In vitro antimicrobial activity of extracts and compounds isolated from Cladonia uncialis

Heptane (Hep), diethyl ether (Et₂O), acetone (Me₂CO) and methanolic (MeOH) extracts, as well as ( ? )-usnic acid and squamatic acid, were obtained from thallus of Cladonia uncialis (Cladoniaceae). The antimicrobial activities of these extracts, ( ? )-usnic acid and squamatic acid, were tested against reference strains: Staphylococcus aureus, Escherichia coli and Candida albicans. In addition, Me₂CO extract was analysed against 10 strains of Methicillin-resistant S. aureus (MRSA) isolated from patients. All extracts exerted antibacterial activity against the reference strain S. aureus, comparably to chloramphenicol [minimum inhibitory concentration (MIC) = 5.0 μg/mL]. The Me₂CO extract exhibited the strongest activity against S. aureus (MIC = 0.5 μg/mL), higher than ( ? )-usnic acid, whereas squamatic acid proved inactive. The Me₂CO extract showed potent antimicrobial activity against MRSA (MIC 2.5–7.5 μg/mL). Also no activity of C. uncialis extracts against E. coli and C. albicans was observed.     

Inspiration from Old Dyes: Tris(stilbene) Compounds as Potent Gram‐Positive Antibacterial Agents

Herein we describe the preparation and structure‐activity relationship studies on range of stilbene based compounds and their antibacterial activity. Two related compounds, each bearing carboxylic acid moieties, exhibit good activity against several bacterial strains, including methicillin‐resistant Staphylococcus aureus MRSA (ATCC 33592 and NCTC 10442). Compound 10 was most active against Moraxella catarrhalis with minimum inhibitory concentrations (MICs) of 0.12–0.25 μg mL^?1 and against Staphylococcus spp. with MICs ranging from 2–4 μg mL^?1. The derivative 17 showed increased activity with MICs of 0.06–0.25 μg mL^?1 against M. catarrhalis and 0.12–1 against Staphylococcus spp. This level of activity is similar to that reported for S. aureus for antibiotics, such as vancomycin, with MICs of ≤2.0 μg mL^?1 and clindamycin with MICs of ≤0.5 μg mL^?1. As an indicator of toxicity, 17 was tested for its ability to lyse sheep erythrocytes, and showed low haemolytic activity. Such results highlight the value of tris(stilbene) compounds as antibacterial agents providing suitable properties for further development.     

Antimicrobial,DPPH scavenging and tyrosinase inhibitory activities of Thymus vulgaris,Helichrysum arenarium and Rosa damascena mill. ethanol extracts by using TLC bioautography and chemical screening methods

Antimicrobial, DPPH scavenging and tyrosinase inhibitory activities of Thymus vulgaris, Helichrysum arenarium and Rosa damascena Mill. ethanol extracts by using TLC bioautography and chemical screening methods. The ethanol extracts of Thymus vulgaris (Tv), Helichrysum arenarium (Ha) and Rosa damascena Mill. (Rm) (red) were screened for their antimicrobial, 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and tyrosinase inhibitory activities. The test microorganisms included bacteria of Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923). Thin Layer Chromatography (TLC) - bioautography, disk diffusion and well diffusion methods were used for the antimicrobial activity assays. Rosa damascena Mill. extract was effective against E. coli and all plant extracts showed antimicrobial activity against S. aureus. The phenolic acids in the structure of the extracts were also identified by LC-MS analysis. Human blood agar well diffusion method and TLC-DPPH assays were used to identify the hemolytic and antioxidant activity of plant extracts, respectively, along with 10 compounds including phenolic acids as a standard. Among these compounds, caffeic acid (Rf = 0.68) was detected in all extracts while vanillic acid (Rf = 0.75), and gallic acid (Rf = 0.51) was found in Tv extract. Kojic acid (Rf = 0.36), on the other hand, was detected in Rm extract as a tyrosinase inhibitor. All plant extracts presented tyrosinase inhibitory activities on TLC-bioautography assay.     

Oxidatively rearranged cycloartane triterpenoids from the seeds of Pseudolarix amabilis

One novel and eight known oxidatively rearranged cycloartane triterpenoids were isolated from the seeds of Pseudolarix amabilis. The structure of the new isolate was elucidated on extensive spectroscopic analyses. Results indicated that pseudolarolide Q (4) exhibited strong antimicrobial activity against Gram-positive Staphylococcus aureus and Candida albicans at the MICs of 6.08 and 24.32 μM, respectively. Pseudolarolide I (2) showed the 11β-HSD1 inhibitory property at the IC₅₀ value of 34.5 nM.     

Synthesis of Silver Nanoparticles from Extracts of Wild Ginger (Zingiber zerumbet) with Antibacterial Activity against Selective Multidrug Resistant Oral Bacteria

Antibiotic resistance rate is rising worldwide. Silver nanoparticles (AgNPs) are potent for fighting antimicrobial resistance (AMR), independently or synergistically. The purpose of this study was to prepare AgNPs using wild ginger extracts and to evaluate the antibacterial efficacy of these AgNPs against multidrug-resistant (MDR) Staphylococcus aureus, Streptococcus mutans, and Enterococcus faecalis. AgNPs were synthesized using wild ginger extracts at room temperature through different parameters for optimization, i.e., pH and variable molar concentration. Synthesis of AgNPs was confirmed by UV/visible spectroscopy and further characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy analysis (EDXA), and Fourier-transform infrared spectroscopy (FTIR). Disc and agar well diffusion techniques were utilized to determine the in vitro antibacterial activity of plant extracts and AgNPs. The surface plasmon resonance peaks in absorption spectra for silver suspension showed the absorption maxima in the range of 400–420 nm. Functional biomolecules such as N–H, C–H, O–H, C–O, and C–O–C were present in Zingiber zerumbet (Z. zerumbet) (aqueous and organic extracts) responsible for the AgNP formation characterized by FTIR. The crystalline structure of ZZAE-AgCl-NPs and ZZEE-AgCl-NPs was displayed in the XRD analysis. SEM analysis revealed the surface morphology. The EDXA analysis also confirmed the element of silver. It was revealed that AgNPs were seemingly spherical in morphology. The biosynthesized AgNPs exhibited complete antibacterial activity against the tested MDR bacterial strains. This study indicates that AgNPs of wild ginger extracts exhibit potent antibacterial activity against MDR bacterial strains.     

Antimicrobial activities,toxicity and phenolic composition of Asphodeline anatolica E. Tuzlaci leaf extracts from Turkey

The antimicrobial activity of acetone, methanol and aqueous extracts of Asphodeline anatolica E. Tuzlaci leaves was evaluated against American type culture collection, food and clinical isolates (Listeria monocytogenes and Staphylococcus aureus including methicillin-resistant strains-MRSA). Biofilm formation, toxicity and characterisation of the polyphenolic content were analysed. The acetone extract demonstrated a higher antibacterial activity against S. aureus including MRSA strains, L. monocytogenes and Pseudomonas aeruginosa than against other extracts. No effect was observed in biofilm formation. The extracts resulted non-toxic against Artemia salina Leach. The phytochemical screening of extracts indicated that they mainly contained six polyphenols identified as catechin 3-O-gallate, protocatechuic acid, diosmin, rutin, cirsimaritin and kaempferol glucoside. This study is the first report on antimicrobial activity and phenolic content of A. anatolica and contributes to enrich the literature data on the biological properties of this plant. A. anatolica leaves have a potential as source of natural antimicrobial compounds.     

Antioedematogenic activity,acetylcholinesterase inhibition and antimicrobial properties of Jacaranda oxyphylla

Jacaranda oxyphylla Cham. (Bignoniaceae) is a shrub found in the Brazilian cerrado and used in folk medicine to treat microbial infections. The aim of this study was to carry out a phytochemical screening and evaluate antioedematogenic, antimicrobial and antiacetylcholinesterase properties of J. oxyphylla crude extracts. All extracts analysed showed presence of terpenoids, which are potentially active chemical substances. A high AChE inhibitory activity for hexane extract from leaves and for the extracts from twigs was found. Ethanol extract from leaves of J. oxyphylla showed activity against Gram-positive (Staphylococcus aureus and Bacillus cereus) and Gram-negative (Escherichia coli) bacteria. This extract was also effective in inhibiting the stages of inflammation evaluated. Biological investigation and phytochemical screening of J. oxyphylla extracts provided additional evidence of its traditional medicinal value.     

An in vitro evaluation of the antibacterial activity of the non-volatile phenolic fraction from rosemary leaves

In this study, the aim was to evaluate the antimicrobial action of the non-volatile phenols of rosemary leaves against two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and two Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis). Three extracts with different phenolic compositions were tested. By the agar disc diffusion method, Gram-positive bacteria were more sensitive to the extracts, and S. epidermidis showed the highest inhibition zones. Overall, all the extracts tested by the broth dilution method showed higher activity than results from the agar disc diffusion method. The minimal bactericidal concentration values indicated that E. coli was the most susceptible strain. This study demonstrated that the flavonoidic fraction of rosemary leaves does not play a crucial role as antimicrobial agents against these microorganisms. The most active extract was characterised by the highest amount of non-volatile terpenoidic compounds.     

In Vitro Antimicrobial Activity of Lavender,Mint, and Rosemary Essential Oils and the Effect of Their Vapours on Growth of Penicillium spp. in a Bread Model System

The chemical composition, antioxidant activity, and antimicrobial properties of three commercially available essential oils: rosemary (REO), lavender (LEO), and mint (MEO), were determined in the current study. Our data revealed that the major components of REO, MEO, and LEO were 1,8-cineole (40.4%), menthol (40.1%), and linalool acetate (35.0%), respectively. The highest DPPH radical-scavenging activity was identified in MEO (36.85 ± 0.49%) among the investigated EOs. Regarding antimicrobial activities, we found that LEO had the strongest inhibitory efficiencies against the growth of Pseudomonas aeruginosa and Candida (C.) tropicalis, MEO against Salmonella (S.) enterica, and REO against Staphylococcus (S.) aureus. The strongest antifungal activity was displayed by mint EO, which totally inhibited the growth of Penicillium (P.) expansum and P. crustosum in all concentrations; the growth of P. citrinum was completely suppressed only by the lowest MEO concentration. The lowest minimal inhibitory concentrations (MICs) against S. enterica, S. aureus, and C. krusei were assessed for MEO. In situ analysis on the bread model showed that 125 µL/L of REO exhibited the lowest mycelial growth inhibition (MGI) of P. citrinum, and 500 µL/L of MEO caused the highest MGI of P. crustosum. Our results allow us to make conclusion that the analysed EOs have promising potential for use as innovative agents in the storage of bakery products in order to extend their shelf-life.     

Chemical compositions and antibacterial activity of extracts obtained from the inflorescences of Cirsium canum (L.) all

The aim of this study was to investigate phenolic acids and flavonoids in methanolic, dichloromethane, acetone and ethyl acetate extracts and fractions from inflorescences of Cirsium canum (L.). RP-HPLC analysis enabled identification of the following: chlorogenic acid, caffeic acid, p-coumaric acid, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, syringic acid, trans-cinnamic acid, luteolin-7-glucoside, apigenin-7-glucoside, kaempferol-3-glucoside, linarin, apigenin, rutoside, luteolin and kaempferol. The antimicrobial activity of tested extracts was determined in vitro against reference microorganisms, including bacteria or fungi, belonging to yeasts. Our data showed that the tested extracts had no influence on the growth of the reference strains of Gram-negative bacteria and yeasts belonging to Candida spp. Among them, the fractions possessed the highest activity against Gram-positive bacteria, especially Streptococcus aureus and Streptococcus pneumoniae belonging to pathogens and Streptococcus epidermidis, Bacillus cereus and Bacillus subtilis belonging to opportunistic microorganisms.     

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.     

Quantification of polyphenols and flavonoid content and evaluation of anti-inflammatory and antimicrobial activities of Stenocereus stellatus extracts

The hexanic, ethyl acetate and methanolic extracts from branches of Stenocereus stellatus were tested in both the 12-O-tetradecanoylphorbol-13-acetate (TPA) – induced ear oedema model and antimicrobial activity assay. The % of oedema inhibition, the Minimum Inhibitory Concentration (MIC), as well as the polyphenolic and flavonoid content were determined. Also, extracts were analysed by gas chromatography–mass spectrometry (GC–MS). In TPA model, the three extracts showed moderate oedema inhibition. In the antimicrobial activity assay, methanolic extract shows better MIC against all strains. The lowest MICs were for Candida albicans (31 μg/mL) and Rhizopus sp. (15 μg/mL). Also, 50.78 mg eq. of gallic acid/g extract of polyphenol and 115.12 mg eq. of catequine/g extract of flavonoids content were founded in ethyl acetate extract. In the chromatographic analysis, β-sitosterol, β-amyrine, betulin and some other molecules were identified. The results show that S. stellatus possess antimicrobial activities against some fungus species.     

A One‐Step Process for the Antimicrobial Finishing of Textiles with Crystalline TiO2 Nanoparticles

Titanium oxide (TiO₂) nanoparticles (NPs) in their two forms, anatase and rutile, were synthesized and deposited onto the surface of cotton fabrics by using ultrasonic irradiation. The structure and morphology of the nanoparticles were analyzed by using characterization methods such as XRD, TEM, STEM, and EDS. The antimicrobial activities of the TiO₂–cotton composites were tested against Escherichia coli (Gram‐negative) and Staphylococcus aureus (Gram‐positive) strains, as well as against Candida albicans. Significant antimicrobial effect was observed, mainly against Staphylococcus aureus. In addition, the combination of visible light and TiO₂ NPs showed enhanced antimicrobial activity.     

Comparative study of the phenolic profile,antioxidant and antimicrobial activities of leaf extracts of five Juniperus L. (Cupressaceae) taxa growing in Turkey

Abstract

The purpose of this study was to conduct a comparative evaluation of some biological properties of methanol and water extracts of leaves of five Juniperus taxa growing in Turkey: J. communis L. var. communis (Jcc), J. communis L. var. saxatilis Pall. (Jcs), J. drupacea Labill. (Jd), J. oxycedrus L. subsp. oxycedrus (Joo), J. oxycedrus L. subsp. macrocarpa (Sibth. & Sm.) Ball. (Jom). The antioxidant properties were examined in vitro; both in the DPPH and in the reducing power tests, Joo methanol extract resulted the most active (IC₅₀?=?0.09?±?0.01mg/mL and ASE/mL?=?2.56?±?0.06). In the TBA assay, Jcs methanol extract exhibited the highest activity (IC₅₀?=?4.39?±?0.47?μg/mL). The extracts displayed bacteriostatic activity against Staphylococcus aureus, and Jd methanol extract resulted the most effective (MIC?=?19.53?μg/mL); no effect on the S. aureus biofilm formation was observed. The extracts resulted non-toxic in the Artemia salina lethality bioassay. Finally, the phenolic profile of the methanol extracts was characterized by HPLC-PDA/ESI-MS.     

Telechelic,Antimicrobial Hydrophilic Polycations with Two Modes of Action

Telechelic antimicrobial poly(2‐oxazoline)s with quaternary ammonium (quat) end groups are shown to be potent antimicrobial polymers against Gram‐positive bacterial strains. In this study, the activity against the Gram‐negative bacterium Escherichia coli is additionally implemented by hydrolyzing the poly(2‐methyl‐2‐oxazoline) with two quart end groups to poly(ethylene imine) (PEI). The resulting telechelic polycations are active against Staphylococcus aureus and E. coli. The contribution of the PEI backbone is determined by measuring the antimicrobial activity in the presence of calcium ions. The influence of PEI on the overall activity strongly depends on the molecular weight and increases with higher mass. The PEI dominates the activity against E. coli at lower masses than against S. aureus. The quart end groups require an alkyl substituent of dodecyl or longer to dominate the antimicrobial activity. Additionally, PEI and quart end groups act synergistically.     

Antibacterial and antifungal properties of crude extracts and isolated compounds from Lychnophora markgravii

Abstract

Antimicrobial activity of dichloromethane and ethanol extracts and five compounds: pinostrobin (I), pinocembrin (II), tectochrysin (III), galangin 3-methyl ether (IV) and tiliroside (V) isolated from Lychnophora markgravii aerial parts against fifteen microorganisms was determined. The structures of these compounds were elucidated based on ESI-MS and NMR spectroscopic data. Both extracts showed antimicrobial activity against several tested microorganisms. Pinostrobin, tectochrysin and galangin 3-methyl ether showed the strongest antibacterial and antifungal effects.     

Synthesis and Antimicrobial Activities of Some 1-[(N,N-Disubstitutedthiocarbamoylthio)acetyl]-3,5-diaryl-2-pyrazolines

The increasing clinical importance of drug-resistant fungal and bacterial pathogens has lent additional urgency to microbiological research and new antimicrobial compound development. For this purpose, new pyrazoline derivatives were synthesized and evaluated for antimicrobial activity.

Some 1-[(N, N-disubstitutedthiocarbamoylthio)acetyl]-3,5-diaryl-2-pyrazolines derivatives were synthesized by reacting 1-(chloroacetyl)-3,5-diaryl-2-pyrazolines with appropriate potassium salts of secondary amine dithiocarbamic acids. The chemical structures of the compounds were elucidated by IR, ¹ H-NMR, and FAB⁺-MS spectral data. Their antimicrobial activities against Staphylococcus aureus (B-767), Escherichia coli (B-3704), Pseudomonas aeruginosa (ATCC 27853), Proteus vulgaris (NRLL B-123), and Candida albicans (NRRL-27077) were investigated. The results showed that some of the compounds have notable activity against S. aureus and C. albicans.     

Comparative effects of some extraction solvents on the antimicrobial activity of Eucalyptus camaldulensis leaf,bud, capsule and seed crude extracts

Well diffusion method was used to evaluate the antibacterial activity of Eucalyptus camaldulensis, while the antifungal effect was assessed by calculating the reduction percent in the radial growth of mycelia. The inhibition zones exerted by E. camaldulensis crude extracts varied significantly (p ≤ 0.01). The capsule crude extract (acetone 30%) highly inhibited the growth of Acinetobacter baumannii (35 mm clear zone). The highest antifungal activity was against Rhizopus stolonifer with a reduction percent in its radial growth reached to 96%. The bacterial MICs ranged from 20 to 0.5 mg/mL against Escherichia coli and Bacillus subtilis respectively. The MIC values for fungi were between 18 mg/mL (Mucor sp.) and 4 mg/mL (R. stolonifer). Both type and concentration of the solvent greatly affected the antimicrobial potentials of E. camaldulensis. The empty capsule and bud of E. camaldulensis are recognized for the first time as potentially natural resources of effective antimicrobial agents.     

The Antimicrobial Activity,Mosquito Larvicidal Activity,Antioxidant Property and Tyrosinase Inhibition of Piper Betle

The essential oil and methanolic and aqueous extracts of Piper betle L. were assayed for their antimicrobial activity, mosquito larvicidal activity, antioxidant property and mushroom tyrosinase inhibition. The methanolic and aquaous extracts showed strong activity against the yeasts: C. albicans, and M. pachydermatis. The crude essential oil exhibited a broad‐spectrum strong antimicrobial activity against all test organisms. The strongest activity was observed against C. albicans, followed by S. aureus and M. pachydermatis. The chemical composition of the essential oil and its fractions was analyzed by GC/MS analysis. Eugenol (36.2%), chavibetol acetate (16.9%), 4‐allylphenyl acetate (9.4%) and 4‐allylphenol (7.2%) were the main components, comprising 69.7% of the oil. The fractionation of the essential oil gave two fractions. Fraction I was rich in eugenol (71.3%) and fraction II in eugenol (46.4%), chavibetol acetate (19.4%) and 4‐allylphenyl acetate (11.8%). The essential oil exhibited the mosquito larvicidal activity with 2 h and 24 h LD₅₀ value of 86 and 48 ppm, respectively. The methanolic extract of P. betle showed larvicidal activity with 2 h and 24 h LD₅₀ value of 153 and 125 ppm, respectively, whereas the aqueous extract showed slight active. The individual antioxidant assays such as DPPH scavenging activity, chelating effect of ferrous ions and reducing power have been used. P. betle showed remarkable antioxidant activity in DPPH and reducing power assays. The activity observed can be attributed to the presence of the phenolic compounds. The essential oil exhibited concentration‐dependent inhibition of mushroom tyrosinase, giving an IC₅₀ value of 126 ppm. The fraction I showed a strong inhibition of tyrosinase activity, giving an IC₅₀ value of 115 ppm. The presence of 4‐allylphenolic components in the essential oil may play an important role in the inhibition of tyrosinase. In conclusion, the results presented here show that Piper betle essential oil could be considered as a natural antimicrobial, mosquito larvicidal, antioxidant and tyrosinase inhibition source.     

Antioxidant and Antimicrobial Evaluation and Chemical Investigation of Rosa gallica var. aegyptiaca Leaf Extracts

Rosa gallica var. aegyptiaca is a species of flowering plant belonging to the Rosaceae family that plays an important role as a therapeutic agent for the treatment of specific types of cancer, microbial infections, and diabetes mellitus. This work presents the first report on the evaluation of the antioxidant and antimicrobial potential along with the phytochemical analysis of Rosa gallica var. aegyptiaca leaves. Five leaf extracts of hexane, chloroform, methanol, hydromethanol 80%, and water were prepared. Assessment of antioxidant activity was carried out via DPPH radical scavenging assay. Antimicrobial activity against five foodborne pathogenic bacteria—including Listeria monocytogenes, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Salmonella enteritidis—and the fungus Candida albicans, was examined using the disc diffusion method. Total phenolic content and total flavonoid content were determined using the Folin–Ciocalteu reagent and aluminum chloride methods, respectively. Isolation, identification, and quantification of phenolic compounds were performed using HPLC-DAD analysis. Amongst the five leaf extracts that were investigated, hydromethanol 80% extract possessed the highest extraction yield, antioxidant activity, total phenolic content, and antimicrobial activity against all tested microbial strains. Moreover, this extract furnished six active phenolic compounds: gallic acid (1), (+) catechin (2), chlorogenic acid (3), (–) epicatechin (4), quercetin-3-O-α-d-(glucopyranoside) (5), and quercetin (6). This study provides an alternative utilization of R. gallica var. aegyptiaca leaves as a readily accessible source of natural antioxidants and antimicrobials in the food and pharmaceutical industries.