Synthesis,characterization and antibacterial activity of some new pyrazole based Schiff bases

In the present study a series of new Schiff bases were synthesized. All the synthesized compounds were characterized by IR, ¹H NMR, mass spectral and elemental analyses. Newly synthesized compounds were screened for their antibacterial (Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa) activity. The results revealed that, compounds 3f and 3c have exhibited significant biological activity against the tested microorganisms.     

Flavanone Glycosides,Triterpenes, Volatile Compounds and Antimicrobial Activity of Miconia minutiflora (Bonpl.) DC. (Melastomataceae)

Chemical composition of the essential oils and extracts and the antimicrobial activity of Miconia minutiflora were investigated. The flavanone glycosides, pinocembroside and pinocembrin-7-O-[4″,6″-HHDP]-β-D-glucose, were identified, along with other compounds that belong mainly to the triterpene class, besides the phenolics, gallic acid and methyl gallate. Sesquiterpenes and monoterpenes were the major compounds identified from the essential oils. Screening for antimicrobial activity from the methanolic extract of the leaves showed that the MIC and MMC values against the tested microorganisms ranged from 0.625 to 5 mg·mL⁻¹ and that the extract was active against microorganisms, Staphyloccocus aureus, Escherichia coli, and Bacillus cereus.     

Synthesis,Characterization, and Antimicrobial Properties of New 1,3,4‐Thiadiazoles Derived from Azo Dyes

Some new 1,3,4‐thiadiazoles derived from azo dyes were synthesized. Two different synthesis methods were used for these compounds: Esters pertaining to the azo dyes were converted into 1,3,4‐thiadiazoles, or benzothiazole ester derivatives were converted to 1,3,4‐thiadiazoles followed by the synthesis of azo dye derivatives. The desired products were successfully obtained using the latter method. The molecular structures of these compounds were characterized using spectroscopic methods such as FTIR, ¹H NMR, ¹³C NMR, and elemental analysis. Furthermore, antimicrobial activity was studied for the synthesized compounds. Compound 3e exhibited antimicrobial activity against three different microorganisms. Compounds 3a , 3b , and 3d had activity against two different microorganisms, while compound 3c showed activity against only one microorganism.     

Synthesis,characterization and antimicrobial evaluation of 2,5-disubstituted-4-thiazolidinone derivatives

In the present study novel derivatives of 4-thiazolidinone were prepared from biphenyl-4-carboxylic acid and evaluated for their in vitro antimicrobial activity against two Gram negative strains (Escherichia coli and Pseudomonas aeruginosa) and two Gram positive strains (Bacillus subtilis and Staphylococcus aureus) and fungal strain Candida albicans and Aspergillus niger. The newly synthesized compounds were characterized by IR, ¹H NMR and C, H, N analyses. The results revealed that all synthesized compounds have a significant biological activity against the tested microorganisms. Among the synthesized derivatives 4g (biphenyl-4-carboxylic acid [2-(3-bromophenyl)-5-(3-nitrobenzylidene)-4-oxo-thiazolidin-3-yl]-amide) and 4i (biphenyl-4-carboxylic acid [5-(3-bromobenzylidene)-2-(3-bromophenyl)-4-oxo-thiazolidin-3-yl]-amide) were found to be most effective antimicrobial compounds.     

Porphyrin–Schiff Base Conjugates Bearing Basic Amino Groups as Antimicrobial Phototherapeutic Agents

New porphyrin–Schiff base conjugates bearing one (6) and two (7) basic amino groups were synthesized by condensation between tetrapyrrolic macrocycle-containing amine functions and 4-(3-(N,N-dimethylamino)propoxy)benzaldehyde. This approach allowed us to easily obtain porphyrins substituted by positive charge precursor groups in aqueous media. These compounds showed the typical Soret and four Q absorption bands with red fluorescence emission (Φ_F ~ 0.12) in N,N-dimethylformamide. Porphyrins 6 and 7 photosensitized the generation of O₂(¹Δ_g) (Φ_Δ ~ 0.44) and the photo-oxidation of L-tryptophan. The decomposition of this amino acid was mainly mediated by a type II photoprocess. Moreover, the addition of KI strongly quenched the photodynamic action through a reaction with O₂(¹Δ_g) to produce iodine. The photodynamic inactivation capacity induced by porphyrins 6 and 7 was evaluated in Staphylococcus aureus, Escherichia coli, and Candida albicans. Furthermore, the photoinactivation of these microorganisms was improved using potentiation with iodide anions. These porphyrins containing basic aliphatic amino groups can be protonated in biological systems, which provides an amphiphilic character to the tetrapyrrolic macrocycle. This effect allows one to increase the interaction with the cell wall, thus improving photocytotoxic activity against microorganisms.     

Synthesis and antimicrobial screening of tetra Schiff bases of 1,2,4,5-tetra (5-amino-1,3,4-thiadiazole-2-yl)benzene

In the present study, novel tetra Schiff bases were synthesized by condensation of 1,2,4,5-tetra (5-amino-1,3,4-thiadiazole-2-yl)benzene with different aromatic aldehydes. The chemical structures were confirmed by means of IR, ¹H NMR, ¹³C NMR, and elemental analysis. All compounds were screened for antibacterial (Staphylococcus aureus ATCC-9144, Staphylococcus epidermidis ATCC-155, Micrococcus luteus ATCC-4698, Bacillus cereus ATCC-11778, Escherichia coli ATCC-25922, and Pseudomonas aeruginosa ATCC-2853) and antifungal (Aspergillus niger ATCC-9029 and Aspergillus fumigatus ATCC-46645) activities by paper disc diffusion technique. The minimum inhibitory concentrations (MICs) of the compounds were also determined by agar streak dilution method. Among the synthesized compounds 1,2,4,5-tetra[5-(4-nitrobenzylideneamino)-1,3,4-thiadiazole-2-yl]benzene 7 was found to be the most potent antimicrobial activity with MICs of 3.4, 2.1, 1.2, 2.0, 3.1, 2.4, 1.1, and 1.7 μg/mL against the above mentioned respective strains.     

Zeolite‐Supported One‐Pot Synthesis of Bis‐azetidinones under Microwave Irradiation

In an attempt to synthesize antibacterial agents effective against gram‐positive and gram‐negative bacteria, the efficient synthesis of novel bis‐azetidinones ( 3a–j ) has been established. Thus, cycloaddition reaction of substituted bis‐imines with chloroacetylchloride under microwave irradiation in the presence of zeolite yielded bis‐azetidinones ( 3a–j ). Structures of the synthesized compounds have been elucidated on the basis of their elemental analysis and spectral data (IR, ¹H‐NMR, ¹³C‐NMR, and mass spectra). The synthesized bis‐azetidinones were screened for their antibacterial activity against five microorganisms: Bacillus subtilis, Proteus vulgaris, Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli. They were found to exhibit good to moderate antibacterial activity.     

POCl3 catalyzed,one-step,solvent-free synthesis of some novel thieno[2,3-d]pyrimidin-4(3H)-one derivatives as antimicrobial agent

A POCl₃ catalyzed, efficient, one-step and solvent-free synthesis of novel thieno[2,3-d]pyrimidin-4(3H)-one derivatives from 2-amino-4,5-substitutedthiophene-3-carbonitrile has been developed under conventional heating and microwave irradiation. The formation of compounds was confirmed using elemental analysis and spectroscopic techniques like IR, NMR (¹H and ¹³C) and mass spectroscopy. Furthermore, they were screened in vitro to study their antimicrobial activity, which shows weak to moderate activity against all tested microorganisms.     

Synthesis, structural elucidation and biological activities of organotin(IV) derivatives of (E)-3-(4-methoxyphenyl)-2-(4-chlorophenyl)-2-propenoic acid

A new series of di- and tri-organotin(IV) compounds with the general formula R_4?n SnL _n , where R?=?Me (1,2), Et (3), n-Bu (4,5), n-Oct (6), Ph (7) and L?=?(E)-3-(4-methoxyphenyl)-2-(4-chlorophenyl)-2-propenoate, were synthesized by reaction of silver salt of ligand or ligand acid with diorganotin dichloride/oxide and triorganotin chloride in 2:1 and 1:1 molar ratio, respectively. These compounds were characterized by elemental analyses, FT-IR, multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR and mass spectrometry. The spectroscopic results revealed that all the diorganotin(IV) compounds possess trigonal bipyramidal structures in solution and octahedral geometry in the solid state around the tin atom. A linear polymeric trigonal bipyramidal structure in the solid state and a tetrahedral environment around the tin atom in non-coordinating solvents has been proposed for the triorganotin(IV) compounds. All synthesized compounds were tested in vitro against a number of microorganisms to assess their biocidal activity. These studies revealed that ligand acid and some of its organotin compounds show promising activity against different strains of bacteria and fungi but lowered than reference drugs.     

Synthesis and Biological Activity of Novel Furan/Thiophene and Piperazine‐Containing (Bis)1,2,4‐triazole Mannich Bases

Series of novel furan/thiophene and piperazine‐containing 1,2,4‐triazole Mannich bases and bis(1,2,4‐triazole) Mannich bases have been conveniently synthesized via Mannich reaction with triazole Schiff bases, various piperazine derivatives, and formaldehyde as intermediates in good yields. Their structures were characterized by melting points, ¹H NMR, ¹³C NMR, IR and elemental analysis. The preliminary bioassay showed that most compounds exhibited significant in vitro and in vivo fungicidal activity against several test plant fungi. Among 32 new compounds, the trifluoromethyl‐containing compounds showed superior activity than the methyl‐containing ones. Several compounds, such as F8 , F9 , F10 , G5 , H7 , H8 , I3 and I4 , were comparable with some commercial fungicides against different fungi during the present study and could be further structurally optimized. Meanwhile, several compounds showed good herbicidal activity against Brassica campestris at 100 µg/mL and KARI inhibitory activity at 200 µg/mL. However, compounds exhibited poor insecticidal activity against oriental armyworm at 200 µg/mL in the preliminary studies. The research results will provide useful information for the design and discovery of new agrochemicals with novel heterocyclic structures.     

Design and synthesis of some novel pyridothienopyrimidine derivatives and their biological evaluation as antimicrobial and anticancer agents targeting EGFR enzyme

A new series of pyridothienopyrimidine derivatives was designed and evaluated as antimicrobial and anticancer agents. The target compounds were synthesized starting with 3-aminothieno[2,3-b]pyridine-2-carboxamide derivative 1 which underwent cyclocondensation reaction with aromatic aldehydes to give the key intermediates 2a,b. By further treatment of 2a,b with various reagents, the target 2,4-disubstituted-pyrido[3′,2′:4,5]thieno[2,3-d]pyrimidines 3a,b–11a,b were obtained. To evaluate the antimicrobial activity of the new compounds, they were tested against five bacterial and five fungal strains. Compounds 6c, 8b, 9a and 9b revealed the most significant antimicrobial activity against the tested microorganisms with MIC values range (4–16 μg/mL). Also, compounds 2a,b–11a,b were screened for their in vitro cytotoxic activity against HepG-2 and MCF-7 cancer cell lines compared with doxorubicin and cisplatin as references drugs. Moreover, compounds (2b, 4a, 6a, 7b, 7c and 9a) which exhibited the most potent anticancer activity, were further subjected to EGFR^WT enzyme inhibition assay utilizing erlotinib as a standard drug. The compounds 6a, 7b, 7c and 9a which showed the most promising suppression effects were also evaluated as inhibitors against the mutant forms EGFR^L858R and EGFR^T790M. The 4-aminopyrazolone analogue 9a showed superior anticancer activity against both HepG-2 and MCF-7 cell lines (IC50 = 1.27, 10.80 μM, respectively) and more potent enzymatic inhibition activity against EGFR^WT and its mutant forms EGFR^L858R and EGFR^T790M than that obtained by erlotinib (IC₅₀ = 0.021, 0.053, 0.081 µM, respectively, IC_50erlotinib; 0.027, 0.069, 0.550 µM, respectively). Finally, the molecular docking study showed good binding patterns of the most active compounds with the prospective target EGFR^WT.     

Synthesis of bifunctional thieno[3,2-c]pyrazole,pyrazolothieno[2,3-d]pyrimidin derivatives and their antimicrobial activities

A simple and convenient route was performed for the synthesis of some new heterocyclic compounds based on thieno[3,2-c]pyrazole derivative for antimicrobial evaluation. The key intermediate, 5-amino-3-methyl-1-phenyl-1H-thieno[3,2-c]pyrazole-6-carbohydrazide 3, was prepared by Gewald’s synthesis of Ethyl 5-amino-3-methyl-1-phenyl-1H-thieno[3,2-c]pyrazole-6-carboxylate 2. This intermediate reacted with various reagents to afford different fused and polyfunctional substituted. The structures of these compounds were confirmed by elemental analysis, IR, ¹H NMR, ¹³C NMR and mass spectral data. All the new synthesized compounds were screened for various microorganisms such as Aspergillus fumigatus; Geotrichum candidum; Syncephalastrum racemosum (Fungus); Candida albicans (Yeast fungus); Staphylococcus aureus; Bacillus subtilis (as Gram-positive bacteria); Pseudomonas aeruginosa and Escherichia coli (as Gram-negative bacteria) by the disc diffusion method. In general, the novel synthesized compounds possessed moderate to high antimicrobial activity against the previously mentioned microorganisms.     

Design,synthesis, biological evaluation and in silico studies of N-(pyridin-2-yl)-benzamides derivatives as quorum sensing inhibitors

The emergence of bacterial resistance against chemical treatment is a big threat to the efficacy of bacterial infection treatment. One of the major reasons for resistance to antimicrobial agents is growth of microorganisms in biofilm. An alternative treatment by developing novel anti-biofilm agents had led to the concept of quorum sensing (QS) inhibition, which primarily targets QS signaling system by disrupting cell-cell communication. Therefore, this study focuses to develop novel antimicrobial agents which work by QS inhibition and act as anti-biofilm agents against Bacillus Subtilis and Pseudomonas Aeruginosa. In this work, a natural product-like scaffolds from Asinex library were screened and N-pyridin-2-yl-benzamide moiety was chosen to design and synthesize. Synthesized compounds were evaluated for potential anti-biofilm activity for the aforesaid microorganisms and also checked for cell viability assay, where two potent compounds 3a and 3c showed their static biofilm activity to ∼59% and ∼58% at 100 μM, respectively against Bacillus subtilis. These synthesized compounds were investigated for physicochemical parameters and binding mode prediction through molecular modelling tools. The interactions and stability of these compounds showed better affinity towards TasA and LasR proteins from Bacillus subtilis and Pseudomonas aeruginosa, respectively. Furthermore, molecular dynamic simulation for 100 ns was executed in order to appreciate the stability of the protein and ligand complex. The overall results promised that N-pyridin-2-yl-benzamide derivatives can be discovered as a lead in developing potent anti-quorum sensing agents against various bacteria.     

Synthesis and pharmacological evaluation of 9(10H)-acridone bearing 1,3,4-oxadiazole derivatives as antimicrobial agents

In the present study a new acridone derivatives were synthesized. The newly synthesized compounds were characterized by IR, NMR and C, H, N, S analyses. All newly synthesized compounds were screened for their antibacterial (Staphylococcus aureus, Streptococcus viridans and Escherichia coil) and antifungal (Gibberela, Cercospora arachidicola, Physolospora piricola and Fusarium oxysporum) studies. The results revealed that all synthesized compounds have a significant biological activity against the tested microorganisms.     

Synthesis of hydrazone derivatives of benzofuran and their antibacterial and antifungal activity

A series of benzofuran hydrazones 6a–6n were synthesized from benzofuran aldehyde and substituted aromatic hydrazides 5a–5n. Structures of all compounds were confimed by IR, ¹H and ¹³C NMR, and Mass spectral data. These compounds were evaluated for their antibacterial activity against gram-negative bacteria (Escherichia coli, –ve), gram-positive bacteria (Bacillus Subtillis, +ve), and antifungal activity against Candida albicans. All compounds demonstrated considerable activity against bacteria and fungi.     

Design,synthesis and biological evaluation of novel isoniazid hybrids

We herein report the design and synthesis of novel isoniazid derivatives. Isoniazid derived Schiff bases (3 a-d) were subjected to cyclization with acetic anhydride and sulphuric acid to yield the 5′-substituted-3′-acetyl-5-(pyridin-4-yl)-3H-spiro[indole-3, 2-[1′, 3′, 4’]oxadiazol]-2′-yl acetates (4 a-d) and 8′-substituted-3’-(pyridin-4-yl)[1′,3′,4’]oxadiazino [6,5-b]indoles (5 a-d) respectively. The advantages of spectral methods were used for the confirmation of the structure of all the newly synthesized hybrid molecules. Further, these compounds were evaluated for their antibacterial activity against B. Subtilis, S. aureus, E. coli & S. typhi, antifungal activity against C. albicans, C. oxysporum, A. Flavus & A. niger, and antimycobacterial activity against M. tuberculosis. Amongst, the compounds 4b, 4c and 5c showed excellent inhibitory activity against tested microorganisms. Also, the DNA cleavage activity of selected compounds was carried out by the AGE method.     

Synthesis and antifungal activity of d-glucopyranosyl ureas and d-glucofurano-imidazolidine-2-ones

A series of N-β-d-glucopyranosyl-N’-substituted phenyl ureas were synthesized by reaction of glucosyl isocyanate with arylamines and glycosamine with aryl isocyanates, and a series of d-glucofurano-imidazolidine-2-ones were obtained via deacetylation of glycosylureas. Although some of the compounds have already been described, most were prepared for the first time in this work. The structures of all the compounds synthesized were confirmed by IR, ¹H NMR, and, in part, by ¹³C NMR. Antifungal activity of the title compounds was determined against four kinds of plant pathogenic fungi, Sclerotinia sclerotiorum, Fusarium graminearum, Fusarium oxysporum, and Bipolaris maydis. Preliminary bioassay indicates that most of glycosylureas had some activity against S. sclerotiorum; for some, the antifungal activity was strong. However, most of the imidazolidine-2-ones had weak antifungal activity.     

Synthesis,antimicrobial activity and QSAR studies of 2,5-disubstituted benzoxazoles

In this study, a new series of 2,5-disubstituted benzoxazoles was synthesized and their structures were elucidated by elemental analysis, MASS, ¹H-NMR, ¹³C-NMR and IR spectral data. Newly and previously synthesized 2,5-disubstituted benzoxazole derivatives were evaluated for antibacterial and antifungal activity against standard strains and their drug-resistant isolates. Microbiological results showed that the compounds presented a large spectrum of activity having MIC values of 250–7.8 µg mL^?1 against the tested microorganisms. Among the newly synthesized derivatives 3–22, compound 11 was the most active against Candida krusei out of all; however, it was one dilution less potent than standard drug fluconazole. In addition, all the new and previous compounds were more active than standard drugs ampicillin trihydrate and rifampicin against Pseudomonas aeruginosa and its gentamicin-resistant isolate. The 2D-QSAR (Quantitative Structure–Activity Relationship) analysis of a set of newly and previously synthesized benzoxazoles tested for growth inhibitory activity against methicillin-resistant Staphylococcus aureus (MRSA) was also performed by using multivariable regression analysis. The activity contributions for substituent effects of these compounds were determined from the correlation equation for predictions of the lead optimization.     

Synthesis,characterization, biological applications,and molecular docking studies of amino-phenol-derived mixed-ligand complexes with Fe(III), Cr(III), and La(III) ions

A new series of Fe(III), Cr(III), and La(III) mixed-ligand complexes, resulting from the interaction of 2-aminophenol with 2-hydroxy acetophenone (HL₁) as primary ligand and L- histidine (L₂) as a secondary ligand, has been investigated using various physicochemical studies such as elemental analyses, molar conductivity, magnetic moment, infrared, UV/Vis, ¹H NMR, and mass spectroscopic techniques. The microanalytical results indicate that the mixed ligand complexes were designed in a 1:1:1 M ratio. The electronic spectral data indicated that all the synthesized complexes have an octahedral structure. The disc diffusion assay was used to determine the disc inhibition zone (IZ, mm) and minimum inhibitory concentration (MIC, g/mL) of the investigated compounds against the growth of the pathogenic bacterial strains S. aureus, E. faecalis, P. aeruginosa, Klebsiella sp., and E. coli. The MTT test was used to determine the cytotoxicity of these reported compounds against the human hepatocellular liver cancer (HEPG-2) cell lines. The molecular docking study for the compounds against the EGFR tyrosine kinase receptor (PDB code: 1 M17) was conducted to examine the interactions in protein–ligand complexes. Furthermore, the biological activity of the ligand was investigated using quantitative structure–activity relationship studies (QSAR).     

Synthesis ofN1‐3‐{(4‐Substituted aryl‐3‐chloro‐2‐oxo‐azetidine)‐iminocarbamyl}‐propyl‐6‐nitroindazole Derivatives and Their Biological Significance

Synthesis ofN¹‐3‐{(4‐substitute daryl‐3‐chloro‐2‐oxo‐azetidine)‐iminocarbamyl}‐propyl‐6‐nitroindazole 4a – 4s was conducted by a conventional method. All the compounds were synthesized and characterized by IR, ¹H NMR, ¹³C NMR, FAB‐Mass techniques and chemical methods. All the final synthesized compounds were evaluated for their antimicrobial activity and antitubercular activity with MIC values against some selected microorganisms.