Synthesis, characterization and antimicrobial activities of some novel bis-chalcones

A series of novel bis-chalcones 3a–n were synthesized in excellent yields by condensation reaction of 1,4-diacetylbenzene with various aldehydes in ethanol 96% and aqueous NaOH at room temperature. All compounds were characterized by IR, ¹H and ¹³C NMR, UV spectroscopy and elemental analysis. The antimicrobial activities of synthesized compounds were also evaluated. The most of these compounds exhibited a good activity against Staphylococcus aureus, Escherichia coli and Candida albicans microorganisms. Some of them showed significant activities.     

Synthesis and antimicrobial activities of highly functionalised novel β-lactam and thiazolidine-grafted tetrahydrobenzothiophenes

A series of biologically active N-(3-chloro-2-oxo-4-phenylazetidin-1-yl)/3-N-(4-oxo-2-arylthiazolidin-3-yl)-2-(methylsulfonamido)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamides derivatives have been synthesised in good yield. The structures of compounds have been established on the basis of IR, ¹H, ¹³C NMR, and elemental analysis. The structure–activity relationships have been studied by screening of antimicrobial activity over a representative panel of bacterial and fungal strains using two-fold serial dilution method. All these synthesised compounds exhibited significant activities against all bacterial and fungal strains.     

Synthesis,Antimicrobial and cytotoxic activity of New Heterocyclic Hybrids Based on 2,5-Dimethylpyrrole and Pyrrole Scaffolds

A series of 4-(2,5-dimethylpyrrol-1-yl)/4-pyrrol-1-yl benzoic acid hydrazide analogs, some derived triazoles, azetidinones, thiazolidinones, and pyrroles have been synthesized in good yields and structures of these compounds were established by IR, ¹H NMR, ¹³C NMR, mass spectral, and elemental analysis. These compounds were evaluated for their preliminary in vitro antibacterial, antifungal, and antitubercular activity against Mycobacterium tuberculosis H₃₇ Rv strain by the broth dilution assay method. Twenty one of these compounds displayed good antimicrobial activity, with a MIC value of 1-4 μg/ml. Several compounds 4c, 8-10, 15b-15h, and 16b-16d exhibited good in vitro antitubercular activity with MIC value 1-2 μg/ml. Further, some title compounds were also assessed for their cytotoxic activity (IC₅₀) against mammalian Vero cell lines and A₅₄₉ (lung adenocarcinoma) cell lines using the MTT assay method. The results revealed that these compounds exhibit antitubercular activity at non-cytotoxic concentrations.     

Synthesis, characterization, and in vitro antimicrobial evaluation of new 5-chloro-8-bromo-3-aryl-1,2,4-triazolo[4,3-c]pyrimidines

A series of new 5-chloro-8-bromo-3-aryl-1,2,4-triazolo[4,3-c]pyrimidines (4a–j) have been accomplished in excellent yields by the oxidative cyclization of pyrimidinylhydrazines (3a–j) of various aryl aldehydes with one equivalents of iodobenzene diacetate in methanol. The chemical structures of the synthesized compounds were confirmed by elemental analyses, FT-IR, ¹H NMR, ¹³C NMR, and mass spectral studies. Ten new compounds (4a–j) were tested in vitro for their antimicrobial activity against clinically isolated strains. Variable and modest activities were observed against the investigated strains of bacteria and fungi. Compounds 4f, 4i, and 4j demonstrated good antimicrobial activity against all the tested microbial strains.     

New N-arylamino biquinoline derivatives: microwave-assisted synthesis and their antimicrobial activities

A new series of N-arylamino biquinoline derivatives 5a–x were synthesized under microwave irradiation technique in good yields compared with conventional method and screened for their antimicrobial activity. All the synthesized compounds have been established by elemental analysis, IR, ¹H NMR, ¹³C NMR and mass spectral data. In vitro antimicrobial activity was carried out against three Gram-positive bacteria (Bacillus subtilis, Clostridium tetani, Streptococcus pneumoniae), three Gram-negative bacteria (Escherichia coli, Salmonella typhi, Vibrio cholerae) and two fungal species (Aspergillus fumigatus, Candida albicans) using broth microdilution method. Of the compounds studied, compound 5u exhibited promising antimicrobial activity against Streptococcus pneumoniae and Salmonella typhi.     

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.     

Microwave-assisted synthesis of pyrido[1,2-a]benzimidazole derivatives of β-aryloxyquinoline and their antimicrobial and antituberculosis activities

A new series containing pyrido[1,2-a]benzimidazole derivatives of β-aryloxyquinoline has been synthesized via base catalyzed microwave-assisted multi-component cyclocondensation reaction. This methodology allowed us to achieve the desired products in good yields in very short time with the use of 10 mol% NaOH as a non-hazardous organic base. The chemical structures of compounds 6a–x were elucidated by ¹H NMR, ¹³C NMR, FT-IR, elemental analysis, and mass spectral data. The titled derivatives were tested against a panel of pathogenic strains of bacteria and fungi for antimicrobial activity and against Mycobacterium tuberculosis H37Rv for their antitubercular activity. The structural activity relationship study revealed that antimicrobial and antitubercular potency of the title compounds depends not only on the bicyclic heteroaromatic pharmacophore appended through ether linked aryl ring but also on the nature of the peripheral substituents and may also upon their spatial relationship and positional changes.     

Synthesis and evaluation of 4-(substituted)-acetylamino-3-mercapto-5-(4-substituted) phenyl-1,2,4-triazole derivatives as antimicrobial agents

Triazoles and its derivatives are found to possess diverse applications in the field of medicine and industry. A series of novel 1,2,4-triazole derivatives have been synthesized as novel antimicrobial agents starting from different 4-substituted benzoic acids. The chemical structures of these newly synthesized compounds were elucidated by Fourier transform infrared spectroscopy (FTIR), ¹H NMR, ¹³C NMR, FAB⁺-MS spectral data, and elemental analysis. Their antimicrobial activities were investigated against four bacterial strains S. aureus (ATCC-25923), P. aeruginosa (ATCC-27853), E. coli (ATCC-8739), B. subtilis (ATCC-6633) and three fungal strains C. albicans (MTCC-227), A. niger (MTCC-3323), and F. oxysporum (MTCC-2087). Preliminary results indicate that some of them exhibit promising activities and deserve further consideration.     

Synthesis and biological evaluation of novel <Emphasis Type="SmallCaps">d</Emphasis>-glucose-derived 1,2,3-triazoles as potential antibacterial and antifungal agents

A series of novel d-glucose-derived 1,2,3-triazoles have been synthesized in excellent yields via Cu(I)-catalyzed 1,3-dipolar cycloaddition by using methyl α-d-glucopyranoside as starting material. All the new compounds were confirmed by ¹H NMR, ¹³C NMR, IR, MS, and HRMS spectra, and their antimicrobial activities were screened against Gram-Positive, Gram-Negative bacteria, and fungi. Bioactive assay manifested that some of the synthesized glucose-derived 1,2,3-triazoles exhibited good antibacterial and antifungal activities. Notably, compound 5k gave the most potent efficiency with MIC₅₀ value of 6 µM against Candida albicans, which was nine-fold more active than the reference drug Fluconazole. It also exhibited good antibacterial activity against Escherichia coli with the MIC₅₀ value of 10.8 µM compared to Chloramphenicol while the corresponding hydrochloride 4k revealed remarkable inhibitory against Bacillus subtilis with an MIC₅₀ value of 11 µM.     

Synthesis and bioevaluation of Schiff and Mannich bases of isatin derivatives with 4-amino-5-benzyl-2,4-dihydro-3H-1,2,4-triazole-3-thione

Isatin (2,3-dioxindole) and its derivatives show a wide range of biological activities. In the present study, a series of Schiff and Mannich bases of isatin derivatives were prepared using 4-amino-5-benzyl-2,4-dihydro-3H-1,2,4-triazole-3-thione. The structures of these derivatives were characterized by IR, ¹H NMR and elemental analysis. In vitro antimicrobial activities were evaluated by agar dilution method and the zone of inhibition values of these derivatives were compared with ciprofloxacin and fluconazole. Chloro and Bromo groups at fifth position of isatin broaden the spectrum of antibacterial activity against S. aures, P. aeruginoa, and E. coli, respectively. For the antifungal activity, the compound 6h showed equipotent activity against A. niger. The remaining majority of the compounds were found active in the biological screening. The efforts were also made to establish structure activity relationships among synthesized compounds.     

7-(3-氨基-4-烷氧亚胺基-1-哌啶基)喹诺酮类化合物的合成与抗菌作用

为寻找新的更加优秀的喹诺酮类抗菌药，设计合成了21个7-(3-氨基-4-烷氧亚胺基-1-哌啶基)喹诺酮类化合物，并测定其体内外抗菌活性。化合物结构经¹H NMR和HRMS得到确证，并用单晶X-衍射分析确定其双键构型。化合物14a和14m表现出优秀的广谱抗菌活性，它们对所实验的12株革兰氏阳性菌的活性，总体上明显优于3个对照药，特别是对包括MRSA和MRSE在内的金葡菌和表葡菌的活性是吉米沙星和巴罗沙星的4～16倍、左氧氟沙星的8～64倍。它们对金葡菌的MIC值分别是0.25～1 mg·L^-1和0.125～1 mg·L^-1，对表葡菌的MIC值分别是0.5～4 mg·L^-1和1～8 mg·L^-1，对小鼠系统感染的体内保护作用与吉米沙星、莫西沙星基本相当(P>0.05)。     

Synthesis and biological evaluation of 1-(3-chloro-2-oxo-4-phenylazetidin-1-yl)-3-(2-oxo-2-(10H-phenothiazin-10-yl)ethyl)urea derivatives

A new series of eleven novel 1-(3-chloro-2-oxo-4-phenylazetidin-1yl)-3-(2-oxo-2-(10H-phenothiazin-10-yl)ethyl)urea derivatives were synthesized by cyclocondensation of various Schiff bases of phenothiazine with chloroacetyl chloride in the presence of triethylamine. Various Schiff bases of phenothiazine were synthesized by condensation of 4-(2-oxo-2-(10H-phenothiazin-10-yl)ethyl semicarbazide with various aryl aldehydes. The synthesized compounds were characterized by IR, MASS and ¹H NMR spectral data and evaluated for in vitro antimicrobial, antitubercular, antioxidant and anticancer activities by disc diffusion method, MIC method, REMA, DPPH, FRAP and MTT assay method, respectively. All synthesized compounds showed moderate-to-significant anti-bacterial and anti-fungal activity and compound 4d, 4g, 4h and 4k showed good antioxidant activity with EC₅₀ value of 55, 57, 56 and 47 μg/ml tested by DPPH method. The compounds 4j at a concentration of 10 μg/ml showed inhibition against the growth of Mycobacterium tuberculosis and 4f showed significant activity against human cervical cancer cell line with IC₅₀ values of 18.26 μM.     

Microwave-assisted synthesis and biological evaluation of carbazole-based chalcones,aurones and flavones

A new class of chalcones, aurones and flavones derived from carbazole is designed as potential antimicrobial and antioxidant agents. Synthesis of (Z)-2-((9-ethyl-9H-carbazol-3-yl)methylene)benzofuran-3(2H)-ones and 2-(9-ethyl-9H-carbazol-3-yl)-4H-chromen-4-ones was carried out by the oxidation of (E)-3-(9-ethyl-9H-carbazol-3-yl)-1-(2-hydroxyphenyl)prop-2-en-1-ones under microwave irradiation and conventional heating. All the newly synthesized compounds were characterized on the basis of IR, ¹H NMR, ¹³C NMR, mass and analytical data. All the synthesized compounds were evaluated for their antibacterial, antifungal and antioxidant activities. Synthesized compounds were screened in vitro for antibacterial activity against two gram-positive bacterial strains like Staphylococcus aureus and Bacillus subtilis and two gram-negative bacterial strains like Escherichia coli and Klebsiella pneumonia and antifungal activity by inhibitory action against three fungal strains like Fusarium oxysporum, Aspergillus niger and Aspergillus flavus. The synthesized compounds were also evaluated for their DPPH radical scavenging activity. All the newly synthesized compounds have shown good antibacterial, antifungal and antioxidant activities.     

Synthesis,Characterization and In Vitro Antimicrobial Evaluation of Novel Pyrazolothiazol-4(5H)-one Derivatives

Antimicrobial screening of several novel pyrazolothiazol-4(5H)-one derivatives (3a-3j) has been performed. Reaction of aromatic aldehydes with aromatic ketones yielded starting chalcones (1a-1j) which have been subsequently reacted with thiosemicarbazide for obtaining N-thiocarbamoylpyrazole derivatives (2a-2j). These were further cyclized to pyrazolothiazol-4(5H)-one derivatives (3a-3j) in the presence of ethylbromoacetate. The structures of newly synthesized compounds were confirmed by FTIR and ¹H NMR and/or MS. The in vitro antimicrobial activity of these compounds was evaluated against Gram positive bacteria, Gram negative bacteria and fungi. Their minimum inhibitory concentration was determined by tube dilution method. The results showed that most of the compounds have promising antimicrobial activity as compared to standard drugs. Among the test compounds, 2-[5(4-chlorophenyl)-3-phenyl-4,5-dihydropyrazol-1-yl]-thiazol-4(5H)-one (3e) was found to show the most potent antimicrobial activity.     

Novel functionalized β-nitrostyrenes: Promising candidates for new antibacterial drugs

The process of searching for new antibacterial agents is more and more challenging due to the increasing drug resistance which has become a major concern in the field of infection management. Our study presents a synthesis and characterization by IR, UV, ¹H NMR and ¹³C NMR spectra of a homogenous series of 1-EWG functionalized 2-aryl-1-nitroethenes which could prove good candidates for the replacement of traditional antibacterial drugs In vitro screening against a panel of the reference strains of bacteria and fungi and their cytotoxicity towards cultured human HepG2 and HaCaT cells was performed. Antimicrobial results indicated that four of the synthesized compounds exhibited a significant antimicrobial activity against all tested reference bacteria and fungi belonging to yeasts with a specific and strong activity towards B. subtilis ATCC 6633. Two of these compounds had no detectable cytotoxicity towards the cultured human cell lines, making them promising candidates for new antibacterial drugs.     

Synthesis and antiproliferative activities of some pyrazole-sulfonamide derivatives

In this study, a series of pyrazole-sulfonamide derivatives were designed and synthesized from 1-(4-aminophenyl)-4-benzoyl-5-phenyl-N-(5-sulfamoyl-1,3,4-thiadiazol-2-yl)-1H-pyrazole-3-carboxamide (1). The newly synthesized sulfonamides were characterized by FT-IR, ¹H NMR, ¹³C NMR, and elemental analyses. The compounds were tested for their in vitro antiproliferative activities against HeLa and C6 cell lines. The tests were carried out as dose-dependent assay starting from 5 to 100 μg/mL. All compounds showed especially cell selective effect against rat brain tumor cells (C6). Some of the tested compounds (3) and (7) showed promising broad spectrum antitumor activity comparable to the activities of the commonly used anticancer drugs, 5-fluorouracil and cisplatin.     

A search of novel antimicrobial based on benzimidazole and 2-pyridone heterocycles

The increasing incidence of bacterial drug resistance imposes a new search on existing antimicrobial drugs leading to the development of new bioactive molecules. In continuation to this, the present article deals with the synthesis and antimicrobial activity of 1-(1-(1H-benzo[d]imidazol-2-yl)ethylideneamino)-6-(arylideneamino)-4-(2-hydroxyphenyl)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitriles (4a–k). All newly synthesized compounds have been evaluated against two gram positive bacteria (Staphylococcus aureus, Streptococcus pyogenes), two gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa), and three fungi (Candida albicans, Aspergillus niger, Aspergillus clavatus) using serial broth dilution method. Compounds reported in the present article bearing chloro and hydroxy groups exhibit very good to excellent antimicrobial activity. All the newly synthesized compounds have been characterized by IR, ¹H NMR, ¹³C NMR, and mass spectra.     

Novel approach for synthesis of potent antimicrobial hybrid molecules containing pyrimidine-based imidazole scaffolds

This report describes the novel approach for the synthesis and exploration of hybrid molecules containing pyrimidine-based imidazole scaffolds as potent antimicrobial agents. The targeted compounds N-(4-arylidene-2-mercapto-5-oxo-4,5-dihydro-1H-imidazol-1-yl)-6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine-5-carboxamides (5a–l) were achieved by the Knoevenagel condensation of a key precursor (4) with different aldehydes in good yields having moderate to excellent antimicrobial activity. The structural identification of final products was carried out by known classical spectral techniques like IR, ¹H NMR, ¹³C NMR, and mass spectra. The obtained data indicated that the majority of the tested compounds exhibited good antibacterial activity over antifungal activity, particularly compounds 5j and 5b (having MIC values 12.5 μg/mL) showed a comparable effect to a standard antibacterial and antifungal agents.     

Green approach towards synthesis of substituted pyrazole-1,4-dihydro,9-oxa,1,2,6,8-tetrazacyclopentano[b]naphthalene-5-one derivatives as antimycobacterial agents

In the present communication, a simple and efficient synthesis of some new Pyrano-[2,3-c]-pyrazoles derivatives are described by the one-pot condensation of a mixture of 3-methyl-1-phenyl-1H-pyrazole-5(4H)-one, substituted heterylaldehydes and malononitriles in polyethylene glycol (PEG-400) as green reaction solvent, further reacted with substituted acetophenones in the presence of polyethylene glycol (PEG-400) to form naphthalene analogues. Synthesis of novel substituted naphthalene analogues libraries are currently of high interest. The chemical structures of newly synthesized compounds were confirmed by IR, ¹H NMR and Mass spectral analysis. In vitro antimycobacterial activities of newly synthesized compounds were investigated against Mycobacterium smegmatis, Mycobacterium pheli and Mycobacterium tuberculosis species. The result revealed that most of the compounds showed good to moderate Antimycobacterial activity.     

Efficient identification of fungal antimicrobial principles by tandem MS and NMR database

The continuous re-isolation of the known and non-applicable compounds that is time-consuming and wasting resources is still a critical problem in the discovery of bioactive entities from natural resources. To efficiently address the problem, high performance liquid chromatography-diode array detector-microfractionation (HPLC-DAD-microfractionation) guided by disk agar diffusion assay was developed, and the active compounds were further identified using the tandem mass spectrometry (MS/MS)-based molecular networking. Of 150 fungal strains screened, the methanolic extracts of Phoma herbarum PPM7487, Cryptosporiopsis ericae PPM7405, and Albifimbria verrucaria PPM945 exhibited potent antimicrobial activity against Candida albicans SC5314 and Cryptococcus neoformans H99 in the preliminary agar diffusion assay. The concept of OSMAC (one strain many compounds) was employed in the fungal cultures in order to enrich the diversity of the 2^nd metabolites in this study. HPLC coupled with off-line bioactivity-directed profiling of the extracts enabled a precise localization of the compounds responsible for the conspicuous antimicrobial activity. The purified active compounds were identified based mainly on MS/MS database, and further supported by ¹³C nuclear magnetic resonance (NMR) spectral data compared to the literatures. In addition to nineteen known compounds, a new trichothecene derivative 1, namely trichoverrin D, was isolated and identified through this protocol. The antifungal activities of all the pure isolates were evaluated, and the structure activity relationships were also inferred. This report has demonstrated the combination of HPLC microfractination and MS/MS coupled by NMR spectral dereplication for speeding up the antimicrobial natural products discovery process.