Synthesis and biological evaluation of coumarin derivatives containing imidazole skeleton as potential antibacterial agents

Effect of organic solvents on solvatochromic, fluorescence, and electrochemical properties of synthesized thiazolylcoumarin derivatives

In this present investigation, thiazolylcoumarin derivatives (5a-5k) were synthesized from thiosemicarbazide, ethyl acetoacetate, and naphthaldehyde through a multistep route. The formation of thiazolylcoumarin derivatives with bioactive scaffolds was confirmed through nuclear magnetic resonance spectroscopy. A solvatochromic study of synthesized thiazolylcoumarin derivatives was carried out using ultraviolet-visible methods for dimethylformamide (DMF), ethyl acetate, and ethanol solvents. The redox behaviour of as-synthesized thiazolylcoumarin derivatives (5a-5k) was examined in dimethyl sulphoxide by conducting an electrochemical study. Fluorescence properties of thiazolylcoumarin derivatives were studied in DMF, ethanol, and ethyl acetate to visualize the solvent effect on the emitting ability of thiazolylcoumarin derivatives.

Imidazole and Imidazolium Antibacterial Drugs Derived from Amino Acids

The antibacterial activity of imidazole and imidazolium salts is highly dependent upon their lipophilicity, which can be tuned through the introduction of different hydrophobic substituents on the nitrogen atoms of the imidazole or imidazolium ring of the molecule. Taking this into consideration, we have synthesized and characterized a series of imidazole and imidazolium salts derived from L-valine and L-phenylalanine containing different hydrophobic groups and tested their antibacterial activity against two model bacterial strains, Gram-negative E. coli and Gram-positive B. subtilis. Importantly, the results demonstrate that the minimum bactericidal concentration (MBC) of these derivatives can be tuned to fall close to the cytotoxicity values in eukaryotic cell lines. The MBC value of one of these compounds toward B. subtilis was found to be lower than the IC₅₀ cytotoxicity value for the control cell line, HEK-293. Furthermore, the aggregation behavior of these compounds has been studied in pure water, in cell culture media, and in mixtures thereof, in order to determine if the compounds formed self-assembled aggregates at their bioactive concentrations with the aim of determining whether the monomeric species were in fact responsible for the observed antibacterial activity. Overall, these results indicate that imidazole and imidazolium compounds derived from L-valine and L-phenylalanine—with different alkyl lengths in the amide substitution—can serve as potent antibacterial agents with low cytotoxicity to human cell lines.

A review: Biologically active 3,4-heterocycle-fused coumarins

The combination of heterocycles offers a new opportunity to create novel multicyclic compounds having improved biological activity. Coumarins are ubiquitous natural heterocycle widely adopted in the design of various biologically active compounds. Fusing different heterocycles with coumarin ring is one of the interesting approaches to generating novel hybrid molecules having highlighted biological activities. In the efforts to develop heterocyclic-fused coumarins, a wide range of 3,4-heterocycle-fused coumarins have been introduced bearing outstanding biological activity. The effect of heterocycles annulation at 3,4-positions of coumarin ring on the biological activity of the target structures were discussed. This review focuses on the important progress of 3,4-heterocycle-fused coumarins providing better insight for medicinal chemists on the design and preparation of biologically active heterocycle-fused coumarins with a significant therapeutic effect in the future.

Effects of Bacillus cereus and coumarin on growth performance, blood biochemical parameters, and meat quality in broilers

Background and Aim:

Progressive antibiotic resistance has become the primary threat to public health. The search for alternative substances with similar effects is now a global challenge for poultry farming. The aim of this study was to investigate the action of the probiotic Bacillus cereus (BC) and coumarin (CO) on broiler productivity, biochemical indicators of blood, and muscular and liver tissues.

Materials and Methods:

The trial of this study included Arbor Acres cross broiler chickens that were grown up to the age of 42 days. The experiment was conducted on 200 broiler chickens divided into four experimental groups of 50 individuals each: The control group received ration without additives (main ration [MR]), the first experimental group received MR+BC, the second received MR+CO, and the third received −MR+BC+CO. A biochemical and hematological analyzer was used to estimate elemental concentrations using inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectrometry.

Results:

Inclusion of CO and CO+BC in the diet improved growth rates and reduced feed consumption (FC) per kg of live weight gain. Decreased white blood cell count, increased creatinine and triglycerides (CO), changes in aminotransferase and transpeptidase activity, and increases in chemical elements in the liver and pectoral muscles (BC+CO) were observed. The inclusion of BC+CO in the diet contributed to increases in a greater number of chemical elements in the liver (calcium [Ca], K, magnesium, Mn, Si, and Zn) and the pectoral muscles (Ca, Na, Co, Cu, Fe, Mn, Ni, and Zn).

Conclusion:

The inclusion of CO and CO+BC in the diet improves growth rates and reduces FC in broilers against a background of the absence of mortality during the experiment.

A highly substituted and fluorescent aromatic-fused imidazole derivative that shows enhanced antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA)

A novel highly substituted and fluorescent aromatic-fused imidazole derivative has been synthesized by rational design. This novel fluorescent material acts as an alternative antibacterial agent against Gram positive bacteria strains. It shows superior antibacterial activity (with MIC value of 8 μg/mL) against methicillin-resistant Staphylococcus aureus (MRSA) when compared with standard antibiotic drugs Ampicillin (with MIC value of 128 μg/mL) and Kanamycin (with MIC value of >512 μg/mL). The interaction of this novel compound with the bacterial cell and genomic DNA has also been studied to elucidate antibacterial mode of action. Fluorescence spectroscopy and microscopy studies have proved the intracellular uptake of this special compound. Likewise, UV-vis and fluorescence spectroscopy studies have revealed a significant decrease in the absorption and emission bands of the compound upon its interaction with plasmid and genomic DNA, which is likely due to its DNA intercalation property. Furthermore, these findings have been supported by gel electrophoresis of genomic DNA of S. aureus cells treated with the compound. The results indicate that this novel compound exerts its antibacterial activity by causing DNA damage, suggesting the potential utility of fluorescent probes for real-time diagnosis and treatment of bacterial infections.

An Updated Review on the Synthesis and Antibacterial Activity of Molecular Hybrids and Conjugates Bearing Imidazole Moiety

The rapid growth of serious infections caused by antibiotic resistant bacteria, especially the nosocomial ESKAPE pathogens, has been acknowledged by Governments and scientists and is one of the world's major health problems. Various strategies have been and are currently investigated and developed to reduce and/or delay the bacterial resistance. One of these strategies regards the design and development of antimicrobial hybrids and conjugates. This unprecedented critical review, in which our continuing interest in the synthesis and evaluation of the bioactivity of imidazole derivatives is testified, aims to summarise and comment on the results obtained from the end of the 1900s until February 2020 in studies conducted by numerous international research groups on the synthesis and evaluation of the antibacterial properties of imidazole-based molecular hybrids and conjugates in which the pharmacophoric constituents of these compounds are directly covalently linked or connected through a linker or spacer. In this review, significant attention was paid to summarise the strategies used to overcome the antibiotic resistance of pathogens whose infections are difficult to treat with conventional antibiotics. However, it does not include literature data on the synthesis and evaluation of the bioactivity of hybrids and conjugates in which an imidazole moiety is fused with a carbo- or heterocyclic subunit.

In vitro and in vivo evaluation of antiviral activity of a phenylpropanoid derivative against spring viraemia of carp virus

Phenylpropanoids, common natural compounds, possess many different biological activities such as antioxidant, anti-inflammatory and antiviral. Spring viraemia of carp virus (SVCV) can cause a high mortality in common carp (Cyprinus carpio). However, there are currently no licenced drugs that effectively cure this disease. In this study, we designed and synthesized a phenylpropanoid derivative 4-(4-methoxyphenyl)-3,4-dihydro-2H-chromeno[4,3-d]pyrimidine-2,5(1 H)-dione (E2), and explored the antiviral effect against SVCV in vitro and in vivo. Up to 25 mg/L of E2 significantly inhibited the expression levels of SVCV protein genes in the epithelioma papulosum cyprini (EPC) cell line by a maximum inhibitory rate of >90%. As expected, E2 remarkably declined the apoptotic of SVCV-infected cells and suppressed potential enhancement of the mitochondrial membrane potential (ΔΨm), these data implied that E2 could protect mitochondria from structural damage in response to SVCV. Meanwhile, E2 was added to EPC cells under four different conditions: time-of-addition, time-of-removal, pre-treatment of viruses and pre-treatment of cells indicated that E2 may block the post-entry transport process of the virus. Additionally, the up-regulation of six interferon (IFN)-related genes also demonstrated that E2 indirectly activated IFNs for the clearance of SVCV in common carp. Drug cure effect showed that treatment with E2 at 0.5 d post infection (dpi) is more effective than at 0, 1 or 2 dpi. Most importantly, intraperitoneal therapy of E2 markedly improved common carp survival rate and reduced virus copies in body. Therefore, the E2 has potential to be developed into a novel anti-SVCV agent.

Contemporary Progress in the Synthetic Strategies of Imidazole and its Biological Activities

Heterocyclic compounds are pervasive in many areas of life and one of the heterocycles, imidazole is a unique heterocyclic five-membered aromatic compound having two sp2 hybridized nitrogen atoms. Its integral name is 1, 3 diazole and previously, it was known as glyoxalin. This moiety has achieved a considerable place among scientists in recent years by reason of its divergent synthetic strategies and uncommon biological and pharmacological activities, for example, anti-convulsant, anti-microbial, anti-cancer, anti-inflammatory, anti-tumor, anti-viral, anti-ulcer, analgesic, etc. Due to distinct therapeutic actions, it is still an engrossed area of research. Researchers currently are inventing new greener methods to synthesize its derivatives and to improve its pharmacological activities. The purpose of this review is to study the literature that can help researchers to explore this area, its prevailing program for synthesis in environmentally friendly conditions and biological profile throughout past decades.

FabI (enoyl acyl carrier protein reductase) - A potential broad spectrum therapeutic target and its inhibitors

Development of new anti-bacterial agents acting upon underexploited targets and thus evading known mechanisms of resistance is the need of the hour. The highly conserved and distinct bacterial fatty acid biosynthesis pathway (FAS-II), presents a validated and yet relatively underexploited target for drug discovery. FabI and its isoforms (FabL, FabK, FabV and InhA) are essential enoyl-ACP reductases present in several microorganisms. In addition, the components of the FAS-II pathway are distinct from the multi-enzyme FAS-I complex found in mammals. Thus, inhibition of FabI and its isoforms is anticipated to result in broad-spectrum antibacterial activity. Several research groups from industry and academic laboratories have devoted significant efforts to develop effective FabI-targeting antibiotics, which are currently in various stages of clinical development for the treatment of multi-drug resistant bacterial infections. This review summarizes all the natural as well as synthetic inhibitors of gram-positive and gram-negative enoyl ACP reductases (FabI). The knowledge of the reported inhibitors can aid in the development of broad-spectrum antibacterials specifically targeting FabI enzymes from S. aureus, S. epidermidis, B. anthracis, B. cereus, E. coli, P. aeruginosa, P. falciparum and M. tuberculosis.

Overview on developed synthesis procedures of coumarin heterocycles

Considering highly valuable biological and pharmaceutical properties of coumarins, the synthesis of these heterocycles has been considered for many organic and pharmaceutical chemists. This review includes the recent research in synthesis methods of coumarin systems, investigating their biological properties and describing the literature reports for the period of 2016 to the middle of 2020. In this review, we have classified the contents based on co-groups of coumarin ring. These reported methods are carried out in the classical and non-classical conditions particularly under green condition such as using green solvent, catalyst and other procedures.

Organic Polymer Nanoparticles with Primary Ammonium Salt as Potent Antibacterial Nanomaterials

Bacterial infections induced by drug-resistant strains have become a global crisis. A membrane-disrupted mechanism is considered as an effective way to kill bacteria with little chance to trigger drug resistance. It is necessary to explore and develop new materials based on the membrane-disrupted mechanism to combat bacterial resistance. Here we report the design of organic nanoparticles based on a polymer (PDCP) as highly effective inhibition and bactericidal reagents. The PDCP is devised to have a hydrophobic skeleton and hydrophilic side chain modified with protonated primary amines, which could self-assemble to form organic nanoparticles (PDCP-NPs). By taking advantage of the large surface to volume ratio of nanoparticles, the synthesized PDCP-NPs have enriched positive charges and multiple membrane-binding sites. Research results display that PDCP-NPs have highly potent antibacterial activity in vitro and vivo, especially for Gram-negative bacteria with low toxicity against mammalian cells. This work design will inspire researchers to develop more membrane-disrupted bactericide and advance the applications of organic nanoparticles in the antibacterial area.

Medicinal chemistry insights into novel CDC25 inhibitors

Cell division cycle 25 (CDC25) phosphatases, a kind of cell cycle regulators, have become an attractive target for drug discovery, as they have been found to be over-expressed in various human cancer cells. Several CDC25 inhibitors have achieved significant attention in clinical trials with possible mechanistic actions. Prompted by the significance of CDC25 inhibitors with medicinal chemistry prospect, it is an apt time to review the various drug discovery methods involved in CDC25 drug discovery including high throughput screening (HTS), virtual screening (VS), fragment-based drug design, substitution decorating approach, structural simplification approach and scaffold hopping method to seek trends and identify promising new avenues of CDC25 drug discovery.

Coumarin-containing hybrids and their antibacterial activities

Infections caused by Gram-positive and -negative bacteria are one of the foremost causes of morbidity and mortality globally. Antibiotics are the mainstay of therapy for bacterial infections, but the emergence and wide spread of drug-resistant pathogens have already become a huge issue for public healthcare systems. The coumarin moiety, which is ubiquitous in nature, could bind to the B subunit of DNA gyrase in bacteria and inhibit DNA supercoiling by blocking the ATPase activity; hence, coumarin derivatives possess potential antibacterial activity. Several coumarin-containing hybrids such as coumermycin A1, clorobiocin, and novobiocin have already been used in clinical practice for the treatment of various bacterial infections; thus, it is conceivable that hybridization of the coumarin moiety with other antibacterial pharmacophores may provide opportunities for the development of novel antibiotics. This review outlines the advances in coumarin-containing hybrids with antibacterial potential in the recent 5 years and the structure-activity relationships are also discussed.

Treatment of Brain Edema by Wogonoside Is Associated with Inhibition of Neuronal Apoptosis and SIRT1 Activation in Rats

Background

Brain edema and neuronal apoptosis are closely associated with loss of neurological function and death in rats with subarachnoid hemorrhage (SAH). The present study investigated the effect of wogonoside on brain edema induced by SAH in rats and studied the mechanism involved.

Material/Methods

The rats were intra-gastrically administered 10, 20, 50, 100, 150 and 200 mg/kg doses of wogonoside 24 h prior to SAH induction. Western blotting was used to assess levels of pro-apoptotic protein, SIRT1, ZO-1, and p53 protein expression. Apoptotic nuclei were detected using immunofluorescence and TUNEL staining.

Results

Wogonoside treatment significantly suppressed edema formation in SAH-induced rats. Pre-treatment with wogonoside exhibited an inhibitory effect on SAH-induced extravascular Evans blue staining in rats. The expression of ZO-1, Occludin, and Claudin-5 proteins was increased by wogonoside in the SAH-induced rats. The inhibitory effect of SAH was completely reversed in the rats treated with the 200 mg/kg dose of wogonoside. The expression of SIRT1 protein was upregulated, and p53 and AC-p53 were downregulated by wogonoside in SAH rats. Wogonoside treatment significantly reduced SAH-mediated promotion of Bax, Puma, Noxa, Bid, and cleaved Caspase-3 expression. In the SAH-induced rats, pre-treatment with wogonoside reduced the TUNEL-positive cell count.

Conclusions

The present study demonstrated that wogonoside prevents brain edema development and apoptosis of neurons in rats by promoting SIRT1 expression and suppression of p53 activation. Therefore, wogonoside has therapeutic potential for the treatment of edema and needs to be investigated further to completely define the mechanism involved.

Hydroxypyridinone-Coumarin Inhibits the Proliferation of MHCC97 and HepG2 Human Hepatocellular Carcinoma Cells and Down-Regulates the Phosphoinositide-3 Kinase Pathway

Background

Worldwide, hepatocellular carcinoma (HCC) is one of the most commonly diagnosed malignant diseases and is the third leading cause of cancer-related death. This study aimed to investigate the effect of hydroxypyridinone-coumarin (HPC) on MHCC97 and HepG2 human HCC cells and the mechanisms involved.

Material/Methods

MHCC97 and HepG2 human HCC cells were cultured in vitro. An MTT cytotoxicity assay was used to assess cell viability and proliferation, with and without treatment with HPC. Cell autophagosomes were labeled with GFP-LC3 using confocal fluorescence microscopy. Western blot was used to measure protein expression.

Results

HPC significantly reduced the cell proliferation rate in a concentration-dependent manner, with 2 μM of HPC resulting in a reduced proliferation rate of MHCC97 cells (by 36%) and HepG2 cells (by 29%) (P<0.02). HPC significantly reduced autophagy in MHCC97 and HepG2 cells. Western blot showed that treatment with HPC significant upregulated Atg5, beclin-1, LC3-phosphatidylethanolamine conjugate (LC3-II), and Atg-3, reduced p62 and Akt protein expression, and induced phosphorylation of ERK1/2. GFP-LC3B labeling in MHCC97 and HepG2 cells was increased following HPC treatment.

Conclusions

HPC induced autophagy and inhibited the proliferation of MHCC97 and HepG2 HCC cells in vitro and involved activation of ERK1/2 and down-regulation of the Akt pathway.

Design, Synthesis and Evaluation of 3-Substituted Coumarin Derivatives as Anti-inflammatory Agents

Coumarin moiety has garnered momentous attention especially in the design of compounds with significant biological activities. In this work, a series of 3-substituted coumarin derivatives 6a-6l were synthesized and fully characterized. Most of the compounds could obviously inhibit the activity of cyclooxygenase-1 (COX-1) at the concentration of 10 µM. Besides, 6h and 6l exhibited highest inhibitory effects against COX-2 with inhibition rates of 33.48 and 35.71%, respectively. Detailed structure-activity relationships (SARs) were also discussed. In vivo studies, 6b, 6i and 6l could remarkably repress the xylene-induced ear swelling in mice at the dose of 20 mg/kg. Especially, 6l seemed to be the most effective compound at the dose of 10 mg/kg, displaying favorable anti-inflammatory activity comparable to indomethacin. All of these findings suggested that 6l might be utilized as a candidate for the treatment of inflammatory diseases.

Ferulic Acid Induces Apoptosis of HeLa and Caski Cervical Carcinoma Cells by Down-Regulating the Phosphatidylinositol 3-Kinase (PI3K)/Akt Signaling Pathway

Background

Ferulic acid is an antioxidant phenolic compound derived from plants, which has effects on cancer cells. This study aimed to investigate the effects of ferulic acid on HeLa and Caski human cervical carcinoma cells and the molecular mechanisms involved.

Material/Methods

HeLa and Caski human cervical carcinoma cells were grown in culture and treated with increasing doses of ferulic acid. The MTT assay was used to evaluate cell viability. Flow cytometry was performed with 4′,6-diamidino-2-phenylindole (DAPI) and Annexin V staining for cell apoptosis. The expression of myeloid leukemia cell differentiation-1 (Mcl-1) protein and MCL-1 mRNA were determined by Western blot and reverse transcription-polymerase chain reaction (RT-PCR).

Results

Ferulic acid significantly reduced HeLa and Caski cell viability in the concentration range of 4–20 μM (P<0.05). Ferulic acid treatment promoted DNA condensation and significantly increased apoptosis in Caski cells (P<0.05). Ferulic acid treatment resulted in the activation of pro-caspase-3, pro-caspase-8, pro-caspase-9, and PARP. The MTT assay showed that ferulic acid did not reduce the viability of Caski cells treated with the caspase inhibitor, z-VAD-fmk. Ferulic acid reduced the levels of Bcl-2 and Mcl-1, and increased the levels of Bax and reactive oxygen species (ROS). In Caski cells, Akt and PI3K phosphorylation were reduced by ferulic acid in a concentration-dependent manner.

Conclusions

The effects of ferulic acid were dose-dependent and resulted in cell cytotoxicity and apoptosis of HeLa and Caski cells, and the PI3K/Akt signaling pathway was down-regulated in Caski cells.

Inhibition of Colon Cancer Cell Growth by Imidazole Through Activation of Apoptotic Pathway

Background

This study aimed to investigate the inhibitory effect of imidazole on colon cancer cell proliferation and understand the mechanism involved.

Material/Methods

MTT assay and flow cytometry using Hoechst 33258 staining were used to assess cell proliferation and morphology, respectively. Changes in protein expression was determined by western blotting assay. The reactive oxygen species (ROS) production in DLD-1 cells was analyzed by flow cytometry using DCFH-DA (2′,7′-dichlorofluorescein diacetate) stain.

Results

DLD-1 and HCT-116 cell viability was suppressed by imidazole in a concentration-based manner. At the concentration of 36 μM, imidazole reduced DLD-1 and HCT-116 cell viability to 22% and 28%, respectively. Treatment with imidazole led to chromatin material condensation, detaching of cells, and apoptotic nuclei. In imidazole treated cells, the G1/G0 phase cell proportion increased, whereas in the S and G2/M phases the cell proportion decreased. Imidazole treatment of DLD-1 cells markedly promoted activation of caspase-3, caspase-8, and caspase-9. The level of cleaved PARP1 was also upregulated in DLD-1 cells with imidazole treatment. Treatment of DLD-1 cells with imidazole suppressed Bcl-2 and promoted Bax, p53, and cytc expression. The Akt activation was suppressed by imidazole treatment in DLD-1 cells. ROS generation in DLD-1 cells was enhanced markedly by treatment with imidazole.

Conclusions

The present study demonstrated that imidazole inhibited colon cancer cell viability through activation of apoptosis and cell cycle arrest by increasing the generation of ROS, caspase activation, and apoptotic protein expression. Therefore, imidazole can act as a therapeutic molecule for the treatment of colon cancer.

Coumarin-containing hybrids and their anticancer activities

Cancer is the second leading cause of death worldwide, and it results in around 9 million deaths annually. The anticancer agents play an intriguing role in the treatment of cancers, while the severe anticancer scenario and the emergence of drug-resistant especially multidrug-resistant cancers create a huge demand for novel anticancer drugs with different mechanisms of action. The coumarin scaffold is ubiquitous in nature and is a highly privileged motif for the development of novel drugs due to its biodiversity and versatility. Coumarin derivatives can exert diverse antiproliferative mechanisms, and some of them such as Irosustat are under clinical trials for the treatment of various cancers, revealing their potential as putative anticancer drugs. Hybridization of coumarin moiety with other anticancer pharmacophores is a promising strategy to reduce side effects, overcome the drug resistance, and may provide valuable therapeutic intervention for the treatment of cancers. Thus, coumarin-containing hybrids occupy an important position in the development of novel anticancer agents. This review aims to summarize the recent advances made towards the development of coumarin-containing hybrids as potential anticancer agents, covering articles published between 2015 and 2019, and the structure-activity relationship together with mechanisms of action are also discussed.

Monocarbonyl Curcumin-Based Molecular Hybrids as Potent Antibacterial Agents

Keeping in view various pharmacological attributes of curcumin, coumarin, and isatin derivatives, triazole-tethered monocarbonyl curcumin-coumarin and curcumin-isatin molecular hybrids have been synthesized and evaluated for their antibacterial potential against Gram-positive (Enterococcus faecalis and Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa and Escherichia coli) human pathogenic bacterial strains. Among all hybrid molecules, A-4 and B-38 showed the most potent antibacterial activity with inhibition zones of 29 and 31 mm along with MIC values of 12.50 and 6.25 μg/mL, respectively. Structure-activity relationship that emerged from biological data revealed that the two-carbon alkyl chain between triazole and coumarin/isatin moiety is well tolerable for the activity. Bromo substitution at the fifth position of isatin, para-cholo substitution in the case of curcumin-isatin, and para-methoxy in the case of curcumin-coumarin hybrids on ring A of curcumin are most suitable groups for the antibacterial activity. Various types of binding interactions of A-4 and B-38 within the active site of dihydrofolate reductase (DHFR) of S. aureus are also streamlined by molecular modeling studies, suggesting their capability in completely blocking DHFR.

Design, Synthesis, Antimicrobial Evaluation, and Molecular Modeling Studies of Novel Indolinedione-Coumarin Molecular Hybrids

Keeping in view various pharmacological attributes of indole and coumarin derivatives, a new series of indolindione-coumarin molecular hybrids was rationally designed and synthesized. All synthesized hybrid molecules were evaluated for their antimicrobial potential against Gram-negative bacterial strains (Escherichia coli and Salmonella enterica), Gram-positive bacterial strains (Staphylococcus aureus and Mycobacterium smegmatis), and four fungal strains (Candida albicans, Alternaria mali, Penicillium sp., and Fusarium oxysporum) by using the agar gel diffusion method. Among all synthetics, compounds K-1 and K-2 were found to be the best antimicrobial agents with the minimum inhibitory concentration values of 30 and 312 μg/mL, against Penicillium sp. and S. aureus, respectively. The biological data revealed some interesting facts about the structure-activity relationship which state that the electronic environment on the indolinedione moiety and carbon chain length between indolinedione and triazole moieties considerably affect the antimicrobial potential of the synthesized hybrids. Various types of binding interactions of K-2 within the active site of S. aureus dihydrofolate reductase were also streamlined by molecular modeling studies, which revealed the possible mechanism for potent antibacterial activity of the compound.

Discovery of novel coumarin derivatives as potent and orally bioavailable BRD4 inhibitors based on scaffold hopping

The bromodomain and extra-terminal (BET) bromodomains, particularly BRD4, have been identified as promising therapeutic targets in the treatment of many human disorders such as cancer, inflammation, obesity, and cardiovascular disease. Recently, the discovery of novel BRD4 inhibitors has garnered substantial interest. Starting from scaffold hopping of the reported compound dihydroquinazolinone (PFI-1), a series of coumarin derivatives were designed and synthesised as a new chemotype of BRD4 inhibitors. Interestingly, the representative compounds 13 exhibited potent BRD4 binding affinity and cell proliferation inhibitory activity, and especially displayed a favourable PK profile with high oral bioavailability (F = 49.38%) and metabolic stability (T_1/2 = 4.2 h), meaningfully making it as a promising lead compound for further drug development.

Rational Optimization and Action Mechanism of Novel Imidazole (or Imidazolium)-Labeled 1,3,4-Oxadiazole Thioethers as Promising Antibacterial Agents against Plant Bacterial Diseases

The emergence and widespread occurrence of plant bacterial diseases that cause global production constraints have become major challenges to agriculture worldwide. To promote the discovery and development of new bactericides, imidazole-labeled 1,3,4-oxadiazole thioethers were first fabricated by integrating the crucially bioactive scaffolds of the imidazole motif and 1,3,4-oxadiazole skeleton in a single molecular architecture. Subsequently, a superior antibacterial compound A₆ was gradually discovered possessing excellent competence against plant pathogens Xanthomonas oryzae pv oryzae and Xanthomonas axonopodis pv citri with EC₅₀ values of 0.734 and 1.79 μg/mL, respectively. These values were better than those of commercial agents bismerthiazol (92.6 μg/mL) and thiodiazole copper (77.0 μg/mL). Further modifying the imidazole moiety into the imidazolium scaffold led to the discovery of an array of potent antibacterial compounds providing the corresponding minimum EC₅₀ values of 0.295 and 0.607 μg/mL against the two strains. Moreover, a plausible action mechanism for attacking pathogens was proposed based on the concentration dependence of scanning electron microscopy, transmission electron microscopy, and fluorescence microscopy images. Given the simple molecular structures, easy synthetic procedure, and highly efficient bioactivity, imidazole (or imidazolium)-labeled 1,3,4-oxadiazole thioethers can be further explored and developed as promising indicators for the development of commercial drugs.

Synthesis of arctigenin derivatives against infectious hematopoietic necrosis virus

Infectious hematopoietic necrosis virus (IHNV) is a common pathogen that causes severe disease and huge economic losses in the salmonid aquaculture industry. Herein, a series of arctigenin derivatives are synthesized to evaluate their antiviral activity against IHNV. The results indicate that the length of linker and imidazole substituent groups play an important role in decreasing IHNV replication. In this study, the arctigenin-imidazole hybrid derivative 15 with an eight carbon atoms length of the linker reduces IHNV replication with an IC₅₀ value of 1.3 μM. In addition, derivative 15 significantly inhibits apoptosis and cellular morphological damage induced by IHNV. Mechanistically, derivative 15 can not damage the viral particle directly. While time-of-addition and viral binding assays reveal that derivative 15 mainly affect the early replication of IHNV but do not interfere with IHNV adsorption. Overall, derivative 15 could be considered to develop as a promising agent to treat IHNV infection.

Transition metal-free oxidative and deoxygenative C-H/C-Li cross-couplings of 2H-imidazole 1-oxides with carboranyl lithium as an efficient synthetic approach to azaheterocyclic carboranes

The direct C-H functionalization methodology has first been applied to perform transition metal-free C-H/C-Li cross-couplings of 2H-imidazole 1-oxides with carboranyllithium. This atom- and step-economical approach, based on one-pot reactions of nucleophilic substitution of hydrogen (SN H) in non-aromatic azaheterocycles, affords novel imidazolyl-modified carboranes of two types (N-oxides and their deoxygenative analogues), which are particularly of interest in the design of advanced materials.