Chemical composition and antibacterial activity of Tussilago farfara (L.) essential oil from Quebec,Canada

Abstract

The chemical composition of Tussilago farfara L. essential oil from the Saguenay-Lac-St-Jean region of Quebec, Canada was analyzed by gas chromatography–flame ionisation detector (GC-FID) and gas chromatography–mass spectrometry (GC-MS), and the antibacterial activity of the oil was tested against Escherichia coli and Staphylococcus aureus. Forty-five (45) compounds were identified from the GC profile. The main components were 1-nonene (40.1%), α-phellandrene (26.0%) and ρ-cymene (6.6%). The essential oil demonstrated antibacterial activity against E. coli (MIC₅₀ = 468 µg·mL^?1; MIC₉₀ = 6869 µg·mL^?1) and S. aureus (MIC₅₀ = 368 µg·mL^?1; MIC₉₀ = 773 µg·mL^?1). Dodecanoic acid was found to be active against both bacteria having a MIC₅₀ and MIC₉₀ of 16.4 µg·mL^?1 and 95 µg·mL^?1, respectively for E. coli and a MIC₅₀ and MIC₉₀ of 9.8 µg·mL^?1 and 27.3 µg·mL^?1, respectively for S. aureus. In addition, 1-decene and (E)-cyclodecene were also found to be active against E. coli.     

Synthesis,biological evaluation,quantitative-SAR and docking studies of novel chalcone derivatives as antibacterial and antioxidant agents

In the present study, a series of chalcone derivatives including 17 new compounds were synthesised; their antibacterial activities against eleven bacteria, and their free radical-scavenging activities using DPPH were evaluated. All compounds showed significant antibacterial activities against both Gram-positive and Gram-negative bacteria. In particular, compound IIIf strongly inhibited Staphylococcus aureus (JMC 2151) and Enterococcus faecalis (CARS 2011-012) with MIC values of 6.25 µg mL^?1 and 12.5 µg mL^?1, respectively, which are comparable to that of the standard antibiotic, nalidixic acid. Compound IIIg also inhibited S. aureus with a MIC value similar to that of nalidixic acid (6.25 µg mL^?1). Furthermore, like nalidixic acid (MIC value of 25 µg mL^?1), compounds IIIa, IIIc and IIId inhibited Listeria monocytogenes (ATCC 43256) with MIC values of 25 µg mL^?1, 12.5 µg mL^?1 and 25 µg mL^?1, respectively. Quantitative structure-activity relationship (Q-SAR) studies using physicochemical calculations indicated that the antibacterial activities of chalcone derivatives correlated well with predicted physicochemical parameters (logP and PSA). Docking simulation by positioning the most active compound IIIf in the active site of the penicillin-binding protein (PBP-1b) of S. aureus was performed to explore the feasible binding mode. Furthermore, most of the compounds synthesised exhibited significant DPPH radical-scavenging activity, although compounds IIc and IIIc exhibited the greatest antioxidant activity with IC₅₀ values of 1.68 µM and 1.44 µM, respectively, comparable to that of the standard antioxidant, ascorbic acid (1.03 µM).     

Effect of the topology on the antibacterial activity of cationic polythioether synthesized by all-click chemistry

Cationic compounds often serve as antibacterial materials for a wide range of applications. However, the relationship of topology−antibacterial activity has been rarely revealed. Herein, three cationic polythioethers (CPTEs) with hyperbranched topologies are well designed and facilely synthesized via an all-click chemistry strategy (including thiol-ene and epoxy-amine additions). These as-prepared CPTEs were found to exhibited outstanding antibacterial activity against Escherichia coli and Staphylococcus aureus with minimum inhibitory concentrations against E. coli of 7.3, 14.6, and 14.6 μg ml⁻¹, and against S. aureus of 14.6, 29.2, and 29.2 μg ml⁻¹, respectively. The antibacterial activity is coincident with their degree of branching (DB, their DB values of 0.81, 0.48, and 0.27), which is mainly attributed to the inherent three-dimensional structure. The present strategy reveals the relationship of polymer topology and antibacterial activity, providing a novel possibility for designing and/or synthesis of high-efficiency antibacterial agents.     

Synthesis and Antimicrobial Evaluation of 1,4-Naphthoquinone Derivatives as Potential Antibacterial Agents

1,4-Naphthoquinones are an important class of compounds present in a number of natural products. In this study, a new series of 1,4-naphthoquinone derivatives were synthesized. All the synthesized compounds were tested for in vitro antimicrobial activity. In this present investigation, two Gram-positive and five Gram-negative bacterial strains and one pathogenic yeast strain were used to determine the antibacterial activity. Naphthoquinones tested for its antibacterial potencies, among seven of them displayed better antimicrobial activity against Staphylococcus aureus (S. aureus; 30–70 μg/mL). Some of the tested compounds showed moderate to low antimicrobial activity against Pseudomonas aeruginosa (P. aeruginosa) and Salmonella bongori (S. bongori; 70–150 μg/mL). In addition, most active compounds against S. aureus were evaluated for toxicity to human blood cells using a hemolysis assay. For better understanding, reactive oxygen species (ROS) generation, time-kill kinetic study, and apoptosis, necrosis responses were investigated for three representative compounds.     

A new pyrimidine-derived ligand,N-pyrimidine oxalamic acid,and its Cu(II), Co(II), Mn(II), Ni(II), Zn(II), Cd(II), and Pd(II) complexes: synthesis,characterization, electrochemical properties,and biological activity

A new heterocyclic compound N-(5-benzoyl-2-oxo-4-phenyl-2H-pyrimidin-1-yl)-oxalamic acid has been synthesized from N-amino pyrimidine-2-one and oxalylchloride. Bis-chelate complexes of the ligand were prepared from acetate/chloride salts of Cu(II), Co(II), Mn(II), Ni(II), Zn(II), Cd(II), and Pd(II) in methanol. The structures of the ligand and its metal complexes were characterized by microanalyses, IR, AAS, NMR, API-ES, UV-Vis spectroscopy, magnetic susceptibility, and thermogravimetric analyses. An octahedral geometry has been suggested for all the complexes, except for Pd(II) complex, in which the metal center is square planar. Each ligand binds using C(2)=O, HN, and carboxylate. The cyclic voltammograms of the ligand and the complexes are also discussed. The new synthesized compounds were evaluated for antimicrobial activities against Gram-positive, Gram-negative bacteria and fungi using the microdilution procedure. The Cu(II) complex displayed selective and effective antibacterial activity against one Gram-positive spore-forming bacterium (Bacillus cereus ATCC 7064), two Gram-positive bacteria (Staphylococcus aureus ATCC 6538 and S. aureus ATCC 25923) at 40–80 µg mL^?1, but poor activity against Candida species. The Cu(II) complex might be a new antibacterial agent against Gram-positive bacteria.     

Using Diphenylphosphoryl Azide (DPPA) for the Facile Synthesis of Biodegradable Antiseptic Random Copolypeptides

A facile method has been developed for the large‐scale synthesis of random copolypeptides composed of multiple (i.e., cationic, hydrophobic, and hydrophilic) amino acids and their relative ratios have been optimized for broad‐spectrum antibacterial effect. The copolypeptides obtained have measured compositions close to the design ratios in spite of the differing reactivities of the different amino acids. An optimized random copolypeptide of lysine, leucine, and serine (denoted as KLS‐3) mimicking the composition of LL‐37 host defense peptide gives broad spectrum antibacterial activity against clinically relevant Gram‐negative and Gram‐positive bacteria such as methicillin‐resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO1) with minimum inhibitory concentrations (MICs) of 32–64 μg mL⁻¹, as well as good MICs against multidrug resistant Gram‐negative bacteria of Escherichia coli EC 958 (64 μg mL⁻¹) and Klebseilla pneumoniae PTR3 (128 μg mL⁻¹). This method can be applied to the facile large‐scale copolymerization of multiple amino acids, including unnatural amino acids, to make effective antibacterial copolypeptides.

     

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

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

Design,synthesis, antimicrobial activity and computational studies of novel azo linked substituted benzimidazole,benzoxazole and benzothiazole derivatives

Novel azo linked substituted benzimidazole, benzoxazole, and benzothiazole were synthesized by diazo coupling and characterized by ¹H NMR, elemental analysis, FTIR and UV–vis spectroscopy. The newly synthesized compounds were evaluated for invitro antibacterial activity against Staphylococcus aureus and Escherichia Coli strains by Resazurin microtiter assay method (REMA). The minimum inhibitory concentration (MIC in μg/mL) were used to express the antibacterial activities. The azo linked compounds exhibited good to moderate or high antibacterial activities in vitro. Computational studies were performed to correlate HOMO-LUMO gap with antibacterial activity. The comparative molecular docking studies revealed better insights into binding mechanisms.     

Drug screening in human plasma by cloud-point extraction and HPLC

Cloud-point extraction (CPE) with RP-HPLC/DAD detection was used to develop a screen for six model basic drugs (paracetamol, promazine, amitriptyline, nortriptyline, clomipramine and chlorpromazine) in human plasma. These drugs’ varied hydrophobicities entail different affinities for the micelle-rich phase and CPE extraction efficiencies. Extraction recovery (except paracetamol) was above 80% and reproducibility (RSD%) ranged from 2.88 to 10.26 intraday and from 3.12 to 12.33 interday. The limits of detection were: 0.125 μg mL^?1 (promazine and chlorpromazine), 0.25 μg mL^?1 (amitriptyline and nortriptyline) and 0.5 μg mL^?1 (paracetamol and clomipramine). The method was linear over the ranges: 0.125–1.0 μg mL^?1 (promazine and chlorpromazine), 0.25–1.0 μg mL^?1 (amitriptyline and nortriptyline), 0.5–1.0 μg mL^?1 (clomipramine) and 0.5–10 μg mL^?1 (paracetamol). The procedure is a good alternative to the SPE or LLE sample preparation usually used.     

Synthesis and antibacterial evaluation of novel Schiff base derivatives containing 4(3<Emphasis Type="Italic">H</Emphasis>)-quinazolinone moiety

A series of novel Schiff base derivatives containing 4(3H)-quinazolinone moiety were synthesised and their antibacterial activities against tobacco and tomato bacterial wilts evaluated in vitro. Out of the synthesised compounds, 5g, 5j, 5n, 5m and 5p exhibited excellent antibacterial activities against tobacco bacterial wilt, with half maximal effective concentrations (EC50): 160.34, 158.03, 125.94, 148.09 and 133.67 (all in εg mL^?1), respectively, which were better than the EC50 of thiodiazole–copper (216.70 εg mL^?1). Compounds 5j, 5n and 5o also showed good antibacterial activities against tomato bacterial wilt, with EC50 of 95.20, 90.03 and 83.21 (all in εg mL^?1) respectively, which were better than the EC50of thiodiazole–copper (99.80 εg mL^?1). These compounds may prove to be useful as potential antibacterial agents.     

Synthesis,characterization, and antibacterial activity of metal complexes of phenylthiourea: the X-ray single crystal structure of [Zn(SC(NH2)NHC6H5)2(OOCCH3)2] · C2H5OH

Co(II), Cu(II), Zn(II), and Fe(III) complexes of phenylthiourea have been synthesized and characterized by elemental analyses, molar conductivity, magnetic susceptibility, FT-IR, and electronic spectroscopy. The spectroscopic data of the complexes are consistent with four-coordinate geometry for the metal(II) complexes and six-coordinate octahedral for the Fe(III) complex. Single crystal X-ray analysis of the Zn(II) complex revealed distorted tetrahedral geometry around the metal ion with two molecules of phenylthiourea and two acetate ions. The in vitro antibacterial activity of the complexes was studied against six bacterial strains using disc diffusion and broth microdilution methods. The complexes showed selective antibacterial activity against Staphylococcus aureus and Bacillus pumilus when compared to standard antibiotic ampicillin. The minimum inhibitory concentrations of the sensitive compounds are between 0.625 and 5.0 mg mL^?1.     

Guanidinylated Amphiphilic Polycarbonates with Enhanced Antimicrobial Activity by Extending the Length of the Spacer Arm and Micelle Self‐Assembly

Nine guanidinylated amphiphilic polycarbonates are rationally designed and synthesized. Each polymer has the same biodegradable backbone but different side groups. The influence of the hydrophobic/hydrophilic effect on antimicrobial activities and cytotoxicity is systematically investigated. The results verify that tuning the length of the spacer arm between the cationic guanidine group and the polycarbonate backbone is an efficient design strategy to alter the hydrophobic/hydrophilic balance without changing the cationic charge density. A spacer arm of six methylene units (CH₂)₆ shows the best antimicrobial activity (minimum inhibitory concentration, MIC = 40 µg mL^?1 against Escherichia coli, MIC = 20 µg mL^?1 against Staphylococcus aureus, MIC = 40 µg mL^?1 against Candida albicans) with low hemolytic activity (HC₅₀ > 2560 µg mL^?1). Furthermore, the guanidinylated polycarbonates exhibit the ability to self‐assemble and present micelle‐like nanostructure due to their intrinsic amphiphilic macromolecular structure. Transmission electron microscopy and dynamic light scattering measurements confirm polymer micelle formation in aqueous solution with sizes ranging from 82 to 288 nm.     

Antimicrobial anilinium polymers: The properties of poly(N,N‐dimethylaminophenylene methacrylamide) in solution and as coatings

Antimicrobial polymers have been widely reported to exert strong biocidal effects against bacteria. In contrast with antimicrobial polymers with aliphatic ammonium groups, polymers with anilinium groups have been rarely studied and applied as biocidal materials. In this study, a representative polymer with aniline side functional groups, poly(N,N‐dimethylaminophenylene methacrylamide) (PDMAPMA), was explored as a novel antimicrobial polymer. PDMAPMA was synthesized and its physicochemical properties evaluated. The methyl iodide‐quaternized polymer was tested against the Gram‐positive Staphylococcus aureus, with a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 16–32 and 64–128 μg mL^?1, respectively. Against the Gram‐negative Escherichia coli, the MIC and MBC were both 64–128 μg mL^?1. To broaden the range of applications, PDMAPMA was coated on substrates via crosslinking to endow the surface with contact‐kill functionality. The effect of charge density of the coatings on the antimicrobial behavior was then investigated, and stronger biocidal performance was observed for films with higher charge density. This study of the biocidal behavior of PDMAPMA both in solution and as coatings is expected to broaden the application of polymers containing aniline side groups and provide more information on the antimicrobial behavior of such materials. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1908–1921     

Microcalorimetric investigation of the antibacterial activity of curcumin on Staphylococcus aureus coupled with multivariate analysis

The antibacterial effect of Curcumin on Staphylococcus aureus growth was evaluated by microcalorimetry. The heat flow power?Ctime curves and nine quantitative parameters of the S. aureus growth were applied to investigate the inhibitory effect with Curcumin. By analyzing these curves and some quantitative parameters using multivariate analytical methods, similarity analysis and principal component analysis, the antibacterial activity of Curcumin on S. aureus could be accurately evaluated from the change of the two main parameters, the second exponential growth rate constant k ₂ and the maximum heat flow power P _m ² . The main two thermal parameters played more important role in the evaluation: at low concentration (0?C10.5???g?mL^?1), Curcumin hardly influence the growth of S. aureus, while at high concentration (10.5?C43.4???g?mL^?1) it could notably inhibit the growth. All these illustrated that the antibacterial activity of Curcumin on S. aureus was enhanced with the increase of the concentration of this compound. This study might provide an useful method and idea accurately evaluate the antibacterial effects of Curcumin, which provides some useful methods for evaluate the nature antibacterial agents.     

Preparation and antibacterial activity of aromatic derivatives of β-aminopropionic and γ-aminobutyric acid

Ten aromatic derivatives of β-aminopropionic acid and γ-aminobutyric acid were prepared.Their compositions and structures were identified by elemental analysis,IR,and 1H NMR.They have been examined for their antibacterial action against Staphylococcua aurens and Escherichia coli.These compounds showed higher activity than the aromatic derivatives of ct-amino acid which were reported previously.The general conclusion to be drawn is that the distance between amino and carboxylic group in these molecules could affect their antibacterial activity.Furthermore,those compounds with p-methyl substituent in phenyl ring exhibit higher activity than the others,and all the compounds exhibit higher activity against Escherichia coli and against Staphylococcua aureus.     

Phenanthrenes from Arundina graminifolia and in vitro evaluation of their antibacterial and anti-haemolytic properties

Chemical investigation and activity test of Arundina graminifolia led to the isolation of six phenanthrenes: blestriarene A (1), shancidin (2), densiflorol B (3), ephemeranthoquinone (4), coelonin (5) and lusianthridin (6). The isolated compounds demonstrated antibacterial and anti-haemolytic activities. It was found that compounds 1 and 2 had medium antibacterial activity against Staphylococcus aureus, Bacillus subtilis and Escherichia coli, with MICs of 20–40 μg/mL and MBCs of 40–320 μg/mL. Bactericidal mechanisms were explored. Rupture of cell wall and membrane and leakage of nuclear mass were observed by transmission electron microscopy (TEM). Moreover, compounds 1–3 attenuated the erythrocyte damage. Compounds 1 and 2 showed significant anti-haemolytic activity with inhibition rate about 50% at 16 μg/mL.     

Synthesis,characterization, molecular docking,biological activity and density functional theory studies of novel 1,4‐naphthoquinone derivatives and Pd(II), Ni(II) and Co(II) complexes

Two novel heterocyclic ligands, 2‐[(5‐fluoro‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (HL¹) and 2‐[(5‐methyl‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (HL²), and their Pd(II), Ni(II) and Co(II) complexes were prepared and characterized using ¹H NMR, ¹³C NMR, infrared and UV–visible spectroscopic techniques, elemental analysis, magnetic susceptibility, thermogravimetry and molar conductance measurements. The infrared spectral data showed that the chelation behaviours of the ligands towards the transition metal ions were through one of the carbonyl oxygen and deprotonated nitrogen atom of the secondary amine group. Molar conductance results confirmed that the complexes are non‐electrolytes in dimethylsulfoxide. The geometries of the complexes were deduced from magnetic susceptibility and UV–visible spectroscopic results. Second‐order perturbation analysis using density functional theory calculation revealed a stronger intermolecular charge transfer between ligand and metal ion in [NiL¹(H₂O)₂(CH₃COO‐)] and CoL¹ compared to the other complexes. The in vitro antibacterial activity of the compounds against some clinically isolated bacteria strains showed varied activities. [NiL¹(H₂O)₂(CH₃COO‐)] exhibited the best antibacterial results with a minimum inhibitory concentration of 50 μg mL^?1. The molecular interactions of the compounds with various drug targets of some bacterial organisms were established in a bid to predict the possible mode of antibacterial action of the compounds. The ferrous ion chelating ability of the ligands indicated that HL¹ is a better Fe²⁺ ion chelator, with an IC₅₀ of 29.79 μg mL^?1, compared to HL² which had an IC₅₀ of 98.26 μg mL^?1.     

Monooxovanadium(V) 2-phenylphenoxides: synthesis,characterization, and antimicrobial potential

Monooxovanadium(V) complexes of the composition VOCl_{3? n} (L) _n (where L = 2-phenylphenoxide ion; n = 1–3) (1–3) have been synthesized in quantitative yields by the reaction of VOCl₃ with 2-phenylphenol in toluene. The characterization of the complexes has been accomplished by elemental analysis, molar conductance measurements, IR, ¹H-NMR, electronic, mass spectral, and thermal studies. The ligands as well as the complexes have been screened for their in vitro antimicrobial activity against the pathogenic bacteria Escherichia coli and Staphylococcus aureus and fungi Candida albicans, Aspergillus niger, and Fusarium oxysporum by a twofold serial dilution. An increase in the biocidal activity was observed for the vanadium complexes. The minimum inhibitory concentration (MIC) values were 6.25–25 µg mL^?1 for complexes, relative to that of the free ligand of 25–50 µg mL^?1.     

Discovery of 4,6-bis(2-((E)-benzylidene)hydrazinyl)pyrimidin-2-Amine with Antibiotic Activity

Robenidine (E)-N′-((E)-1-(4-chlorophenyl)ethylidene)-2-(1-(4-chlorophenyl)ethylidene)hydrazine-1-carboximidhydrazide displays methicillin-resistant Staphyoccoccus aureus (MRSA) and vancomycin-resistant Enterococci (VRE) MICs of 2 μg mL⁻¹. Herein we describe the structure-activity relationship development of a novel series of guanidine to 2-aminopyrimidine isosteres that ameliorate the low levels of mammalian cytotoxicity in the lead compound while retaining good antibiotic activity. Removal of the 2-NH₂ pyrimidine moiety renders these analogues inactive. Introduction of a central 2-NH₂ triazine moiety saw a 10-fold activity reduction. Phenyl to cyclohexyl isosteres were inactive. The 4-BrPh and 4-CH₃Ph with MIC values of 2 and 4 μg mL⁻¹, against MRSA and VRE respectively, are promising candidates for future development.     

Simultaneous Capture,Detection, and Inactivation of Bacteria as Enabled by a Surface‐Enhanced Raman Scattering Multifunctional Chip

Herein, we present a multifunctional chip based on surface‐enhanced Raman scattering (SERS) that effectively captures, discriminates, and inactivates pathogenic bacteria. The developed SERS chip is made of a silicon wafer decorated with silver nanoparticles and modified with 4‐mercaptophenylboronic acid (4‐MPBA). It was prepared in a straightforward manner by chemical reduction assisted by hydrogen fluoride etching, followed by the conjugation of 4‐MPBA through Ag? S bonds. The dominant merits of the fabricated SERS chip include excellent reproducibility with a relative standard deviation (RSD) value smaller than 11.0 %, adaptable bacterial‐capture efficiency (ca. 60 %) at low concentrations (500–2000 CFU mL^?1), a low detection limit (down to a concentration of 1.0×10² cells mL^?1), and high antibacterial activity (an antibacterial rate of ca. 97 %). The SERS chip enabled sensitive and specific discrimination of Escherichia coli and Staphylococcus aureus from human blood.