA model exhibited good predictive ability with the cross-validated q2 and non-cross-validated r2 values of 0.674 and 0.993, respectively. Meanwhile, the microscale thermophoresis (MST) experimental showed that the compound M6 may interaction with the tobacco mosaic virus coat protein (TMV CP).

[HPLC Fingerprint Study and Quantitative Determination of Index Components of Pilea aquarum].

OBJECTIVE: To establish an HPLC fingerprint and a quantitative determination method for determination of index components of Pilea aquarum. METHODS: The HPLC fingerprint of Pilea aquarum were determined on an Agilent Zorbax SB-C18 column (250 mm x 4.6 mm, 5 µm), eluted with mobile phase containing of acetonitrile-0.2% acetic acid in a gradient mode. The temperature of column was 30 °C. The flow rate was 0.8 mL/min and the detection wavelength was set at 330 nm. The chromatograms of 24 batches of Pilea aquarum were compared by the software of Similarity Evaluation System for Chromatographic Fingerprint of Traditional Chinese Medicine (version 2004 A). The contents of luteoloside and cosmosiin were also determined simultaneously. RESULTS: The HPLC fingerprint of Pilea aquarum had been established. There were ten common peaks,two chromatographic peaks of which were identified by reference substances. The samples of Pilea aquarum from different habitats can be distinguished from their fingerprints, the contents of luteoloside and cosmosiin varied greatly. CONCLUSION: This method has desirable precision, stability, repeatability, and can be applied for identification and quality control of Pilea aquarum.

Design, Synthesis, and Herbicidal Activity of Natural Naphthoquinone Derivatives Containing Diaryl Ether Structures.

Photosynthesis system II (PS II) is an important target for the development of bioherbicides. In this study, a series of natural naphthoquinone derivatives containing diaryl ether were designed and synthesized based on the binding model of lawsone and PS II D1. Bioassays exhibited that most compounds had more than 80% inhibition of Portulaca oleracea and Echinochloa crusgalli roots at a dose of 100 µg/mL and compounds B4, B5, and C3 exhibited superior herbicidal activities against dicotyledonous and monocotyledon weeds to commercial atrazine. In particular, compound B5 exhibited excellent herbicidal activity at a dosage of 150 g a.i./ha. In addition, compared with atrazine, compound B5 causes less damage to crops. Molecular docking studies revealed that compound B5 effectively interacted with Pisum sativum PS II D1 via diverse interaction models, such as π-π stacking and hydrogen bonds. Molecular dynamics simulation studies and chlorophyll fluorescence measurements revealed that compound B5 acted on PS II. This is the first report of natural naphthoquinone derivatives targeting PS II and compound B5 may be a candidate molecule for the development of new herbicides targeting PS II.

Discovery of Novel N-Phenyltriazinone Derivatives Containing Oxime Ether or Oxime Ester Moieties as Promising Protoporphyrinogen IX Oxidase Inhibitors.

Protoporphyrinogen IX oxidase (PPO, EC 1.3.3.4) is one of the most important targets for the discovery of green herbicides. In order to find novel PPO inhibitors with a higher herbicidal activity, a series of novel N-phenyltriazinone derivatives containing oxime ether and oxime ester groups were designed and synthesized based on the strategy of pharmacophore and scaffold hopping. Bioassay results revealed that some compounds showed herbicidal activities; especially, compound B16 exhibited broad-spectrum and excellent 100% herbicidal effects to Echinochloa crusgalli, Digitaria sanguinalis, Setaria faberii, Abutilon juncea, Amaranthus retroflexus, and Portulaca oleracea at a concentration of 37.5 g a.i./ha, which were comparable to trifludimoxazin. Nicotiana tabacum PPO (NtPPO) enzyme inhibitory assay indicated that B16 showed an excellent enzyme inhibitory activity with a value of 32.14 nM, which was similar to that of trifludimoxazin (31.33 nM). Meanwhile, compound B16 revealed more safety for crops (rice, maize, wheat, peanut, soybean, and cotton) than trifludimoxazin at a dose of 150 g a.i./ha. Moreover, molecular docking and molecular dynamics simulation further showed that B16 has a very strong and stable binding to NtPPO. It indicated that B16 can be used as a potential PPO inhibitor and herbicide candidate for application in the field.

Discovery of Novel Pyridazine Herbicides Targeting Phytoene Desaturase with Scaffold Hopping.

Phytoene desaturase (PDS) is a critical functional enzyme in blocking ζ-carotene biosynthesis and is one of the bleaching herbicide targets. At present, norflurazon (NRF) is the only commercial pyridazine herbicide targeting PDS. Therefore, developing new and diverse pyridazine herbicides targeting PDS is urgently required. In this study, diflufenican (BF) was used as the lead compound, and a scaffold-hopping strategy was employed to design and synthesize some pyridazine derivatives based on the action mode of BF and PDS. The preemergence herbicidal activity tests revealed that compound 6-chloro-N-(2,4-difluorophenyl)-3-(3-(trifluoromethyl)phenoxy)pyridazine-4-carboxamide (B1) with 2,4-diF substitution in the benzeneamino ring showed 100% inhibition rates against the roots and stems of Echinochloa crus-galli and Portulaca oleracea at 100 µg/mL, superior to the inhibition rates of BF. Meanwhile, compound B1 demonstrated excellent postemergence herbicidal activity against broadleaf weeds, which was similar to that of BF (inhibition rate of 100%) but superior to that of NRF. This indicated that 6-Cl in the pyridazine ring is the key group for postemergence herbicidal activity. In addition, compound B1 could induce downregulation of PDS gene expression, 15-cis-phytoene accumulation, and Y(II) deficiency and prevent photosynthesis. Therefore, B1 can be considered as a promising candidate for developing high-efficiency PDS inhibitors.

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.

Design, Synthesis, and Herbicidal Activity of Novel Tetrahydrophthalimide Derivatives Containing Oxadiazole/Thiadiazole Moieties.

Protoporphyrinogen oxidase (PPO, EC 1.3.3.4) has a high status in the development of new inhibitors. To develop novel and highly effective PPO inhibitors, active substructure linking and bioisosterism replacement strategies were used to design and synthesize novel tetrahydrophthalimide derivatives containing oxadiazole/thiadiazole moieties, and their inhibitory effects on Nicotiana tobacco PPO (NtPPO) and herbicidal activity were evaluated. Among them, compounds B11 (Ki = 9.05 nM) and B20 (Ki = 10.23 nM) showed significantly better inhibitory activity against NtPPO than that against flumiclorac-pentyl (Ki = 46.02 nM). Meanwhile, compounds A20 and B20 were 100% effective against three weeds (Abutilon theophrasti, Amaranthus retroflexus, and Portulaca oleracea) at 37.5 g a.i./ha. It was worth observing that compound B11 was more than 90% effective against three weeds (Abutilon theophrasti, Amaranthus retroflexus, and Portulaca oleracea) at 18.75 and 9.375 g a.i./ha. It was also safer to rice, maize, and wheat than flumiclorac-pentyl at 150 g a.i./ha. In addition, the molecular docking results showed that compound B11 could stably bind to NtPPO and it had a stronger hydrogen bond with Arg98 (2.9 Å) than that of flumiclorac-pentyl (3.2 Å). This research suggests that compound B11 could be used as a new PPO inhibitor, and it could help control weeds in agricultural production.