New Fluoroquinolone-1,2,4-triazoles as Potent Antibacterial Agents: Design,Synthesis, Docking Studies and in Silico ADME Profiles

Our current work is aimed at synthesizing novel substituted 1,2,4-triazolyl-fluoroquinolone analogs and study of their biological activity to find active promising molecules. The structural elucidation of the products was demonstrated by a variety of spectroscopic methods such as IR, ¹H-NMR, ¹³C-NMR, mass and elemental analysis. The newly synthesized 1,2,4-triazole derivatives were tested in vitro for their ability to inhibit the growth of seven different microbes including S. epidermidis, S. pneumoniae, S. aureus, B. subtilis, K. pneumoniae, E. coli, and P. aeruginosa. Five FQ derivatives 5d , 5e , 5h , 5j , and 5b have demonstrated good antibacterial activity against S. pneumoniae with MICs ranging from 2.5–22.0 μg/mL, while 5c , 5g reported comparable activity against P. aeruginosa with respect to the standard drugs moxifloxacin and ciprofloxacin. The possible mechanism of antibacterial activity of fluoroquinolones was investigated via molecular docking by using DNA gyrase of S. pneumoniae (3RAE). The pefloxacin derivatives also tended a good antibacterial ability based on the results of the molecular docking, ligand 5h with good binding affinity (−9.92 Kcal/mol) and binding site interactions via ValA:86, SerA:79, TyrA:82, MetA:116, AspA:78, AlaA:63, ArgA:117, ProA:112, ProA:113, AlaA:115, AlaA:114. These scaffolds were further evaluated for their ADMET and physicochemical properties by using SwissADME, ADMETlab2.0 web server as a good oral bioavailability.     

Rational questing for potential novel inhibitors of FabK from Streptococcus pneumoniae by combining FMO calculation,CoMFA 3D-QSAR modeling and virtual screening

Enoyl-acyl carrier protein (ACP) reductase (ENR) is an attractive and potential target for developing selective antibacterial agents. Recent studies showed that FabK is the sole isoform of ENR in Streptococcus pneumoniae, and at the same time an X-ray crystallographic study of FabK from S. pneumoniae (SpFabK) was reported for the first time. Based on above information, the interaction mechanism and pair interaction energies between ligand and the active site of SpFabK were analyzed with the ab initio fragment molecular orbital (FMO) calculation based on the FlexX docking model at the FMO-RHF/6-31G* level. Subsequently, the first molecular docking-based 3D-QSAR model with comparative molecular field analysis (CoMFA) was established with cross-validated coefficients (q ²) up to 0.511 and regression coefficients (r ²) up to 0.986. Then integrating the 3D-QSAR CoMFA predicted model, molecular docking, and FMO pair interaction analysis structure-based virtual screening was performed, six novel and potential lead compounds were sorted out for further study.     

Structural Modification and Expression of Attacin A from Glossina morsitans morsitans in E. coli and its Antibacterial Activities

Attacin A from Glossina morsitans morsitans belongs to the type of Gly-rich antimicrobial peptides, with mature peptide of 188 amino acids and molecular weight of 19.4 kDa. In this work, a truncated form of Attacin A was studied to evaluate its N-terminal and G1 domain for antibacterial activities with the help of genetic engineering technology. Genes coding for mature full length Attacin A together with its truncated form Attacin AP1 containing 1–99 amino acids of Attacin A were cloned, expressed and purified. The expression level for Attacin A and Attacin AP1 were about 10 and 20% of total cell protein, respectively. The purity of bioactive recombinant proteins, which showed virtually homogenous as determined by SDS–PAGE, was over 90%. Antibacterial testing shows that Attacin A could inhibit the growth of Gram-negative bacteria such as E. coli, Enterobacter cloacae and Klebsiella pneumoniae at relatively high concentration comparing with Ampicillin, but had little activity against Gram-positive Staphylococcus aureus. Attacin AP1 maintained the inhibitory activities against E. coli, E. cloacae and K. pneumoniae. This result makes it possible for better understanding of the structure–activity relationship of antimicrobial peptides.     

Discovery of antimicrobial compounds targeting bacterial type FAD synthetases

The increase of bacterial strains resistant to most of the available antibiotics shows a need to explore novel antibacterial targets to discover antimicrobial drugs. Bifunctional bacterial FAD synthetases (FADSs) synthesise the flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These cofactors act in vital processes as part of flavoproteins, making FADS an essential enzyme. Bacterial FADSs are potential antibacterial targets because of differences to mammalian enzymes, particularly at the FAD producing site. We have optimised an activity-based high throughput screening assay targeting Corynebacterium ammoniagenes FADS (CaFADS) that identifies inhibitors of its different activities. We selected the three best high-performing inhibitors of the FMN:adenylyltransferase activity (FMNAT) and studied their inhibition mechanisms and binding properties. The specificity of the CaFADS hits was evaluated by studying also their effect on the Streptococcus pneumoniae FADS activities, envisaging differences that can be used to discover species-specific antibacterial drugs. The antimicrobial effect of these compounds was also evaluated on C. ammoniagenes, S. pneumoniae, and Mycobacterium tuberculosis cultures, finding hits with favourable antimicrobial properties.     

Purified C-phycocyanin from <Emphasis Type="Italic">Spirulina platensis</Emphasis> (Nordstedt) Geitler: a novel and potent agent against drug resistant bacteria

The experimental data on the study of the antibacterial activity of purified phycocyanin, a protein-bound pigment isolated from blue-green alga, Spirulina platensis (Nordstedt) Geitler, Oscillatoriaceae are generalized and it was shown that phycocyanin was able to markedly inhibit the growth of drug resistant bacteria Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus while, no activity was recorded in Acinetobacter baumanii and Enterococcus durans, this is the first report of the activity of purified C-phycocyanin against drug resistant bacteria. The possible use of phycocyanin as a drug with associated antibacterial activity is discussed.     

Monocyclic β-lactam and unexpected oxazinone formation: synthesis,crystal structure,docking studies and antibacterial evaluation

Novel monocyclic β-lactam derivatives bearing aryl, phenyl and heterocyclic rings were synthesized as possible antibacterial agents. Cyclization of imines (3h, 3t) with phenylacetic acid in the presence of phosphoryl chloride and triethyl amine did not afford the expected β-lactams. Instead, highly substituted 1,3-oxazin-4-ones (4h, 4t) were isolated as the only product and confirmed by single crystal X-ray analysis of 4t. The results of antibacterial activity showed that compound 4l exhibited considerable antibacterial activity with MIC and MBC values of 62.5?µg/mL against Klebsiella pneumoniae. Cytotoxicity assay on Chinese Hamster Ovary (CHO) cell line revealed non-cytotoxic behavior of compounds 4d, 4h, 4k and 4l up to 200?μg/mL conc. Molecular docking was performed for compound 4l with penicillin binding protein-5 to identify the nature of interactions. The results of both in silico and in vitro evaluation provide the basis for compound 4l to be carried as a potential lead molecule in the drug discovery pipeline against bacterial infections.     

Effect of Eucalyptus Essential Oil on Respiratory Bacteria and Viruses

The activity of Eucalyptus globulus essential oil was determined for 120 isolates of Streptococcus pyogenes, 20 isolates of S. pneumoniae, 40 isolates of S. agalactiae, 20 isolates of Staphylococcus aureus, 40 isolates of Haemophilus influenzae, 30 isolates of H. parainfluenzae, 10 isolates of Klebsiella pneumoniae, 10 isolates of Stenotrophomonas maltophilia and two viruses, a strain of adenovirus and a strain of mumps virus, all obtained from clinical specimens of patients with respiratory tract infections. The cytotoxicity was evaluated on VERO cells by the MTT test. The antibacterial activity was evaluated by the Kirby Bauer paper method, minimum inhibitory concentration, and minimum bactericidal concentration. H. influenzae, parainfluenzae, and S. maltophilia were the most susceptible, followed by S. pneumoniae. The antiviral activity, assessed by means of virus yield experiments titered by the end-point dilution method for adenovirus, and by plaque reduction assay for mumps virus, disclosed only a mild activity on mumps virus.     

Antibacterial activity of ZnO nanoparticles prepared via non-hydrolytic solution route

The antibacterial activity of ZnO nanoparticles has been investigated and presented in this paper. Nanoparticles were prepared via non-hydrolytic solution process using zinc acetate di-hydrate (Zn(CH₃COO)₂·2H₂O) and aniline (C₆H₅NH₂) in 6 h refluxing at ∼65 °C. In the presence of four pathogens such as Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, and Klebsiella pneumoniae, the antibacterial study of zinc oxide nanoparticles were observed. The antibacterial activity of ZnO nanoparticles (ZnO-NPs) were studied by spectroscopic method taking different concentrations (5–45 μg/ml) of ZnO-NPs. Our investigation reveals that the lowest concentration of ZnO-NPs solution inhibiting the growth of microbial strain is found to be 5 μg/ml for K. pneumoniae, whereas for E. coli, S. aureus, and S. typhimurium, it was calculated to be 15 μg/ml. The diameter of each ZnO-NPs lies between “20 and 30 nm” as observed from FESEM and transmission electron microscopy images. The composition of synthesized material was analyzed by the Fourier transform infrared spectroscopy, and it shows the band of ZnO at 441 cm⁻¹. Additionally, on the basis of morphological and chemical observations, the chemical reaction mechanism of ZnO-NPs was also proposed.     

Antibacterial effect of extracts of Hermetia illucens (Diptera: Stratiomyidae) larvae against Gram‐negative bacteria

Larvae of the black soldier fly, Hermetia illucens are well‐known fly larvae that inhabit many countries around the world. Antimicrobial agents derived from the larvae may be among the substances that are produced in the body for their survival. This study was carried out to identify the antimicrobial effects of H. illucens larvae that commonly inhabit animal waste and food waste. To evaluate the pharmacological effects of H. illucens larvae extracts, the larvae were extracted by various organic solvents, and their antibacterial effects were determined by antimicrobial methods, such as agar disk diffusion and turbidometric assays. The methanol extracts (ME) indicated antibacterial effects against the proliferation of Klebsiella pneumoniae, Neisseria gonorrhoeae and Shigella sonnei. However, antibacterial effects were not induced in Gram‐positive bacteria such as Bacillus subtilis, Streptococcus mutans and Sarcina lutea. The bacterial growth treated with ME was strongly inhibited from 20 mg/mL in a dose‐dependent manner compared with other extracts, and antibacterial activity gradually decreased after 24 h. Moreover, the minimal inhibitory concentration (MIC) values of ME against Klebsiella pneumoniae, Neisseria gonorrhoeae and Shigella sonnei for 12 h were measured as 44.74 mg/mL, 43.98 mg/mL and 43.96 mg/mL, respectively. These results demonstrate that ME of H. illucens larvae not only has antibacterial activity which strongly inhibits the growth and proliferation of the bacteria but also unique properties which effectively block the viability of the bacteria.     

In vitro compared activity of telithromycin and azithromycin against northwest Italian isolates of Streptococcus pyogenes and Streptococcus pneumoniae with different erythromycin susceptibility

Aims: This study compared the in vitro activity of telithromycin with that of azithromycin against 438 Streptococcus pyogenes and 198 Streptococcus pneumoniae, isolated over the period 2005–2007 from specimens of different human origin obtained in three Piemonte Region’s hospitals. Methods and Results: The determination of antimicrobial activity was evaluated by the microdilution broth method and the erythromycin‐resistant (Ery‐R) phenotypes by the triple‐disc test. Exactly 78·8% of S. pyogenes and 69·2% of S. pneumoniae were erythromycin‐susceptible (Ery‐S). Concerning S. pyogenes, telithromycin was active against M and inducible MLS_B, subtype‐C, phenotypes but not against constitutive MLS_B strains. Telithromycin acted well against all S. pneumoniae, irrespective of their mechanism of macrolide‐resistance. On the contrary, the Ery‐R isolates, both S. pyogenes and S. pneumoniae, were resistant to azithromycin. Conclusions: Our results indicate that macrolide resistance in streptococci still persist in northwest Italy (21·2% of S. pyogenes and 30·8% of S. pneumoniae) and that telithromycin is confirmed as being extremely active even against recent clinical Ery‐R streptococcal isolates. Significance and Impact of the Study: The present study emphasizes that an active surveillance of the phenotype distribution and antibacterial resistance in streptococci is essential in guiding the effective use of empirical treatment option for streptococcal infections, also at regional level.     

Antimicrobial activity of sodium citrate against Streptococcus pneumoniae and several oral bacteria

Aims: The aim of this study is to assess the antibacterial activity of sodium citrate against Streptococcus pneumoniae and several oral bacteria. Methods and Results: The antibacterial activity was determined by broth microdilution method. The results showed that although Enterocuccus faecium OB7084 and Klebsiella pneumoniae OB7088 had high tolerance to sodium citrate, several oral bacteria including Fusobacterium nucleatum JCM8532^T, Streptococcus mutans JCM5705^T and Strep. pneumoniae NBRC102642^T were susceptible. Furthermore, the bactericidal activity of sodium citrate against Strep. pneumoniae NBRC102642^T was not influenced by pH in the range of 5·0–8·0, whereas that of sodium lactate was weakened at neutral or weak alkaline pH. When Strep. pneumoniae NBRC102642^T was treated with sodium citrate for 2 h, many burst cells were observed. However, addition of MgCl₂ or CaCl₂ to an assay medium weakened the antimicrobial activity although ZnCl₂ or MnCl₂ did not influence. Conclusions: Independent of pH, sodium citrate inhibited the growth of oral bacteria, which suggests that the mechanism is different from that of sodium lactate. Significance and Impact of the Study: The results presented in this study would be available for understanding the antimicrobial property of sodium citrate.     

Synthesis,molecular docking,binding free energy calculation and molecular dynamics simulation studies of benzothiazol-2-ylcarbamodithioates as Staphylococcus aureus MurD inhibitors

Abstract

A new series of benzothiazol-2-ylcarbamodithioate functional compounds 5a-f has been designed, synthesized and characterized by spectral data. These compounds were screened for their in vitro antibacterial activity against strains of Staphylococcus aureus (NCIM 5021, NCIM 5022 and methicillin-resistant isolate 43300), Bacillus subtilis (NCIM 2545), Escherichia coli (NCIM 2567), Klebsiella pneumoniae (NCIM 2706) and Psudomonas aeruginosa (NCIM 2036). Compounds 5a and 5d exhibited significant activity against all the tested bacterial strains. Specifically, compounds 5a and 5d showed potent activity against K. pneumoniae (NCIM 2706), while compound 5a also displayed potent activity against S. aureus (NCIM 5021). Compound 5d showed minimum IC₅₀ value of 13.37?μM against S. aureus MurD enzyme. Further, the binding interactions of compounds 5a-f in the catalytic pocket have been investigated using the extra-precision molecular docking and binding free energy calculation by MM-GBSA approach. A 30?ns molecular dynamics simulation of 5d/modeled S. aureus MurD enzyme was performed to determine the stability of the predicted binding conformation.     

Biosynthesis of Al2O3 and europium-doped Al2O3 nanoparticle using Cymbopogon citratus (lemongrass) extract and its antibacterial property

Cymbopogon citratus-mediated pure aluminium oxide (Al₂O₃) and europium (Eu)-doped Al₂O₃ with different amounts of metal ion were prepared using a green synthesis method. Synthesised nanoparticles were characterised by ultraviolet (UV)-visible spectroscopy, photoluminescence (PL), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Synthesis of nanoparticles is confirmed by using UV-visible spectroscopy showing maximum absorption at 411 and 345 nm for Al₂O₃ and Eu-doped Al₂O₃, respectively. The antibacterial activity of prepared nanoparticles was evaluated against Pseudomonas aeruginosa, Streptococcus aureus, Escherichia coli and Klebsiella pneumoniae using a well-diffusion technique. The effect of pure Al₂O₃ and Eu-doped nanoparticles shows excellent results against P. aeruginosa, S. aureus, E. coli and K. pneumoniae.     

Biological evaluation and molecular modelling study of thiosemicarbazide derivatives as bacterial type IIA topoisomerases inhibitors

In the present article, we describe the inhibitory potency of nine thiosemicarbazide derivatives against bacterial type IIA topoisomerases, their antibacterial profile and molecular modelling evaluation. We found that one of the tested compounds, compound 7, significantly inhibits activity of Staphylococcus aureus DNA gyrase with an IC₅₀ below 15?μM. Besides, this compound displays antibacterial activity on reference Staphylococuss spp. and Enterococcus faecalis strains as well as clinical S. aureus isolates at non-cytotoxic concentrations in mammalian cells with MIC values ranging from 16 to 32?μg/mL thereby indicating, in some cases, equipotent or even more effective action than standard drugs such as vancomycin, ampicillin and nitrofurantoin. The computational studies showed that both molecular geometry and the electron density distribution have a great impact on antibacterial activity of thiosemicarbazide derivatives.     

Comparative Analysis of Antioxidant,Anticholinesterase, and Antibacterial Activity of Microbial Chondroitin Sulfate and Commercial Chondroitin Sulfate

Chondroitin synthesis was performed using the recombinant Escherichia coli(C2987) strain created by transforming the plasmid pETM6-PACF-vgb, which carries the genes responsible for chondroitin synthesis, kfoA, kfoC, kfoF, and the Vitreoscilla hemoglobin gene (vgb). Then, Microbial chondroitin sulfate (MCS)’s antioxidant, anticholinesterase, and antibacterial activity were compared with commercial chondroitin sulfate (CCS). The antioxidant studies revealed that the MCS and CCS samples could be potential targets for scavenging radicals and cupric ion reduction. MCS demonstrated better antioxidant properties in the ABTS assay with the IC50 value of 0.66 mg than CCS. MCS showed 2.5-fold for DPPH and almost 5-fold for ABTS⋅+ (with a value of 3.85 mg/mL) better activity than the CCS. However, the compounds were not active for cholinesterase enzyme inhibitions. In the antibacterial assay, the Minimum inhibitory concentration (MIC) values of MCS against S. aureus, E. aerogenes, E. coli, P. aeruginosa, and K. pneumoniae (0.12, 0.18, 0.12, 0.18, and 0.18 g/mL, respectively) were found to be greater than that of CCS (0.42, 0.48, 0.36, 0.36, and 0.36 g/mL, respectively). This study demonstrates that MCS is a potent pharmacological agent due to its physicochemical properties, and its usability as a therapeutic-preventive agent will shed light on future studies.     

Molecular cloning and antibacterial activity of bombolitin isolated from the venom of a bumblebee, Bombus terrestris

Three major components of bumblebee venom are bombolitin, phospholipase A₂, and a serine protease, with bombolitin being the most abundant. Here, we describe the molecular cloning of bombolitin isolated from the venom of a bumblebee, Bombus terrestris, and demonstrate its antibacterial activity. The B. terrestris bombolitin gene consists of 2 exons encoding 56 amino acid residues. Comparative analysis shows that mature B. terrestris bombolitin consists of 18 amino acid residues, which are identical to those of B. ignitus bombolitin. B. terrestris bombolitin displayed antibacterial activity against both the Gram-negative bacterium Klebsiella pneumoniae and the Gram-positive bacterium Staphylococcus aureus, indicating that B. terrestris bombolitin may be a potential antimicrobial agent.     

Chemical Composition and Antimicrobial Activity of the Essential Oil from the Edible Aromatic Plant Aristolochia delavayi

The essential oil obtained by hydrodistillation from the aerial parts of Aristolochia delavayi Franch. (Aristolochiaceae), a unique edible aromatic plant consumed by the Nakhi (Naxi) people in Yunnan, China, was investigated using GC/MS analysis. In total, 95 components, representing more than 95% of the oil composition, were identified, and the main constituents found were (E)‐dec‐2‐enal (52.0%), (E)‐dodec‐2‐enal (6.8%), dodecanal (3.35%), heptanal (2.88%), and decanal (2.63%). The essential oil showed strong inhibitory activity (96% reduction) of the production of bacterial volatile sulfide compounds (VSC) by Klebsiella pneumoniae, an effect that was comparable with that of the reference compound citral (91% reduction). Moreover, the antimicrobial activity of the essential oil and the isolated major compound against eight bacterial and six fungal strains were evaluated. The essential oil showed significant antibacterial activity against Providencia stuartii and Escherichia coli, with minimal inhibitory concentrations (MIC) ranging from 3.9 to 62.5 μg/ml. The oil also showed strong inhibitory activity against the fungal strains Trichophyton ajelloi, Trichophyton terrestre, Candida glabrata, Candida guilliermondii, and Cryptococcus neoformans, with MIC values ranging from 3.9 to 31.25 μg/ml, while (E)‐dec‐2‐enal presented a lower antifungal activity than the essential oil.     

In-vitro antibacterial,antifungal and cytotoxic properties of sulfonamide—derived Schiff's bases and their metal complexes

A series of new antibacterial and antifungal Schiff's bases derived from sulfonamides, as well as their transition metal complexes incorporating cobalt (II), copper (II), nickel (II) and zinc (II) were synthesized, characterized and screened for their in-vitro antibacterial activity against six Gram-negative (Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi and Shigella dysentriae) and four Gram-positive (Bacillus cereus, Corynebacterium diphtheriae, Staphylococcus aureous and Streptococcus pyogenes) bacterial strains and for in-vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani, Candida glaberata. The results of these studies show the metal complexes to be more antibacterial and antifungal as compared to the uncomplexed Schiffs' bases. The brine shrimp bioassay was also carried out to study the in-vitro cytotoxic properties of these synthesized ligands and their complexes.     

N‐6 From Different Sources Protect From Metabolic Alterations to Obese Patients: A Factor Analysis

First, to analyze the interactions among fatty acids (FAs) from diet, plasma and subcutaneous and visceral adipose tissue (AT), and second, the relationship among FAs from these different sources and obesity‐related alterations in extreme obesity. We studied 20 extreme obese subjects. A food‐frequency questionnaire was used to determine the FA intakes. Serum and AT (subcutaneous and visceral) FA concentrations were determined by gas chromatography. Cardiometabolic risk parameters were assessed. Principal factor analysis was performed to define specific FA factors in the metabolic alterations. We found important associations among diet, plasma, and AT FA and cardiometabolic parameters. In this regard, it is interesting to highlight the negative associations between plasma cholesterol and dietary n‐3 FA. In the subcutaneous depot, as occurred in plasma, n‐6 and polyunsaturated FAs (PUFA) were negatively associated with triacylglycerols (TGs). Factor analysis revealed TGs as the unique cardiovascular risk parameter appearing in the first factor (F1), together with n‐6 (load factor = 0.94) and PUFA (0.91). Besides, n‐3 from diet and plasma appeared in the third factor inversely related to cholesterol, low‐density lipoprotein cholesterol (LDL‐c), and insulin. In an opposite way, dietary and AT trans FAs and saturated FA (SFA) were associated to an increase of the metabolic risk. We have shown, for the first time, the importance of n‐6 and PUFAs composition as protective factors against metabolic alterations in extreme obese subjects. These findings support current dietary recommendations to increase PUFA intakes and restrict saturated and trans FA intakes even in extreme obesity.