Antimicrobial evaluation of thiadiazino and thiazolo quinoxaline hybrids as potential DNA gyrase inhibitors; design, synthesis, characterization and morphological studies

Exploring quinoxaline derivatives: An overview of a new approach to combat antimicrobial resistance

Antimicrobial resistance (AMR) has emerged as a long-standing global issue ever since the introduction of penicillin, the first antibiotic. Scientists are constantly working to develop innovative antibiotics that are more effective and superior. Unfortunately, the misuse of antibiotics has resulted in their declining effectiveness over the years. By 2050, it is projected that approximately 10 million lives could be lost annually due to antibiotic resistance. Gaining insight into the mechanisms behind the development and transmission of AMR in well-known bacteria including Escherichia coli, Bacillus pumilus, Enterobacter aerogenes, Salmonella typhimurium, and the gut microbiota is crucial for researchers. Environmental contamination in third world and developing countries also plays a significant role in the increase of AMR. Despite the availability of numerous recognized antibiotics to combat bacterial infections, their effectiveness is diminishing due to the growing problem of AMR. The overuse of antibiotics has led to an increase in resistance rates and negative impacts on global health. This highlights the importance of implementing strong antimicrobial stewardship and improving global monitoring, as emphasized by the World Health Organization (WHO) and other organizations. In the face of these obstacles, quinoxaline derivatives have emerged as promising candidates. They are characterized by their remarkable efficacy against a broad spectrum of harmful bacteria, including strains that are resistant to multiple drugs. These compounds are known for their strong structural stability and adaptability, making them a promising and creative solution to the AMR crisis. This review aims to assess the effectiveness of quinoxaline derivatives in treating drug-resistant infections, with the goal of making a meaningful contribution to the global fight against AMR.

Explore new quinoxaline pharmacophore tethered sulfonamide fragments as in vitro α-glucosidase, α-amylase, and acetylcholinesterase inhibitors with ADMET and molecular modeling simulation

A new series of quinoxaline-sulfonamide derivatives 3-12 were synthesized using fragment-based drug design by reaction of quinoxaline sulfonyl chloride (QSC) with different amines and hydrazines. The quinoxaline-sulfonamide derivatives were evaluated for antidiabetic and anti-Alzheimer's potential against α-glucosidase, α-amylase, and acetylcholinesterase enzymes. These derivatives showed good to moderate potency against α-amylase and α-glucosidase with inhibitory percentages between 24.34 ± 0.01%-63.09 ± 0.02% and 28.95 ± 0.04%-75.36 ± 0.01%, respectively. Surprisingly, bis-sulfonamide quinoxaline derivative 4 revealed the most potent activity with inhibitory percentages of 75.36 ± 0.01% and 63.09 ± 0.02% against α-glucosidase and α-amylase compared to acarbose (IP = 57.79 ± 0.01% and 67.33 ± 0.01%), respectively. Moreover, the quinoxaline derivative 3 exhibited potency as α-glucosidase and α-amylase inhibitory with a minute decline from compound 4 and acarbose with inhibitory percentages of 44.93 ± 0.01% and 38.95 ± 0.01%. Additionally, in vitro acetylcholinesterase inhibitory activity for designed derivatives exhibited weak to moderate activity. Still, sulfonamide-quinoxaline derivative 3 emerged as the most active member with inhibitory percentage of 41.92 ± 0.02% compared with donepezil (IP = 67.27 ± 0.60%). The DFT calculations, docking simulation, target prediction, and ADMET analysis were performed and discussed in detail.

Photoinduced Dehydrogenative Amination of Quinoxalin-2(1H)-ones with Air as an Oxidant

A facile and eco-friendly photoinduced dehydrogenative amination of quinoxalin-2(1H)-ones with aliphatic amines without any metal, strong oxidant, and photocatalyst has been established for the first time. This reaction proceeding efficiently with air as the sole oxidant at room temperature obtains a wide range of 3-aminoquinoxaline-2(1H)-ones in high yields with excellent functional group tolerance. The mechanistic studies show an interesting involvement of quinoxalin-2(1H)-ones as a photosensitizer, which eliminates the requirement for external photocatalysts.

Schematic-portfolio of potent anti-microbial scaffolds targeting DNA gyrase: Unlocking ways to overcome resistance

Drug development process demands validation of specific drug target impeding the Multi Drug Resistance (MDR). DNA gyrase, as a bacterial target has been in trend for developing newer antibacterial candidates due to its absence in higher eukaryotes. The fluoroquinolones are the leading molecules in the drug discovery pipeline for gyrase inhibition due to its diversity. The fluoroquinolones like levofloxacin and moxifloxacin have been listed in class A drugs for treating MDR. Gatifloxacin and ciprofloxacin also proved its efficacy against MDR TB and MDR enteric fever in adults, whereas nemonoxacin can induce anti-MDR activity of other antibiotics already suggested by studies. Though fluoroquinolones already proved its effectiveness against gyrase, other molecules viz., benzothiazinone, phenyl pyrrolamide, substituted oxadiazoles, triazolopyrimidine, arylbenzothiazole, coumarinyl amino alcohols and ciprofloxacin uracil, can inhibit the target more precisely. The structure-activity-relationships of the different scaffolds along with their synthetic strategies have been deciphered in the current review. Also, the naturally occurring compounds along with their extraction procedure have also been highlighted as potent DNA gyrase inhibitors. In addition to fluoroquinolone, the natural compounds novobiocin and simocyclinone could also inhibit the gyrase, impressively which has been designed with the gyrase structure for better understanding. Herein, ongoing clinical development of some novel drugs possessing triazaacenaphthylenes, spiropyrimidinetriones, and oxazolidinone-quinolone hybrids have been highlighted which could further assist the future generation antibiotic development corroborating gyrase as a potential target against MDR pathogens.

One-pot synthesis of pyrazolo[4,3-d]thiazole derivatives containing α-aminophosphonate as potential Mur A inhibitors against MDR pathogens with radiosterilization and molecular modeling simulation

The present study involves the synthesis of a new series of α-aminophosphonate derivatives in good yields with a simple workup via the Kabachnik-Fields reaction using lithium perchlorate (LiClO4) as a catalyst to facilitate the reaction. All the newly synthesized compounds were confirmed using various physical, spectroscopic, and analytical data, and the obtained results correlated with the proposed molecular structure. The in vitro antimicrobial activities of each compound were evaluated against different clinical isolates. The results indicated that among these derivatives, two compounds (5a and 5b) were the most active and displayed potent activity with MICs in the range from 0.06 to 0.25 μg mL-1 compared with fosfomycin and fluconazole as standard antibiotics. Moreover, the synthesized phosphonates displayed a broad spectrum of bactericidal and fungicidal activities depending on MICs, MBCs/MFCs, and the time-kill kinetics. In addition, the checkerboard assay showed synergistic and partial synergistic activities between the active compounds combined with fosfomycin and fluconazole. Furthermore, the SEM images showed distinct ruptures of the OM integrity of the FOS-R E. coli at their MICs, which was further indicated by the increased EtBr accumulation within the bacterial cells. Moreover, active derivatives revealed MurA inhibitory activity with IC50 values of 3.8 ± 0.39 and 4.5 ± 0.23 μM compared with fosfomycin (IC50 = 12.7 ± 0.27 μM). To our surprise, exposing 5a and 5b compounds to different gamma radiation doses revealed that 7.0 kGy eradicated the microbial load completely. Finally, the results of quantum chemical study supported the binding mode obtained from the docking study performed inside the active site of MurA (PDB: 1UAE), suggesting that these phosphonates may be promising safe candidates for MDR infection therapy clinical trials with no toxic effects on the normal human cells.

Thiazole-based analogues as potential antibacterial agents against methicillin-resistant Staphylococcus aureus (MRSA) and their SAR elucidation

In recent years, the overuse of antibiotics has resulted in the emergence of antibiotic resistance, which is a serious global health problem. Methicillin-resistant Staphylococcus aureus (MRSA) is a common and virulent bacterium in clinical practice. Numerous researchers have focused on developing new candidate drugs that are effective, less toxic, and can overcome MRSA resistance. Thiazole derivatives have been found to exhibit antibacterial activity against drug-sensitive and drug-resistant pathogens. By hybridizing thiazole with other antibacterial pharmacophores, it is possible to obtain more effective antibacterial candidate drugs. Thiazole derivatives have shown potential in developing new drugs that can overcome drug resistance, reduce toxicity, and improve pharmacokinetic characteristics. This article reviews the recent progress of thiazole compounds as potential antibacterial compounds and examines the structure-activity relationship (SAR) in various directions. It covers articles published from 2018 to 2023, providing a comprehensive platform to plan and develop new thiazole-based small MRSA growth inhibitors with minimal side effects.

Crystal structure and Hirshfeld surface analysis of 3-eth-oxy-1-ethyl-6-nitro-quinoxalin-2(1H)-one

The asymmetric unit of the title compound, C12H13N3O4, consists of two mol-ecules differing to a small degree in their conformations. In the crystal, layers of mol-ecules are connected by weak C-H⋯O hydrogen bonds and slipped π-stacking inter-actions. These layers lie parallel to (10) and are stacked along the normal to that plane. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing arise from H⋯H (43.5%) and H⋯O/O⋯H (30.8%) contacts. The density functional theory (DFT) optimized structure of the title compound at the B3LYP/ 6-311 G(d,p) level agrees well with the experimentally determined mol-ecular structure in the solid state.

Design and Synthesis of 2-(4-Bromophenyl)Quinoline-4-Carbohydrazide Derivatives via Molecular Hybridization as Novel Microbial DNA-Gyrase Inhibitors

Microbial DNA gyrase is regarded as an outstanding microbial target. Hence, 15 new quinoline derivatives (5-14) were designed and synthesized. The antimicrobial activity of the afforded compounds was pursued via in vitro approaches. The investigated compounds displayed eligible MIC values, particularly against G-positive Staphylococcus aureus species. Consequently, an S. aureus DNA gyrase supercoiling assay was performed, using ciprofloxacin as a reference control. Obviously, compounds 6b and 10 unveiled IC₅₀ values of 33.64 and 8.45 μM, respectively. Alongside, ciprofloxacin exhibited an IC₅₀ value of 3.80 μM. Furthermore, a significant docking binding score was encountered by compound 6b (-7.73 kcal/mol), surpassing ciprofloxacin (-7.29 kcal/mol). Additionally, both compounds 6b and 10 revealed high GIT absorption without passing the blood brain barrier. Finally, the conducted structure-activity relationship study assured the usefulness of the hydrazine moiety as a molecular hybrid for activity either in cyclic or opened form.

A new class of anti-proliferative activity and apoptotic inducer with molecular docking studies for a novel of 1,3-dithiolo[4,5-b]quinoxaline derivatives hybrid with a sulfonamide moiety

A new series of 6-(pyrrolidin-1-ylsulfonyl)-[1,3]dithiolo[4,5-b]quinoxaline-2-ylidines 10a-f, 12, 14, 16, and 18 were designed, synthesized, and evaluated for their in vitro anticancer activity. The structures of the novel compounds were systematically characterized by ¹H NMR, ¹³C NMR, and elemental analysis. The synthesized derivatives were evaluated for their in vitro antiproliferative activity against three human cancer cell lines (HepG-2, HCT-116, and MCF-7) with more sensitivity to MCF-7. Moreover, three derivatives 10c, 10f, and 12 were the most promising candidates with sub-micromole values. These derivatives were further evaluated against MDA-MB-231, and the results displayed significant IC₅₀ values ranging from 2.26 ± 0.1 to 10.46 ± 0.8 μM and showed low cellular cytotoxicity against WI-38. Surprisingly, the most active derivative 12 revealed sensitivity towards the breast cell lines MCF-7 (IC₅₀ = 3.82 ± 0.2 μM) and MDA-MB-231 (IC₅₀ = 2.26 ± 0.1 μM) compared with doxorubicin (IC₅₀ = 4.17 ± 0.2 and 3.18 ± 0.1 M). Cell cycle analysis showed that compound 12 arrests and inhibits the growth of MCF-7 cells in the S phase with values of 48.16% compared with the untreated control 29.79% and exhibited a significantly higher apoptotic effect in MCF-7 with a value of 42.08% compared to control cell at 1.84%. Furthermore, compound 12 decreased Bcl-2 protein 0.368-fold and activation on pro-apoptotic genes Bax and P53 by 3.97 and 4.97 folds, respectively, in MCF-7 cells. Compound 12 exhibited higher inhibitory activity to EGFR^Wt, EGFR^L858R, and VEGFR-2 with IC₅₀ values (0.19 ± 0.009, 0.026 ± 0.001, and 0.42 ± 0.021 μM) compared with erlotinib (IC₅₀ = 0.037 ± 0.002 and 0.026 ± 0.001 μM) and sorafenib (IC₅₀ = 0.035 ± 0.002 μM). Finally, in silico ADMET prediction presented that 1,3-dithiolo[4,5-b]quinoxaline derivative 12 obeys the Lipinski rule of five and the Veber rule with no PAINs alarms and moderately soluble properties. Additionally, toxicity prediction revealed that compound 12 demonstrated inactivity to hepatotoxic carcinogenicity, immunotoxicity, mutagenicity, and cytotoxicity. Moreover, molecular docking studies showed good binding affinity with lower binding energy inside the active site of Bcl-2 (PDB: 4AQ3), EGFR (PDB: 1M17), and VEGFR (PDB: 4ASD).

Design, synthesis, antimicrobial screening and molecular modeling of novel 6,7 dimethylquinoxalin-2(1H)-one and thiazole derivatives targeting DNA gyrase enzyme

New 6,7-dimethylquinoxalin-2(1H)-one and hydrazineylidene thiazol-4-one derivatives were synthesized, and evaluated for their in vitro antimicrobial activity. The obtained results revealed marked antimicrobial potential against four bacterial, and two fungal strains. Both 6,7-dimethyl-3-(2-(4-nitrophenyl)-2-oxoethyl)quinoxalin-2(1H)-one (4d), and 2-(2-(9H-fluoren-9-ylidene)hydrazineyl)-5-(2-(p-tolyl)hydrazineylidene)thiazol-4(5H)-one (11b) displayed significant antibacterial and antifungal activities having MIC ranges (1.98-15.6 mg/mL) and (1.98-3.9 mg/mL) compared to Tetracycline and Amphotericin B as standard drugs. In addition, they showed noticeable inhibitory activity against DNA gyrase enzyme. Interestingly the thiazole derivative (11b) showed marked inhibitory activity against DNA gyrase with IC₅₀ = 7.82 ± 0.45 μM better than that of ciprofloxacin. The time-kill kinetics profile of the most active compounds against S. aureus and E. coli microorganisms displayed both concentration dependent and time dependent reduction in the number of viable cells. Furthermore, molecular docking study of both compounds in the DNA gyrase binding site was performed, showing agreement with the in vitro inhibitory activities.

Development and radiosterilization of new hydrazono-quinoline hybrids as DNA gyrase and topoisomerase IV inhibitors: Antimicrobial and hemolytic activities against uropathogenic isolates with molecular docking study

This study aimed to synthesize new potent quinoline derivatives based on hydrazone moieties and evaluate their antimicrobial activity. The newly synthesized hydrazono-quinoline derivatives 2, 5a, 9, and 10b showed the highest antimicrobial activity with MIC values ≤1.0 μg/ml against bacteria and ≤8.0 μg/ml against the fungi. Further, these derivatives exhibited bactericidal and fungicidal effects with MBC/MIC and MFC/MIC ratio ≤4. Surprisingly, the most active compounds displayed good inhibition to biofilm formation with MBEC values ranging between (40.0 ± 10.0 - 230.0 ± 31.0) and (67.0 ± 24.0 - 347.0 ± 15.0) μg/ml against Staphylococcus aureus and Pseudomonas aeruginosa, respectively. The hemolytic assays confirmed that the hydrazono-quinoline derivatives are non-toxic with low % lysis values ranging from 4.62% to 14.4% at a 1.0 mg/ml concentration. Besides, compound 5a exhibited the lowest hemolytic activity value of ~4.62%. Furthermore, the study suggests that the hydrazono-quinoline analogs exert their antibacterial activity as dual inhibitors for DNA gyrase and DNA topoisomerase IV enzymes with IC₅₀ values ranging between (4.56 ± 0.3 - 21.67 ± 0.45) and (6.77 ± 0.4 - 20.41 ± 0.32) μM, respectively. Additionally, the recent work advocated that compound 5a showed the reference SAL at the ɣ-radiation dose of 10.0 kGy in the sterilization process without affecting its chemical structure. Finally, the in silico drug-likeness, toxicity properties, and molecular docking simulation were performed. Besides, the result exhibited good oral-bioavailability, lower toxicity prediction, and lower binding energy with good binding mode rather than the positive control.

Therapeutic strategies for Covid-19 based on molecular docking and dynamic studies to the ACE-2 receptors, Furin, and viral spike proteins

SARS-CoV-2 is a pandemic virus that caused infections and deaths in many world countries, including the Middle East. The virus-infected human cells by binding via ACE-2 receptor through the Spike protein of the virus with Furin's help causing cell membrane fusion leading to Covid-19-cell entry. No registered drugs or vaccines are triggering this pandemic viral disease yet. Our present work is based on molecular docking and dynamics simulation that performed to spike protein-ACE-2 interface complex, ACE-2 receptor, Spike protein (RBD), and Furin as targets for new small molecules. These drugs target new potential therapies to show their probabilities toward the active sites of mentioned proteins, strongly causing inhibition and/or potential therapy for covid-19. All target proteins were estimated against new target compounds under clinical trials and repurposing drugs currently present. Possibilities of those molecules and potential therapeutics acting on a certain target were predicted. MD simulations over 200 ns with molecular mechanics-generalized Born surface area (MMGBSA) binding energy calculations were performed. The structural and energetic analyses demonstrated the stability of the ligands-M^Pros complex. Our present work will introduce new visions of some biologically active molecules for further studies in-vitro and in-vivo for Covid-19, repurposing of these molecules should be taking place under clinical works and offering different strategies for drugs repurposing against Covid-19 diseases.Communicated by Ramaswamy H. Sarma.

Structure based design and synthesis of 3-(7-nitro-3-oxo-3,4-dihydroquinoxalin-2-yl)propanehydrazide derivatives as novel bacterial DNA-gyrase inhibitors: In-vitro, In-vivo, In-silico and SAR studies

Antimicrobial resistance (AMR) is one of the critical challenges that have been encountered over the past years. On the other hand, bacterial DNA gyrase is regarded as one of the most outstanding biological targets that quinolones can extensively inhibit, improving AMR. Hence, a novel series of 3-(7-nitro-3-oxo-3,4-dihydroquinoxalin-2-yl)propanehydrazide derivatives (3-6j) were designed and synthesized employing the quinoxaline-2-one scaffold and relying on the pharmacophoric features experienced by the quinolone antibiotic; ciprofloxacin. The antibacterial activity of the synthesized compounds was assessed via in-vitro approaches using eight different Gram-positive and Gram-negative bacterial species. Most of the synthesized compounds revealed eligible antibacterial activities. In particular, compounds 6d and 6e displayed promising antibacterial activity among the investigated compounds. For example, compounds 6d and 6e displayed MIC values of 9.40 and 9.00 µM, respectively, regarding S. aureus, and 4.70 and 4.50 µM, respectively, regarding S. pneumonia in comparison to ciprofloxacin (12.07 µM). The cytotoxicity of compounds 6d and 6e were performed on normal human WI-38 cell lines with IC50 values of 288.69 and 227.64 μM, respectively assuring their safety and selectivity. Besides, DNA gyrase inhibition assay of compounds 6d and 6e was carried out in comparison to ciprofloxacin, and interestingly, compounds 6d and 6e disclosed promising IC50 values of 0.242 and 0.177 μM, respectively, whereas ciprofloxacin displayed an IC50 value of 0.768 μM, assuring the proposed mechanism of action for the afforded compounds. Consequently, compounds 6d and 6e were further assessed via in-vivo approaches by evaluating blood counts, liver and kidney functions, and histopathological examination. Both compounds were found to be safer on the liver and kidney than the reference ciprofloxacin. Moreover, in-silico molecular docking studies were established and revealed reasonable binding affinities for all afforded compounds, particularly compound 6d which exhibited a binding score of -7.51 kcal/mol, surpassing the reference ciprofloxacin (-7.29 kcal/mol) with better anticipated stability at the DNA gyrase binding pocket. Moreover, ADME studies were conducted, disclosing an eligible bioavailability score of >0.55 for all afforded compounds, and reasonable GIT absorption without passing the blood brain barrier was attained for most investigated compounds, ensuring their efficacy and safety. Lastly, a structure activity relationship study for the synthesized compounds was established and unveiled that not only the main pharmacophores required for DNA gyrase inhibition are enough for exerting promising antimicrobial activities, but also derivatization with diverse aryl/hetero aryl aldehydes is essential for their enhanced antimicrobial potential.

A new exploration toward adamantane derivatives as potential anti-MDR agents: Design, synthesis, antimicrobial, and radiosterilization activity as potential topoisomerase IV and DNA gyrase inhibitors

Developing novel antimicrobial agents has become a necessitate due to the increasing rate of microbial resistance to antibiotics. All the newly adamantane derivatives were evaluated for their antimicrobial activities against six MDR clinical pathogenic isolates. The results exhibited that 13 compounds have from potent to good activity. Among those, five derivatives (6, 7, 9, 14a, and 14b) displayed the potent activities against the different isolates tested (MIC < 0.25 µg/ml with bacteria and <8 µg/ml with fungi) compared with Ciprofloxacin (CIP) and Fluconazole (FCA). Additionally, the potent adamantanes showed bactericidal and fungicidal effects based on (MBCs and MFCs) and the time-kill assay. The most active adamantane derivatives 7 and 14b exhibited a synergistic effect of ΣFIC ≤ 0.5 with CIP and FCA against the bacterial and fungal isolates. Moreover, no antagonistic effect appeared for the tested derivatives. Additionally, the interaction of DNA gyrase and topoisomerase IV enzymes with the compounds 6, 7, 9, 14a, and 14b exhibited potent antimicrobial activity using in vitro biochemical assays and gel-based DNA-supercoiling inhibition method. The activity of DNA gyrase and topoisomerase IV enzymes showed inhibitory activity (IC₅₀ ) of 6.20 µM and 9.40 µM with compound 7 and 10.14 µM and 13.28 µM with compound 14b, respectively. Surprisingly, exposing compound 7 to gamma irradiation sterilized and increased its activity. Finally, the in-silico analysis predicted that the most active derivatives had good drug-likeness and safe properties. Besides, molecular docking and quantum chemical studies revealed several important interactions inside the active sites and showed the structural features necessary for activity.

Synthetic approach toward spiro quinoxaline-β-lactam based heterocyclic compounds: Spectral characterization, SAR, pharmacokinetic and biomolecular interaction studies

Series of spiro quinoxaline-β-lactam based heterocyclic compounds (QL 1 - QL 21) were synthesized and characterized by spectroscopic techniques like ¹H-NMR, LC-MS, FT-IR spectroscopy and elemental analysis. The binding mode and binding strength between compounds and calf thymus-DNA were estimated by UV-visible spectroscopy, viscosity measurement and molecular docking studies. The compounds bind with the DNA through partial intercalation mode. In the absorption titration experiment, the K_b values for all the synthesized compounds were found in the range of 0.24-0.64 × 10⁵ M^-1. The protein binding studies of all the synthesized compounds were evaluated by absorption titration experiment, and the K_b value for all the compounds was obtained in the range of 0.030-1.571 × 10⁴ M^-1. The compounds were screened against two Gram (+ve) and three Gram (-ve) bacteria for antimicrobial activity. The MIC values for all the synthesized compounds were found in 95-255 µM. The LC₅₀ values (cytotoxicity) of the synthesized compounds (QL 1-QL 21) were found in the range of 4.00-12.89 µg/mL. The ADME study was carried out using the online platform SwissADME and admetSAR to evaluate the pharmacokinetic profile of all the synthesized compounds. All the compounds were screened for anticancer activity against the human osteosarcoma (MG-63) cell line. The result shows that all the compounds exhibit effective anticancer activity.Communicated by Ramaswamy H. Sarma.

Synthesis, characterization, thermal properties, antimicrobial evaluation, ADMET study, and molecular docking simulation of new mono Cu (II) and Zn (II) complexes with 2-oxoindole derivatives

One of the interesting research fields is developing and assessing novel metal-containing medications. A new isatin-3-thiosemicarbazone derivative 4 was synthesized by two different methods based on hydrazone derivatives 2 and 3. Additionally, the chelation of thiosemicarbazone with copper (II) and zinc (II) forms a monobasic tridentate (ONS) complex with two five-member rings and a tetrahedral geometry structure. The structure of synthesized complexes was characterized using elemental analysis, FT-IR, mass spectra, and ¹H/¹³C NMR. Thermogravimetric analysis revealed the upgrading of the thermal stability of metal complexes compared to their thiosemicarbazone ligand. The stoichiometric ratio of the coordination confirmed the formation of 1:1 (M: L) stoichiometry. In vitro antimicrobial activity was screened against two gram-positive, two gram-negative, and one fungal strain. Both ligand 4 and Zn complex 6 displayed high antimicrobial activity compared with copper complex 5 based on the zone of inhibition. Further, MIC and MBC were determined for both zinc and ligand. The zinc complex 6 displayed excellent antimicrobial activity with (MIC = 3.9-27.77 μg/mL) against bacterial strains and (MIC = 7.81 μg/mL) against C. albicans, as well as exhibited MBC values ranging between (MBC = 6.51-45.58 μg/mL) and (MFC = 13.58 μg/mL), respectively, and demonstrated bactericidal and fungicidal behavior. The in-silico ADMET study for ligand and two complexes were determined and showed non-AMES toxicity, non-carcinogenic, and obey the rule of five. A comparative docking study provided more insight into the binding mechanisms and suggested that antimicrobial activity may be due to inhibition of different targets.

Synthesis and characterization of new functionalized chitosan and its antimicrobial and in-vitro release behavior from topical gel

Recently, chitosan and its derivatives have been gaining more attention due to their high integration into various biomedical applications. Herein, a new chitosan derivative was prepared by linking the chitosan (Cs) with a novel heterocyclic compound, Benzoimidazolyl-thiadiazole (BzimTD) to form Cs-BzimTD. The synthesis of the new chitosan derivative was confirmed by Fourier-Transform Infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance (¹H NMR), thermogravimetric (TGA-DTG) analysis, elemental analysis, and UV-Visible spectrophotometer. Data showed the high efficacy of functionalized Cs-BzimTD to inhibit the growth of pathogenic microbes, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans, with inhibition zones of 15.3 ± 0.6 - 9.2 ± 0.3 mm. Also, Cs-BzimTD was applied in a topical gel formulation by using two different polymers, Carbopol 940 (CP) and Carboxymethyl Cellulose (CMC) to form three gel formulations: Cs-BzimTD-CP, Cs-BzimTD-CMC, and Cs-BzimTD-CP-CMC. The new gels were checked for physical appearance, viscosity, Cs-BzimTD release, pH, spread-ability, and drug content. The results showed that all formulations were clear, transparent, and homogeneous with non-irritant pH values for skin (6.4 - 6.8). The spread-ability was found in the range of 7.1 - 9.4 g.cm/s. The Cs-BzimTD-CP formula showed the maximal Cs-BzimTD content percentage (86.5%) and the Cs-BzimTD release varied from 89.9 to 81.6% after 8 h depending on the gel formulation, with a maximum release achieved for Cs-BzimTD-CMC.

Upregulation of BAX and caspase-3, as well as downregulation of Bcl-2 during treatment with indeno[1,2-b]quinoxalin derivatives, mediated apoptosis in human cancer cells

Cancer is the world's foremost cause of death. There are over 100 different forms of cancer. Cancers are frequently named after the organs or tissues in which they develop. As a part of our aim to develop promising anticancer agents, a series of new indeno[1,2-b]quinoxaline derivatives were synthesized. All of the synthesized compounds were tested for anticancer activity in vitro in three human cancer cell lines: the HCT-116 colon cancer cell line, the HepG-2 liver cancer cell line, and the MCF-7 breast cancer cell line. Among the tested derivatives, 2, 3, 5, 12, 21, and 22 showed exceptional antiproliferative activities against the three tested cell lines compared to the reference standard imatinib. These compounds were, therefore, selected for further investigations. Evaluation of their cytotoxicity against a normal human cell line (WI-38) was performed, to ensure their safety and selectivity (IC₅₀  > 92 μM). Then, induction of apoptosis by the most active compounds was found to be accomplished by downregulation of Bcl-2 and upregulation of BAX and caspase-3. After that, the most promising apoptotic compound that increases the caspase-3 and BAX expression and downregulates Bcl-2 activity (3) was assessed for its impact on the cell cycle distribution in HepG-2 cells: The most potent derivative (3) induced cell cycle arrest at the G2/M phase. Finally, in silico evaluation of the ADME properties indicated that compound 3 is orally bioavailable and can be readily synthesized on a large scale.

Elhagali G, A. Eyada H, S. Aboul-Magd D, Ragab A. In Vitro Antimicrobial Evaluation, Single-Point Resistance Study, and Radiosterilization of Novel Pyrazole Incorporating Thiazol-4-one/Thiophene Derivatives as Dual DNA Gyrase and DHFR Inhibitors against MDR Pathogens

A series of thiazol-4-one/thiophene-bearing pyrazole derivatives as pharmacologically attractive cores were initially synthesized using a hybridization approach. All structures were confirmed using spectra analysis techniques (IR, ¹H NMR, and ¹³C NMR). In vitro antimicrobial activities, including the minimum inhibitory concentration (MIC), minimum bactericidal/fungicidal concentration (MBC/MFC), and time-kill assay, were evaluated for the most active derivatives 4a, 5a, 7b, 10, and 13. These derivatives were significantly active against the tested pathogens, with compound 7b as the most active derivative (MIC values range from 0.22 to 0.25 μg/mL). In the MBC and MFC, the active target pyrazole derivatives showed -cidal activities toward the pathogenic isolates. Further, the inhibition of biofilm formation of Staphylococcus aureus and Staphylococcus epidermidis was also carried out. Additionally, these derivatives displayed significant antibiofilm potential with a superior % reduction in the biofilm formation compared with Ciprofloxacin. The target derivatives behaved synergistically with Ciprofloxacin and Ketoconazole, reducing their MICs. Hemolytic results revealed that these derivatives were nontoxic with a significantly low hemolytic activity (%lysis range from 3.23 to 15.22%) compared with Triton X-100 and showed noncytotoxicity activity with IC₅₀ values > 60 μM. In addition, these derivatives proved to be active DNA gyrase and DHFR inhibitors with IC₅₀ ranging between 12.27-31.64 and 0.52-2.67 μM, respectively. Furthermore, compound 7b showed bactericidal activity at different concentrations in the time-kill assay. Moreover, a gamma radiation dose of 10.0 kGy was efficient for sterilizing compound 7b and enhancing its antimicrobial activity. Finally, molecular docking simulation of the most promising derivatives exhibited good binding energy with different interactions.

Development of novel indolin-2-one derivative incorporating thiazole moiety as DHFR and quorum sensing inhibitors: Synthesis, antimicrobial, and antibiofilm activities with molecular modelling study

Nowadays, it's imperative to develop novel antimicrobial agents active against both drug-sensitive and drug-resistant bacterial infections with favorable profiles as high efficacy, low toxicity, and short therapy duration. Accordingly, a series of new thiazolo-indolin-2-one derivatives were synthesized based on acid and base catalyzed condensation or reaction of thiosemicarbazone 8 with different electrophilic reagents. The structure of the new compounds was confirmed based on elemental analysis and spectral data. Based on the MIC results, the most active thiazolo-indoline derivatives 2, 4, 7a, and 12 exhibited promising antibacterial activity against gram-positive and gram-negative bacteria with weak to moderate antifungal activities. Surprisingly, the N-(thiazol-2-yl)benzenesulfonamide derivative 4 was found to be most active on antibiofilm activity against both S. aureus (ATCC 29213) with BIC₅₀ (1.95 ± 0.01 µg/mL), while 5-(2-oxoindolin-3-ylidene)-thiazol-4(5H)-one derivative 7a exhibited the strongest antibiofilm activity against P. aeruginosa pathogens with BIC₅₀ (3.9 ± 0.16 µg/mL). Further, the thiazole derivatives 2, 4 and 12 exhibited a significant inhibition activity against the fsr system in a dose-dependent manner without affecting bacterial growth. The target derivatives behaved synergistic and additively effect against MDR p. aeruginosa, and thiazole derivative 12 exhibited a high synergistic effect with most tested antibiotics except Cefepime with FIC value ranging between 0.249 and 1.0, reducing their MICs. Interestingly, the 3-(2-(4-thiazol-2-yl)hydrazono)indolin-2-one derivative 12 displayed the highest selectivity to DHFR inhibitory with IC₅₀ value 40.71 ± 1.86 nM superior to those of the reference Methotrexate. Finally, in silico molecular modeling simulation, some physicochemical properties and toxicity predictions were performed for the most active derivatives.

Design, synthesis, molecular modeling, and antimicrobial potential of novel 3-[(1H-pyrazol-3-yl)imino]indolin-2-one derivatives as DNA gyrase inhibitors

A series of 3-[(1H-pyrazol-3-yl)imino]indolin-2-one derivatives were designed using the molecular hybridization method, characterized using different spectroscopic techniques, and evaluated for their in vitro antimicrobial activity. Most of the target compounds demonstrated good to moderate antimicrobial activity compared with ciprofloxacin and fluconazole. Four compounds (8b, 9a, 9c, and 10a) showed encouraging results, with minimal inhibitory concentration (MIC) values (53.45-258.32 µM) comparable to those of norfloxacin (100.31-200.63 µM) and ciprofloxacin (48.33-96.68 µM). Noticeably, the four derivatives revealed excellent bactericidal and fungicidal activities, except for the bacteriostatic potential of compounds 8b and 9a against Escherichia coli and Staphylococcus aureus, respectively. The time-killing kinetic study against S. aureus confirmed the efficacy of these derivatives. Furthermore, two of the four promising derivatives, 9a and 10a, could prevent the formation of biofilms of S. aureus without affecting the bacterial growth at low concentrations. A combination study with seven commercial antibiotics against the multidrug-resistant bacterium P. aeruginosa showed a notable reduction in the antibiotic MIC values, represented mainly through a synergistic or additive effect. The enzymatic assay implied that the most active derivatives had inhibition potency against DNA gyrase comparable to that of ciprofloxacin. Molecular docking and density functional theory calculations were performed to explore the binding mode and study the reactivity of the promising compounds.

Hydrazonoyl bromide precursors as DHFR inhibitors for the synthesis of bis-thiazolyl pyrazole derivatives; antimicrobial activities, antibiofilm, and drug combination studies against MRSA

Microbial resistance is a big concern worldwide, making the development of new antimicrobial drugs difficult. The thiazole and pyrazole rings are important heterocyclic compounds utilized to produce a variety of antimicrobial medications. As a result, a series of new bis-thiazolyl-pyrazole derivatives 3, 4a-c, 5a, b, and 6a-c was synthesized by reacting bis hydrazonoyl bromide with several active methylene reagents in a one-pot reaction. The assigned structure was characterized entirely based on elemental and spectral analyses. The antimicrobial activity represented by MIC was performed using a resazurin-based turbidimetric (TB) assay. The results exhibited good antimicrobial activity against gram-positive strains, especially S. aureus (ATCC6538) while showing poor to moderate activity against gram-negative and fungal strains. Furthermore, the most active derivatives 3, 4a, 4c, and 5b were evaluated for MIC, MBC, antibiofilm, hemolytic assay, and drug combination testing against two S. aureus (ATCC6538) and MRSA (ACL18) strains. Additionally, bis-thiazolyl pyrazole 3, 4c, and 5b exhibited more potent inhibitory activity for DHFR with IC₅₀ values (6.34 ± 0.26, 7.49 ± 0.28, and 3.81 ± 0.16 µM), respectively, compared with Trimethoprim (8.34 ± 0.11 µM). The bis-1-(substituted-thiazol-2-yl)-1H-pyrazole-4-carbonitrile derivative 5b was the most active member with MIC values ranging from (0.12-0.25 µM) compared to Vancomycin (1-2 µM), and MBC values ranging from (0.5-1 µM) for S. aureus (ATCC6538) and MRSA (ACL18). Surprisingly, compound 5b displayed bactericidal behavior, synergistic effect with three commercial antibiotics, and inhibited DHFR with 2.1 folds higher than Trimethoprim. Finally, good findings were obtained from in silico investigations incorporating toxicity prediction and molecular docking simulation.

A Compendium of the Most Promising Synthesized Organic Compounds against Several Fusarium oxysporum Species: Synthesis, Antifungal Activity, and Perspectives

Vascular wilt caused by F. oxysporum (FOX) is one of the main limitations of producing several agricultural products worldwide, causing economic losses between 40% and 100%. Various methods have been developed to control this phytopathogen, such as the cultural, biological, and chemical controls, the latter being the most widely used in the agricultural sector. The treatment of this fungus through systemic fungicides, although practical, brings problems because the agrochemical agents used have shown mutagenic effects on the fungus, increasing the pathogen's resistance. The design and the synthesis of novel synthetic antifungal agents used against FOX have been broadly studied in recent years. This review article presents a compendium of the synthetic methodologies during the last ten years as promissory, which can be used to afford novel and potential agrochemical agents. The revision is addressed from the structural core of the most active synthetic compounds against FOX. The synthetic methodologies implemented strategies based on cyclo condensation reactions, radical cyclization, electrocyclic closures, and carbon-carbon couplings by metal-organic catalysis. This revision contributes significantly to the organic chemistry, supplying novel alternatives for the use of more effective agrochemical agents against F. oxysporum.

In vitro antimicrobial evaluation and in silico studies of coumarin derivatives tagged with pyrano-pyridine and pyrano-pyrimidine moieties as DNA gyrase inhibitors

Several coumarin-containing substitute nitrogen heterocycles have recently received considerable importance due to their diverse pharmacological properties. One-pot and rapid synthesis of coumarin derivatives was achieved via reactions of acetyl-coumarin with p-chloro-benzaldehyde and malononitrile to provide compound 2-containing cyano-amine using conventional heating. Compound 2 was condensed with different carbon electrophiles triethyl orthoformate, phenyl isocyanate, carbon disulfide, benzoyl chloride, and acetyl chloride that afforded the corresponding chromene derivatives 3-17. All the newly synthesized compounds were characterized by elemental and spectroscopic evidences. All of the synthesized compounds were tested for antimicrobial activity against S. Pneumoniae, S. Epidermidis, S. Aureus, and E. coli as Gram + ve Bacteria, K. Pneumoniae, S. Paratyphi as Gram -ve Bacteria, P. Italicum, A. Fumigatus representative for Fungi. The preliminary screening results showed that most of the compounds had moderate to high activity against all tested organisms. The most potent four compounds were subjected to further investigation against E. Coli DNA gyrase and topoisomerase IV inhibitory activity, and the results showed that all of these derivatives inhibit DNA gyrase and thus cell division. Also, in silico studies were done for the most active compounds which showed good results.

Development of adamantane scaffold containing 1,3,4-thiadiazole derivatives: Design, synthesis, anti-proliferative activity and molecular docking study targeting EGFR

A new series of 1,3,4-thiadiazolo-adamantane derivatives were synthesized through molecular hybridization approach, then used as starting material to synthesize chloro and cyano acetamide-thiadiazole derivatives 2, 3. The newly designed compounds 1-3 were treated with different reagents to design 5-adamantyl thiadiazole derivatives 4-17 and evaluate their in vitro anti-proliferative activity against three cancer cell lines (MCF-7, HepG-2 and A549). Doxorubicin was used as a positive control. The most promising compounds 5, 6, 10a, 10b, 14b, 14c, and 17 showed up-regulation for BAX and down-regulation of Bcl-2, these findings proved their role as hopeful apoptotic inducers. In addition, the inhibitory activity against both wild EGFR^WT and mutant EGFR^L858R-TK for these derivatives revealed that compounds 5, 14c, and 17 have IC₅₀ value ranging from 85 nM to 71.5 nM against wild EGFR^WT and 37.85-41.19 nM against the mutant type, Lapatinib was used as a reference standard with IC₅₀ values of 31.8 nM and 39.53 nM, respectively. The most potent derivatives were subjected to further evaluation against double mutant EGFR ^L858R/T790M and showed good IC₅₀ values between (0.27-0.78 nM) compared to Lapatinib (0.18 nM) and Erlotinib (0.21 nM). Among them, thiazolo-thiadiazole adamantane derivative 17 exhibited the strongest inhibitory activity to the EGFR. Molecular docking studies were performed inside the active site of EGFR (1M17), and binding energy scores ranged between (-19.19 to -22.07 Kcal/mol) compared to Erlotinib (-19.10 Kcal/mol). Furthermore, oral bioavailability beside some pharmacokinetics properties of these derivatives were also investigated in this research work.

Novel Synthetic Routes to Prepare Biologically Active Quinoxalines and Their Derivatives: A Synthetic Review for the Last Two Decades

Quinoxalines, a class of N-heterocyclic compounds, are important biological agents, and a significant amount of research activity has been directed towards this class. They have several prominent pharmacological effects like antifungal, antibacterial, antiviral, and antimicrobial. Quinoxaline derivatives have diverse therapeutic uses and have become the crucial component in drugs used to treat cancerous cells, AIDS, plant viruses, schizophrenia, certifying them a great future in medicinal chemistry. Due to the current pandemic situation caused by SARS-COVID 19, it has become essential to synthesize drugs to combat deadly pathogens (bacteria, fungi, viruses) for now and near future. Since quinoxalines is an essential moiety to treat infectious diseases, numerous synthetic routes have been developed by researchers, with a prime focus on green chemistry and cost-effective methods. This review paper highlights the various synthetic routes to prepare quinoxaline and its derivatives, covering the literature for the last two decades. A total of 31 schemes have been explained using the green chemistry approach, cost-effective methods, and quinoxaline derivatives' therapeutic uses.

In vivo and in vitro anti-inflammatory, antipyretic and ulcerogenic activities of pyridone and chromenopyridone derivatives, physicochemical and pharmacokinetic studies

Throughout this study, we present the victorious synthesis of a novel class of 2(1H)-pyridone molecules, bearing a 4-hydroxyphenyl moiety through a one-pot reaction of 2-cyano-N-(4-hydroxyphenyl)acetamide with cyanoacetamide, acetylacetone or ethyl acetoacetate, and their corresponding aldehydes. In addition, the chromene moiety was introduced into the pyridine skeleton through the cyclization of the cyanoacetamide 2 with salicylaldehyde, followed by treatment with malononitrile, ethyl cyanoacetate, and cyanoacetamide, in order to improve their biological behaviour. Due to their anti-inflammatory, ulcerogenic, and antipyretic characters, the target molecules have undergone in-vitro and in-vivo examination, that display promising results. Moreover, in order to predict the physicochemical and ADME traits of all synthesized compounds and standard reference drugs, paracetamol and phenylbutazone, the in-silico prediction methodology was provided.

Sulfaguanidine Hybrid with Some New Pyridine-2-One Derivatives: Design, Synthesis, and Antimicrobial Activity against Multidrug-Resistant Bacteria as Dual DNA Gyrase and DHFR Inhibitors

Herein, a series of novel hybrid sulfaguanidine moieties, bearing 2-cyanoacrylamide 2a-d, pyridine-2-one 3-10, and 2-imino-2H-chromene-3-carboxamide 11, 12 derivatives, were synthesized, and their structure confirmed by spectral data and elemental analysis. All the synthesized compounds showed moderate to good antimicrobial activity against eight pathogens. The most promising six derivatives, 2a, 2b, 2d, 3a, 8, and 11, revealed to be best in inhibiting bacterial and fungal growth, thus showing bactericidal and fungicidal activity. These derivatives exhibited moderate to potent inhibition against DNA gyrase and DHFR enzymes, with three derivatives 2d, 3a, and 2a demonstrating inhibition of DNA gyrase, with IC₅₀ values of 18.17-23.87 µM, and of DHFR, with IC₅₀ values of 4.33-5.54 µM; their potency is near to that of the positive controls. Further, the six derivatives exhibited immunomodulatory potential and three derivatives, 2d, 8, and 11, were selected for further study and displayed an increase in spleen and thymus weight and enhanced the activation of CD4⁺ and CD8⁺ T lymphocytes. Finally, molecular docking and some AMED studies were performed.

Discovery of New Schiff Bases Tethered Pyrazole Moiety: Design, Synthesis, Biological Evaluation, and Molecular Docking Study as Dual Targeting DHFR/DNA Gyrase Inhibitors with Immunomodulatory Activity

A series of Bis-pyrazole Schiff bases (6a–d and 7a–d) and mono-pyrazole Schiff bases (8a–d and 9a–d) were designed and synthesized through the reaction of 5-aminopyrazoles 1a–d with aldehydes 2–5 using mild reaction condition with a good yield percentage. The chemical structure of newly formed Schiff bases tethered pyrazole core was confirmed based on spectral and experimental data. All the newly formed pyrazole Schiff bases were evaluated against eight pathogens (Gram-positive, Gram-negative, and fungi). The result exhibited that, most of them have good and broad activities. Among those, only six Schiff bases (6b, 7b, 7c, 8a, 8d, and 9b) displayed MIC values (0.97–62.5 µg/mL) compared to Tetracycline (15.62–62.5 µg/mL) and Amphotericin B (15.62–31.25 µg/mL), MBC values (1.94–87.5 µg/mL) and selectivity to tumor cell than normal cells. Immunomodulatory activities showed that the promising Schiff bases increase the immunomodulator effect of defense cell and the Schiff base 8a is the highest one by (Intra. killing activity = 136.5 ± 0.3%) having a pyrazole moiety as well as amide function (O=C-NH₂) and piperidinyl core. Furthermore, the most potent one exhibited broad activity depending on both MIC and MBC values. Moreover, to study the mechanism of these pyrazole Schiff bases, two active Schiff bases 8a and 9b from six derivatives were introduced to study the enzyme assay as dihydrofolate reductase (DHFR) on E. coli organism and DNA gyrase with two different organisms, S. aureus and B. subtilis, to determine the inhibitory activities with lower values in the case of DNA gyrase (8a and 9b) or nearly as DHFR compound 9b, while pyrazole 8a showed excellent inhibitory against all enzyme assay. The molecular docking study against dihydrofolate reductase and DNA gyrase were performed to study the binding between active site in the pocket with the two Schiff bases (8a and 9b) that exhibited good binding affinity with different bond types as H-bonding, aren-aren, and arene-cation interaction as well as study the physicochemical and pharmacokinetic properties of the two active Schiff bases 8a and 9b.