Preparation, characterization and antimicrobial activity of 6-amino-6-deoxychitosan

6-Amino-6-deoxychitosans with molecular weights from 0.23 × 10⁴ to 1.41 × 10⁴ and degree of substitution from 0.85 to 0.96 were prepared via N-phthaloylation, tosylation, azidation, hydrazinolysis and reduction of azide groups. Their structures were characterized by FT-IR, ¹H NMR, ¹³C NMR, gel permeation chromatography (GPC) and elemental analysis. The antimicrobial activities of 6-amino-6-deoxychitosans against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Aspergillus niger were investigated. The results showed that 6-amino-6-deoxychitosans had a wide spectrum of effective antimicrobial activities. Compared with chitosan, 6-amino-6-deoxychitosans had much better antimicrobial activities. Their minimum inhibitory concentrations (MICs) were between 0.025% and 0.1% (w/v) in acetic/sodium acetate solution with different pH from 5.4 to 7.5. 6-Amino-6-deoxychitosans could also inhibit growth of bacteria tested in distilled water under pH 6.6-8.45. The antimicrobial mechanism was complex and the positive charge on the amino groups was not the sole factor resulting in the antimicrobial activities.     

Functional and structural characterization of recombinant dermcidin-1L, a human antimicrobial peptide

Antimicrobial peptides from human skin are an important component of the innate immune response and play a key role as a first line of defense against infections. One such peptide is the recently discovered dermcidin-1L. To better understand its mechanism and to further investigate its antimicrobial spectrum, recombinant dermcidin-1L was expressed in Escherichia coli as a fusion protein and purified by affinity chromatography. The fusion protein was cleaved by factor Xa protease to produce recombinant dermcidin-1L. Antimicrobial and hemolytic assays demonstrated that dermcidin-1L displayed microbicidal activity against several opportunistic nosocomial pathogens, but no hemolytic activity against human erythrocytes even at concentrations up to 100 microM. Structural studies performed by circular dichroism spectroscopy indicated that the secondary structure of dermcidin-1L was very flexible, and both alpha-helix and beta-sheet structures might be required for the antimicrobial activity. Our results confirmed previous findings indicating that dermcidin-1L could have promising therapeutic potentials and shed new light on the structure-function relationship of dermcidin-1L.     

Functional expression,purification, and antimicrobial activity of a novel antimicrobial peptide MLH in Escherichia coli

In this study, a novel heterozygous antimicrobial peptide MLH was synthesized, expressed, purified, and characterized. The peptide Md-cec-LL-37_Hp (MLH) was selected through bioinformatic analysis using musca domestica antimicrobial peptide (Cec-Med), human antimicrobial peptide LL-37, and helicobacter pylori antimicrobial peptide (Hp) as parent peptides. The target gene was synthesized by overlap extension PCR (SOE-PCR) and connected to the expression vector pET-32a (+), and the recombinant plasmid pET-32a-MLH was transformed to Escherichia coli for constructing pET-32a-MLH/BL21 (DE3). Isopropyl β-D-thiogalactoside (IPTG) was used to induce protein expression, and SDS-PAGE and western blot were adopted to test the target protein. And fermentation condition was optimized to get the mass expression of the fusion protein. The Ni²⁺ affinity chromatographic column was used to purify. Active heterozygous peptide was obtained after renaturation. Finally, the activity of the heterozygous antimicrobial peptide was identified. The fusion peptide showed significant antimicrobial effect on both E. coli and Staphylococcus aureus.     

Benzimidazolium-based novel silver N-heterocyclic carbene complexes: synthesis,characterisation and in vitro antimicrobial activity

This study reports the synthesis, characterisation and antimicrobial activity of five novel silver N-heterocyclic carbene (Ag–NHC) complexes obtained by N-propylphthalimide and N-methyldioxane substituted benzimidazolium salts with silver oxide. The reactions were performed at room temperature for 24?h in the absence of light. The obtained complexes were identified and characterised by ¹H and ¹³C NMR, FT-IR and elemental analysis techniques. The minimum inhibitory concentration (MIC) of the complexes was determined for E. coli, P. aeruginosa, E. faecalis, S. aureus, C. tropicalis and C. albicans in vitro through agar and broth dilution. The results indicated that these complexes exhibit antimicrobial activity. In particular, complex 3 presented the significant broad spectrum antimicrobial activity.     

Palladium(II) complexes of quinolinylaminophosphonates: synthesis, structural characterization, antitumor and antimicrobial activity

Three types of palladium(II) halide complexes of quinolinylaminophosphonates have been synthesized and studied. Diethyl and dibutyl [α-anilino-(quinolin-2-ylmethyl)]phosphonates (L1, L2) act as N,N-chelate ligands through the quinoline and aniline nitrogens giving complexes cis-[Pd(L1/L2)X₂] (X═Cl, Br) (1-4). Their 3-substituted analogues [α-anilino-(quinolin-3-ylmethyl)]phosphonates (L3, L4) form dihalidopalladium complexes trans-[Pd(L3/L4)₂X₂] (5-8), with trans N-bonded ligand molecules only through the quinoline nitrogen. Dialkyl [α-(quinolin-3-ylamino)-N-benzyl]phosphonates (L5, L6) give tetrahalidodipalladium complexes [Pd₂(L5/L6)₃X₄] (9-12), containing one bridging and two terminal ligand molecules. The bridging molecule is bonded to the both palladium atoms, one through the quinoline and the other through the aminoquinoline nitrogen, whereas terminal ligand molecules are coordinated each only to one palladium via the quinoline nitrogen. Each palladium ion is also bonded to two halide ions in a trans square-planar fashion. The new complexes were identified and characterized by elemental analyses and by IR, UV-visible, ¹H, ¹³C and ³¹P nuclear magnetic resonance and ESI-mass spectroscopic studies. The crystal structures of complexes 1-4 and 6 were determined by X-ray structure analysis. The antitumor activity of complexes in vitro was investigated on several human tumor cell lines and the highest activity with cell growth inhibitory effects in the low micromolar range was observed for dipalladium complexes 11 and 12 derived from dibutyl ester L6. The antimicrobial properties in vitro of ligands and their complexes were studied using a wide spectrum of bacterial and fungal strains. No specific activity was noted. Only ligands L3 and L4 and tetrahalidodipalladium complexes 9 and 11 show poor activities against some Gram positive bacteria.     

Structural characterization of a new steroidal saponin from Agave angustifolia var. Marginata and a preliminary investigation of its in vivo antiulcerogenic activity and in vitro membrane permeability property

A new furostane steroidal saponin was isolated from the leaves of Agave angustifolia var. marginata. On the basis of chemical conversions and spectroscopic analyses, its structure was established as 3-[O-β-d-glucopyranosyl-(1→3)-O-β-d-glucopyranosyl-(1→3)-O]-[O-6-deoxy-α-l-mannopyranosyl-(1→4)-β-d-xylopyranosyl-(1→2)-O-β-d-glucopyranosyl-(1→4)-β-d-galactopyranosyl)oxy]-(3β,5α,22α,25R)-26-(β-d-glucopyranosyloxy)-22-methoxy-furostane (1). Results of preliminary biological investigations indicated that compound 1 showed significant protective effects against induced gastric ulcers using in vivo experimental models and demonstrated negligible toxicity on membrane integrity in the in vitro assays.     

Synthesis,characterization, in vitro cytotoxicity and antimicrobial investigation and evaluation of physicochemical properties of novel 4-(2-methylacetamide)benzenesulfonamide derivatives

In this study, several sulfonamide derivatives, 4-(2-methylacetylamino)benzenesulfonamides were synthesized. Chemical structures of the derivatives were characterized by ¹H NMR, ¹³C NMR, LC–MS–MS, UV–Vis, FTIR, photoluminescence and elemental analysis. Sulfanilamide was reacted with 2-bromopropionyl bromide, in the presence of pyridine, to form bromo-substituted sulfonamide key intermediates, which were subsequently treated with secondary amines to obtain novel sulfonamide derivatives. All the synthesized compounds were evaluated for in vitro antimicrobial activities and cytotoxicity. Increases in ring size, and rings bearing a nitrogen heteroatom led to improvements in antimicrobial activities. As the presence of CA IX and CA XII enzymes have been implicated in some cancerous tumors, the studies presented herein focuses on targeting these enzymes. It was found that the synthesized derivatives had in vitro anti-cancer properties, where compounds (3–6) were found to be active against all cancerous cells, and no cytotoxic effects on normal cells were observed.     

Chemical composition and antimicrobial activity of Satureja hortensis L. essential oil

Essential oil of Satureja hortensis L. was analyzed by GC and GC/MS and tested by a broth micro-well dilution method for activity against multiresistant clinical isolates of pathogenic bacteria from 10 different genera: Klebsiella, Escherichia, Proteus, Staphylococcus, Streptococcus, Pseudomonas, Enterococcus, Enterobacter, Citrobacter and Acinetobacter. The main compounds in the oil were carvacrol (67%), γ-terpinene (15.3%) and p-cymene (6.73%). The oil showed activity against all tested strains. MIC/MBC values were in the range of 0.78-25 μl/ml, with the exception of the strain P. aeruginosa. Microbicidal concentration for this particular strain (50 μl/ml) was the highest tested concentration. The oil showed inhibitory and bactericidal effect at the same concentration (MIC=MBC) for all but three strains.     

Molecular characterization and antimicrobial activity of endophytic fungi from coffee plants

Endophytic filamentous fungi from coffee plants (Coffea arabica and C. robusta) deposited in the Brazilian Collection of Environmental and Industrial Microorganisms (CBMAI) were characterized taxonomically by using molecular tools and investigated concerning their antimicrobial activity against different human pathogenic bacteria. Thirty-seven out of 39 CBMAI strains investigated were identified to at least at genus level by ITS and rDNA D1/D2 sequencing and phylogenetic analyses. Bioactivity screening of fungal extracts against Salmonella choleraesuis (CBMAI 484), Staphylococcus aureus (CBMAI 485), Pseudomonas aeruginosa (CBMAI 489) and against four different Escherichia coli serotypes showed that 17 fungi inhibited at least one of the bacteria studied. The endophytic fungi Trichoderma harzianum (CBMAI 43), Guignardia sp. (CBMAI 69) and Phomopsis sp. (CBMAI 164) inhibited from four to five bacterial species, while five fungi were active against all pathogenic bacteria tested and were identified as Aspergillus versicolor (CBMAI 46), Fusarium oxysporum (CBMAI 53), Glomerella sp. (CBMAI 63) and Cladosporium spp. (CBMAI 64 and CBMAI 66). The Minimal Inhibitory Concentration (MIC) for the fungus extracts varied from 0.025 to 1.0 mg ml⁻¹, demonstrating antimicrobial potential of some of these fungi.     

Synthesis of novel lignan-like compounds and their antimicrobial activity

Herein we report the preparation of 3,4-dibenzylfurans and some oxidized derivatives with lignan backbone. The compounds were prepared using the Friedel-Crafts reaction with BF₃ etherate as catalyst, demethylation with iodocyclohexane, acetylation and oxidation reactions. The antimicrobial activity was evaluated through their capacity to inhibit the growth of Gram positive and Gram negative bacteria, and of the yeast Candida albicans. Among ten products assayed four furans displayed a good antimicrobial activity against Staphylococcus aureus, S. epidermidis and C. albicans; on the contrary, none of the compounds were active against Pseudomonas aeruginosa. One of them inhibited the growth of S. aureus, S. epidermidis (biofilm producer strain) and C. albicans at 16 μg/mL, showing a bactericidal activity already after one hour of treatment. In summary, the results suggest a possible use of these derivatives for general disinfection practices or antimicrobial agents in cosmesis skin-care.     

Biosynthesis,characterization and antimicrobial activity of silver nanoparticles by a halotolerant Bacillus endophyticus SCU-L

Abstract

We have conducted a thorough study on extracellular biosynthesis of silver nanoparticles (AgNPs) by a halotolerant bacterium Bacillus endophyticus SCU-L, which was identified by 16S rRNA gene sequencing analysis. This strain was selected during an ongoing research programme aimed at finding a novel biological method for green nanosynthetic routes using the extremophiles in unexplored hypersaline habitats. The biosynthesized AgNPs were characterized and analyzed with UV–vis spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, atomic force microscopy and X-ray diffraction. Further, the AgNPs were found to be spherical in shape with an average particle size of about 5.1?nm, and it was stable in aqueous solution for three months period of storage at room temperature under dark condition. Also, the synthesized AgNPs significantly presented antimicrobial activity against Candida albicans, Escherichia coli, Salmonella typhi and Staphylococcus aureus. The above results suggested that the present work may provide a valuable reference and theoretical basis for further exploration on microbial biosynthesis of AgNPs by halotolerant bacteria.     

Purification and characterization of a novel antimicrobial peptide from Brevibacillus laterosporus strain A60

A novel antimicrobial peptide, with molecular mass of 1602.0469Da, produced by Brevibacillus laterosporus strain A60 was isolated and purified from the soil of mango plants. The purification procedure consisted of ammonium sulfate precipitation, cation exchange chromatography on an HiTrap SP HP column, thin layer chromatography and High Performance Liquid Chromatography (HPLC) on C18 reversed-phase column. After the four isolation procedures, one peptide with antimicrobial activity was obtained and named BL-A60. The determination of the complete amino acid sequences of this peptide showed that it contains eleven amino acid residues, L-Y-K-L-V-K-V-V-L-N-M, and a choline connected to the N-terminal and a tenuazonic acid modified of the C-terminal. This peptide shows relatively low identification to other antimicrobial peptides from bacteria. Purified BL-A60 showed high pH and thermal stability and a strong inhibition of different stages of the life cycle of Phytophthora capsici, including mycelial growth, sporangia formation and cystospore germination, with EC(50) values of 7.89, 0.60 and 21.96 μg ml(-1), respectively.     

Self-assembled synthesis, characterization and antimicrobial activity of zinc(II) salicylaldimine complexes

One-pot metal promoted reactions between salicylaldehyde and 4-methyl-1,3-phenylenediamine in the presence of metal salts acting as template agents yield zinc(II) salicylaldimine complexes containing N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine (H₂L) as a result of the [2 + 1] Schiff base condensation. The complexes of formula [Zn(HL)Cl(H₂O)₂] · C₂H₅OH and [Zn(H₂L)₂Cl(NO₃)(H₂O)] · CH₃OH were characterized as powder solids and in solution by spectroscopic methods (IR, ¹H and ¹³C NMR, FAB-MS, ESI-MS, UV-Vis), thermogravimetric and elemental analysis, potentiometry, and tested for antimicrobial activity against Staphylococcusaureus in a minimum inhibitory concentration (MIC) experiment. In these two powder solid species, the salicylaldimine, formed in a self-assembly process, acts in two different coordination modes: as monodeprotonated bidentate chelator with an N,O donor set or as a neutral monodentate using exclusively oxygen as the donor atom without involving the nitrogen atoms in the coordination. However, crystals of these two complexes are isomorphous, with 1:2 metal:ligand stoichiometry, and display the latter, relatively rare coordination pattern. In solution, the presence of a 1:1 complex of monodeprotonated state is only detected. The complexes exhibit antimicrobial activity against S.aureus.     

Peroxidase-like activity and antimicrobial properties of curcumin-inorganic hybrid nanostructure

For the first time in this study, curcumin was utilized as an organic component reacting with Cu (II) ion (Cu²⁺) as an inorganic component for fabrication of curcumin based Cu hybrid nanostructure (Cu-hNs). We also systematically examined the catalytic effect towards guaiacol and antimicrobial activities of Cu-hNs towards fish pathogen bacteria. For the characterization of Cu-hNs, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectrometry (FT-IR) analysis were used. We claimed that hydroxyl group might react with Cu²⁺ in phosphate solution (PO₄^-3) to form Cu-hNs. However, more uniform and spherical Cu-hNs were not seen owing to absence of more reactive functional groups like amine and carboxyl groups on structure of curcumin. In addition to our findings, synthesis of Cu-hNs were carried out in the various pH values to evaluate the effect of pHs on formation of Cu-hNs. The Cu-hNs exhibited remarkable catalytic activity throught the Fenton reaction in the presence of hydrogen peroxide (H₂O₂) and effective antimicrobial activities against Gram-positive/negative fish pathogen bacteria. In this study, cheap and efficient synthesis of nanoflowers (NFs) using plant extracts is proposed for biomedical applications rather than expensive molecules such as amino acids and DNA.     

华重楼内生菌抗菌肽的分离纯化及其特性

摘要：【目的】华重楼内生菌PCE45具有较强的抗菌活性,本文将对PCE45产生的抗菌物质进行分离纯化和性质分析报道。【方法】PCE45发酵液经硫酸铵盐析、丙酮沉淀、SephadexG75柱、DE52纤维素柱和SephadexG25凝胶柱纯化分离得到抗菌肽PCP-1。【结果】稳定性测试表明该抗菌肽对蛋白酶不敏感,对高温、强酸、强碱有较好的耐受性,可造成稻瘟病菌菌丝畸形并抑制孢子萌发。抑菌谱表明该抗菌肽对玉米弯胞病菌等真菌和大肠杆菌等细菌有较强的抑菌效果。质谱测得其分子量为1058.3D。氨基酸组成分析表明该     

Molecular cloning and biological characterization of novel antimicrobial peptides, pilosulin 3 and pilosulin 4, from a species of the Australian ant genus Myrmecia

Venom of an Australian ant species of the Myrmecia pilosula species complex (mss. name Myrmecia banksi Taylor) contains two major allergenic peptides, pilosulin 1 and pilosulin 2. To obtain novel cDNA clones that encode the pilosulin-related bioactive peptides, mRNA of another Myrmecia species was subjected to RT-PCR in which the forward primer corresponds to a nucleotide sequence in the leader sequences of pilosulin 1 and pilosulin 2. As a result, we isolated cDNA clones encoding the novel antimicrobial peptides pilosulin 3 and pilosulin 4. The nucleotide and the amino acid sequences of all four pilosulins have high homology except for the mature peptide coding regions. Synthetic pilosulin 3 and pilosulin 4 peptides displayed antimicrobial activity with histamine-releasing and low hemolytic activities.     

Synthesis and antimicrobial activity of novel amphiphilic aromatic amino alcohols

We report in this work the preparation and in vitro antimicrobial evaluation of novel amphiphilic aromatic amino alcohols synthesized by reductive amination of 4-alkyloxybenzaldehyde with 2-amino-2-hydroxymethyl-propane-1,3-diol. The antibacterial activity was determined against four standard strains (Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa) and 21 clinical isolates of methicillin-resistant Staphylococcus aureus. The antifungal activity was evaluated against four yeast (Candida albicans, Candida tropicalis, Candida glabrata and Candida parapsilosis). The results obtained showed a strong positive correlation between the lipophilicity and the antibiotic activity of the tested compounds. The best activities were obtained against the Gram-positive bacteria (MIC = 2–16 μg ml^?1) for the five compounds bearing longer alkyl chains (4c–g; 8–14 carbons), which were also the most active against Candida (MIC = 2–64 μg ml^?1). Compound 4e exhibited the highest levels of inhibitory activity (MIC = 2–16 μg ml^?1) against clinical isolates of MRSA. A concentration of twice the MIC resulted in bactericidal activity of 4d against 19 of the 21 clinical isolates.     

In vitro antimicrobial activity of propolis and synergism between propolis and antimicrobial drugs

The aim of this study was to investigate antimicrobial properties of ethanolic extract of 13 propolis (EEP) samples from different regions of Serbia against 39 microorganisms (14 resistant or multiresistant to antibiotics), and to determine synergistic activity between antimicrobials and propolis. Antimicrobial activity of propolis samples was evaluated by agar diffusion and agar dilution method. The synergistic action of propolis with antimicrobial drugs was assayed by the disc diffusion method on agar containing subinhibitory concentrations of propolis. Obtained results indicate that EEP, irrespectively of microbial resistance to antibiotics, showed significant antimicrobial activities against Gram-positive bacteria (MIC 0.078%–1.25% of EEP) and yeasts (0.16%–1.25%), while Gram-negative bacteria were less susceptible (1.25&%ndash;>5%). Enterococcus faecalis was the most resistant Gram-positive bacterium, Salmonella spp. the most resistant Gram-negative bacteria, and Candida albicans the most resistant yeast. EEP showed synergism with selected antibiotics, and displayed ability to enhance the activities of antifungals. The shown antimicrobial potential of propolis alone or in combination with certain antibiotics and antifungals is of potential medical interest.     

Synthesis and antimicrobial activity of cysteine-free coprisin nonapeptides

Coprisin is a 43-mer defensin-like peptide from the dung beetle, Copris tripartitus. CopA3 (LLCIALRKK-NH₂), a 9-mer peptide containing a single free cysteine residue at position 3 of its sequence, was derived from the α-helical region of coprisin and exhibits potent antibacterial and anti-inflammatory activities. The single cysteine implies a tendency for dimerization; however, it remains unknown whether this cysteine residue is indispensible for CopA3’s antimicrobial activity. To address this issue, in the present study we synthesized eight cysteine-substituted monomeric CopA3 analogs and two dimeric analogs, CopA3 (Dimer) and CopIK (Dimer), and evaluated their antimicrobial effects against bacteria and fungi, as well as their hemolytic activity toward human erythrocytes. Under physiological conditions, CopA3 (Mono) exhibits a 6/4 (monomer/dimer) molar ratio in HPLC area percent, indicating that its effects on bacterial strains likely reflect a CopA3 (Mono)/CopA3 (Dimer) mixture. We also report the identification of CopW, a new cysteine-free nonapeptide derived from CopA3 that has potent antimicrobial activity with virtually no hemolytic activity. Apparently, the cysteine residue in CopA3 is not essential for its antimicrobial function. Notably, CopW also exhibited significant synergistic activity with ampicillin and showed more potent antifungal activity than either wild-type coprisin or melittin.     

The novel economical synthesis and antimicrobial activity of a trithiocarbonate derivative

The compound diethyl 2,2′-(thiocarbonyl-bis(sulfanediyl))-diacetate 4 belongs to the trithiocarbonate class containing a trithiocarbonate function group flanked by ethyl acetate. In this procedure, a novel economic synthesis route to obtain compound 4 is described. This compound proved to possess broad-spectrum antimicrobial activity both in vitro and in vivo, and could be used as a lead compound. It is worth mentioning that this compound has been patented [No. US 9,988,348 B1; date of patent: June 5, 2018].