Considerable Antimicrobial Activity Research Articles

Antioxidant and antimicrobial activities of Chowlai (Amaranthus viridis L.) leaf and seed extracts

The present study was conducted to evaluate the phenolics, antioxidant and antimicrobial activities of leaf and seed extracts from an edible herb namely Amaranthus viridis L. The extract yields of active components, produced using pure and aqueous methanol, from the leaves and seeds ranged from 5.4 to 6.0 and 2.4 to 3.7%, respectively. The extracts contained appreciable levels of total phenolic contents (1.03 to 3.64 GAE, g/100 g) and total flavonoid contents (18.4 – 5.42 QE, g/100 g) and also exhibited good 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity as revealed by IC50 (14.25 - 83.43 µg/ml). Besides, the tested extracts showed considerable antimicrobial activity against selected bacterial and fungal strains with minimum inhibitory concentrations (MIC) ranging from 179-645 µg/ml. Of the parts tested, the seed extracts exhibited superior antioxidant and antimicrobial activity. It was concluded that A. viridis leaf and seed can be explored as a potential source for isolation of antioxidant and antimicrobial agents for uses in functional food and pharmaceuticals. Key words: Amaranthus viridis, phytochemical constituents, minimum inhibitory concentrations (MIC), total phenolics, total flavonoids, 1,1-diphenyl-2-picrylhydrazyl (DPPH), radical scavengers.

Antimicrobial susceptibility of non-fermenting Gram-negative isolates to isepamicin in a region with high antibiotic resistance

The alarmingly increasing resistance rates among non-fermenting Gram-negative species, particularly Pseudomonas aeruginosa and Acinetobacter baumannii, intensified the interest in alternative antibiotic treatment options. Isepamicin, an old aminoglycoside, may play a role in the treatment of patients with infections caused by those multi-drug resistant pathogens. We evaluated the antimicrobial activity of isepamicin against non-fermenting Gram-negative isolates collected of the microbiological laboratory at the University Hospital of Heraklion, Crete, Greece from 2004 to the first trimester of 2011. We tested a total of 4,219 isolates (66.2% Pseudomonas spp., 30% Acinetobacter spp., 3.8% other non-fermenters). The lower respiratory tract, pus, and urine were the most frequent sites of isolation (29.7%, 19.9%, and 12.9%, respectively). Overall, 2768 (65.6%) of the evaluated isolates were susceptible to isepamicin (including 79.9 % of Pseudomonas spp, 37.2 % of Acinetobacter spp, 43.1 % of other non-fermenters). Isepamicin exhibited higher antimicrobial activity compared to broad spectrum penicillins, cephalosporins, other aminoglycosides, carbapenems, and fluoroquinolones. Only colistin was more active than isepamicin. Additionally, 41.7% of carbapenem-resistant and 53.2% of colistin-resistant P. aeruginosa isolates were susceptible to isepamicin. The susceptibility rates for the respective types of A. baumannii isolates were 12% and 6.2%. Yet, isepamicin was active against 29.2% of A. baumannii that were resistant to all other tested aminoglycosides. Isepamicin exhibits considerable antimicrobial activity against Gram-negative non-fermenters in a region with high antimicrobial resistance. Particularly, isepamicin may provide a therapeutic option for infections from carbapenem- and colistin-resistant P. aeruginosa and other aminoglycoside-resistant A. baumannii. Further modifications in the aminoglycoside molecule may provide formulations with enhanced antimicrobial activity.

Study of Synthesis and Physicochemical Properties of Arginine Derived Cationic Surfactants

The invention concerns the preparation of cationic surfactants derived from the condensation of an acid chloride, preferably a fatty acid with a number of carbon atoms 8 and 14 with esterified amino acids, preferably basic-type amino acids, like (L)-Lysine and (L)-arginine, more preferably (L)-arginine. The method comprises a first step in which the esterification of the amino acid with an alcohol is performed and a second step for the condensation with a chloride of fatty acid, using Schotten Baumann conditions. These surfactants constitute a novel class of chemicals of low toxicity with excellent surface properties and considerable antimicrobial activity. The physicochemical properties of the compounds of invention are compared against commercially available LAE (Lauroylarginine Et ester) and SDS (sodium dodecyl sulfate).

Layer by Layer Deposition of Polyethylene Glycol Capped Silver Nanoparticles/Chitosan on Polyethylene Substrate

Multilayers of silver nanoparticles and chitosan were deposited on polyethylene film by a layer-by-layer (LBL) self-assembly technique. Silver nanoparticles with a size of about 5 nm were prepared by chemical reduction and then fabricated onto a polyethylene (PE) substrate, which led to the formation of a colored film with the thicknesses of 2, 4, 8, 12, and 20 layers. Silver nanocomposites were characterized by atomic force microscopy (AFM) and UV-visible spectroscopy, X-ray diffraction (XRD), and infrared spectroscopy (FTIR). Results showed that nanoparticles deposited homogenously on the surface of the polyethylene film. LBL silver nanocomposites showed considerable antimicrobial activity by agar diffusion test.

Spectral Characterization and Antimicrobial Activity of Some Schiff Bases Derived from 4‐Methyl‐2‐aminophenol

AbstractA series of N‐(5‐methyl‐2‐hydroxyphenyl)‐(2/3/4/5‐substituted)‐benzaldimines (I–XIII) were synthesized using appropriate synthetic route. Their structures were characterized by FT‐IR, UV‐Visible, ESI‐MS, 1H‐ and 13C‐NMR spectroscopic techniques and analytical methods. The crystal structure of N‐(5‐methyl‐2‐hydroxyphenyl)‐3,4‐dimethoxybenzaldimine (XIII) was determined by X‐ray diffraction at room temperature. Relationship between the melting points and the structures of the compounds were examined. Antibacterial activities of the compounds were evaluated against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Proteus mirabilis. Antifungal activities were reported for Candida albicans. Some of the Schiff bases showed considerable antimicrobial activity against S. aureus and C. albicans.

Antimicrobial and Synergistic Effects of Silver Nanoparticles Synthesized Using Soil Fungi of High Altitudes of Eastern Himalaya

Fifty three fungi isolated from soils of different microhabitats of eastern Himalayan range (3,400~3,600 msl) were screened for mycosynthesis of silver nanaoparticles (AgNPs) and their efficacy as antimicrobials were assessed in combination with commonly used antibiotics. Three isolates Aspergillus terreus SP5, Paecilomyces lilacinus SF1 and Fusarium sp. MP5 identified based on morphological and 18S rRNA gene sequences were found to synthesize AgNPs. These nanoparticles were characterized by visual observation followed by UV-visible spectrophotometric analysis. The AgNPs synthesized by Aspergillus terreus SP5, Paecilomyces lilacinus SF1 and Fusarium sp. MP5 showed absorbance maxima at 412, 419, and 421 nm respectively in the visible region. Transmission electron microscopy micrograph showed formation of spherical AgNPs of 5~50 nm size. The antimicrobial activity of the mycosynthesized nanoparticles were investigated alone and in combination with commonly used antibiotics for analysis of growth inhibition zone against test organisms, namely, Staphylococcus aureus MTCC96, Streptococcus pyogenes MTCC1925, Salmonella enterica MTCC735 and Enterococcus faecalis MTCC2729. The mycosynthesized nanoparticles showed potent antibacterial activity and interestingly their syngergistic effect with erythromycin, methicillin, chloramphenicol and ciprofloxacin was significantly higher as compared to inhibitions by AgNPs alone. The present study indicates that silver nanoparticles synthesized using soil borne indigenous fungus of high altitudes show considerable antimicrobial activity, deserving further investigation for potential applications.

Spectral Characterization and Antimicrobial Activity of Some Schiff Bases Derived from 4‐Chloro‐2‐aminophenol and Various Salicylaldehyde Derivatives

AbstractA series of N‐(5‐chloro‐2‐hydroxyphenyl)‐(3/4/5‐substituted)‐salicylaldimines (I–XI) were synthesized using appropriate synthetic route. Their structures were characterized by FT‐IR, UV‐Visible, ESI‐MS, 1H and 13C NMR spectroscopic techniques and analytical methods. The crystal structure of N‐(5‐chloro‐2‐hydroxyphenyl)‐5‐bromosalicylaldimine (V) was determined by X‐ray diffraction at room temperature. Relationship between the melting points and the structures of the compounds was examined. Antimicrobial activity of the compounds was evaluated against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis. Antifungal activities were reported for Candida albicans. Schiff bases showed considerable antimicrobial activity against S. aureus, S. epidermidis and C. albicans. N‐(5‐Chloro‐2‐hydroxyphenyl)‐3‐hydroxy‐salicylaldimine (II) has the broadest and highest antimicrobial activity according to the others.

Comparative evaluation of antioxidant and antimicrobial activity of crude extract and secondary metabolites isolated from Artemisia kulbadica

ObjectiveTo investigate the antimicrobial and antioxidant properties of Et2O/MeOH/petrol extract and three isolated compounds from Artemisia kulbadica (A. kulbadica). MethodsThe antimicrobial activity was tested by using the disc-diffusion method and determining the minimal inhibitory concentration (MIC) using the agar dilution method against Gram positive and Gram negative bacteria, and fungi. The antioxidant activities of crude extract and tree isolated compounds were evaluated using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assays. ResultsThe plant extract was showed moderate values DPPH radical scavenging activity (IC50= (422.4 ± 2.4) μg/mL) while it was showed no considerable antimicrobial activity against tested microorganisms. Three isolated compounds tested for the first time, demonstrated antimicrobial and antioxidant activities. Two sesquiterpenes showed higher antimicrobial activity than the flavone while the later compound was better antioxidant than the sesquiterpens. ConclusionsThe present study clearly demonstrated that A. kulbadica and some of its isolates each one separately possess antimicrobial or antioxidant properties and may act as potential antioxidant for biological systems susceptible to free radical-mediated reactions.

Synthesis and Biological Evaluation of a Series of 2-(Substitutedphenyl) benzothiazoles

A series of 2-phenylbenzothiazoles has been synthesized either by i) condensation of different aromatic aldehydes with 2-aminothiophenol or ii) condensation of N-(2-chlorophenyl)benzothioamides in KOH catalyzed by potassium fericyanide. The structures of synthesized compounds were confirmed by IR, MS, and (1)H-NMR. The results of biological activity screening showed that six compounds including 2-phenylbenzothiazol (1a), 2-(2-chlorophenyl)benzothiazole (1b), 2-(3-chlorophenyl)benzothiazole (1c), 2-(4-hydroxyphenyl)benzothiazole (1e), 2-(4-dimethylaminophenyl)benzothiazole (1h) and 2-(2,3,4-trimethoxyphenyl)benzothiazole (1i) exhibited significant antibacterial activities; two compounds (1a, 1e) exhibited antifungal activities. Especially, 1e showed considerable antimicrobial activity against both A. niger and F. oxysporum. The brominated derivative of 1e displayed extended spectrum against all four bacterial strains tested with lower MIC values. In vitro cytotoxicity of the synthesized compounds was evaluated on three cancer cell lines (A549, HT1080, MCF7-MDR). The results indicated that three compounds (1e, 1g, 1i) exhibited significant cytotoxic activity on A549 and MCF7-ADR cells (IC(50), 10.07-13.21 μg/ml). Brominated and nitrated derivatives (1k, 1l, respectively) of 1e exhibited even more potent cytotoxicity.

Condensed Oxaziridine-Mediated [3+2] Cycloaddition: Synthesis of Polyhetero-bicyclo Compounds

Polyhetero-bicyclo compounds were synthesized by a regioselective [3+2]-cycloaddition reaction between stable condensed oxaziridines and alkenes, alkynes, and nitriles. These molecules showed considerable antimicrobial activity against several gram-positive bacteria.

New bioactive altersolanol derivatives from the endophytic fungus Stemphylium globuliferum isolated from Mentha pulegium

Extracts of the fungus Stemphylium globuliferum, an endophyte of the Moroccan medicinal plant Mentha pulegium, exhibited considerable cytotoxic and antimicrobial activities when tested in vitro. Chemical investigation of the extracts yielded four new secondary metabolites, including altersolanol K (1), altersolanol L (2), altersolanol M (3), and altersolanol N (4), together with the known compounds 6-O-methylalaternin (5), macrosporin (6), altersolanol A (7), tetrahydroaltersolanol B (8), altersolanol C (9), altersolanol J (10), stemphypyrone (11) and indole-3-carboxaldehyde (12). The structures of all compounds were determined on the basis of one- and two-dimensional NMR spectroscopy and mass spectrometry. Among the altersolanol derivatives tested, compound (3) was the most active congener against L5178Y cell line with an EC50 value of 1.14 µM. Moreover, all anthraquinones exhibited antibiotic activity against several pathogenic microbes. Interestingly, the new altersolanol N together with altersolanol C showed considerable antiviral activity against HRV39, whereas tetrahydroaltersolanol B was very active against HRV2, HRV8 and HRV16.

Synthesis, characterisation and antibacterial applications of water-soluble, silver nanoparticle-encapsulated β-cyclodextrin

This paper describes a simple method for the synthesis of water-soluble, silver nanoparticle-encapsulated β-cyclodextrin by phase transfer of silver nanoparticles from organic to aqueous phase using β-cyclodextrin as a capping agent. β-Cyclodextrin–silver nanoparticle inclusion complex was purified, characterised by spectroscopic and microscopic analyses and tested in vitro against Pseudomonas aeruginosa, Staphylococcus aureus, Serratia marcescens, Escherichia coli and Klebsiella pneumoniae. The silver nanoparticle-encapsulated β-cyclodextrin inclusion complex displayed considerable antimicrobial activity and stability.

Synthesis of novel selenium containing sulfa drugs and their antibacterial activities

Synthesis of 3-[4-(N-substituted sulfamoyl)phenyl]-3,4-dihydro-4-oxo-7,9-dimethylpyrido[3',2':4,5]selenolo[3,2-d]pyrimidines, 7-[4-(N-substituted sulfamoyl)phenyl]-7,8-dihydro-8-oxo-3,4-diphenylpyrimido[4',5':4,5]selenolo [2,3-c]pyridazines and 1-[4-(N-substituted sulfamoyl)phenyl]-1,11-dihydro-11-oxo-4-methylpyrimido[4',5':4,5]selenolo[2,3-b]quinolines is reported. 4-Amino-N-pyrimidine-2-ylbenzene sulfonamide (a), 4-amino-N-(2,6-dimetnylpyrimidin-4-yl)benzene sulfonamide (b), N-[(4-aminophenyl)sulfonyl] acetamide (c) with N-ethoxymethyleneamino of selenolo pyridine, selenolo pyridazine and selenolo quinoline derivatives respectively were obtained starting from 1-amino-N-substituted sulfanilamides. Spectroscopic data (IR, (1)H NMR, (13)C NMR and Mass spectral) confirmed the structure of the newly synthesized compounds. Substituted pyrimidines, pyridazines and quinolines were screened for antibacterial activity against gram-positive and gram-negative bacteria. Selenolo derivative of N-[(4-aminophenyl)sulfonyl] acetamide (substitutent of sulfacetamide c) showed strong bactericidal effect against all the tested organisms. Selenolo[3,2-d]pyrimidin (substitutent a) showed a good bactericidal effect against Serratia marcescens, Staphylococcus aureus and Escherichia coli. Compounds Selenolo[2,3-c]pyridazine (substitutent b), Selenolo[2,3-b]quinoline(substitutents c)) exhibited a moderate bactericidal effect against Serratia marcescens. None of the synthesized selenopyridazines has a considerable antimicrobial activity against the tested organisms. The minimum inhibitory concentration (MIC) of the most active compound - 3-[4-(N-acetyl sulfamoyl)phenyl]-3,4-dihydro-4-oxo-7,9-dimethylpyrido[3',2':4,5]selenolo [3,2-d]pyrimidine was 10 mg mL(-1).

Essential oils composition, antioxidant and antimicrobial activity of the leaves and flowers of Chaerophyllum macropodum Boiss

This study reports the essential oils chemical composition and in vitro antioxidant and antimicrobial potentials of the leaves and flowers of Chaerophyllum macropodum. GC and GC/MS analysis of the plant essential oils led to the identification of 49 components making 98.3–99.4% of its oils. The main constituents of the essential oils were trans- β-farnesene, trans- β-ocimene, β-pinene, limonene, spathulenol and myrcene constituting 49.6–73.1% of the oils. The extracts from the leaves and flowers showed moderate antioxidant activities in 1,1-diphenyl-2-picrylhydrazyl (DPPH) test (IC 50 values = 196.8 and 167.1 μg/ml respectively) and β-carotene/linoleic acid assay (inhibitions percentages = 69.9% and 62.7% respectively), but the essential oils were almost inactive in these tests. On the other hand, only the essential oils of the plant showed considerable antimicrobial activity against most of the tested microorganisms.

Apolar constituents of some biologically active Dianthus species from Western Anatolia

The apolar constituents of four Dianthus (Caryophyllaceae) species were determined by GC-MS. Palmitic, linoleic, and oleic acids were detected as dominant components in all species. D. elegans d’Urv. var. elegans had the highest antioxidant activity. All four species also showed considerable antimicrobial activity against S. epidermidis and C. albicans.

Composition and antioxidant and antimicrobial activity of the essential oil and extracts of Stachys inflata Benth from Iran

Composition and antioxidant and antimicrobial activities of essential oil and methanol extract polar and nonpolar subfractions of Stachys inflata were determined. GC and GC/MS analyse of the essential oil showed 45 constituents representing 95.46% of the oil, the major components linalool (28.55%), α-terpineol (9.45%), spathulenol (8.37%) and (2E)-hexenal (4.62%) constituted 50.99% of it. Essential oil and extracts were also tested for their antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene/linoleic acid assays. In the DPPH test, IC50 value for the polar subfraction was 89.50 μg/ml, indicating an antioxidant potency of about 22% of that of butylated hydroxytoluene (IC50 = 19.72 μg/ml) for this extract. In β-carotene/linoleic acid assay, the best inhibition belonged to the nonpolar subfraction (77.08%). Total phenolic content of the polar and nonpolar extract subfractions was 5.4 and 2.8% (w/w), respectively. The plant also showed a week antimicrobial activity against three strains of tested microorganisms. Linalool and α-terpineol were also tested as major components of the oil and showed no antioxidant but considerable antimicrobial activities.

Rubiacordone A: A New Anthraquinone Glycoside from the Roots of Rubia cordifolia

A new anthraquinone, Rubiacordone A (1) (6-acetoxy-1-hydroxy-2-methylanthraquinone-3-O-α-l-rhamnopyranoside), was isolated together with the known anthraquinone, 1-acetoxy-6-hydroxy-2-methylanthraquinone-3-O-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranoside] (2), from the dried roots of Rubia cordifolia. Their structures were elucidated on the basis of extensive 1D and 2D-NMR, as well as HRESI-MS spectroscopic analysis. Metabolites 1 and 2 showed considerable antimicrobial activity against Gram-positive bacteria.

In Vitro Antimicrobial Screening of Alkaloid Fractions from Strychnos potatorum

Alkaloid fractions isolated from Strychnos potatorum L.f. (Loganiaceae) seed were tested for their antimicrobial properties against some pathogenic gram positive, gram negative and acid‐fast bacteria and fungi. These fractions have shown considerable antimicrobial activity against both bacteria and fungi at the tested concentrations (100 & 200 μg/mL). Further, the growth of Proteus vulgaris, taphylococcus aureus, Salmonella typhimurium, Vibrio cholerae, Mycobacterium tuberculosis, Aspergillus niger and Candida albicans were significantly inhibited. These findings have confirmed the use of this plant in treating of several microbial infections both in traditional and folk medicine in India.

Synthesis and antimicrobial activity of 2-alkenylchroman-4-ones, 2-alkenylthiochroman-4-ones and 2-alkenylquinol-4-ones

2-Alkenylchroman-4-ones, 2-alkenylthiochroman-4-ones, and 2-alkenylquinol-4-ones were prepared with very good regioselectivity by Me 3SiOTf-mediated conjugate addition of alkenylmagnesium bromides and alkenyllithium compounds to chromones thiochromones, and quinol-4-ones. A number of products exhibit a considerable antimicrobial activity. The best activity, with respect to the spectrum of antimicrobial activity, was observed for 2-vinylchroman-4-ones containing an unsubstituted vinyl group and a chloride group located at the chromanone moiety.

Expression, purification and structural characterization of recombinant hepcidin, an antimicrobial peptide identified in Japanese flounder, Paralichthys olivaceus

The cysteine-rich peptide hepcidin is an antimicrobial peptide and iron transport regulator that has been found in vertebrates including birds, fish and mammals. To elucidate the structure and biological function of fish hepcidin, which is difficult to produce synthetically, we have cloned several plasmid constructs encoding hepcidin from Japanese flounder, Paralichthys olivaceus, and tested expression of recombinant peptides, each with an N-terminal hexahistidine (6×His) tag, in inclusion bodies or the periplasmic space of Escherichia coli. Hepcidin expressed in inclusion bodies was reduced, and subsequently refolded using a dilution technique with a cysteine redox system. The oxidized His-hepcidin monomer was separated from protein multimers and mass spectrometry analysis showed that the peptide was of the predicted size and contained four disulfide bonds. Removal of the 6×His tag was attempted using enzymatic cleavage by Factor Xa and tobacco etch virus (TEV) protease or chemical cleavage by hydroxylamine. The Factor Xa cleavage was unsuccessful and hydroxylamine cleavage resulted in aggregation of cleaved peptide. TEV protease cleavage was successful but immediately resulted in hexamer formation despite varying reaction conditions (redox, non-redox, pH, temperature, target protein concentration, type of buffer). However, the recombinant His-hepcidin fusion peptide monomer showed considerable antimicrobial activity. NMR-based studies showed that hepcidin contained a rare vicinal disulfide linkage at the top of a loop structure and a short β-sheet structure encompassing residues 7–13 and 19–25 that is stabilized by three disulfide bonds.