Synthesis, characterization, and antimicrobial screening of some Mannich base sydnone derivatives

The title compounds (5a–j), (6a–j), and (7a–j) were prepared via a four-step procedure using starting material 4-methoxyaniline (1). The structure of all synthesized compounds was confirmed by FT-IR, ¹H NMR, ¹³C NMR, and CHN analysis. The synthesized compounds were tested for their antibacterial and antifungal activity (MIC) in vitro against organisms viz. B. subtilis, S. aureus, E. coli, P. aeruginosa, and C. albicans taking ciprofloxacin, ampicillin, streptomycin, penicillin-G, fluconazole, and nystatin as the standard drugs. Some of the compounds have shown significant activities.     

An efficient, solvent-free microwave-assisted synthesis and antimicrobial screening of 1,6-dihydropyrimidine analogues

A series of compounds 4-(4-(4-aminophenyl)-6-(aryl)-1,6-dihydropyrimidin-2-ylthio)butanenitriles 5a–l were synthesised by the reaction of allyl cyanide 4 with 3a–l. Compounds 3a–l were prepared from reaction between various chalcones 1a–l and thiourea in presence of catalytic amount of potassium hydroxide. Compounds 3a–l, and 5a–l were prepared by classical as well as MWI methods. Structures of the compounds were characterized by IR, ¹H NMR, ¹³C NMR and mass spectral data. The newly synthesized compounds 5a–l were screened for their antimicrobial activity against different strains of bacteria and fungi using serial broth dilution method. Compounds 5e, 5g and 5k were found to be most active with MIC of 25?μg/mL against selected bacterial strains, while compound 5d, 5f, 5j and 5k were found to be most active with MIC 50?μg/mL against selected fungal strains.     

Synthesis, characterization, and antimicrobial evaluation of novel naphthalene-based 1,2,4-triazoles

In order to search for new bioactive molecules with significant antimicrobial action, a series of 1,2,4-triazole and naphthalene analogs bearing structurally diverse substituents, N-(3-mercapto-5-(naphthalen-1-yl)-4H-1,2,4-triazol-4-yl)(aryl)amides 3a–l were synthesized in good yield by a multi-step synthetic procedure. Their antimicrobial activity was screened against various Gram-positive and Gram-negative bacteria and fungi. Compounds 3a, 3f, 3g, 3j, and 3k exerted strong inhibition of the investigated bacterial and fungal strains compared to control antibiotic ampicillin and antifungal griseofulvin. On the basis of statistical analysis, it is observed that the compounds give significant co-relation. All the synthesized compounds have been characterized by IR, ¹H NMR, ¹³C NMR, and mass spectral data.     

Microwave-assisted synthesis and antimicrobial screening of new imidazole derivatives bearing 4-thiazolidinone nucleus

A new series of compounds 2-((1-(4-(4-arylidene-2-methyl-5-oxo-4,5-dihydro-1H-imidazol-1-yl)phenyl)ethylidene)hydrazono)thiazolidin-4-ones (4a–o) have been synthesized under conventional and microwave irradiation method. All compounds were characterized by IR, ¹H NMR, ¹³C NMR and mass spectra. Newly synthesized compounds were screened for their antibacterial and antifungal activities on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus pyogenes, Candida albicans, Aspergillus niger and Aspergillus clavatus by bioassays, namely serial broth dilution. The synthesized compounds showed potent antimicrobial activity against tested microorganisms. Compounds 4h, 4j, 4m and 4n were the most potent amongst tested compounds.     

Synthesis,antimicrobial, and antioxidant activity of benzofuran barbitone and benzofuran thiobarbitone derivatives

The synthesis of novel series of benzofuran derivatives, containing barbitone moiety, 5-[(2/4-substitutedphenyl)(5-substituted-1-benzofuran-2-yl) methylidene]pyrimidin-2,4,6(1H,3H,5H)-trione (4a–i) and thiobarbitone moiety, 5-[(2/4-substitutedphenyl)(5-substituted-1-benzofuran-2-yl)methylidene]-2-thioxodihydropyrimidin-4,6(1H, 5H)-dione (5a–i) have been reported. The target compounds (4a–i) and (5a–i) were synthesized by the Knoevenagel condensation of (5-substituted-1-benzofuran-2-yl)(2/4-substitutedphenyl) methanone (3a–i) with barbituric acid and thiobarbituric acid, respectively, in acid medium. These compounds were screened for the antimicrobial and antioxidant activities. From antimicrobial activity results it was found that compounds 4a, 5a, 4c, and 5c displayed good antibacterial and antifungal activity against all tested strains. Further, the synthesized compounds were studied for docking on the enzyme, Glucosamine-6-phosphate synthase and the compounds 4c and 5c have emerged has an active antimicrobial agent with least binding energy (?5.27 and ?4.85 kJ mol^?1). Compounds 4e, 4f, 5e, and 5f showed promising free radical scavenging activity and compounds 5a and 5b showed good chelating ability with Fe²⁺ ions.     

Synthesis,antimicrobial, and cytotoxic activities of novel benzimidazole derivatives bearing cyanopyridine and 4-thiazolidinone motifs

A series of 6-(1H-benzo[d]imidazol-2-yl)-2-(2-(3-nitrophenyl)-4-oxothiazolidin-yl)-4-(aryl)nicotinonitriles 5a–l were synthesized and characterized by IR, ¹H NMR, ¹³C NMR, and mass spectrometry techniques. These novel compounds 5a–l were screened for their in vitro antimicrobial activity against different bacterial and fungal strains and in vitro cytotoxicity study (HeLa cell line) using MTT colorimetric assay. The results demonstrated that compounds 5c, 5e, and 5i–k exhibited excellent antibacterial activity, while compounds 5d, 5i, and 5k were found to be the most potent antifungal agents. From the standpoint of SAR studies, it was observed that the presence of electron donating groups remarkably enhanced the antimicrobial activity of newly synthesized compounds. Further, the results of preliminary MTT cytotoxicity studies on HeLa cells suggested that potent antimicrobial activity of 5c–e and 5i–k was accompanied by low cytotoxicity.     

New 4-thiazolidinones from 5-ethyl pyridine-2-ethanol: their antibacterial,antifungal, and antitubercular activity

New thiazolidinones 5a–o were prepared from Schiff base 4a–o and thioglycolic acid in the presence of ZnCl₂ from 4-[2-(5-ethylpyridin-2-yl)ethoxy]benzaldehyde. The structures of the synthesized compounds were assigned on the basis of elemental analysis, IR, ¹H NMR ¹³C NMR, and mass spectral data. All the compounds were screened against different strains of bacteria and fungi. Compounds 4e, 4n, 4m, 4o, 5e, 5f, 5j, and 5m possessed very good activity against bacterial and fungal species. These active compounds impelled us to study their antitubercular activity. Schiff base 4n and 4e showed M. tuberculosis MIC value 25 and 62.5 μg/ml, respectively. Thiazolidinone 5m displayed M. tuberculosis MIC at 25 μg/ml, which is better antitubercular activity compared with rifampicin.     

Synthesis, characterization and antimicrobial studies of a few novel thiazole derivatives

A series of novel N-[4-(substituted)-1,3-thiazol-2-yl]-2-(substituted)acetamide (9a–m) and methyl 2-(2-(2-(substituted)acetamido)thiazol-4-yl)acetate (9n–o) derivatives have been synthesized and compounds were characterised by spectral and analytical studies. All compounds were screened for their in vitro antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumonia by disc diffusion method and for antifungal activity against Penicillium marneffei, Trichophyton mentagrophytes, Aspergillus flavus and Aspergillus fumigatus by serial plate dilution method. Compounds 9b, 9e, 9m and 9o exhibited growth inhibition against all the tested bacterial strains, with MIC values varying from 12.5 to 6.25 μg/ml. Among the compounds tested for antifungal activity, 9a, 9b, 9d, 9j, 9k, 9p and 9n showed wide range of activity against all the tested strains. Most of the newly synthesized compounds were effective against fungal strains rather than bacterial strains. However, some of the compounds like 9a, 9e, 9j, 9k and 9i showed selective sensitivity against some of the bacterial strains whereas they were unable to sustain the growth of other strains.     

Synthesis and biological evaluation of novel 4,5-dihydropyrazole derivatives as potent anticancer and antimicrobial agents

A focused library of 4,5-dihydropyrazole dervivatives (4, 5, 6, 7a–h, 8, 9a–g, and 10a–g) were synthesized from novel 5-(2,6-difluorophenyl)-3-phenyl-4,5-dihydropyrazole-1-carbothioamide 4. The synthesized compounds were characterized using elemental analysis and spectral data (IR, mass spectra, ¹H and ¹³C NMR) and evaluated for antimicrobial activity by broth dilution method and in vitro anticancer activity. Among the synthesized compounds 7a, 9c, 9g, and 10d exhibit broad spectrum antimicrobial activity against tested microbial strains. The in vitro cancer results ascertain 7a, 9c, and 10d are most potent molecules in comparison to reference standard cisplatin.     

Synthesis, characterization and antimicrobial screening of hybrid molecules containing benzimidazole-pyrazole and pyridine nucleus

The rising prevalence of multi-drug resistant Gram-positive, Gram-negative bacteria and fungi continues to provide momentum for search and development of novel active antimicrobial agents against these pathogens. In continuation to this, the present article deals with the synthesis and antimicrobial activity of a novel series of (3-(1H-benzo[d]imidazol-2-yl)-5-(aryl)-4,5-dihydro-1H-pyrazol-1-yl)(pyridin-4-yl)methanones 4a–n, synthesized by the reaction of benzimidazolyl chalcones with isoniazide 3. The structures of synthesized compounds were elucidated on the basis of IR, NMR, and mass spectra. The newly synthesized compounds 4a–n were screened for their antimicrobial activity against different strains of bacteria and fungi using serial broth dilution method. Compounds 4d, 4f, 4h, and 4g were found to be most active with MIC of 25?μg/mL against selected bacterial strains. Compounds 4c, 4g, and 4n were found to be most active with MIC of 100?μg/mL against selected fungal strains.     

Design, synthesis of some 2,6,9-trisubstituted purinyl thioureido derivatives and evaluation of antimicrobial activity

Some new trisubstituted purinyl thioureido were synthesized and evaluated for their in vitro antimicrobial activity against Gram positive and Gram negative strains and antifungal strain using a micro dilution procedure. Synthesized compounds 6a–j prove to be effective with minimum inhibitory concentration (MIC) (mg?ml^?1), among them 6a, 6d, and 6e showed excellent activity against a panel of microorganisms. The newly synthesized compounds were characterized using IR, ¹H-NMR, and elemental analysis.     

Synthesis, antioxidant, and antibacterial studies of phenolic esters and amides of 2-(1-benzofuran-2-yl) quinoline-4-carboxylic acid

A new series of phenolic esters 2(a–j) and amides 3(a–c) of 2-(1-benzofuran-2-yl) quinoline-4-carboxylic acid were synthesized by the reaction of 2-(1-benzofuran-2-yl)-quinoline-4-carboxylic acid (1) with various substituted phenols and secondary amines using ethyl-(N′,N′-dimethylamino)propyl carbodiimide hydrochloride (EDC.HCl) as a coupling agent. The newly synthesized compounds were evaluated for in vitro antioxidant and antibacterial activity. Among all tested compounds 2a, 2c, 2e, and 2h showed good chelating ability with Fe⁺² ions, whereas compounds 2g and 2j exhibited good scavenging activity with DPPH free radicals. Concerning antibacterial activities compounds 2a, 2b, 2c, and 2h were found to be equipotent to ampicillin against Enterococcus sp and Staphylococcus aureus, while compound 2e is found to be as potent as ampicillin against Pantoea Dispersa and Ochrobactrum sp. amide derivatives 3(a–c) were found to be less potent when compared to standard.     

Synthesis and characterization of flurbiprofen hydrazide derivatives as potential anti-HCV, anticancer and antimicrobial agents

A novel series of new flurbiprofen hydrazide derivatives 2-(2-fluorobiphenyl-4-yl)-N′-[(substituted phenyl/5-nitro-2-furyl)methylene]propanehydrazide (3a–k), 2-(2-fluorobiphenyl-4-yl)-N-(2-substituted-4-oxo-1,3-thiazolidine-3-yl)propanamide (4a–b, 4d–k), 2-[2-(2-fluorobiphenyl-4-yl) propanoyl]-N-substituted hydrazinecarbothioamide (5a–h) and 2-(2-fluorobiphenyl-4-yl)-N′-[(3-methyl-4-oxo-1,3-thiazolidin-2-ylidene]propanehydrazide (6a–b, 6e and 6g) has been synthesized in this study. All synthesized compounds were screened for antimicrobial activity against various bacterial and fungal strains. Additionally, compounds were evaluated for the ability to inhibit Hepatitis C virus NS5B polymerase. The most active 4-thiazolidinone compound was 4k (SGK119) with 67.0 % and thiosemicarbazide compound was 5d (SGK123) with 69.50 % inhibition at 200 μM against hepatitis C virus NS5B RNA polymerase. Anticancer activity of the selected compounds (3i, 3j, 3h, 4d, 4i and 6b) was determined at a single dose towards the full panel of 60 human cancer cell lines by the National Cancer Institute (NCI). 2-(2-Fluoro-4-biphenylyl)-N-[2-[4-(trifluoromethyl)phenyl]-4-oxo-1,3-thiazolidine-3-yl]propanamide 4d, containing thiazolidinone ring, demonstrated the most marked effect with 20.80 % growth percent on leukaemia cancer cell line SR at 10^?5 M. The results demonstrated that none of the compounds tested have anticandidal and antifungal activities, but two of them (4a and 4i) showed antibacterial inhibition against Micrococcus luteus, and Staphylococcus cohnii and Staphylococcus aureus, respectively.     

Synthesis, physicochemical properties, antimicrobial and antioxidant studies of pyrazoline derivatives bearing a pyridyl moiety

A series of new pyrazoline compounds bearing a pyridyl moiety (4a–i) were synthesized by condensing appropriate chalcones with hydrazine hydrate and tested for antimicrobial and antioxidant activities. According to in vitro antimicrobial activity against Bacillus subtilis, Staphylococcus epidermidis, Proteus vulgaris, Pseudomonas aeruginosa, Aspergillus niger and Penicillium chrysogenum and antioxidant activity by DPPH method, the compounds 4a, 4d, 4i and 4e, 4f, 4h showed maximum antimicrobial and antioxidant activities, respectively. Physiochemical properties and Lipinski’s ‘Rule of Five’ analysis predicted higher intrinsic quality of the synthesized compounds and revealed that these compounds have good bioavailability and druglikeness properties.     

Antibacterial and free radical scavenging potential of synthesized 7-hydroxy-2-aryl-6-aryldiazenyl-4H-chromen-4-ones

A series of 7-hydroxy-2-aryl-6-aryldiazenyl-4H-chromen-4-one derivatives (6a–m) was synthesized in quantitative yields and their structures were corroborated on the basis of FT-IR, ¹H, ¹³C NMR, ESI–MS, and elemental analysis data. The synthesized compounds were screened for in vitro antibacterial activities against a representative panel of Gram-positive and Gram-negative bacteria, as well as to evaluate their antioxidant potential using DPPH assay method. Bio-evaluation studies revealed that compounds 6c, 6d, 6e, 6j, and 6l exhibited moderate to good antibacterial activity against all the tested bacterial strains. Furthermore, from the antioxidant screening results, it has been observed that compounds 6c, 6e, and 6g manifested profound antioxidant potential (IC₅₀ <7.68 μM) in comparison to the standard antioxidant ascorbic acid.     

Newer thiazolopyrimidine-based sulfonamides clubbed with benzothiazole moiety: synthesis and biological evaluation

A new class of thiazolopyrimidine-based sulfonamides (5a–j) was synthesized from a parent compound 2-methoxy benzoic acid by multistep reaction in order to find new agents to fight against microbial infections. Substituted thiazolopyrimidines (3a–e) were prepared by cyclocondensation of substituted thiazolidinediones (2a–e) with urea in the presence of acid catalyst P₂O₅. Finally, desired compounds (5a–j) were synthesized from intermediates (4a–e) prepared from compounds (3a–e) by chlorosulfonation followed by condensation with corresponding benzothiazole moiety. The synthesized compounds were characterized by IR, ¹H-NMR, ¹³C-NMR spectral data, and elemental analysis, and were evaluated for in vitro antimicrobial activity against certain bacterial and fungal strains using the broth microdilution method as well as antitubercular activity against H₃₇Rv using Lowenstein–Jensen agar method.     

Antimicrobial and antiquorum-sensing studies. Part 2: synthesis, antimicrobial, antiquorum-sensing and cytotoxic activities of new series of fused [1,3,4]thiadiazole and [1,3]benzothiazole derivatives

New series of [1,3,4]thiadiazolo[3,2-a]pyrimidines, [1,3,4]thiadiazolo[2,3-b]quinazolines, and pyrimido[2,1-b][1,3]benzothiazoles have been synthesized and characterized by analytical and spectrometrical methods (IR, MS, ¹H, and ¹³C NMR). Sixteen of the synthesized compounds; namely, 3a, b, 5a–f, 8a, b, 10, 11a–c, and 13a, b were screened for antibacterial activity against Escherichia coli, Staphylococcus aureus, and Bacillus cereus. They were found to be either moderately active, slightly active or inactive against the selected microorganisms. The antifungal activity of these compounds were also tested against Candida albicans, Aspergillus fumigatus 293, and Aspergillus flavus 3375. Compound 11a showed potent antifungal activity against the three selected fungi; the rest of the tested compounds displayed either weaker activity or were completely inactive. The same compounds were examined for antiquorum-sensing activity against Chromobacterium violaceum ATCC 12472, where compounds 3a, 10, 11a, and 13a, b exhibited promising activity. The in vitro cytotoxic activity of these compounds was also studied by brine shrimp lethality bioassay, and results indicated that compounds 3a, 11a, and 13a have the highest cytotoxic activity.     

Zn(OTf)2-catalyzed three component, one-pot cyclocondensation reaction of some new octahydroquinazolinone derivatives and access their bio-potential

An efficient synthesis of some new octahydroquinazolinone derivatives 4a–x by the cyclocondensation reaction of corresponding 2-thi(oxo)-1,2-dihydroquinoline-3-carbaldehyde 1a–e, 1,3-dicarbonyl compounds 2a–b, and substituted urea 3a–c using zinc triflate as a catalyst in refluxing ethanol in high yield is described. The structures of new compounds have been characterized on the basis of elemental analysis, FT- IR, ¹H NMR, ¹³C NMR, and mass spectral data. All the synthesized compounds were evaluated for their antimicrobial activities against various microbes. Minimum inhibitory concentration values of all the 24 synthesized compounds were also determined. Some of the synthesized compounds exhibited excellent antimicrobial activity.     

Synthesis, antimicrobial, and antioxidant activities of some new indole analogues containing pyrimidine and fused pyrimidine systems

To examine new leads with potential antimicrobial and antioxidant activities, a new series of tetrahydropyrimidines (2a–c, 3a–c and 4a–c), pyrazolo[3,4-d]pyrimidines (5a–c), and ditetrazolo[1,5-a;1′,5′-c]pyrimidines (6a–c) were synthesized in this study using appropriate synthetic routes. The newly synthesized compounds have been tested for their antimicrobial and antioxidant activities against DPPH stable free radical. In the case of antibacterial activity, compounds 2a, 6a, and 6c exhibited the maximum zone of inhibition against Staphylococcus aureus; compound 6c exhibited maximum zone of inhibition against Pseudomonas aeruginosa; and compound 2a showed maximum inhibitory growth against Klebsiella pneumonia. While in the case of antifungal activities, compound 5a showed good zone of inhibition against Aspergillus oryzae, compounds 2b and 6a exhibited maximum zone of inhibition against Aspergillus niger. In case of antioxidant activities, compound 2a showed the highest DPPH radical scavenging activity.     

Synthesis and evaluation of analgesic, anti-inflammatory, and anticancer activities of new pyrazole-3(5)-carboxylic acid derivatives

In this article, we synthesized a series of novel 1-benzyl-5(3)-p-tolyl-1H-pyrazole-3(5)-carboxylic acid derivatives and characterized by IR, ¹H NMR, and mass spectroscopy. Compounds were evaluated for their in vivo analgesic and anti-inflammatory activity using the p-benzoquinone-induced writhing test and the carrageenan-induced paw edema model, respectively. Out of 14 compounds tested, 7a, 7c, 7e, 7f, 7i, 8a–b, and 8f–g exhibited potent analgesic and/or anti-inflammatory activity as compared to reference drugs aspirin and indomethacin. Anticancer activity of these compounds was assessed against five cancer cell lines with the MTT assay (HL-60, human promyelocytic leukemia cells; HeLa, human cervical cancer cells; Raji, human B lymphocyte cell line; MCF7, human breast adenocarcinoma cell line; MDA-MB-231, estrogen-independent human breast cancer cell line). Compounds 7a, 8a, and 8b with high anti-inflammatory activity, and also 7d and 7j with mild anti-inflammatory activity exhibited promising anticancer activity against some selected cell lines.