Novel chalcone derivatives containing a 1,2,4-triazine moiety: design, synthesis, antibacterial and antiviral activities

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

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

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

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

Synthesis, antifungal activity and mechanism of action of novel chalcone derivatives containing 1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazole

A series of chalcone derivatives containing 1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazole was designed and synthesized. Structures of all compounds were characterized by 1H NMR, 13C NMR, 19F NMR, and HRMS. The biological activities of the compounds were determined with the mycelial growth rate method, and further studies showed that some compounds had good antifungal activities at the concentration of 100 μg/mL. The EC50 value of compound L31 was 15.9 μg/mL against Phomopsis sp., which were better than that of azoxystrobin (EC50 value was 69.4 μg/mL). In addition, the mechanism of action of compound L31 shown that compound can affect mycelial growth by disrupting membrane integrity against Phomopsis sp., and that the higher the concentration of the compound is, the greater the disruption of membrane integrity is.

Design, synthesis, and bioactivity studies of chalcone derivatives containing [1,2,4]-triazole-[4,3-a]-pyridine

In this study, 30 chalcone derivatives containing [1,2,4]-triazole-[4,3-a]-pyridine were designed and synthesized. The results of antibacterial activity showed that EC50 values of N26 against Xoo, Pcb was 36.41, 38.53 μg/mL, respectively, which were better than those of thiodiazole copper, whose EC50 values were 60.62, 106.75 μg/mL, respectively. The bacterial inhibitory activity of N26 against Xoo was verified by SEM. Antibacterial mechanism between N26 and Xoo was preliminarily explored, the experimental results showed that when the drug concentration was 100 mg/L, N26 had a good cell membrane permeability of Xoo, and it can inhibit the production of EPS content and extracellular enzyme content to disrupt the integrity of the Xoo biofilms achieving the effect of inhibiting Xoo. At 200 mg/L, N26 can protect and inhibit the lesions of post-harvested potatoes in vivo. The activities of N1-N30 against TMV were determined with half leaf dry spot method. The EC50 values of the curative and protective activity of N22 was 77.64 and 81.55 μg/mL, respectively, which were superior to those of NNM (294.27, 175.88 μg/mL, respectively). MST experiments demonstrated that N22 (Kd = 0.0076 ± 0.0007 μmol/L) had a stronger binding ability with TMV-CP, which was much higher than that of NNM (Kd = 0.7372 ± 0.2138 μmol/L). Molecular docking results showed that N22 had a significantly higher affinity with TMV-CP than NNM.

Molecular dynamics simulation approach of hybrid chalcone-thiazole complex derivatives for DNA gyrase B inhibition: lead generation

Compounds bearing thiazole and chalcone groups have been reported to be excellent leads for antibacterial, antitubercular and anticancer activities. In view of this, we performed quantitative structure-activity relationship studies using QSARINS for dataset preparation and for developing validated QSAR models that can predict novel series of thiazole-chalcone hybrids and further evaluate them for bioactivities. The molecular descriptors AATS8i, AVP-1, MoRSEE17 and GATSe7 were found to be active in predicting the structure-activity relationship. Molecular docking and dynamics simulation studies of the developed leads have shown insights into structural analysis. Furthermore, computational studies using AutoDock and Desmond predicted the key binding interactions responsible for the activity and the SwissADME tool computed the in silico drug likeliness properties. The lead compound 178 generated through this study creates a route for the optimization and development of novel drugs against tuberculosis infections. RMSD, RMSF, RoG, H-bond and SASA analysis confirmed the stable binding of compound 178 with the 6J90 structure. In addition, MM-PBSA and MM-GBSA also confirm the docking results. We propose the designed compound 178 as the best theoretical lead, which may further be experimentally studied for selective inhibition.

Design, Synthesis, and Anti-PVY Biological Activity of 1,3,5-Triazine Derivatives Containing Piperazine Structure

In this study, a commercial agent with antivirus activity and moroxydine hydrochloride were employed to perform a lead optimization. A series of 1,3,5-triazine derivatives with piperazine structures were devised and synthesized, and an evaluation of their anti-potato virus Y (PVY) activity revealed that several of the target compounds possessed potent anti-PVY activity. The synthesis of compound C35 was directed by a 3D-quantitative structure-activity relationship that used the compound's structural parameters. The assessment of the anti-PVY activity of compound C35 revealed that its curative, protective, and inactivation activities (53.3 ± 2.5%, 56.9 ± 1.5%, and 85.8 ± 4.4%, respectively) were comparable to the positive control of ningnanmycin (49.1 ± 2.4%, 50.7 ± 4.1%, and 82.3 ± 6.4%) and were superior to moroxydine hydrochloride (36.7 ± 2.7%, 31.4 ± 2.0%, and 57.1 ± 1.8%). In addition, molecular docking demonstrated that C35 can form hydrogen bonds with glutamic acid at position 150 (GLU 150) of PVY CP, providing a partial theoretical basis for the antiviral activity of the target compounds.

Synthesis and evaluation of anti-yellow fever virus activity of new 6-aryl-3-R-amino-1,2,4-triazin-5(4H)-ones

Yellow fever disease is one of public health concerns in the tropics. Despite its significant medicinal and economic impact among large groups of the population, there is a lack of effective treatment against yellow fever. In this regard, here we describe the synthesis of a series of new 6-aryl-3-R-amino-1,2,4-triazin-5(4H)-ones and evaluation of their in vitro inhibitory activity against yellow fever virus. Among all tested compounds 4 derivatives possessing strong inhibitory activity at μM concentrations were identified. All the active compounds revealed a good toxicity profile. These facts make the compounds interesting candidates for further evaluation of their efficacy in the treatment of yellow fever virus infection in vivo.

Design, Synthesis, and Bioactivity of Chalcone Derivatives Containing Indanone

A series of chalcone derivatives containing indanone were designed and synthesized by aldehyde-ketone condensation and etherification. The activity test demonstrated that the majority of the compounds had good therapeutic and protective activities against tobacco mosaic virus (TMV) at a concentration of 500 μg/mL when being tested. Among them, the target compounds N2 and N7 showed good therapeutic activities against TMV with EC₅₀ values of 70.7 and 89.9 μg/mL, respectively, which were better than that of ningnanmycin (158.3 μg/mL). N2 and N10 showed better protective activities against TMV with EC₅₀ values of 60.8 and 120.3 μg/mL, which were superior to that of ningnanmycin (175.6 μg/mL). A hydrogen bond interaction was observed between N2 and ARG-341 with a bond length of 3.08 Å and a hydrogen bond was observed between ningnanmycin and ASP-66 with a bond length of 3.72 Å. In contrast, the hydrogen bond length of compound N2 was shorter and its binding was closer. Meanwhile, when the heartleaf tobacco was being treated with N2, its increasing rate of malondialdehyde slowed and its content of defense enzymes significantly increased, again reflecting the good activity of N2 against TMV.

Novel 1,3,4-oxadiazole sulfonate/carboxylate flavonoid derivatives: synthesis and biological activity

BACKGROUND

With the long-term use of traditional bactericides and antiviral agents, drug resistance has become increasingly prominent, resulting in impaired crop growth and yields. Based on this, the introduction of small molecular active groups into natural products has become the direction of research for green pesticides.

RESULTS

In this study, novel 1,3,4-oxadiazole sulfonate/carboxylate flavonoid derivatives were explored. Among them, D4 exhibited good inhibitory effects on plant bacteria. It is worth mentioning that D4 (15 μg ml^-1 ) exhibited an excellent median effective concentration (EC₅₀ ) value against Xanthomonas oryzae pv. oryzae (Xoo), which was better than bismerthiazol (73 μg ml^-1 ) and thiodiazole copper (100 μg ml^-1 ). The EC₅₀ for D4 was much lower than the two positive controls (bismerthiazol, thiodiazole copper), making D4 more potent in this assay of bacterial growth inhibition. In addition, mechanism research using scanning electron microscopy revealed that D4 could cause deformation or rupture of the cell membranes of Xoo and Pseudomonas syringae pv. actinidiae. Moreover, D4 exhibited the best EC₅₀ for in vivo curative (132 μg ml^-1 ) and protective (101 μg ml^-1 ) activities against tobacco mosaic virus, which were more effective than ningnanmycin. Microscale thermophoresis data suggested that D4 [dissociation constant (K_d ) = 0.038 ± 0.011 μmol L^-1 ] exhibited a stronger binding capacity than the control agent ningnanmycin (K_d = 4.707 ± 2.176 μmol L^-1 ).

CONCLUSION

The biological activity data and mode of action demonstrated that D4 had the best antibacterial and antiviral effects. Compound D4 discovered in the current work may be a very promising agricultural drug. © 2022 Society of Chemical Industry.

Design, Synthesis, and Biological Evaluation of Novel 1,4-Pentadien-3-one Derivatives Containing a Sulfonamide Moiety

Novel 1,4-pentadien-3-one derivatives containing a sulfonamide moiety were synthesized, and their antifungal, antibacterial, and antiviral activities were verified. These compounds exhibited better activity against five bacteria, with EC₅₀ values ranging from 9.6 to 60.1 μg/mL, prominently, which are superior to those of the commercial agent. A great amount of compounds had excellent fungicidal activity in vitro at 100 μg/mL. Strikingly, compound E6 exhibited moderate activity against Phytophthora litchii than azoxystrobin, with the EC₅₀ value of compound E6 (0.5 μg/mL) drawing near azoxystrobin (0.3 μg/mL). Furthermore, compound E17 had a marked impact on in vivo anti-tobacco mosaic virus, according to the data of microscale thermophoresis, with a K_d value of the intermolecular binding force of 0.002 ± 0.001 μM, which was better than the commercial agent of ningnanmycin (K_d = 0.121 ± 0.031 μM). In addition, the results of these studies suggest that the use of active splicing can improve the biological activity of natural compounds and provide further complement to the development of novel pesticides.

Chalcone: A Promising Bioactive Scaffold in Medicinal Chemistry

Chalcones are a class of privileged scaffolds with high medicinal significance due to the presence of an α,β-unsaturated ketone functionality. Numerous functional modifications of chalcones have been reported, along with their pharmacological behavior. The present review aims to summarize the structures from natural sources, synthesis methods, biological characteristics against infectious and non-infectious diseases, and uses of chalcones over the past decade, and their structure–activity relationship studies are detailed in depth. This critical review provides guidelines for the future design and synthesis of various chalcones. In addition, this could be highly supportive for medicinal chemists to develop more promising candidates for various infectious and non-infectious diseases.

Computational investigation of benzalacetophenone derivatives against SARS-CoV-2 as potential multi-target bioactive compounds

Benzalacetophenones, precursors of flavonoids are aromatic ketones and enones and possess the immunostimulant as well as antiviral activities. Thus, benzalacetophenones were screened against the COVID-19 that could be lethal in patients with compromised immunity. We considered ChEBI recorded benzalacetophenone derivative(s) and evaluated their activity against 3C-like protease (3CL^pro), papain-like protease (PL^pro), and spike protein of SARS-Cov-2 to elucidate their possible role as antiviral agents. The probable targets for each compound were retrieved from DIGEP-Pred at 0.5 pharmacological activity and all the modulated proteins were enriched to identify the probably regulated pathways, biological processes, cellular components, and molecular functions. In addition, molecular docking was performed using AutoDock 4 and the best-identified hits were subjected to all-atom molecular dynamics simulation and binding energy calculations using molecular mechanics Poisson-Boltzmann surface area (MMPBSA). The compound 4-hydroxycordoin showed the highest druglikeness score and regulated nine proteins of which five were down-regulated and four were upregulated. Similarly, enrichment analysis identified the modulation of multiple pathways concerned with the immune system as well as pathways related to infectious and non-infectious diseases. Likewise, 3'-(3-methyl-2-butenyl)-4′-O-β-d-glucopyranosyl-4,2′-dihydroxychalcone with 3CL^pro, 4-hydroxycordoin with PL^pro and mallotophilippen D with spike protein receptor-binding domain showed highest binding affinity, revealed stable interactions during the simulation, and scored binding free energy of −26.09 kcal/mol, −16.28 kcal/mol, and −39.2 kcal/mol, respectively. Predicted anti-SARS-CoV-2 activities of the benzalacetophenones reflected the requirement of wet lab studies to develop novel antiviral candidates.

Design, Synthesis, and Antifungal Activity of Novel Chalcone Derivatives Containing a Piperazine Fragment

In an attempt to find the biorational pesticides, 20 novel chalcone derivatives containing a piperazine fragment were designed and synthesized. Their fungicidal activities and preliminarily action mechanism against Rhizoctonia solani were evaluated. Strikingly, the biological activity of compound D2 was obtained by optimizing the structure of the system. Subsequently, the practical value of compound D2 was ascertained by the relative surveys on in vivo anti-R. solani and anti-Colletotrichum gloeosporioides. The results revealed by scanning electron microscopy demonstrated that compound D2 could induce irregular and shrivelled growth of mycelium and rupture of the mycelium surface. This study indicates that chalcone derivatives containing a piperazine skeleton had better inhibitory effect on plant fungi, providing further complementary research on new pesticides.

Synthesis of novel antibacterial and antifungal quinoxaline derivatives

A series of quinoxaline derivatives were designed, synthesized and evaluated as antimicrobial agents against plant pathogenic bacteria and fungi. Some of these compounds exhibited significant antibacterial and antifungal activities in vitro. Compound 5k displayed good antibacterial activity against Acidovorax citrulli (Ac). Compounds 5j and 5t exhibited the most potent anti-RS (Rhizoctonia solani) activity, with the corresponding EC50 values of 8.54 and 12.01 μg mL-1, respectively, which are superior to that of the commercial azoxystrobin (26.17 μg mL-1). Further, the scanning electron microscopy results proved that compound 5j had certain effects on the cell morphology of RS. Moreover, an in vivo bioassay also demonstrated that the anti-RS activity of compound 5j could effectively control rice sheath blight. These results indicate that quinoxaline derivatives could be promising agricultural bactericides and fungicides.

New chalcone derivatives as effective against SARS-CoV-2 agent

AIMS

Flavonoids and related compounds, such as quercetin-based antiviral drug Gene-Eden-VIR/Novirin, inhibit the protease of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The alkylated chalcones isolated from Angelica keiskei inhibit SARS-CoV proteases. In this study, we aimed to compare the anti-SARS CoV-2 activities of both newly synthesized chalcone derivatives and these two drugs.

METHODS

Determination of the potent antiviral activity of newly synthesized chalcone derivatives against SARS-CoV-2 by calculating the RT-PCR cycling threshold (C_t ) values.

RESULTS

Antiviral activities of the compounds varied because of being dose dependent. Compound 6, 7, 9, and 16 were highly effective against SARS-CoV-2 at the concentration of 1.60 µg/mL. Structure-based virtual screening was carried out against the most important druggable SARS-CoV-2 targets, viral RNA-dependent RNA polymerase, to identify putative inhibitors that could facilitate the development of potential anti-coronavirus disease-2019 drug candidates.

CONCLUSIONS

Computational analyses identified eight compounds inhibiting each target, with binding affinity scores ranging from -4.370 to -2.748 kcal/mol along with their toxicological, ADME, and drug-like properties.

Anticancer Activity of Natural and Synthetic Chalcones

Cancer is a condition caused by many mechanisms (genetic, immune, oxidation, and inflammatory). Anticancer therapy aims to destroy or stop the growth of cancer cells. Resistance to treatment is theleading cause of the inefficiency of current standard therapies. Targeted therapies are the most effective due to the low number of side effects and low resistance. Among the small molecule natural compounds, flavonoids are of particular interest for theidentification of new anticancer agents. Chalcones are precursors to all flavonoids and have many biological activities. The anticancer activity of chalcones is due to the ability of these compounds to act on many targets. Natural chalcones, such as licochalcones, xanthohumol (XN), panduretin (PA), and loncocarpine, have been extensively studied and modulated. Modification of the basic structure of chalcones in order to obtain compounds with superior cytotoxic properties has been performed by modulating the aromatic residues, replacing aromatic residues with heterocycles, and obtaining hybrid molecules. A huge number of chalcone derivatives with residues such as diaryl ether, sulfonamide, and amine have been obtained, their presence being favorable for anticancer activity. Modification of the amino group in the structure of aminochalconesis always favorable for antitumor activity. This is why hybrid molecules of chalcones with different nitrogen hetercycles in the molecule have been obtained. From these, azoles (imidazole, oxazoles, tetrazoles, thiazoles, 1,2,3-triazoles, and 1,2,4-triazoles) are of particular importance for the identification of new anticancer agents.

Antibacterial and Antiviral Activities of 1,3,4-Oxadiazole Thioether 4H-Chromen-4-one Derivatives

Various 1,3,4-oxadiazole thioether 4H-chromen-4-one derivatives were conceived. The title compounds demonstrated striking inhibitory effects against Xac, Psa, and Xoo. EC₅₀ data exhibited that A8 (19.7 μg/mL) had better antibacterial activity against Xoo than myricetin, BT, and TC. Simultaneously, the mechanism of action of A8 had been verified by SEM. The results of anti-tobacco mosaic virus indicated that A9 had the best in vivo antiviral effect compared with ningnanmycin. From the data of MST, it could be seen that A9 (0.003 ± 0.001 μmol/L) exhibited a strong binding capacity, which was far superior to ningnanmycin (2.726 ± 1.301 μmol/L). This study shows that the 1,3,4-oxadiazole thioether 4H-chromen-4-one derivatives may become agricultural drugs with great potential.

Design, Synthesis and Antibacterial Activity of Novel Pyrimidine-Containing 4H-Chromen-4-One Derivatives*

A series of pyrimidine-containing 4H-chromen-4-one derivatives were designed and synthesized by combining bioactive substructures. Preliminary biological activity results showed that most of the compounds displayed significant inhibitory activities in vitro against Xanthomonas axonopodis pv. Citri (X. axonopodis), Xanthomonas oryzae pv. oryzae (X. oryzae) and Ralstonia solanacearum (R. solanacearum). In particular, compound 2-[(3-{[5,7-dimethoxy-4-oxo-2-(3,4,5-trimethoxyphenyl)-4H-1-benzopyran-3-yl]oxy}propyl)sulfanyl]-4-(4-methylphenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile (4c) demonstrated a good inhibitory effect against X. axonopodis and X. oryzae, with the half-maximal effective concentration (EC₅₀ ) values of 15.5 and 14.9 μg/mL, respectively, and compound 2-[(3-{[5,7-Dimethoxy-4-oxo-2-(3,4,5-trimethoxyphenyl)-4H-1-benzopyran-3-yl]oxy}propyl)sulfanyl]-4-(3-fluorophenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile (4h) showed the best antibacterial activity against R. solanacearum with an EC₅₀ value of 14.7 μg/mL. These results were better than commercial reagents bismerthiazol (BT, 51.7, 70.1 and 52.7 μg/mL, respectively) and thiodiazole copper (TC, 77.9, 95.8 and 72.1 μg/mL, respectively). In vivo antibacterial activity results indicated that compound 4c displayed better curative (42.4 %) and protective (49.2 %) activities for rice bacterial leaf blight than BT (35.2, 39.1 %) and TC (30.8, 27.3 %). The mechanism of compound 4c against X. oryzae was analyzed through scanning electron microscopy (SEM). These results indicated that pyrimidine-containing 4H-chromen-4-one derivatives have important value in the research of new agrochemicals.

Plant-based analogues identified as potential inhibitor against tobacco mosaic virus: A biosimulation approach

Benzosuberene compounds with a pyrrolone group adhered to it are compounds extracted from the oils of Cedrus deodara plant, that bear inhibitory capabilities. Tobacco mosaic virus is known to affect crop production every year. The currently known inhibitors against TMV have a weak inhibition effect and also tend to be toxic towards non-target living organisms as well as the environment. Thus, the requirement of non-toxic potent inhibitors is the need of the hour, which led us to test our benzosuberene molecules on the binding site of TMV and check their affinity as well as stability. The non-toxic nature of these molecules has already been experimentally established. Through in-silico analysis involving docking and simulation experiments, we compared the interaction pattern of these ligand molecules with the already present inhibitors. Our investigation proved that the reported ligands (ligands 3, 7, 9, and 17 obtained -177.103, -228.632, -184.134, and - 188.075 kJ/mol binding energies, respectively) interacted with the binding site of TMV much efficiently than the known inhibitors (Ribavirin and Zhao et al. 2020 obtained 121.561 and - 221.393 kJ/mol binding energies, respectively). Moreover, they acquired a stable conformation inside the binding pocket, where a higher number of binding site residues contributed towards interaction. Thus, their structural framework can be optimized for the exploration of their antiviral properties to develop potent botanical viricides against plant virus infection.

Thiazole-Chalcone Hybrids as Prospective Antitubercular and Antiproliferative Agents: Design, Synthesis, Biological, Molecular Docking Studies and In Silico ADME Evaluation

Compounds bearing thiazole and chalcone pharmacophores have been reported to possess excellent antitubercular and anticancer activities. In view of this, we designed, synthesized and characterized a novel series of thiazole-chalcone hybrids (1-20) and further evaluated them for antitubercular and antiproliferative activities by employing standard protocols. Among the twenty compounds, chalcones 12 and 7, containing 2,4-difluorophenyl and 2,4-dichlorophenyl groups, showed potential antitubercular activity higher than the standard pyrazinamide (MIC = 25.34 µM) with MICs of 2.43 and 4.41 µM, respectively. Chalcone 20 containing heteroaryl 2-thiazolyl moiety exhibited promising antiproliferative activity against the prostate cancer cell line (DU-145), higher than the standard methotrexate (IC50 = 11 ± 1 µM) with an IC50 value of 6.86 ± 1 µM. Furthermore, cytotoxicity studies of these compounds against normal human liver cell lines (L02) revealed that the target molecules were comparatively less selective against L02. Additional computational studies using AutoDock predicted the key binding interactions responsible for the activity and the SwissADME tool computed the in silico drug likeliness properties. The lead compounds generated through this study, create a way for the optimization and development of novel drugs against tuberculosis infections and prostate cancer.

Design, synthesis, and antibacterial activity of novel myricetin derivatives containing sulfonate

A series of myricetin derivatives containing sulfonate groups were designed and synthesized. Preliminary antibacterial activity showed that most of the target compounds exhibited significant biological activities against Xanthomonas axonopodis pv. Citri (Xac), Ralstonia solanacearum (Rs), and Xanthomonas oryzae pv. Oryzae (Xoo). In particular, the EC50 value of compound 3e was 13.76 μg/cm3 against Xac, which was better than commercial reagents bismerthiazol (50.32 µg/cm3) and thiodiazole copper. (83.27 µg/cm3), and the EC50 value of compound 3j was 11.92 μg/cm3 against Xoo in vitro, The result was better than that of bismerthiazol (72.08 µg/cm3) and thiodiazole copper (99.26 µg/cm3). Compound 3j displayed the better in vivo activity against rice bacterial leaf blight than bismerthiazol and thiodiazole copper. Meanwhile, the antibacterial mechanism of compounds 3e and 3j was studied by scanning electron microscope (SEM). These results suggested that myricetin derivatives containing sulfonate can be considered as a new antibacterial reagents.

Graphic abstract

Antiviral properties of chalcones and their synthetic derivatives: a mini review

Chalcones (natural or synthetic derivatives) are aromatic ketones possessing a central backbone that form a core for variety important compounds with different substitutions. Recent scientific advances show that chalcones exhibit different bio-medical activities, including antiviral, which is related to the variety substitutions. This review provides general information on the origin, sources, virucidal and direct antiviral properties of chalcones in vitro, as well as a brief overview of the possible application and molecular modes of action of these compounds. The antiviral effect of chalcones probably results from the disruption of the different stage of viral replication cycle, inhibition of viral or cell enzymes, induction of apoptosis and others. Structural requirements for antiviral activities vary according to the mechanisms of action. Based on the published information, it could be considered that synthetic chalcones are very perspective antiviral candidates and deserve further studies for elucidating of their pharmacological potential.

In silico pharmacokinetic and molecular docking studies of natural flavonoids and synthetic indole chalcones against essential proteins of SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is distinctly infective and there is an ongoing effort to find a cure for this pandemic. Flavonoids exist in many diets as well as in traditional medicine, and their modern subset, indole-chalcones, are effective in fighting various diseases. Hence, these flavonoids and structurally similar indole chalcones derivatives were studied in silico for their pharmacokinetic properties including absorption, distribution, metabolism, excretion, toxicity (ADMET) and anti-SARS-CoV-2 properties against their proteins, namely, RNA dependent RNA polymerase (rdrp), main protease (Mpro) and Spike (S) protein via homology modelling and docking. Interactions were studied with respect to biology and function of SARS-CoV-2 proteins for activity. Functional/structural roles of amino acid residues of SARS-CoV-2 proteins and, the effect of flavonoid and indole chalcone interactions which may cause disease suppression are discussed. The results reveal that out of 23 natural flavonoids and 25 synthetic indole chalcones, 30 compounds are capable of Mpro deactivation as well as potentially lowering the efficiency of Mpro function. Cyanidin may inhibit RNA polymerase function and, Quercetin is found to block interaction sites on the viral spike. These results suggest flavonoids and their modern pharmaceutical cousins, indole chalcones are capable of fighting SARS-CoV-2. The in vitro anti-SARS-CoV-2 activity of these 30 compounds needs to be studied further for complete understanding and confirmation of their inhibitory potential.

Design, Synthesis, and Antimicrobial Evaluation of New Annelated Pyrimido[2,1-c][1,2,4]triazolo[3,4-f][1,2,4]triazines

A series of 34 new pyrimido[2,1-c][1,2,4]triazine-3,4-diones were synthesized and fully characterized using IR, NMR, MS, and microanalytical analysis. In vitro investigation of 12 compounds of this series revealed promising antimicrobial activity of the conjugates 15a and 15f-j that were tagged with electron-withdrawing groups, with sensitivities ranging from 77% to as high as 100% of the positive control. The investigation of antimicrobial activity included Bacillus subtilis ATCC 6633, Staphylococcus aureus ATCC 6535, Pseudomonas aeruginosa ATCC 27853, and Escherichia coli ATCC 8739 (EC), and fungal strains Candida albicans ATCC 10231 and Aspergillus brasiliensis ATCC 16404.

Design, synthesis and antibacterial activities against Xanthomonas oryzae pv. oryzae, Xanthomonas axonopodis pv. Citri and Ralstonia solanacearum of novel myricetin derivatives containing sulfonamide moiety

BACKGROUND

Myricetin and sulfonamide derivatives exhibited a wide variety of biological activity. In order to develop highly bioactive molecules, novel myricetin derivatives containing sulfonamide moiety were synthesized and antibacterial activities were investigated.

RESULTS

The results of bioassays indicated that compound A12, having an EC₅₀ value of 4.7 μg mL^-1 , exhibited the best in vitro antibacterial activities against Xanthomonas oryzae pv. oryzae (X. oryzae pv. o.); EC₅₀ values for this compound were even better than those of thiodiazole-copper (TC, 71.4 μg mL^-1 ) and bismerthiazol (BT, 54.7 μg mL^-1 ). Compound A2, having an EC₅₀ value of 1.1 μg mL^-1 , exhibited the best in vitro antibacterial activities against Xanthomonas axonopodis pv. citri (X. axonopodis pv. c); values were notably better than those of TC (60.0 μg mL^-1 ) and BT (48.9 μg mL^-1 ). Scanning electron microscopy analysis indicated that compounds A2 and A12 caused the cell membranes of X. axonopodis pv. c and X. oryzae pv. o. to break or deform, respectively. When the concentration of compound A12 was 100 μg mL^-1 , the effective curative activity against bacterial leaf blight of rice was 44.2% in vivo and the effective protection activity was 58.2% in vivo, results that were both better than values for TC (18.9 and 21.4%, respectively) and BT (12.5 and 12.5%, respectively).

CONCLUSION

Novel myricetin derivatives containing a sulfonamide moiety were synthesized and bioassay results showed that compounds A2 and A12 exhibited the best antibacterial activities. © 2019 Society of Chemical Industry.

Chalcone hybrids and their antimalarial activity

Malaria, one of the most striking, re-emerging infectious diseases caused by the genus Plasmodium, places a huge burden on global healthcare systems. A major challenge in the control and eradication of malaria is the continuous emergence of increasingly widespread drug-resistant malaria, creating an urgent need to develop novel antimalarial agents. Chalcone derivatives are ubiquitous in nature and have become indispensable units in medicinal chemistry applications due to their diverse biological profiles. Many chalcone derivatives demonstrate potential in vitro and in vivo antimalarial activity, so chalcone could be a useful template for the development of novel antimalarial agents. This review covers the recent development of chalcone hybrids as antimalarial agents. The critical aspects of the design and structure-activity relationship of these compounds are also discussed.

Real-time process quality control of ramulus cinnamomi by critical quality attribute using microscale thermophoresis and on-line NIR

Real-time process quality control of ramulus cinnamomi (cassia twig) is still a challenge in pharmaceutical industry. Rapid critical quality attribute (CQA) determination of ramulus cinnamomi is essential for quality control. Microscale thermophoresis (MST) was used to investigate the CQA of ramulus cinnamomi by the interaction with biomacromolecule. There was a good affinity between cinnamaldehyde and human serum albumin (HSA) with K_a as 2.1722×10³mol/L. It was an excellent combination of similarity to ibuprofen with same binding force as discovered as hydrogen bond and van der Waals force. Furthermore, regarding cinnamaldehyde as CQA, on-line near-infrared was used to monitor pilot extraction process of ramulus cinnamomi combined with high performance liquid chromatography (HPLC). Quantitative model was established with R_pre² as 0.9798 and RMSECV as 0.0993, suggesting the NIR model was so robust and accurate for pilot process quality control. This method provided a perfect guideline for rapid CQA determination and real-time process quality control of Chinese materia medica (CMM) based on a vital CQA.

New chalcone derivatives: synthesis, antiviral activity and mechanism of action

In this work, twenty-eight chalcone derivatives containing a purine (sulfur) ether moiety were synthesized and their antiviral activities were evaluated. Biological results showed that compound 5d exhibited outstanding inactive activity against tobacco mosaic virus (TMV) in vivo (EC₅₀ = 65.8 μg mL⁻¹), which is significantly superior to that of ribavirin (EC₅₀ = 154.3 μg mL⁻¹). Transmission electron microscopy indicated that compound 5d can break the integrity of TMV particles. The results of microscale thermophoresis, fluorescence titration and molecular docking showed that compound 5d had stronger combining affinity (K_a = 1.02 ×10⁵ L mol⁻¹, K_d = 13.4 μmol L⁻¹) with TMV coat protein (TMV-CP), which is due to the formation of five hydrogen bonds between compound 5d and the amino-acid residues of TMV-CP. These findings revealed that compound 5d can effectively inhibit the infective ability of TMV. This work provides inspiration and reference for the discovery of new antiviral agents.

The chalcone derivatives containing a purine (sulfur) ether moiety were synthesized. The antiviral mechanism suggested that the antiviral activity of compound 5d may depend on its stronger binding affinity with TMV-CP.

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

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

Fabrication of pH-Sensitive Tetramycin Releasing Gel and Its Antibacterial Bioactivity against Ralstonia solanacearum

Ralstonia solanacearum (R. solanacearum)-induced bacterial wilt of the nightshade family causes a great loss in agricultural production annually. Although there has been some efficient pesticides against R. solanacearum, inaccurate pesticide releasing according to the onset time of bacterial wilt during the use of pesticides still hinders the disease management efficiency. Herein, on the basis of the soil pH change during R. solanacearum growth, and pH sensitivity of the Schiff base structure, a pH-sensitive oxidized alginate-based double-crosslinked gel was fabricated as a pesticide carrier. The gel was prepared by crosslinking oxidized sodium alginate (OSA) via adipic dihydrazide (ADH) and Ca2+. After loading tetramycin into the gel, it showed a pH-dependent pesticide releasing behavior and anti-bacterial activity against R. solanacearum. Further study also showed that the inhibition rate of the tetramycin-loaded gel was higher than that of industrial pesticide difenoconazole. This work aimed to reduce the difficulty of pesticide administration in the high incidence period of bacterial wilt and we believe it has a great application potential in nightshade production.

Synthesis, antiviral and antibacterial activities and action mechanism of penta-1,4-dien-3-one oxime ether derivatives containing a quinoxaline moiety

A series of penta-1,4-dien-3-one oxime ether derivatives containing a quinoxaline moiety were synthesized, and their bioactivities and action mechanism were evaluated.

Synthesis and antibacterial and antiviral activities of myricetin derivatives containing a 1,2,4-triazole Schiff base

A series of novel myricetin derivatives containing a 1,2,4-triazole Schiff base were designed and synthesized. Their structures were systematically characterized using ¹H NMR, ¹³C NMR, and HRMS. During antibacterial bioassays, 6f, 6i, and 6q demonstrated a good inhibitory effect against Xanthomonas axonopodis pv. citri (Xac), with half-maximal effective concentration (EC₅₀) values of 10.0, 9.4, and 8.8 μg mL⁻¹, respectively, which were better than those of bismerthiazol (54.9 μg mL⁻¹) and thiodiazole copper (61.1 μg mL⁻¹). Note that 6w demonstrated a good inhibitory effect against Ralstonia solanacearum (Rs) with and EC₅₀ value of 15.5 μg mL⁻¹, which was better than those of bismerthiazol (55.2 μg mL⁻¹) and thiodiazole copper (127.9 μg mL⁻¹). Similarly, 6a, 6d, and 6e demonstrated a good inhibitory effect against Xanthomonas oryzae pv. oryzae (Xoo) with EC₅₀ values of 47.1, 61.2, and 61.0 μg mL⁻¹, respectively, which were better than those of bismerthiazol (148.2 μg mL⁻¹) and thiodiazole copper (175.5 μg mL⁻¹). Furthermore, we used scanning electron microscopy (SEM) to study the possible sterilization process of the target compound 6q against Xac. The results indicated the possibility of destroying the bacterial cell membrane structure, resulting in an incomplete bacterial structure, and thus achieving inhibition. Furthermore, antiviral bioassays revealed that most compounds exhibited excellent antiviral activity against tobacco mosaic virus (TMV) at a concentration of 500 μg mL⁻¹. The results of the molecular docking studies for 6g with TMV-CP (PDB code: 1EI7) showed that compound 6g had partially interacted with TMV-CP. Therefore, mechanistic studies of the action of compound 6g could be further studied based on that.

The myricetin derivatives containing a 1,2,4-triazole Schiff base were designed and synthesized. Antibacterial mechanism was investigated through SEM.