Synthesis, biological evaluation of 5-carbomethoxymethyl-7-hydroxy-2-pentylchromone, 5-carboethoxymethyl-4',7-dihydroxyflavone and their analogues

In this letter, we describe the first synthesis of two recently isolated flavones 5-carbomethoxymethyl-7-hydroxy-2-pentylchromone (3a), 5-carboethoxymethyl-4',7-dihydroxyflavone (3b) and their derivatives (3c-t), evaluated for their antimicrobial, antioxidant and anticancer activities. Most of the synthesized compounds exhibited antimicrobial activity against the tested microbial strains and some of these compounds were found to be more potent as compared to the standard drugs like neomycin and luteolin. Interestingly, some of these synthesized compounds also showed moderate antioxidant property.     

Design, synthesis and evaluation of clinafloxacin triazole hybrids as a new type of antibacterial and antifungal agents

A series of clinafloxacin triazole hybrids as a new type of antibacterial and antifungal agents were synthesized for the first time and screened for their antimicrobial efficacy against four Gram-positive bacteria, four Gram-negative bacteria and two fungi by two fold serial dilution technique. The bioactive assay indicated that most of the target compounds displayed broad antimicrobial spectrum and good antibacterial and antifungal activities with low MIC values ranging from 0.25 to 2μg/mL against all the tested strains which exhibited comparable or even better efficiency in comparison with the reference drugs Chloramphenicol, Clinafloxacin and Fluconazole, respectively. Notably, some synthesized clinafloxacin triazoles showed stronger efficacy against methicillin-resistant Staphylococcus aureus than their parent Clinafloxacin.     

Synthesis and biological evaluation of novel 2,4,6-triazine derivatives as antimicrobial agents

A series of 2,4,6-trisubstituted [1,3,5]triazines were synthesized and evaluated for their antimicrobial activity against two representative Gram-positive, Gram-negative bacteria and two fungi. Biological data revealed that among all the compounds screened, compounds 3f, 3g, 3h, 3i, 3m, 3o and 3p found to have promising antimicrobial activity against all the selected pathogenic bacteria and fungi. Out of the synthesized compounds seven analogues have shown MIC in the range of 6.25-12.5 μg/mL. These compounds were generally nontoxic and may prove useful as antimicrobial agents.     

Microwave-assisted synthesis and evaluation of indole based benzofuran scaffolds as antimicrobial and antioxidant agents

A novel series of indole based benzofuran derivatives has been synthesized under microwave irradiation and conventional conditions. The structures of the compounds were established on the basis of ¹HNMR, ¹³C NMR, IR and mass spectral data. The analogues were evaluated for their in vitro antimicrobial activity against two gram-positive bacteria, two gram-negative bacteria and two fungal strains. The same series was screened for in vitro antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH). Most of the title compounds exhibited promising antimicrobial and antioxidant activities.     

Design,synthesis, characterization,antimicrobial evaluation and molecular modeling studies of some dehydroacetic acid-chalcone-1,2,3-triazole hybrids

A series of new dehydroacetic acid chalcone-1,2,3-triazole hybrids as potential antimicrobial agents was designed, synthesized and characterized by FTIR, NMR and HRMS spectral techniques. All the synthesized compounds were screened in vitro against four bacterial strains (Staphylococcus epidermidis, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa) and two fungal strains (Aspergillus niger and Candida albicans). The antimicrobial results indicated that some of the compounds showed remarkable activities comparable to the standard drugs. Most of the compounds exhibited better efficacy compared to the DHA, which is itself an antimicrobial agent. The synergistic effect in biological activity was observed when DHA, chalcone and 1,2,3-triazole are conjugated. The molecular modeling studies of compound 5j into E. coli topoisomerase II DNA gyrase B were also performed.     

Synthesis of coumarin appended pyrazolyl-1,3,4-oxadiazoles and pyrazolyl-1,3,4-thiadiazoles: Evaluation of their in vitro antimicrobial and antioxidant activities and molecular docking studies

A series of semicarbazones, thiocarbazones, 1,3,4-oxadiazoles, and 1,3,4-thiadiazoles bearing coumarin and pyrazole moiety have been synthesized. The new synthesized compounds were screened in vitro for their antimicrobial and antioxidant activities. Preliminary studies showed that among the synthesized new compounds, chloro-substituted thiosemicarbazone showed excellent activities against all tested organisms; at the same time, methyl substituted thiosemicarbazone showed greater activity against E. coli. Chloro-substituted 1,3,4-oxadiazole and 1,3,4-thiadiazole demonstrated greater DPPH and hydroxyl radical scavenging abilities. Molecular docking studies indicate that 1,3,4-oxadiazoles and 1,3,4-thiadiazoles manifest better interaction with CAT (catalase) and GPx (glutathione peroxidase) than that with SOD (superoxide dismutase). Studies on the antimicrobial and antioxidant activities of the synthesized compounds compared with those of their starting compounds are discussed.     

Studies on synthetic and structural characterization of new fluorine substituted phthalides of pharmaceutical interest

An efficient and economical synthesis of some new fluorine substituted phthalides was accomplished from two γ-keto acids, 2-(4-fluorobenzoyl)benzoic acid and 2-(3,5-dinitro-4-flurobenzoyl)benzoic acid. Each acid was reacted with various phenolic compounds in presence of catalytic quantity of concentrated sulphuric acid to get the phthalides. The structures of the synthesized compounds were established on the basis of their elemental analysis, spectral data and chemical reactions. Some of the synthesized phthalides exhibited antibacterial and antifungal activity on antimicrobial screening against human pathogenic bacteria and fungi.     

Conventional and microwave assisted synthesis of 2-oxo-4-substituted aryl-azetidine derivatives of benzotriazole: a new class of biological compounds

We report herein the synthesis and biological activity of a new kind of azetidinone derivatives of benzotriazole. The reaction was carried out by both conventional and microwave methods. The chemical structures of all the synthesized compounds were deduced according to FTIR, (1)H NMR, (13)C NMR and FAB-mass spectral along with microanalytical data. All the synthesized compounds of series 5a-i were evaluated for their antitubercular activity against Mycobacterium tuberculosis H37RV and antimicrobial activity against some selected microorganism. Unexpectedly, some azetidinone derivatives of benzotriazole displayed better activities.     

Studies on synthetic and structural characterization of new fluorine substituted phthalides of pharmaceutical interest

An efficient and economical synthesis of some new fluorine substituted phthalides was accomplished from two γ-keto acids, 2-(4-fluorobenzoyl)benzoic acid and 2-(3,5-dinitro-4-flurobenzoyl)benzoic acid. Each acid was reacted with various phenolic compounds in presence of catalytic quantity of concentrated sulphuric acid to get the phthalides. The structures of the synthesized compounds were established on the basis of their elemental analysis, spectral data and chemical reactions. Some of the synthesized phthalides exhibited antibacterial and antifungal activity on antimicrobial screening against human pathogenic bacteria and fungi.     

Synthesis of short cationic antimicrobial peptidomimetics containing arginine analogues

Worldwide efforts are underway to develop new antimicrobial agents against bacterial resistance. To identify new compounds with a good antimicrobial profile, we designed and synthesized two series of small cationic antimicrobial peptidomimetics (1–8) containing unusual arginine mimetics (to introduce cationic charges) and several aromatic amino acids (bulky moieties to improve lipophilicity). Both series were screened for in vitro antibacterial activity against a representative panel of Gram‐positive (Staphylococcus aureus and Staphylococcus epidermidis) and Gram‐negative (Escherichia coli and Klebsiella pneumoniae) bacterial strains, and Candida albicans. The biological screening showed that peptidomimetics containing tryptophan residues are endowed with the best antimicrobial activity against S. aureus and S. epidermidis in respect to the other synthesized derivatives (MIC values range 7.5–50 µg/ml). Moreover, small antimicrobial peptidomimetics derivatives 2 and 5 showed an appreciable activity against the tested Gram‐negative bacteria and C. albicans. The most active compounds (1–2 and 5–6) have been tested against Gram‐positive established biofilm, too. Results showed that the biofilm inhibitory concentration values of these compounds were never up to 200 µg/ml. The replacement of tryptophan with phenylalanine or tyrosine resulted in considerable loss of the antibacterial action (compounds 3–4 and 7–8) against both Gram‐positive and Gram‐negative bacterial strains. Furthermore, by evaluating hemolytic activity, the synthesized compounds did not reveal cytotoxic activities, except for compound 5. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Omega-pyridiniumalkylethers of steroidal phenols: new compounds with potent antibacterial and antiproliferative activities

Novel omega-pyridiniumalkylethers of two steroidal phenols were synthesized as compounds with potential antimicrobial activity. 3-Hydroxy-estra-1,3,5(10)-triene-17-one and 1-hydroxy-4-methyl-estra-1,3,5(10)-triene-17-one were reacted with omega,omega'-dibromoalkanes to omega-bromoalkoxy-estra-1,3,5(10)-trienes followed by reaction with pyridine to obtain the desired steroidal omega-pyridiniumalkoxy compounds as bromides. Their antimicrobial activity against strains of multiresistant Staphylococcus aureus (MRSA), a vancomycin resistant Enterococcus faecalis and fast growing mycobacteria depends clearly on the length of the alkyl chain. A strong broadband activity has been found for the compounds with eight or 10 C-atoms; in some cases better than ciprofloxacin or cetylpyridinium salts. In addition, the antiproliferative and cytotoxic activity depends on the chain length, too. The differentiation between antibacterial and cytotoxic activity is better for the steroid hybrid molecules than the cetylpyridinium salts. These new compounds can serve as lead compounds for further optimization.     

Synthesis and Antimicrobial Evaluation of Novel Chiral 2‐Amino‐4,5,6,7‐tetrahydrothieno[2,3‐c]pyridine Derivatives

New N‐substituted‐2‐amino‐4,5,6,7‐tetrahydrothieno[2,3‐c]pyridine derivatives were synthesized employing a convenient one‐pot three‐component method and their structures were characterized by ¹H‐NMR and single crystal X‐ray diffraction analysis. All the synthesized compounds were in vitro screened for antimicrobial activity against Gram‐positive (Sarcina lutea) and Gram‐negative bacteria (Escherichia coli). In this work, we introduced a chiral residue on the tetrahydropyridine nitrogen, the hitherto the less investigated position on this pharmacophore in order to explore the effect. The antibacterial results showed that the synthesized compounds were active only against Gram‐positive bacteria and the (R)‐enantiomers displayed a greater antimicrobial potency than their (S)‐counterparts. The structure–activity relationship here investigated may provide some interesting clues for future development of tetrahydrothienopyridine derivatives with higher antimicrobial activity.     

Synthesis and antimicrobial activity of new 1,2,4-triazole and 1,3,4-thiadiazole derivatives

In this study, new 3-[(1(2H)-phthalazinone-2-yl(methyl/ethyl]-4-aryl-1,2,4-triazole-5-thione and 2-[[1(2H)-phthalazinone-2-yl]methyl/ethyl]-5-arylamino-1,3,4-thiadiazole derivatives were synthesized. Antimicrobial properties of the title compounds were investigated against two Gram (+) bacteria (S. aureus, B. subtilis), two Gram ( ? ) bacteria (P. aeruginosa, E. coli) and two yeast-like fungi (C. albicans and C. parapsilosis) using the broth microdilution method. Generally the compounds were found to be active against B. subtilis and the fungi. Derivatives carrying a 1,3,4-thiadiazole ring generally showed higher antimicrobial activity against B. subtilis and the fungi when compared to other synthesized compounds.     

Synthesis and antimicrobial activity of 2-fluorophenyl-4,6-disubstituted [1,3,5]triazines

A series of 2-fluorophenyl-4,6-disubstituted [1,3,5]triazines (1) and (2) were synthesized and evaluated for their antimicrobial activity against three representative gram-positive bacteria and two fungi. The structure–activity relationship (SAR) demonstrates that the 3- or 4-fluorophenyl component attached directly to the triazine ring was essential for activity. Of these compounds, 14, 15, and 25 demonstrated significant activity against all selected organisms compared to control. These compounds were generally nontoxic and may prove useful as antimicrobial agents.     

Synthesis and biological evaluation of novel N-acyl substituted quinolin-2(1H)-one derivatives as potential antimicrobial agents

A series of novel N-acyl substituted quinolin-2(1H)-one derivatives were synthesized and screened in vitro for their antibacterial and antifungal activities by disc diffusion method. All the compounds exhibited moderate to good antimicrobial activities, some of these compounds displayed comparable or better antibacterial or antifungal activities against some tested strains compared to the reference drugs Streptomycin and Fluconazole.     

Synthesis and biological evaluation of novel 3-substituted amino-4-hydroxylcoumarin derivatives as chitin synthase inhibitors and antifungal agents

A series of novel 3-substituted amino-4-hydroxycoumarin derivatives have been designed and synthesized as chitin synthase (CHS) inhibitors. All the synthesized compounds have been screened for their CHS inhibition activity and antimicrobial activity in vitro. The enzymatic assay indicated that most of the compounds have good inhibitory activity against CHS, in which compound 6o with IC₅₀ of 0.10?mmol/L had stronger activity than that of polyoxins B, which acts as control drug with IC₅₀ of 0.18?mmol/L. As far as the antifungal activity is concerned, most of the compounds possessed moderate to excellent activity against some representative pathogenic fungi. Especially, compound 6b was found to be the most potent agent against Cryptococcus neoformans with minimal inhibitory concentration (MIC) of 4?μg/mL. Moreover, the results of antibacterial screening showed that these compounds have negligible actions to some tested bacteria. Therefore, these compounds would be promising to develop selective antifungal agents.     

Synthesis and antimicrobial studies of silver N-heterocyclic carbene complexes bearing a methyl benzoate substituent

Due to the properties of silver as an antimicrobial, our research group has synthesized many different silver carbene complexes. Two new silver N-heterocyclic carbene complexes derived from 4,5-dichloroimidazole and theobromine bearing methyl benzoate substituents were synthesized by in situ carbene formation using silver acetate as the base in the reaction. The new compounds were fully characterized by several methods including NMR spectroscopy and X-ray crystallography. Preliminary antimicrobial efficacy studies against Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli were conducted. The results of this study demonstrated antimicrobial efficacy of the two complexes comparable to silver nitrate, showing their potential for use in the treatment of bacterial infections.     

Synthesis,antimicrobial and antiviral activity of substituted benzimidazoles

In the present study we have synthesized (4-nitrophenyl)-[2-(substituted phenyl)-benzoimidazol-1-yl]-methanones, (2-bromophenyl)-[2-(substituted phenyl)-benzoimidazol-1-yl]-methanone analogues (1–14) and evaluated them for their antimicrobial and antiviral potential. The results of antimicrobial screening indicated that none of the synthesized compounds were effective against the tested bacterial strains. Compounds 3, 11, 13 and compounds 5, 11, 12 were found to be active against Aspergillus niger and Candida albicans respectively, and may be further developed as antifungal agents. Furthermore, evaluation against a panel of different viruses pointed out the selective activity of compounds 5 and 6 against vaccinia virus and Coxsackie virus B4.     

Synthesis and antimicrobial activity of new 1,2,4-triazole and 1,3,4-thiadiazole derivatives

In this study, new 3-[(1(2H)-phthalazinone-2-yl(methyl/ethyl]-4-aryl-1,2,4-triazole-5-thione and 2-[[1(2H)-phthalazinone-2-yl]methyl/ethyl]-5-arylamino-1,3,4-thiadiazole derivatives were synthesized. Antimicrobial properties of the title compounds were investigated against two Gram (+) bacteria (S. aureus, B. subtilis), two Gram ( - ) bacteria (P. aeruginosa, E. coli) and two yeast-like fungi (C. albicans and C. parapsilosis) using the broth microdilution method. Generally the compounds were found to be active against B. subtilis and the fungi. Derivatives carrying a 1,3,4-thiadiazole ring generally showed higher antimicrobial activity against B. subtilis and the fungi when compared to other synthesized compounds.     

Synthesis and biological evaluation of some novel thiazole substituted benzotriazole derivatives

A series of novel hybrid molecules 4a-y containing thiazole and benzotriazole templates were designed and synthesized. The structures of the synthesized compounds were elucidated by IR, (1)H NMR, (13)C NMR and mass spectral data. All the synthesized compounds were tested for their antimicrobial activity (zone of inhibition) against Gram-positive, Gram-negative strains of bacteria as well as fungal strains. After that minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs) and minimum fungicidal concentrations (MFCs) of all the synthesized compounds were determined. The investigation of antimicrobial screening data revealed that most of the tested compounds showed moderate to good microbial inhibitions.