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

Recent highlights in the synthesis and biological significance of pyrazole derivatives

Aza-heterocyclic scaffolds are privileged cores in the composition of their potential therapeutic profiles and versatile synthetic intermediates. Pyrazole is one of the frequently studied compounds of "azole" family and consists of nitrogen in a 1,2 linking sequence. These motifs possess a wide-spectrum of applications in the field of pharmaceuticals, agrochemicals, polymer chemistry, cosmetics, food industries and more. In addition, functionalized pyrazole derivatives are frequently used as ligands in coordination chemistry and metal-catalysed reactions. As exemplified by numerous recent reports, pyrazoles are highly promising pharmacophores with excellent therapeutic applications. Owing to their aromaticity, the ring structures have many reactive positions, where electrophilic, nucleophilic, alkylation and oxidative reactions might occur. The structural adroitness and diversity of pyrazole cores further emanated numerous fused bicyclic skeletons with various biological applications. In this review, we highlight the recent synthetic methods developed for the preparation of functionalized pyrazole derivatives (From 2017 to present). In addition, we have also covered the notable biological activities (anti-cancer, anti-inflammatory, anti-bacterial and anti-viral) of this ubiquitous core. Herein, we emphasised the synthesis of pyrazoles from variety of precursors such as, alkynes, α,β-unsaturated carbonyl compounds, diazo reagents, nitrile imines, diazonium salts, 1,3-dicarbonyl compounds and etc. Moreover, the recent synthetic methodologies focusing on the preparation of pyrazolines and pyrazolones and variously fused-pyrazoles are also included. Authors expect this review could significantly help the researchers in finding elegant novel tools to synthesize pyrazole skeletons and expand their biological evaluation.

Novel 3,5‐Dimethylpyrazole‐Linked 1,2,4‐Triazole‐3‐thiols as Potent Antihyperglycemic Agents: Synthesis, Biological Evaluation, and In Silico Molecular Modelling Investigations

In this work, a series of pyrazole‐linked 1,2,4‐triazole‐3‐thiol derivatives (3a–i) were prepared and identified by 13C NMR, 1H NMR, and mass spectrometry (ESI‐MS) data. The newly synthesized molecules were also evaluated in vitro for their α‐amylase and α‐glucosidase inhibitory potential. All newly synthesized compounds exhibited potent α‐glucosidase inhibition activity with IC50 in the range of 1.016 ± 0.70 to 24.40 ± 0.02 µM and good α‐amylase inhibitory with IC50 in the range of 49.91 ± 0.32 to 500 µM, as compared to acarbose. The most potent compound among this series is derivative 3e, with IC50 value of 1.016 ± 0.70 µM, which is many folds more than that of acarbose. In addition, in docking studies, both compounds exhibited good interactions at the active region of target proteins. Therefore, this study may lead via structural modifications to the discovery of new potent α‐amylase and α‐glucosidase inhibitors useful in the diabetes treatment.

Impact of long-term conventional and biodegradable film mulching on microplastic abundance, soil structure and organic carbon in a cotton field

Biodegradable film mulching has attracted considerable attention as an alternative to conventional plastic film mulching. However, biodegradable films generate transitory microplastics during the film degradation. How much of this transitory microplastics is being formed and their impact on soil health during long-term use of biodegradable plastic film are not known. Here, we quantified the amounts of microplastics (0.1 to 5 mm in size) in the topsoil (0-20 cm) of two cotton fields with different mulching cultivations: (1) continuous use of conventional (polyethylene, PE) film for 23 years (Plot 1), and (2) 15 years use of conventional film followed by 8 years of biodegradable (polybutylene adipate-co-terephthalate, PBAT) film (Plot 2). We further assessed the impacts of the microplastics on selected soil health parameters, with a focus on soil carbon contents and fluxes. The total amount of microplastics was larger in Plot 2 (8507 particles kg-1) than in Plot 1 (6767 particles kg-1). The microplastics (0.1-1 mm) were identified as derived from PBAT and PE in Plot 2; while in Plot 1, the microplastics were identified as PE. Microplastics > 1mm were exclusively identified as PE in both plots. Soil organic carbon was higher (27 vs. 30 g C kg-1 soil) but dissolved organic carbon (120 vs. 74 mg C kg-1 soil) and microbial biomass carbon were lower (413 vs. 246 mg C kg-1 soil) in Plot 2 compared to the Plot 1. Based on 13C natural abundance, we found that in Plot 2, carbon flow was dominated from micro- (<0.25 mm) to macroaggregates (0.25-2 and >2 mm), whereas in Plot 1, carbon flow occurred between large and small macroaggregates, and from micro- to macroaggregates. Thus, long-term application of biodegradable film changed the abundance of microplastics, and organic carbon accumulation compared to conventional polyethylene film mulching.

Repairing Host Damage Caused by Tobacco Mosaic Virus Stress: Design, Synthesis, and Mechanism Study of Novel Oxadiazole and Arylhydrazone Derivatives

Tobacco mosaic virus (TMV), as one of the most traditional and extensive biological stresses, poses a serious threat to plant growth and development. In this work, a series of 1-phenyl/tertbutyl-5-amino-4-pyrazole oxadiazole and arylhydrazone derivatives was synthesized. Bioassay evaluation demonstrated that the title compounds (P1-P18) without a "thioether bond" lost their anti-TMV activity, while some of the ring-opening arylhydrazone compounds exhibited superior in vivo activity against TMV in tobacco. The EC50 value of title compound T8 for curative activity was 139 μg/mL, similar to that of ningnanmycin (NNM) (EC50 = 152 μg/mL). Safety analysis revealed that compound T8 had no adverse effects on plant growth or seed germination at a concentration of 250 μg/mL. Morphological observation revealed that compound T8 could restore the leaf tissue of a TMV-stressed host and the leaf stomatal aperture to normal. A mechanism study further revealed that compound T8 not only restored the photosynthetic and growth ability of the damaged host to normal levels but also enhanced catalase (CAT) activity and reduced the content of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in the damaged host, thereby reducing the oxidation damage to the host. TMV-green fluorescent protein (GFP) experiments further demonstrated that compound T8 not only slowed the transmission speed of TMV in the host but also inhibited its reproduction. All of the experimental results demonstrated that compound T8 could reduce the oxidative damage caused by TMV stress and regulate the photosynthetic ability of the host, achieving the ability to repair damage, to make the plant grow normally.

Sulfonate derivatives bearing an amide unit: design, synthesis and biological activity studies

Pest disasters which occurs on crops is a serious problem that not only cause crop yield loss or even crop failure but can also spread a number of plant diseases.Sulfonate derivatives have been widely used in insecticide and fungicide research in recent years. On this basis, a series of sulfonate derivatives bearing an amide unit are synthesized and the biological activities are evaluated. The bioassay results showed that compounds A8, A13, A16, B1, B3, B4, B5, B10, B12 - 20, C3, C5, C9, C10, C14, C15, C17 and C19 showed 100% activity at a concentration of 500 µg/mL against the Plutella xylostella (P. xylostella). Among them, B15 which contains a thiadiazole sulfonate structure still shows 100% activity at 50 µg/mL concentration against P. xylostella and had the lowest median lethal concentration (LC50) (7.61 µg/mL) among the target compounds. Further mechanism studies are conducted on compounds with better insecticidal activity. Molecular docking results shows that B15 formed hydrophobic interactions π-π and hydrogen bonds with the indole ring of Trp532 and the carboxyl group of Asp384, respectively, with similar interaction distances or bond lengths as those of diflubenzuron. Moreover, chitinase inhibition assays are performed to further demonstrate its mode of action. In addition, the anti-bacterial activity of the series of compounds is also tested and the results showed that the series of compounds has moderate biological activity against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc), with inhibition rates of 91%, 92% and 92%, 88% at the concentration of 100 µg/mL, respectively. Our study indicates that B15 can be used as a novel insecticide for crop protection.

Design, Synthesis, and Target Identification of Novel Phenylalanine Derivatives by Drug Affinity Responsive Target Stability (DARTS) in Xanthomonas oryzae pv Oryzae

The increasing resistance displayed by plant phytopathogenic bacteria to conventional pesticides has heightened the urgency for the exploration of novel antibacterial agents possessing distinct modes of action (MOAs). In this study, a series of novel phenylalanine derivatives with the unique structure of acylhydrazone dithioether have been designed and synthesized. Bioassay results demonstrated that most target compounds exhibited excellent in vitro antibacterial activity against Xanthomonas oryzae pv oryzae (Xoo) and Xanthomonas axonopodis pv citri (Xac). Among them, the EC50 values of L3, L4, L6, L21, and L22 against Xoo were 7.4, 9.3, 6.7, 8.9, and 5.1 μg/mL, respectively, superior to that of bismerthiazol (BT) and thiodiazole copper (TC) (41.5 and >100 μg/mL); the EC50 values of L3, L4, L5, L6, L7, L8, L20, L21, and L22 against Xac were 5.6, 2.5, 6.2, 4.1, 4.2, 6.4, 6.3, 3.6, and 5.2 μg/mL, respectively, superior to that of BT and TC (43.3 and >100 μg/mL). An unmodified drug affinity responsive target stability (DARTS) technology was used to investigate the antibacterial MOAs of active compound L22, and the 50S ribosomal protein L2 (RL2) as an unprecedented target protein in Xoo cells was first discovered. The target protein RL2 was then expressed and purified. Furthermore, the in vitro interactions by microscale thermophoresis (Kd = 0.050 μM) and fluorescence titration (Ka = 1.4 × 105 M-1) experiments also demonstrated a strong binding force between compound L22 and RL2. Overall, these results not only facilitate the development of novel antibacterial agents but also establish a reliable method for exploring the targets of bactericides.

Discovery of Novel Compounds for Combating Rising Severity of Plant Diseases Caused by Fungi and Viruses

In recent years, the severity of plant diseases caused by plant pathogenic fungi and viruses has been on the rise. However, there is a limited availability of pesticide chemicals in the market for effectively controlling both fungal and viral infections. To solve this problem, a series of novel pyrimidine derivatives containing a 1,3,4-oxadiazole thioether fragment were synthesized. Among them, compound 6s exhibited remarkable in vivo protection activity against tobacco mosaic virus, demonstrating the superior 50% effective concentration (EC50) value of 0.42 μM, outperforming ningnanmycin (0.60 μM). Meanwhile, compound 6s exhibited remarkable antifungal activity against Botrytis cinerea Pers. in postharvest blueberry in vitro, with an EC50 value of 0.011 μM, surpassing the inhibition rate of Pyrimethanil (0.262 μM). Additionally, compound 6s also demonstrated remarkable curative and protection activities against blueberry fruit gray mold in vivo, with control efficiencies of 54.2 and 60.4% at 200 μg/mL concentration, respectively, which were comparable to those of Pyrimethanil (49.3 and 63.9%, respectively). Scanning electron microscopy showed that the compound 6s-treated hyphae of B. cinerea Pers. in postharvest blueberry became abnormally collapsed and shriveled. Furthermore, the molecular docking simulation demonstrated that compound 6s formed hydrogen bonds with SER-17, ARG-43, and SER-39 of succinate dehydrogenase (SDH), providing a possible explanation for the mechanism of action between the target compounds and SDH. This study represents the first report on the antiviral and antifungal activities of novel pyrimidine derivatives containing a 1,3,4-oxadiazole thioether fragment.

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.

Synthesis, Antifungal Evaluation, 3D-QSAR, and Preliminarily Mechanism Study of Novel Chiral Mandelic Acid Derivatives

To investigate the effect of spatial configuration on the biological activity of the compounds, a series of chiral mandelic acid derivatives with a moiety of 1,3,4-oxadiazole thioether have been designed and synthesized. Bioassay results demonstrated that most title compounds with the S-configuration exhibited better in vitro antifungal activity against three plant fungi, such as H3' (EC₅₀ = 19.3 μg/mL) against Gibberella saubinetii, which was approximately 16 times higher than that of H3 (EC₅₀ = 317.0 μg/mL). CoMFA and CoMSIA models were established for 3D-QSAR analysis and provided an important support for further optimization of this series of compounds. Comparing the preliminary mechanism studies between enantiomers (H3 and H3') found that the S-configuration compound (H3') exhibited a stronger ability to destroy the surface structure of G. saubinetii mycelia, causing the leakage of intracellular substances to accelerate and the growth of the hyphae to be inhibited. The results provided a novel view for the further optimization of this series of active compounds and deep mechanism study of chiral pesticides.

Synthesis, antimycobacterial, cytotoxicity, anti-inflammatory, in silico studies and molecular dynamics of pyrazole-embedded thiazolidin-4-one hybrids

In the present investigation, we devolved and synthesized a new series of pyrazole-embedded thiazolidin-4-one derivatives (9a-p) with the goal to produce promising antitubercular leads. The in vitro antimycobacterial activity of the synthesized compounds was tested against replicating and nonreplicating Mtb H37Rv strains. With MIC ranging from 3.03 to 22.55 µg/ml, five compounds (9a, 9c, 9d, 9e, and 9f) emerged as promising antitubercular agents. The active molecules were nontoxic to normal Vero cells. All the synthesized compounds were evaluated for in vitro anti-inflammatory studies. Compounds 9a, 9b, 9c, 9h, and 9i exhibited excellent anti-inflammatory efficacy. Docking study was performed to understand the binding pattern of the significantly active compound 9a with 1P44.

Anticancer evaluation and molecular docking of new pyridopyrazolo-triazine and pyridopyrazolo-triazole derivatives

3-Amino-4,6-dimethylpyrazolopyridine was applied as a precursor for the synthesis of some new pyridopyrazolo-triazine and pyridopyrazolo-triazole derivatives through diazotization, followed by coupling with many 2-cyanoacetamide compounds, ethyl 3-(phenylamino)-3-thioxopropanoate, 3-oxo-N-phenylbutanethioamide, and α-bromo-ketone reagents [namely; 2-bromo-1-(4-fluorophenyl)ethan-1-one, 5-bromo-2-(bromoacetyl)thiophene, 3-(2-bromoacetyl)-2H-chromen-2-one and/or 3-chloroacetylacetone]. The prepared compounds were identified by spectroscopic analyses as IR, ¹H NMR, and mass data. The anticancer activity of these pyrazolopyridine analogues was investigated in colon, hepatocellular, breast, and cervix carcinoma cell lines. The pyridopyrazolo-triazine compound 5a substituted with a carboxylate group gave a distinguished value of IC₅₀ = 3.89 µM against the MCF-7 cell line compared to doxorubicin as a reference drug. Also, the pyridopyrazolo-triazine compound 6a substituted with the carbothioamide function gave good activity toward HCT-116 and MCF-7 cell lines with IC₅₀ values of 12.58 and 11.71 µM, respectively. The discovered pyrazolopyridine derivatives were studied theoretically by molecular docking, and this study exhibited suitable binding between the active sides of pyrazolopyridine ligands and proteins (PDB ID: 5IVE). The pyridopyrazolo-triazine compound 6a showed the highest free binding energy (- 7.8182 kcal/mol) when docked inside the active site of selected proteins.

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.

Conventional and microwave-assisted synthesis, anticancer evaluation, 99mTc-coupling and In-vivo study of some novel pyrazolone derivatives

New pyrazolone derivatives were successfully synthesized by both microwave-assisted and conventional techniques. Compound 3 (3-(3-Methyl-5-oxo-4,5-dihydro-1H-pyrazol-1-yl)-3-oxopropanehydrazide) displayed remarkable anti-cancer activity (IC₅₀ obtained at 8.71 and 10.63 µM for HCT-116 and MCF-7, respectively. Moreover, biodistribution study using radiolabeling approach revealed a remarked uptake of [^99mTc]Tc-compound 3 complex into tumour induced in mice. The biodistribution showed high accumulation in tumour tissues with T/NT of 6.92 after 60 min post injection. As a result of these promising data, the newly synthesized compounds especially compound 3 affords a potential radio-carrier that could be used as a tumour marker and can be used for cancer therapy after further preclinical studies.

Inhibitory Activities of Pyrazolo-Oxazine Heterocyclic Derivatives

Despite several reports and reviews addressing the biological significance of pyrazoles and oxazines, no comprehensive work on the pyrazolo oxazine fused ring system has been published so far.We report all biological evaluations on pyrazolo-oxazine derivatives in this mini-review to provide an avenue for medicinal and pharmacological researchers to conduct further in-depth exploration.

π-π Noncovalent Interaction Involving 1,2,4- and 1,3,4-Oxadiazole Systems: The Combined Experimental, Theoretical, and Database Study

A series of N-pyridyl ureas bearing 1,2,4- (1a, 2a, and 3a) and 1,3,4-oxadiazole moiety (1b, 2b, 3b) was prepared and characterized by HRMS, 1H and 13C NMR spectroscopy, as well as X-ray diffraction. The inspection of the crystal structures of (1-3)a,b and the Hirshfeld surface analysis made possible the recognition of the (oxadiazole)···(pyridine) and (oxadiazole)···(oxadiazole) interactions. The presence of these interactions was confirmed theoretically by DFT calculations, including NCI analysis for experimentally determined crystal structures as well as QTAIM analysis for optimized equilibrium structures. The preformed database survey allowed the verification of additional examples of relevant (oxadiazole)···π interactions both in Cambridge Structural Database and in Protein Data Bank, including the cocrystal of commercial anti-HIV drug Raltegravir.