Green synthesis and characterization of monodispersed silver nanoparticles obtained using oak fruit bark extract and their antibacterial activity

Green synthesis of silver nanoparticles (Ag NPs) has been achieved using oak fruit bark extract as a reducing, capping and stabilizing agent. The biosynthesized Ag NPs were characterized using various techniques. UV–visible spectrum of prepared silver colloidal solution showed absorption maximum at 433 nm. X‐ray diffraction and transmission electron microscopy analysis revealed that Ag NPs have a face‐centred cubic structure being spherical in shape with an average particle size of 20–25 nm. The toxicity of the Ag NPs was tested on bacterial species such as Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli by comparison based on diameter of inhibition zone in disc diffusion tests and minimum inhibitory concentration and minimum bactericidal concentration of NPs dispersed in liquid cultures. The antimicrobial activity of Ag NPs was greater towards Gram‐positive bacteria (S. aureus and B. subtilis) compared to Gram‐negative bacteria as determined using standard Kirby–Bauer disc diffusion assay and serial dilution. Copyright © 2016 John Wiley & Sons, Ltd.     

Silver nanoparticle‐decorated multiwalled carbon nanotube/pramipexole nanocomposite: Synthesis,characterization and application as an antibacterial agent

This work reports the preparation of multiwalled carbon nanotube/pramipexole/Ag (CNT/pra/Ag) as a novel antibacterial agent, in which pramipexole groups are utilized as linkers to secure Ag nanoparticles to carbon nanotube surfaces without agglomeration. The resulting CNT/pra/Ag sample was characterized by performing transmission and scanning electron microscopy, wavelength‐ and energy‐dispersive X‐ray, X‐ray diffraction, Fourier transform infrared, inductively coupled plasma and Raman measurements. Using this approach, monodisperse spherical Ag nanoparticles in CNT/pra/Ag have narrow size distributions with average diameters of ca 3–8 nm. The antibacterial activity of CNT/pra/Ag was investigated against bacterial species Staphylococcus aureus , methicillin‐resistant S. aureus , Pseudomonas aeruginosa and Escherichia coli using the paper‐disc diffusion method and by determining the minimal inhibitory concentration. CNT/pra/Ag showed better inhibitory activity towards Gram‐positive bacteria than Gram‐negative bacteria in this study, which indicates its potential as an antibacterial material for laboratory and medical purposes.     

Antimicrobial and Antimalarial Activity of Novel Synthetic Mononuclear Ruthenium(II) Compounds

The present work was aimed that the two Ruthenium compounds namely, [Ru(A)₂(B)]Cl₂, where A = 1,10‐phenanthroline; B = 2‐NO₂‐phenyl thiosemicarbazone (Compound R₁)/2‐OH‐phenyl thiosemicarbazone (Compound R₂) have been tested for antibacterial activity at the concentrations of 1 mg/mL against various Gram‐Positive organisms (Lactobacillus, Staphylococcus pyrogenes, Bacillus subtilis, Staphylococcus aureus & Bacillus megatarium) and Gram‐Negative organisms (Pseudomonas aeruginosa, Escherichia coli, Proteus vulgaris, Enterobacter aerogenes, Salmonella paratyphi, Klebsiella pneumonia & Proteus mirabilis). The compounds were also tested for antifungal activity against Aspergillus clavatus, Aspergillus niger, Colletotrichum & Penicillium notatum by using agar diffusion assay and antimalarial activity against Plasmodium falciparum (Strain 3D7) using MTT assay. The results concluded that the compound R₁ exhibited significant antibacterial activity than R₂ against Gram‐Negative bacteria with zones of inhibition ranging from 15‐20 mm. and mild antibacterial activity against Gram‐Positive bacteria in comparison to tetracycline, streptomycin and rifampicin. These complexes were found to have moderate antifungal activity with no activity was however observed against Aspergillus niger. The compound, R₁ exhibited antimalarial activity at 10 μg/mL, whereas R₂ did not show antimalarial activity upto 50 μg/mL. Sensitivity to the compounds was greatest in the gram‐negative bacteria, followed by the gram‐positive bacteria and fungi.     

Antibacterial and antibiofilm activity of nanochelating based silver nanoparticles against several nosocomial pathogens

The emergence of multi‐drug resistant (MDR) bacteria and dynamic pattern of infectious diseases demand to develop alternative and more effective therapeutic strategies. Silver nanoparticles (AgNPs) are among the most widely commercialized engineered nanomaterials, because of their unique properties and increasing use for various applications in nanomedicine. This study for the first time aimed to evaluate the antibacterial and antibiofilm activities of newly synthesized nanochelating based AgNPs against several Gram‐positive and ‐negative nosocomial pathogens. Nanochelating technology was used to design and synthesize the AgNPs. The cytotoxicity was tested in human cell line using the MTT assay. AgNPs minimal inhibitory concentration (MIC) was determined by standard broth microdilution. Antibiofilm activity was assayed by a microtiter‐plate screening method. The two synthesized AgNPs including AgNPs (A) with the size of about 20‐25 nm, and AgNPs (B) with 30‐35 nm were tested against Staphylococcus aureus, Staphylococcus epidermidis, Acinetobacter baumannii, and Pseudomonas aeruginosa. AgNPs exhibited higher antibacterial activity against Gram‐positive strains. AgNPs were found to significantly inhibit the biofilm formation of tested strains in concentration 0.01 to 10 mg/mL. AgNPs (A) showed significant effective antibiofilm activity compared to AgNPs (B). In summary, our results showed the promising antibacterial and antibiofilm activity of our new nanochelating based synthesized AgNPs against several nosocomial pathogens.     

Synthesis and Characterization of Some New Heteroaromatic Compounds Having Chirality Adjacent to a 1,3,4‐Thiadiazole Moiety and Their Antimicrobial Activities

Through a cyclization reaction of 2‐phenylbutyric acid with N‐ phenylthiosemicarbazide and POCl₃, novel 1,3,4‐thiadiazole derivatives were synthesized. Their structures were confirmed using IR, ¹H NMR, and ¹³C NMR spectroscopies and elemental analysis. The antibacterial activities of the obtained 1,3,4‐thiadiazole derivatives were tested against Gram‐negative bacteria (Salmonella enteritidis , Salmonella typhimurium , Enterobacter aerogenes , Salmonella infantis , Salmonella kentucky , and Escherichia coli ) and Gram‐positive bacteria (Staphylococcus aureus , Bacillus subtilis , and Enterococcus durans ) using a disk diffusion method. Moreover, an antifungal activity experiment was performed against Candida albicans using the disk diffusion method. It was observed that the synthesized 1,3,4‐thiadiazole derivatives exhibited effective antimicrobial activity against S. aureus , E. coli , and C. albicans . Based on these results, the 1,3,4‐thiadiazole derivatives can be considered as a source of bioactive agents for pharmacological and medicinal applications.     

Physiochemical properties and novel biological applications of Callistemon viminalis‐mediated α‐Cr2O3 nanoparticles

We report an eco‐friendly synthesis of α‐Cr₂O₃ nanoparticles (NPs) using Callistemon viminalis (Bottle Brush) flower extracts as an efficient reducing and capping agent. NPs of sizes 15 nm and 17 nm were synthesized by annealing them at 400°C and 500°C, respectively, which were characterized by X‐ray diffraction, UV–Vis, Fourier transform‐infrared, high‐resolution‐transmission electron microscopy/scanning electron microscopy, SAED, energy‐dispersive X‐ray spectroscopy and SQUID. Microplate‐based assay was used for examining antibacterial potential against 12 pathogenic bacterial strains, and their minimum inhibitory concentrations were calculated. MTT cytotoxic assay was accomplished on Leishmania tropica amastigotes and promastigotes, which revealed IC₅₀ values of 44 μg/ml and 10.56 μg/ml, respectively. An IC₅₀ value of 46.32 μg/ml was obtained for HepG2 cancer cells. Enzyme inhibition studies indicated good acetylcholinesterase, moderate butyrylcholinesterase and low alpha‐glucosidase inhibition. Hemolytic assay indicated hemocompatibility at low concentration. In addition, good DPPH radical scavenging and moderate reducing power and total antioxidant potential was revealed by α‐Cr₂O₃ NPs.     

Highly Efficient One‐Pot Three‐Component Synthesis and Antimicrobial Activity of 2‐Amino‐4H‐chromene Derivatives

A remarkably efficient three‐component reaction to synthesize 2‐amino‐4H‐chromenes derivatives from malononitrile, various aromatic aldehydes, and orcinol was described at room temperature in CH₂Cl₂ in the presence of catalytic amount of triethylamine. In a facile one‐pot procedure, excellent yields of products were achieved in less than 1 h. Some of the synthesized 2‐amino‐4H‐chromenes derivatives demonstrated potent antibacterial activities against Gram‐positive bacteria including Staphylococcus aureus and Bacillus anthracis, indicated by disk method, minimum inhibitory concentration, and minimum bactericidal concentration approaches. However, none of the tested compounds expressed any antibacterial activities against Enterococcus faecalis and Gram‐negative bacteria.     

Synthesis of novel 2,3‐disubstituted quinazolin‐4(3H)‐one derivatives containing hydrazone skeleton as potent urease inhibitors and their antimicrobial activities

A new series of quinazolinones containing hydrazone moiety were synthesized, and their inhibitory activities on urease were assessed in vitro. Most of the compounds exhibited potent urease inhibitory activity. Among the synthesized compounds, molecule 4a bearing furan ring has the best inhibitory effect against urease with IC₅₀ = 2.90 ± 0.11 μg/mL. Compounds 4f , 4g , 4h , 4i , and 4j have hydroxy group on phenyl ring. Compound 4i is the most active inhibitor among these compounds with IC₅₀ = 5.01 ± 0.10 μg/mL, which has 3‐Cl and 4‐Br on phenyl ring. Also, newly synthesized compounds had been tested for their antimicrobial effects against three of Gram‐positive bacteria (Bacillus cereus 702 Roma, Staphylococcus aureus ATCC 25923, and Streptococcus pyogenes ATCC 19615) and three of Gram‐negative bacteria (Escherichia coli ATCC 25922, Proteus vulgaris ATCC 13315, and Pseudomonas aeruginosa ATCC 27853). Antimicrobial activity results show that compounds 4a , 4h , 4j , 4f , and 4l have the lowest minimum inhibitory concentration (MIC) value of 1000 μg/mL to all tested bacteria. The other compounds have the MIC value of >1000 μg/mL to all tested bacteria.     

Multistep Synthesis of Fluorine‐Substituted Pyrazolopyrimidine Derivatives With Higher Antibacterial Efficacy Based on In Vitro Molecular Docking and Density Functional Theory

Some new fluorine‐substituted pyrazolopyrimidine derivatives ( 1.3 – 1.5 ) have been synthesized by the multistep reactions, starting from reaction of 4‐fluorophenyl malanonitrile ( 1 ) with guanidine, followed by ring closure reaction with hydrazine to give 2,4‐diamino‐6‐aryl‐pyrimidine‐5‐carbonitrile ( 1.2 ). Structure of the compounds was conformed by the spectral and elemental analyses. The antibacterial activity of these compounds was tested in vitro by the disk diffusion assay against two Gram‐positive and two Gram‐negative bacteria, and then the minimum inhibitory concentration was determined with reference to the standard drug chloramphenicol. The results showed that compound 1.5 is better at inhibiting growth as compared with chloramphenicol of both types of bacteria (gram‐positive and gram‐negative). Molecular orbital calculations were carried out by using the density functional theory. The B3LYP/6‐311 + G** level of theory was employed to explore LUMO–HOMO gap energy and charge distribution of compounds 1.1 to 1.5 . Docking studies were performed on bacterial glucosamine‐6‐phosphate synthetase enzyme. Density functional theory calculations and docking studies support the in vitro findings.     

Efficient Synthesis of Novel 3‐Phenyl‐5‐thioxo‐3,4,5,6‐tetrahydroimidazo[4,5‐c]pyrazole‐2(1H)‐carbothioamide Derivatives Using a CeO2–MgO Catalyst and Evaluation of Antimicrobial Activity

Imidazo[4,5‐c ]pyrazole derivatives ( 3a–f , 4a–f , and 5a–f ) were efficiently synthesized by one‐pot three‐component reactions using CeO₂–MgO as the catalyst. The synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, and mass spectroscopic analyses. The in vitro antimicrobial activity of the synthesized compounds against various bacterial and fungal strains was screened. Compound 3b was highly active [minimum inhibitory concentration (MIC): 0.5 μg/mL] against Gram‐positive Staphylococcus aureus , and compounds 3b , 3f , 4d , and 4e were highly active (MIC: 0.5, 2, 2, and 0.5 μg/mL, respectively) against Gram‐negative Pseudomonas aeruginosa and Klebsiella pneumoniae , relative to standard ciprofloxacin in the antibacterial activity screening. Compounds 3b and 4f were highly active (MIC: 4 and 0.5 μg/mL, respectively) against Aspergillus fumigatus and Microsporum audouinii in the antifungal activity screening compared with the clotrimazole standard.     

Synthesis,Characterization, and Bioactivity of Novel Bicinnolines Having 1‐Piperazinyl Moieties

A number of novel bicinnolines containing piperazine moieties, 4a – o , were synthesized via polyphosphoric acid‐catalyzed intramolecular cyclization of the respective acyl amidrazone derivatives ( 3a – o ). On the other hand, the amidrazones ( 3a – o ) were prepared by reaction of N′,N″‐(biphenyl‐4,4′‐diyl)bis(2‐oxopropane hydrazonoyl chloride) ( 2 ) with the appropriate cyclic sec‐amines in the presence of trimethylamine in absolute ethanol. Structures of the newly synthesized compounds were confirmed by NMR and mass spectral data. The antitumor activity of compounds 4a – o was evaluated in vitro on human breast cancer MDA‐231 by a cell viability assay. Results revealed that compounds 4k , 4n , and 4o exhibit potential cytotoxic effects (>70%) on the cancer cells. Additionally, the antimicrobial activity of compounds 4a – o was evaluated against three clinical microbial strains: Escherichia coli (Gram‐negative bacteria), Staphylococcus aureus (Gram‐positive bacteria), and Candida albicans (fungi/yeast). Results revealed that compounds 4e and 4k exhibit good activity against all three strains included in the study and that compound 4d displays excellent activity against S. aureus strain with a minimum inhibitory concentration value of 0.187 mg/mL.     

Sterically Hindered N‐Heterocyclic Salts Utilized as Antimicrobial Agents

By the adoption of annulated ring systems for their steric bulkiness, a new series of symmetric N ‐heterocyclic imidazolium and perimidium salts were synthesized. Also, corresponding asymmetric ferrocenyl N ‐functionalized series were prepared as salts. All the reported salts were fully characterized. The reported X‐ray structure of 4,5‐diphenyl‐1,3‐dimethyl‐1H ‐imidazol‐3‐ium iodide ( 2a ) shows that it crystallized in the orthorhombic space group P 2₁2₁2₁. Low to moderate antimicrobial activities were observed with both sets of salts against important clinical isolates of Staphylococcus aureus , Bacillus subtilis , and Enterococcus faecalis and Escherichia coli , Pseudomonas aeruginosa , and Salmonella enterica . The results were benchmarked against meropenem. Both 1,3‐propyl‐1H ‐phenanthro[9,10‐d ]imidazol‐3‐ium iodide ( 3b ) and 1‐ferrocenyl‐3‐propyl‐1H ‐perimidin‐3‐ium iodide ( 9b ) showed high antimicrobial activities against all tested Gram‐positive bacterial strains, with minimum inhibitory concentration values ranging from 8 to 4 μg/mL (meropenem = 0.5–0.125 μg/mL), while all the salts showed little or no activity against Gram‐negative bacterial strains. In general, the asymmetric ferrocenyl‐containing salts exhibited higher activities than the symmetric ones.     

XPS study of silver and copper nanoparticles demonstrated selective anticancer,proapoptotic, and antibacterial properties

Silver and copper nanoparticles were produced by an ecologically safe metal vapor synthesis (MVS) method using acetone as an organic dispersion medium. Transmission electron microscopy (TEM) showed that the specimens are spherical and polydisperse, and their average size is 2.5 nm for silver nanoparticles (Ag NPs) and 2.6 nm for copper nanoparticles (Cu NPs). X-ray photoelectron spectroscopy analyses showed that the state of silver in the nanoparticles is close to that of silver in the Ag⁰ state, whereas copper black contains two oxidized states of the metal—Cu⁺ and Cu²⁺. Biological in vitro studies demonstrated that the nanoparticles have antibacterial activity against Gram-positive and Gram-negative bacterial species. Cu NPs exhibited more prominent antibacterial effects and induced significant growth inhibition of Bacillus cereus and Escherichia coli. Both types of nanoparticles showed anticancer properties in vitro. Cu NPs induced intense cytotoxicity in cancer and normal fibroblasts in vitro cultures, but their inhibitory effect against noncancerous cells was milder compared with cancer cell lines. Ag NPs demonstrated selective cytotoxicity against human lung and cervical adenocarcinoma cell lines. Further in vitro studies indicated that the mechanism of Ag NPs and Cu NPs anticancer effects involves induction of apoptosis. The present study describes a green synthesis approach for production of biologically active silver and copper nanoparticles and highlights their potential for medical application.     

Pharmacological Evaluation of Novel Organoiron Dendrimers as Antimicrobial and Anti‐Inflammatory Agents

The synthesis of a novel and attractive class of nonsteroidal anti‐inflammatory and antimicrobial organoiron dendrimers attached to the well‐known drug ibuprofen is achieved. The structures of these dendrimers are established by spectroscopic and analytical techniques. The antimicrobial activity of these dendrimers is investigated and tested against five human pathogenic Gram‐positive and Gram‐negative bacteria, and minimum inhibitory concentrations are reported. Some of these synthesized dendrimers exhibit higher inhibitory activity against methicillin‐resistant Staphylococcus aureus, vancomycin‐resistant Enterococcus faecium, and Staphylococcus warneri compare to the reference drugs. As well, the in vitro and in vivo anti‐inflammatory activities of these dendrimers are evaluated. The results of in vivo anti‐inflammatory activity and histopathology of inflamed paws show that all dendrimers display considerable anti‐inflammatory activity; however, second‐generation dendrimer ( G2‐D6 ) shows the best anti‐inflammatory activity, which is more potent than the commercial drug ibuprofen at the same tested dose. Results of the toxicity study reveal that G2‐D6  is the safest drug on biological tissues.     

Facile Heterocyclic Synthesis and Antibacterial Activity of Substituted Isoxazol‐5(4H)‐ones

An efficient, simple, and green procedure for the synthesis of isoxazol‐5(4H)‐one derivatives are described here through a convenient one‐pot, three‐component reaction at room temperature. The title compounds are isolated in high to excellent yields and after short reaction times, and are characterized by various spectroscopic methods such as IR, ¹H NMR, and ¹³C NMR. The synthesized compounds 4a–c and 4e–i were tested for their in vitro activity against a panel of Gram‐positive and Gram‐negative bacteria, demonstrating their ability to inhibit microorganisms with a zone of inhibition ranging from 15 to 30 mm, minimum inhibitory concentration between 250 and 900 μg/mL, and minimum bacterial concentration between 700 and 1000 μg/mL.     

Synthesis,Characterization, and In Vitro Antibacterial Activities of Macromolecules Derived from Bis‐Chalcone

We investigated the antibacterial activity of some new macromolecules such as bis‐pyrazoline, bis‐pyrazole, bis‐pyrimidines prepared from the reaction of bis‐chalcone with thiosemicarbazide/phenyl hydrazine/guanidine hydrochloride/thiourea. All the macromolecules have been characterized by IR, ¹H NMR, ¹³C NMR, mass and elemental analyses. The antibacterial activity of these compounds was first tested in vitro by the disc diffusion assay against two Gram‐positive and two Gram‐negative bacteria, and then the minimum inhibitory concentration was determined with the reference to standard drug chloramphenicol. The results showed that pyrazoline derivative showed better antibacterial activity on S. typhimurium and E. coli than the reference drug chloramphenicol.     

Synthesis,Antibacterial Activity,and Docking Studies of 1,2,3‐triazole‐tagged Thieno[2,3‐d]pyrimidinone Derivatives

Novel (1‐(substituted phenyl)‐1H ‐1,2,3‐triazol‐4‐yl)methyl‐2‐(4‐oxo‐5,6,7,8‐tetrahydrobenzo[1,2]thieno[2,3‐d ]pyrimidin‐3(4H )‐yl)acetate derivatives were synthesized. All the compounds showed significant antibacterial activity against Gram‐negative (Escherichia coli and Klebsiella pneumonia ) and Gram‐positive (Bacillus subtilis and Bacillus cereus ) bacteria. Particularly, (1‐(3‐nitrophenyl)‐1H ‐1,2,3‐triazol‐4‐yl)methyl‐2‐(4‐oxo‐5,6,7,8‐tetrahydrobenzo[1, 2]thieno[2,3‐d ]pyrimidin‐3(4H )‐yl)acetate was found to be most potent against E. coli , K. pneumonia , and B. subtilis with MIC 25 μg/ml. Molecular docking was also performed on purine riboswitch of B. subtilis and thiamine pyrophosphate riboswitch of E. coli .      

Synthesis and Antimicrobial Activity of Novel Derivatives of 7‐aryl‐10‐thioxo‐7, 10, 11, 12 – tertahydro‐9H‐benzo[H] pyrimido [4,5‐b] quinoline‐8‐one

A highly competent synthesis of novel 7‐aryl‐10‐thioxo‐7, 10, 11, 12‐tertahydro‐9H‐benzo [H] pyrimido [4, 5‐b] quinoline‐8‐one derivatives has been reported through a Knoevenagel condensation followed by Michael addition and subsequent cyclization using ethanol:acetic acid (8:2 v/v). The mentioned protocol has advantages like high yields, cleaner reactions, operational simplicity, and environment friendliness. Moreover, these compounds were further screened against the plant pathogenic fungi like Colletotrichum truncatum, Ustilago maydis, Trichosporon, Trichothecium sp., Aspergillus oryze, Aspergillus terreus, and Aspergillus niger by agar well method bioassay. The results were elaborated for minimum inhibitory concentration determination using agar dilution method against fungal strains C. truncatum and U. maydis as well as broth dilution method for bacteria species Gram‐positive Bacillus megaterium and Gram‐negative Proteus vulgaris. Most of the tested compounds showed promising results towards the antimicrobial activity.     

Synthesis,characterization and evaluation of biological properties of selenium nanoparticles from Solanum lycopersicum

Synthesis of nanoparticles by green synthesis has a large number of biomedical applications worldwide. In this study, Selenium Nanoparticles (SeNPs) were synthesized by using sodium salt of selenium and Solanum lycopersicum (tomato) fruit juice and seeds extract. The plant extracts were used as a reducing agent in ratio 1:4 i.e. sodium selenite salt (Na₂SeO₃). SeNPs were characterized by UV–visible spectrophotometry, FTIR and Zeta Sizer analysis. The UV-graphs indicated the highest peak of absorbance at 350 nm. Whereas, FTIR analysis of SeNPs indicated absorbance bands at 3262.35–1633.72 cm^?1. Zeta sizer analysis showed the average size of SeNPs for Fruit juice extract as 1020 d.nm. with PDI 0.432. In case of seeds extract, average size was 1155 d.nm. with PDI 0.761; and the PDI value for both extracts showed polyderse nature of these NPs. SeNPs possessed significant antimicrobial activity against selected strains of E. coli, S. aureus, M. luteus, S. enterica, B. subtilis, K. pneumoniae and P. aureginosa. The α-amylase inhibitory assay of these SeNPs indicated that they had antidiabetic role with IC₅₀ value 24.4642 µg/mL. The DPPH assay showed that SeNPs of Solanum lycopersicum have antioxidant activity with IC₅₀ value of 20.7398 µg/mL.