A new class of nifuroxazide analogues: Synthesis of 5-nitrothiophene derivatives with antimicrobial activity against multidrug-resistant Staphylococcus aureus

N-Heterocyclic Carbene-Catalyzed Facile Synthesis of Phthalidyl Sulfonohydrazones: Density Functional Theory Mechanistic Insights and Docking Interactions

N-heterocyclic carbene catalysis reaction protocol is disclosed for the synthesis of phthalidyl sulfonohydrazones. A broad range of N-tosyl hydrazones react effectively with phthalaldehyde derivatives under open-air conditions, enabling the formation of a new C-N bond via an oxidative path. The reaction proceeds under mild reaction conditions with broad substrate scopes, wide functional group tolerance, and good to excellent yields. The mechanistic pathway is studied successfully using control experiments, competitive reactions, ESI-MS spectral analyses of the reaction mixture, and computational study by density functional theory. The potential use of one of the phthalidyl sulfonohydrazone derivatives as the inhibitor of β-ketoacyl acyl carrier protein synthase I of Escherichia coli is investigated using molecular docking.

Nifuroxazide induces the apoptosis of human non‑small cell lung cancer cells through the endoplasmic reticulum stress PERK signaling pathway

The aim of the present study was to investigate the molecular mechanism of nifuroxazide (NFZ) in the induction of apoptosis of NCI-H1299 human non-small cell lung cancer (NSCLC) cells through the reactive oxygen species (ROS)/Ca²⁺/protein kinase R-like ER kinase (PERK)-activating transcription factor 4 (ATF4)-DNA damage inducible transcript 3 (CHOP) signaling pathway. Morphological changes of cells were observed by microscopy, and the apoptosis and intracellular ROS levels of cells were observed by inverted fluorescence microscopy. Cell viability after the addition of the PERK inhibitor, GSK2606414, were detected by Cell Counting Kit-8 assay. Annexin V-FITC was used to detect cell apoptosis, Brite 670 was used to detect intracellular ROS and Fura Red AM was used to detect Ca²⁺ content. Western blotting was used to detect PERK, phosphorylated (P)-PERK, ATF4, CHOP, P-Janus kinase 2 and P-signal transducer and activator of transcription 3 expression levels. Compared with the dimethyl sulfoxide control group, NFZ inhibited the survival activity in the H1299 NSCLC cell line, in a time- and dose-dependent manner. However, GSK2606414 inhibited the NFZ-induced apoptosis of H1299 cells. GSK2606414 also inhibited the increase in ROS and Ca²⁺ in H1299 cells induced by NFZ. Western blotting results demonstrated that NFZ significantly increased the expression levels of P-PERK, ATF4 and CHOP, whereas GSK2606414 significantly reduced the NFZ-induced increase in these protein expression levels. In conclusion, NFZ may induce the apoptosis of H1299 NSCLC cells through the ROS/Ca²⁺/PERK-ATF4-CHOP signaling pathway.

Effect of Structural Variation on Spectral, NLO Properties, and Biological Activity of Pyrrole Hydrazones

This paper describes spectral, non-linear optical (NLO), and biological activity variation of pyrrole hydrazones as a result of structural variation. In order to study structure-property variation, pyrrole hydrazones (3A, 3B, and 3C) were synthesized in both solid and solution phases. The grinding solvent-free method becomes rapid, easy, convenient, useful, sustainable, and eco-friendly green synthesis as compared to the classical solution phase reactions. The structure of pyrrole hydrazones has been elucidated by microanalysis and quantum chemical calculations. The intense emission at λ_em 521 nm (3A and 3B) and 617 nm (3C) in the visible (green and orange) region with Stokes shifts at 195, 160, and 282 nm reveals that the studied compounds work as good photoluminescent materials. All compounds show strong n-π* and charge transfer (π-π*) transitions in the UV-vis region with high extinction coefficients. In the studied systems (3A, 3B, and 3C), the orbital overlap between σ(NH-O) → σ*(NH-O) is found due to intra-molecular charge transfer. The first hyperpolarizabilities were found to be 48.83 × 10^-30 esu for 3B and 63.89 × 10^-30 esu for 3C, showing variation with structure. Their high values indicate more suitability for NLO application. Incorporation and/or change in position of electron-withdrawing groups increase the β₀ values of 3B and 3C compared to 3A. The β value also increases monotonically as the polarity of the solvents increases. The red shift in N-H and C=O stretching Fourier-transform infrared bonds is due to the formation of dimers. The synthesized 3A, 3B, and 3C show good antimicrobial activity and are predicted to be potential antibacterial and antifungal drugs. The 3B has more molar refractivity (122.16 esu) than 3A and 3C and correlates well with the calculated binding affinity and experimental antimicrobial data.

A Systematic Review on Synthetic and Antimicrobial Bioactivity of the Multifaceted Hydrazide Derivatives

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To overcome the upsurge of antimicrobial resistance that has emerged in recent years, there is a need for the development of newer hits having satisfying anti-infective activity. Hydrazides incorporated with an azomethine hydrogen account for a cardinal class of molecules for the development of newer derivatives. Hydrazide derivatives have gained considerable interest of medicinal chemists owing to their diverse bioactivity. In the present review, we have attempted to compile the recent trends in the synthesis of hydrazides and their substituted derivatives. The structural features that lead to the desired antimicrobial activity are highlighted, which will lead the way for synthetic and medicinal chemists to focus on newer designs in this arena.

Novel Aminoguanidine Hydrazone Analogues: From Potential Antimicrobial Agents to Potent Cholinesterase Inhibitors

A series of thirty-one hydrazones of aminoguanidine, nitroaminoguanidine, 1,3-diaminoguanidine, and (thio)semicarbazide were prepared from various aldehydes, mainly chlorobenzaldehydes, halogenated salicylaldehydes, 5-nitrofurfural, and isatin (yields of 50–99%). They were characterized by spectral methods. Primarily, they were designed and evaluated as potential broad-spectrum antimicrobial agents. The compounds were effective against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus with minimum inhibitory concentrations (MIC) from 7.8 µM, as well as Gram-negative strains with higher MIC. Antifungal evaluation against yeasts and Trichophyton mentagrophytes found MIC from 62.5 µM. We also evaluated inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). The compounds inhibited both enzymes with IC₅₀ values of 17.95–54.93 µM for AChE and ≥1.69 µM for BuChE. Based on the substitution, it is possible to modify selectivity for a particular cholinesterase as we obtained selective inhibitors of either AChE or BuChE, as well as balanced inhibitors. The compounds act via mixed-type inhibition. Their interactions with enzymes were studied by molecular docking. Cytotoxicity was assessed in HepG2 cells. The hydrazones differ in their toxicity (IC₅₀ from 5.27 to >500 µM). Some of the derivatives represent promising hits for further development. Based on the substitution pattern, it is possible to modulate bioactivity to the desired one.

Synthesis, Antimicrobial Activity, and Molecular Docking Studies of Aminoguanidine Derivatives Containing an Acylhydrazone Moiety

A series of aminoguanidine derivatives containing an acylhydrazone moiety was designed based on combination principles to find new antibacterial agents with wide spectra and high activities. The synthesized compounds were characterized by spectral methods and screened for their antibacterial activity. The results showed that several compounds provided great antimicrobial activities against Gram-positive bacteria (including the multidrug-resistant clinical isolates). Especially, this series of compounds presented high potency against Staphylococcus aureus, among which the derivative 3f was the most promising one with a MIC value of 4 μg/mL. Compound 3d, with a tertiary butyl group, was found to have the broad spectrum inhibitory capacity, which is effective to eight strains and showed the most potent inhibitory activity against B. subtilis CMCC 63501 with a MIC value of 4 μg/mL. What’s more, compound 3d also presented high activities against four multidrug-resistant strains, which were comparable or potent to oxacillin and penicillin. Molecular docking studies revealed that H-bond interaction with amino acid residue THR81 and alkyl hydrophobic interaction with residue ALA246 of FabH were crucial for their binding force and in-vitro antimicrobial activities.

Chemically modified and conjugated antimicrobial peptides against superbugs

Antimicrobial resistance (AMR) is one of the greatest threats to human health that, by 2050, will lead to more deaths from bacterial infections than cancer. New antimicrobial agents, both broad-spectrum and selective, that do not induce AMR are urgently required. Antimicrobial peptides (AMPs) are a novel class of alternatives that possess potent activity against a wide range of Gram-negative and positive bacteria with little or no capacity to induce AMR. This has stimulated substantial chemical development of novel peptide-based antibiotics possessing improved therapeutic index. This review summarises recent synthetic efforts and their impact on analogue design as well as their various applications in AMP development. It includes modifications that have been reported to enhance antimicrobial activity including lipidation, glycosylation and multimerization through to the broad application of novel bio-orthogonal chemistry, as well as perspectives on the direction of future research. The subject area is primarily the development of next-generation antimicrobial agents through selective, rational chemical modification of AMPs. The review further serves as a guide toward the most promising directions in this field to stimulate broad scientific attention, and will lead to new, effective and selective solutions for the several biomedical challenges to which antimicrobial peptidomimetics are being applied.

Synthesis, crystal growth, characterization and DFT investigation of a nonlinear optically active cuminaldehyde derivative hydrazone

Single crystals of (E)-N'-(4-isopropylbenzylidene)isonicotinohydrazide monohydrate (IBIHM) were grown from ethanol by the slow evaporation from solution growth technique at room temperature. The structure was elucidated by single-crystal X-ray diffraction analysis and crystallized in the orthorhombic system with noncentrosymmetric space group P2₁2₁2₁. Optical studies reveal that the absorption was minimum in the visible region and the band-gap energy was estimated using the Kubelka-Munk algorithm. The functional groups were identified by Fourier transform infrared spectral analysis. A scanning electron microscopy study revealed the surface morphology of the grown crystal. Investigation of the intermolecular interactions, crystal packing using Hirshfeld surface analysis and single-crystal X-ray diffraction confirm that the close contacts were associated with molecular interactions. Fingerprint plots of Hirshfeld surfaces are used to locate and analyze the percentage of hydrogen-bonding interactions. The second-harmonic generation efficiency of the grown specimen was superior to that of the reference material, potassium dihydrogen phosphate. The grown crystals were further characterized by mass spectrometry and elemental analysis. Theoretical studies using density functional theory (DFT) greatly substantiated the experimental observations. Large first-order molecular hyperpolarizability (β) of about ∼70× was observed for IBIHM. The efficiency of IBIHM in terms of nonlinear optical response was verified and the molecule displayed greater chemical stability and reactivity.

Synthesis, ADMET Properties, and In Vitro Antimicrobial and Antibiofilm Activity of 5-Nitro-2-thiophenecarbaldehyde N-((E)-(5-Nitrothienyl)methylidene)hydrazone (KTU-286) against Staphylococcus aureus with Defined Resistance Mechanisms

The emergence of drug-resistant Staphylococcus aureus is responsible for high morbidity and mortality worldwide. New therapeutic options are needed to fight the increasing antimicrobial resistance among S. aureus in the clinical setting. We, therefore, characterized the in silico absorption, distribution, metabolism, elimination, and toxicity (ADMET) and in vitro antimicrobial activity of 5-nitro-2-thiophenecarbaldehyde N-((E)-(5-nitrothienyl)methylidene)hydrazone (KTU-286) against drug-resistant S. aureus strains with genetically defined resistance mechanisms. The antimicrobial activity of KTU-286 was determined by CLSI recommendations. The ADMET properties were estimated by using in silico modeling. The activity on biofilm integrity was examined by crystal violet assay. KTU-286 demonstrated low estimated toxicity and low skin permeability. The highest antimicrobial activity was observed among pan-susceptible (Pan-S) S. aureus (minimal inhibitory concentration (MIC) 0.5–2.0 µg/mL, IC₅₀ = 0.460 µg/mL), followed by vancomycin resistant S. aureus (VRSA) (MIC 4.0 µg/mL, IC₅₀ = 1.697 µg/mL) and methicillin-resistant S. aureus (MRSA) (MIC 1.0–16.0 µg/mL, IC₅₀ = 2.282 µg/mL). KTU-286 resulted in significant (p < 0.05) loss of S. aureus biofilm integrity in vitro. Further studies are needed for a better understanding of safety, synergistic relationship, and therapeutic potency of KTU-286.

Hydrazides Are Potent Transition-State Analogues for Glutaminyl Cyclase Implicated in the Pathogenesis of Alzheimer's Disease

Amyloidogenic plaques are hallmarks of Alzheimer's disease (AD) and typically consist of high percentages of modified Aβ peptides bearing N-terminally cyclized glutamate residues. The human zinc(II) enzyme glutaminyl cyclase (QC) was shown in vivo to catalyze the cyclization of N-terminal glutamates of Aβ peptides in a pathophysiological side reaction establishing QC as a druggable target for therapeutic treatment of AD. Here, we report crystallographic snapshots of human QC catalysis acting on the neurohormone neurotensin that delineate the stereochemical course of catalysis and suggest that hydrazides could mimic the transition state of peptide cyclization and deamidation. This hypothesis is validated by a sparse-matrix inhibitor screening campaign that identifies hydrazides as the most potent metal-binding group compared to classic Zn binders. The structural basis of hydrazide inhibition is illuminated by X-ray structure analysis of human QC in complex with a hydrazide-bearing peptide inhibitor and reveals a pentacoordinated Zn complex. Our findings inform novel strategies in the design of potent and highly selective QC inhibitors by employing hydrazides as the metal-binding warhead.

OH Group Effect in the Stator of β-Diketones Arylhydrazone Rotary Switches

The properties of several hydrazon-diketone rotary switches with OH groups in the stators (2-(2-(2-hydroxy-4-nitrophenyl)hydrazono)-1-phenylbutane-1,3-dione, 2-(2-(2-hydroxyphenyl)hydrazono)-1-phenylbutane-1,3-dione and 2-(2-(4-hydroxyphenyl)hydrazono)-1-phenylbutane-1,3-dione) were investigated by molecular spectroscopy (UV-Vis and NMR), DFT calculations (M06-2X/TZVP) and X-ray analysis. The results show that, when the OH group is in ortho position, the E’ and Z’ isomers are preferred in DMSO as a result of a stabilizing intermolecular hydrogen bonding with the solvent. The availability, in addition, of a nitro group in para position increases the possibility of deprotonation of the OH group in the absence of water. All studied compounds showed a tendency towards formation of associates. The structure of the aggregates was revealed by theoretical calculation and confirmed by X-ray analysis.

Capsaicin derivatives with nitrothiophene substituents: Design, synthesis and antibacterial activity against multidrug-resistant S. aureus

To address the emergency caused by multi-drug resistant Staphylococcus aureus, a series of novel capsaicin derivatives with nitrothiophene substituents have been designed and evaluated for the antibacterial activities against S. aureus Newman and multidrug-resistant strains (NRS-1, NRS-70, NRS-100, NRS-108, and NRS-271). The structure-activity relationship was further revealed. Compound 13c, 13f, and 13g were highly active against staphylococcal growth, with minimal inhibition concentration (MIC) values of 0.39-1.56 μg/mL. The oxadiazole-derived compound 21, a bioisostere of ester 13f, is the most potent candidate for anti-growth of five multidrug-resistant S. aureus strains with MICs of 0.20-0.78 μg/mL, which is more active compared with vancomycin in vitro. Notably, these anti-staphylococcal compounds are much less cytotoxic to the normal kidney epithelial cell line (HK293T).

A Series of Furan-based Hydrazones: Design, Synthesis, and Evaluation of Antimicrobial Activity, Cytotoxicity and Genotoxicity

Background:

Hydrazones, frequently occurring motifs in many bioactive molecules, have attracted a great deal of interest as potent antimicrobial agents.

Objective:

The aim of this work was to design and synthesize new hydrazone-based antimicrobial agents.

Methods:

4-[2-((5-Arylfuran-2-yl)methylene)hydrazinyl]benzonitrile derivatives (1-10) were obtained via the reaction of 4-cyanophenylhydrazine hydrochloride with 5-arylfurfurals. Compounds 1-10 were evaluated for their antimicrobial effects using a broth microdilution method. Their cytotoxic effects on NIH/3T3 mouse embryonic fibroblast cell line were determined using XTT assay. The most effective antimicrobial agents were investigated for their genotoxic effects using Ames MPF assay. In silico docking and Absorption, Distribution, Metabolism and Excretion (ADME) studies were also performed using Schrödinger’s Maestro molecular modeling package.

Results:

The antifungal effects of the compounds were more significant than their antibacterial effects. Compound 5 bearing 3-nitrophenyl moiety was the most potent antifungal agent against Candida albicans, Trichoderma harzianum and Fusarium species, whereas compound 10 bearing 4- chloro-2-nitrophenyl moiety was the most effective antifungal agent on Aspergillus ochraceus. According to XTT and Ames MPF assays, these compounds were neither cytotoxic nor genotoxic at the concentrations tested. Docking studies suggested that these compounds showed good affinity to the active site of lanosterol 14α-demethylase (CYP51) (PDB code: 5V5Z) and interacted with the key residues such as Hem601 and Cys470. Based on in silico ADME studies, the compounds are expected to have high oral bioavailability.

Conclusion:

According to the in vitro and in silico studies, compounds 5 and 10 stand out as potential orally bioavailable antifungal agents for further studies.

Repurposing of drugs as STAT3 inhibitors for cancer therapy

Drug repurposing is a valuable approach in delivering new cancer therapeutics rapidly into the clinic. Existing safety and patient tolerability data for drugs already in clinical use represent an untapped resource in terms of identifying therapeutic agents for off-label protein targets. The multicellular effects of STAT3 mediated by a range of various upstream signaling pathways make it an attractive therapeutic target with utility in a range of diseases including cancer, and has led to the development of a variety of STAT3 inhibitors. Moreover, heightened STAT3 transcriptional activation in tumor cells and within the cells of the tumor microenvironment contribute to disease progression. Consequently, there are many STAT3 inhibitors in preclinical development or under evaluation in clinical trials for their therapeutic efficacy predominantly in inflammatory diseases and cancer. Despite these advances, many challenges remain in ultimately providing STAT3 inhibitors to patients as cancer treatments, highlighting the need not only for a better understanding of the mechanisms associated with STAT3 activation, but also how various pharmaceutical agents suppress STAT3 activity in various cancers. In this review we discuss the importance of STAT3-dependent functions in cancer, review the status of compounds designed as direct-acting STAT3 inhibitors, and describe some of the strategies for repurposing of drugs as STAT3 inhibitors for cancer therapy.

A Series of New Hydrazone Derivatives: Synthesis, Molecular Docking and Anticholinesterase Activity Studies

BACKGROUND

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are known to be serine hydrolase enzymes responsible for the hydrolysis of acetylcholine (ACh), which is a significant neurotransmitter for regulation of cognition in animals. Inhibition of cholinesterases is an effective method to curb Alzheimer's disease, a progressive and fatal neurological disorder.

OBJECTIVE

In this study, 30 new hydrazone derivatives were synthesized. Then we evaluated their anticholinesterase activity of compounds. We also tried to get insights into binding interactions of the synthesized compounds in the active site of both enzymes by using molecular docking approach.

METHODS

The compounds were synthesized by the reaction of various substituted/nonsubstituted benzaldehydes with 6-(substitute/nonsubstituephenyl)-3(2H)-pyridazinone-2-yl propiyohydrazide. Anticholinesterase activity of the compounds was determined using Ellman's method. Molecular docking studies were done by using the ADT package version 1.5.6rc3 and showed by Maestro. RMSD values were obtained using Lamarckian Genetic Algorithm and scoring function of AutoDock 4.2 release 4.2.5.1 software.

RESULTS

The activities of the compounds were compared with galantamine as cholinesterase enzyme inhibitor, where some of the compounds showed higher BChE inhibitory activity than galantamine. Compound F111 was shown to be the best BChE inhibitor effective in 50 μM dose, providing 89.43% inhibition of BChE (IC50=4.27±0.36 μM).

CONCLUSION

This study supports that novel hydrazone derivates may be used for the development of new BChE inhibitory agents.

Rapid Synthesis of N-Tosylhydrazones under Solvent-Free Conditions and Their Potential Application Against Human Triple-Negative Breast Cancer

Some N-tosylhydrazone derivatives were effectively synthesized under solvent-free conditions by using a grinding method at room temperature. The short reaction time, clean and mild process with simple workup and easy purification of the target compounds were salient features of the present protocol, which enables straightforward access to N-tosylhydrazones. Among the tosylhydrazone derivatives evaluated, compound 3 l exhibits excellent apoptosis-promoting and anticancer potential against triple-negative breast cancer (TNBC) cell lines. This research shows that our synthesized compound 3 l may be a desirable and effective therapeutic drug against TNBC.

Synthesis, antimicrobial, anti-biofilm evaluation, and molecular modelling study of new chalcone linked amines derivatives

A series of amide chalcones conjugated with different secondary amines were synthesised and characterised by different spectroscopic techniques 1H NMR, 13C NMR, and ESI-MS. They were screened for in vitro antibacterial activity. Compounds 36, 37, 38, 42, and 44 are the most active among the synthesised series exhibiting MIC value of 2.0-10.0 µg/ml against different bacterial strains. Compound 36 was equipotent to the standard drug Ampicillin displaying MBC value of 2.0 µg/ml against the bacterial strain Staphylococcus aureus. The products were screened for anti-biofilm activity. Compounds 36, 37, and 38 exhibited promising anti-biofilm activity with IC50 value ranges from 2.4 to 8.6 µg. Molecular modelling was performed suggesting parameters of signalling anti-biofilm mechanism. AspB327 HisB340 (arene-arene interaction) and IleB328 amino acid residues seemed of higher importance to inhibit c-di-GMP. Hydrophobicity may be crucial for activity. ADME calculations suggested that compounds 36, 37, and 38 could be used as good orally absorbed anti-biofilm agents.

Crystal structure of N 2,N 6-bis(1-hydrazinyl-2-methyl-1-oxopropan-2-yl) pyridine-2,6-dicarboxamide, C15H23N7O4

C15H23N7O4, orthorhombic, Aba2, a = 18.4956(11) Å, b = 23.9806(16) Å, c = 8.1572(5) Å, V = 3618.0(4) Å3, Z = 8, R gt(F) = 0.0521, wR ref(F 2) = 0.1144, T = 293(2) K.

Synthesis of Oxadiazolyl, Pyrazolyl and Thiazolyl Derivatives of Thiophene-2-Carboxamide as Antimicrobial and Anti-HCV Agents

Introduction:

Three series of pyrazole, thiazole and 1,3,4-oxadiazole, derivatives were synthesized starting from 5-amino-4-(hydrazinocarbonyl)-3-methylthiophene-2-carboxamide (2).

Methods:

All compounds were investigated for their preliminary antimicrobial activity. They were proved to exhibit remarkable antimicrobial activity against Pseudomonas aeruginosa with insignificant activity towards Gram positive bacterial strains and fungi.

Results:

In-vitro testing of the new compounds on hepatitis-C virus (HCV) replication in hepatocellular carcinoma cell line HepG2 infected with the virus utilizing the reverse transcription polymerase chain reaction technique (RT-PCR) generally showed inhibition of the replication of HCV RNA (–) strands at low concentration, while, eight compounds; 3a, 6, 7a, 7b, 9a, 9b, 10a and 11b proved to inhibit the replication of HCV RNA (+) and (–) strands at very low concentration range 0.08-0.36 μg/mL.

Conclusion:

Compounds 7b and 11b displayed the highest anti-HCV and antimicrobial activities in this study.