Agar Diffusion Assay Research Articles

Heterologous expression of pediocin PA-1 in Pichia pastoris: cloning, expression, characterization, and application in pork bologna preservation.

Pediocin PA-1, an antimicrobial peptide derived from Pediococcus acidilactici PAC1.0, has a potential application as a food preservative thanks to its strong inhibitory activity against the foodborne pathogen L. monocytogenes. This study aimed to produce Pediocin PA-1 from the yeast P. pastoris and evaluate its characteristics. Gene encoding Pediocin PA-1 was integrated into P. pastoris X33 genome to establish the strain X33::ped, which could produce and secrete this peptide into culture medium. The antimicrobial activity of Pediocin PA-1 was examined using agar diffusion assay. The stability of pediocin PA-1 was determined based on its remaining antibacterial activity after exposure to proteases and extreme pH and temperatures. The potential use of this bacteriocin in food preservation was demonstrated using the L. monocytogenes infected pork bologna. The anticancer activity of Pediocin PA-1 was also investigated on some cancer cells using MTT assay. We established the yeast P. pastoris X33::ped capable of producing pediocin PA-1 with antimicrobial activity against L. monocytogenes and some other harmful bacteria. Pediocin PA-1 was stable at 100˚C and resistant against pH 1-12 for 1h, but susceptible to trypsin, α-chymotrypsin, and proteinase K. This peptide could reduce the number of L. monocytogenes in pork bologna by 3.59 log CFU/g after 7 days of storage at 4˚C. Finally, Pediocin PA-1 (25µg/ml) inhibited the proliferation of A549 and Hela cancer cells. We succeeded in producing active Pediocin PA-1 from P. pastoris and demonstrated its potential use in food preservation and pharmaceutical industry.

Антимікробна та противірусна активність нанокомпозитів на основі поліелектролітних комплексів з наночастинками срібла

Recently, nanocomposite materials containing nanoparticles of metals such as silver, copper and zinc oxide have attracted most attention due to their pronounced pharmacological properties, such as antimicrobial, antiviral, antiinflammatory, immunomodulatory ability and high stability in extreme conditions. Polyelectrolyte complexes based on polymers of natural origin, namely polysaccharides of chitosan and pectin, which can stabilize nanoparticles of a smaller size than individual polymers have significant potential for creation of silver-containing nanocomposites. The aim of this article is to study the antimicrobial and antiviral activity of silver-containing nanocomposites based on polyelectrolyte complexes. Methods. Peculiarities of the structural organization of silver-containing nanocomposites were investigated by the method of wide-angle scattering on an XRD-7000 diffractometer. The morphology of Ag nanoparticles in polymer matrixes were studied by transmission electron microscopy method (transmission electron microscope JEOL 100 CXII). The antimicrobial activity of silver-containing nanocomposites was determined by agar diffusion assays against opportunistic pathogens Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. Cytotoxicity and antiviral activity were investigated using the MTT method and staining by gentian violet. Results. Analysis of wide-angle X-ray diffractograms of silver-containing nanocomposites based on polyelectrolyte complexes Na-CMC (pectin) – chitosan showed that at reduction of Ag+ ions to metallic silver, there are two low-intensity diffraction maxima at 2θm ~ 380 and 440 in the diffractograms. These maxima correspond to the crystallographic planes of the face-centered cubic lattice of silver, are characterized by indices (111) and (200), respectively, and confirm the presence of metallic silver in the polymer system. Analysis of micrographs of silver-containing nanocomposites based on Na-CMC and chitosan showed that larger nanoparticles are formed with increasing the molecular weight of chitosan. The dependence of the size of silver nanoparticles on the wavelength of ultraviolet radiation at reduction of silver ion in polyelectrolyte-metal complexes Na-CMC–Ag+–chitosan of low molecular weight was also revealed. In particular, smaller particles are formed under irradiation by light with a shorter wavelength (λ =254 nm) than at λ=365 nm. Silver-containing nanocomposites Na-СMC-Ag-chitosan and pectin citrus-Ag-chitosan, obtained by reduction of Ag+ ions under ultraviolet irradiation at a wavelength λ = 365 nm and λ = 254 nm, exhibit high antimicrobial activity against the test cultures of microorganisms S. aureus, E. coli, and P. aeruginosa C. albicans. No significant dependence of antimicrobial activity on the molecular weight of the studied samples was noted: the obtained data were within close limits and had close values. In addition, no dependence of antimicrobial activity on the type of investigated test cultures of microorganisms was observed either. Nanocomposites based on Na-CMC-chitosan (λ = 365 nm) inhibited infection titer HSV-1 by (3.72–5.45) lgTCID50/mL, whereas the decrease in titer during incubation with samples based on citrus pectin-chitosan was within (2.39–2.42) lgTCID50/mL. A dose-dependent relationship between molecular weight of chitosan and reduction of infection titer was observed. It was found that silver-containing nanocomposites formed by reduction of silver ions in polyelectrolyte-metal complexes under ultraviolet radiation of different wavelengths had no cytotoxic effect on cells of MDCK and BHK. Conclusions. The investigated silver-containing nanocomposites based on Na-CMC (pectin)-chitosan polyelectrolyte complexes show antimicrobial activity against test cultures of S. aureus, E. coli P. aeruginosa, and C. albicans along with antiviral activity against herpes simplex virus type 1 and influenza virus. It was established that the obtained nanocomposites did not show a cytotoxic effect on MDCK and BHK cells. The obtained data allow us to assert that investigated silver-containing nanocomposites are promising antimicrobial means for the development of new effective strategies against microorganisms and viruses and improvement of the population health.

Antimicrobial Effect of Honey Phenolic Compounds against E. coli-An In Vitro Study.

Growing concern over antimicrobial resistance in chronic wound patients necessitates the exploration of alternative treatments from natural sources. This study suggests that honey's phenolic compounds may offer antimicrobial benefits, warranting further investigation for therapeutic development. The main aim of this study was to investigate the antimicrobial activity of phenolic compounds and to determine the effects of their sub-inhibitory concentrations against Escherichia coli (E. coli). 3-phenyllactic acid (PLA), p-coumaric acid (PCA), and phloretin were tested against the bacterial strain of E. coli ATCC 25922. Comparison of the antimicrobial activity of honey constituents in vitro was performed using a broth culture assay. Measurement of the inhibitory properties of constituents in vitro was conducted using disc and well diffusion assays. The effects of sub-inhibitory concentrations of PCA on the susceptibility of E. coli ATCC 25922 to penicillin-streptomycin were tested. The results demonstrated that PLA was the most efficient antimicrobial agent, followed by PCA, whereas phloretin, at lower (2 mg/mL) concentrations, led to an increase in the growth of E. coli. Various modifications of the agar diffusion assay did not reveal the antibacterial properties of the studied phytochemicals. The enhancing effect of a sub-inhibitory concentration of PCA in cooperation with penicillin-streptomycin was shown. These findings might be helpful for the further investigation and development of new antimicrobial agents for the treatment of skin infections and wounds.

Multifunctional application of different iron oxide nanoparticles

Abstract Iron oxide nanoparticles have found wide applications in different fields of biomedicine and advanced catalytic applications. Several studies have suggested using iron oxide nanoparticle (Fe2O3-NPs) be a potential candidate for antibacterial activity assessment. Iron oxide nanoparticles, apart from being available extensively and cheap, also plays a vital part in multiple biological processes, making it an interesting choice of selection. The aim of the present study revolves around synthesis and characterization of iron oxide Fe2O3-NPs, followed by assessment of its antimicrobial activities and its catalytic behaviour. Synthesis of Fe2O3-NPs was performed by co-precipitation approach, and commercial iron oxide samples were studied for the comparison. The silver nanoparticles were also doped to the iron oxide nanoparticles and studied for the synergic effect. The samples characterization was done by UV-visible, X-ray diffraction (XRD), Scanning electron microscopy (SEM) with EDS and transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman Spectroscopy (RAMAN). Antimicrobial activity was checked by agar diffusion assay against Gram positive and Gram negative bacteria. The electrode performance of the iron oxide samples was done by cyclic voltammetry to explore their application in the energy storage and sensor.

Antibacterial, biocompatible, and mineralization-inducing properties of calcium silicate-based cements.

Different pulp capping materials have different origins and compositions, require different preparations, and may vary in their bioactive properties. The purpose of this study was to evaluate the antibacterial activity, biocompatibility, and mineralization-inducing potential of calcium silicate-based pulp capping materials. Six contemporary calcium silicate-based cements, ProRoot MTA, MTA Angelus, Biodentine, EndoSequence, NeoMTA 2, and NeoPutty, were evaluated. The antibacterial effects of these materials against Streptococcus mutans UA159 and Enterococcus faecalis ATCC 29212 were determined by the agar diffusion assay and the direct culture test. The biocompatibility and mineralization-inducing potential of these materials in preodontoblastic 17IIA11 cells were evaluated by the MTT assay and by Alizarin Red S staining, respectively. In agar diffusion test, only Biodentine showed distinct antibacterial effects against S. mutans. All the tested materials, however, showed antibacterial effects against S. mutans and E. faecalis in the direct culture test, with Biodentine showing the strongest growth inhibition against both S. mutans and E. faecalis. All the tested materials showed acceptable biocompatibility and mineralization-supporting potential in our experimental conditions. In summary, ProRoot MTA, MTA Angelus, Biodentine, EndoSequence, NeoMTA 2, and NeoPutty demonstrated acceptable invitro antimicrobial, biocompatible, and mineralization-supporting properties.

Formulation and evaluation of azithromycin-loaded silver nanoparticles for the treatment of infected wounds

Infected wounds pose a significant challenge in healthcare, requiring innovative therapeutic strategies. Therefore, there is a critical need for innovative pharmaceutical materials to improve wound healing and combat bacterial growth. This study examined the efficacy of azithromycin-loaded silver nanoparticles (AZM-AgNPs) in treating infected wounds. AgNPs synthesized using a green method with Quinoa seed extract were loaded with AZM. Characterization techniques, including X-ray Powder Diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and Uv-Vis analysis were utilized. The agar diffusion assay and determination of the MIC were used to assess the initial antibacterial impact of the formulations on both MRSA and E. coli. In addition, the antimicrobial, wound-healing effects and histological changes following treatment with the AZM-AgNPs were assessed using an infected rat model. The nanoparticles had size of 24.9 ± 15.2 nm for AgNPs and 34.7 ± 9.7 nm for AZM-AgNPs. The Langmuir model accurately characterized the adsorption of AZM onto the AgNP surface, indicating a maximum loading capacity of 162.73 mg/g. AZM-AgNPs exhibited superior antibacterial properties in vivo and in vitro compared to controls. Using the agar diffusion technique, AZM-AgNPs showed enhanced zones of inhibition against E. coli and MRSA, which was coupled with decreased MIC levels. In addition, in vivo studies showed that AZM-AgNP treated rats had the best outcome characterized by improved healing process, lower bacterial counts and superior epithelialization, compared to the control group. In conclusion, AZM-AgNPs can be synthesized using a green method with Quinoa seed with successful loading of azithromycin onto silver nanoparticles. In vitro and in vivo studies suggest the promising use of AZM-AgNPs as an effective therapeutic agent for infected wounds.

Evaluation of the antimicrobial and antioxidant properties of synthetic phenolipids

Functionalization of phenolic compounds by lipophilization allowing the synthesis of new compounds with improved biological properties. This study aims to investigate the antimicrobial effects of eight synthesized phenolipids, derived from bioactive coumaric and ferulic acid esters, against Bacillus subtilis, Escherichia coli, and Candida albicans. Antioxidant activity, as well as antimicrobial capacity were evaluated through DPPH assays and classical disc agar diffusion, respectively, concomitantly with the evaluation of cellular viability using flow cytometry assay. Antioxidant activities results showed that ferulic acid esters exhibit higher antiradical activity than coumaric acid esters. Results of agar diffusion assay revealed that, 1-methylpropyl coumarate and 1-methylpropyl ferulate (1-MPF) have an effective antimicrobial activity with Minimum Inhibitory Concentrations (MICs) values between 0.9 and 3.5 mM against all tested microorganisms. Also, flow cytometry showed that 1-MPF and decyl coumarate exhibited significant bactericidal activity (p < 0.05), with almost 63 % of dead Bacillus subtilis cells. Compared to the commonly used agar method, flow cytometry proved to be a fast and straightforward analytical tool to assess antimicrobial activity while providing information on inhibition type. These results suggest the applicability of phenolipids as potent lipophilic bioactive molecules to protect food products and cosmetic formulations from oxidative stress and microbial spoilage.

Antibacterial effects of children's and adults' toothpastes containing different amounts of fluoride: An in vitro study.

In recent years, fluoride concentrations in toothpaste for children and adults have increased. However, the effects of different concentrations on bacterial activity have rarely been compared. We aimed to investigate and compare the antibacterial activity of children's and adults' toothpaste containing 500, 1000‒1100, and 1450‒1500 ppm fluoride. Three strains of bacteria (Streptococcus mutans, Streptococcus salivarius, and Lactobacillus casei) were cultured in brain heart infusion agar. Thirty commercially available toothpaste products for children and adults containing 500, 1000‒1100, and 1450‒1500 ppm fluoride were selected and tested. Toothpaste's ability to inhibit bacterial growth was evaluated by agar diffusion assay, in which plates were incubated for 24 hours, and then the diameter of the microbial inhibition zone was measured. Comparisons between children's and adults' fluoride toothpastes were made using the Mann-Whitney U test. The association between bacterial growth inhibition and sodium lauryl sulfate (SLS) was analyzed by the chi-square test. A P value of <0.05 was considered statistically significant. No difference in the inhibition zone was observed for different fluoride concentrations. However, there were significant differences between toothpastes for children and adults, with higher inhibition zones for adults' toothpastes. Most toothpastes for adults contained SLS, which was associated with antibacterial activity. Fluoride concentrations ranging from 500 to 1500 ppm did not affect bacterial growth. The antibacterial activity of toothpastes for adults was significantly higher than that of toothpastes for children, which was mainly attributed to the SLS usually added to adult formulations.

A novel methodology for stabilization of silver nanoparticles on cotton, nylon and cotton/nylon fabrics using chitosan and triethyl orthoformate for enhanced and elongated antibacterial performance

In the present study, the commercially available three different fabrics cotton, nylon and cotton/nylon were modified by chitosan and silver nanoparticles using a crosslinker triethyl orthoformate (TEOF). Resulted cotton‑silver (Ag-Cs-Cot), nylon‑silver (Ag-Cs-Nyl) and cotton-nylon silver (Ag-Cs-Cot-Nyl) fabrics showed significant anti-bacterial activity even after 50 washing cycles. Silver nanoparticles were prepared by reducing silver nitrate through sodium borohydride at 0 °C. In FTIR spectra the peak at near 1650 cm−1 confirmed that TEOF mediated attachment of chitosan with fabrics (due to C=N) and the stretching of secondary amine near the 3375 cm-1 indicated the silver attachment to the amine group of the chitosan. In Scanning Electron Microscope (SEM) images smooth surfaces of fabrics without any damage by modification process were observed. The antibacterial activity was Analyzed by agar diffusion and broth dilution assays against Escherichia coli and Staphylococcus aureus bacterial strains and results showed 90% bacterial inhibition against E. coli and 89% bacterial inhibition against S. aureus. For testing the antibacterial durability, the modified fabrics were washed with non-ionic detergent (10g/l) for 15 minutes under aggressive stirring (100 rpm) at room temperature. The modified fabrics retained antibacterial activity over the 50 washing cycles. Finally, the commercial potential of cotton-silver fabric was evaluated by stitching it with the socks of football players and interestingly results showed that the modified fabric on the socks showed more than 90% bacterial inhibition as compared to the plain fabric after 70 minutes of playing activity.

Edible microbial cellulose-based antimicrobial coatings and films containing clove extract

Recently, microbial cellulose-based coatings and films have attracted substantial attention because of their promising uses in numerous fields, such as food packaging. The present work was designed to synthesize active microbial cellulose-based coatings and films with a comprehensive investigation of their antimicrobial and structural properties. Microbial cellulose was synthesized by using a gram-negative bacterium called Acetobacter aceti. The produced microbial cellulose was mixed with sodium alginate, chitosan and starch to obtain two different composite solutions, i.e., microbial cellulose + starch + chitosan (MSC) and microbial cellulose + starch + sodium alginate (MSS). The antimicrobial properties were achieved by incorporating four different concentrations of clove extract into the composite solutions. The resulting composite solutions were tested against S. aureus, Shigella, Salmonella, and E. coli through the agar diffusion assay method. The clove extract was found to be effective in inhibiting the growth of these pathogens, as a clear zone of inhibition was observed at all clove extract concentrations, with a maximum zone of inhibition of 4.0 ± 0.05 cm on E. coli for the MSC solution incorporated with 4% clove extract. The best antimicrobial solutions found were then casted into films by pouring the solutions into petri dishes and drying at 50 °C in a tray drier. The antimicrobial activity was again evaluated for the films. The results indicated that MSC 3% showed a greater zone of inhibition against all pathogens (1.7 ± 0.18 cm). Furthermore, structural and thermal analyses of the formed films were conducted. The results indicated distinctive antimicrobial and structural characteristics of the films.Graphical

Synthesis and antibacterial activities of novel hybrid molecules based on benzothiazole, benzimidazole, benzoxazole, and pyrimidine derivatives, each connected to N-arylacetamide and benzoate groups

Novel benzimidazoles, benzothiazoles, and benzoxazoles linked to N-arylacetamide were synthesized in good yields by reacting a series of 2-oxo-2-(arylamino)ethyl 4-formylbenzoates with o-phenylenediamine, 2-aminothiophenol, or 2-aminophenol in ethanol at reflux in the presence of NaHSO3. Attempts to use the new aldehydes as adaptable precursors for the synthesis of fused dihydropyran or fused dihydropyridine via Michael or Hantzsch's reactions were unsuccessful; instead, the processes produced the corresponding arylidene derivatives. The structures of the novel compounds were verified with a variety of spectra. All synthesized compounds were evaluated for antibacterial activity against four different bacterial strains. Compound 6a had good activity against Escherichia coli in an agar diffusion assay, with an inhibitory zone width of 30 mm compared to ofloxacin (20 mm). Compounds 18a and 18b were most effective against Bacillus subtilis, with MICs of 156.3 and 312.5 µg/mL, respectively. Molecular docking investigations demonstrated that compounds 6a, 18a, and 18b had high binding affinities for bacterial tyrosyl-tRNA synthetase and DNA gyrase.

Poly (Lactic Acid) Cellulose Biocomposite Films as Potential Antimicrobial Food Packaging Material

Polylactic acid (PLA)-cellulose bio-composites were developed by incorporating Aloe vera (A. vera) leaf gel at ratios of 100/50 and 50/50. This study aimed to evaluate their physico-chemical, barrier, and antibacterial properties for potential application in sustainable food packaging. Different composite films were prepared and characterized by Fourier-transform infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM), mechanical testing, water absorption, and Ultraviolet (UV) transmission measurements. Their antibacterial activity against E. coli, P. aeruginosa, and S. aureus was assessed through agar diffusion and broth dilution assays. The presence of cellulose significantly affected the properties of the composite films. The 50/50 blend exhibited better chemical resistance and barrier properties compared to the 100/50 blend, highlighting the influence of cellulose content. Both ratios demonstrated promising antibacterial activity against all three target bacteria, while the 50/50 ratio showing pronounced inhibition against E. coli. These PLA-cellulose bio-composite films, with their combined UV-protective and antibacterial properties, present a sustainable and potential alternative to conventional food packaging materials, contributing to a reduced environmental pollution.

Synthesis of Piperidine Conjugated Quinoxalines as Potential Antibiofilm Agents

Background: The most common cause of food-borne illness is bacterial or viral contamination. Although there are several therapeutics available to combat these microbes, they lost their efficacy in long-term medication. Because, over a period of time, microbes developed resistance against drugs and this antimicrobial resistance is a serious threat to global public health as a consequence of the widely disseminated and careless use of antimicrobials. Therefore, there is a need to develop some new chemical moieties with a safety factor and better efficacy. A series of substituted N-(1-benzylpiperidin-4- yl)quinoxalin-2-amines (5a-j) (5ab, 5ac) were synthesized and screened for their in vitro antibacterial activity against Salmonella paratyphi, a well-known food-borne pathogen. Methods: Experimental methods, agar diffusion and broth microdilution assays were carried out to evaluate the antibacterial activity of the lead compounds. Further, antibiofilm methods, crystal violet, and MTT assays were subjected to investigate their biofilm inhibition capacity against S. paratyphi. Results: Among the tested compounds, 5b, 5e, 5h, and 5j bearing 4-chloro, 3,4-dimethoxy, 4-methyl and thienyl groups on the phenyl ring of quinoxalines emerged as potential candidates having significant antisalmonella activity. In these four potential candidates, compounds 5b and 5h were effective against Salmonella whereas compounds 5e and 5j effectively inhibited the biofilm formation of Salmonella. Conclusion: N-(1-benzylpiperidin-4-yl)quinoxalin-2-amines (5a-j) (5ab, 5ac) were synthesized and evaluated for antisalmonella activity against S. paratyphi. Among the series of compounds, four compounds significantly showed good activity and emerged as antibacterial agents for further studies in the future.

Chemical and biological characterization of Melaleuca subulata (Cheel) Craven leaves’ volatile constituents supported by chemometric analysis and molecular docking

BackgroundThe genus Melaleuca (Myrtaceae) comprises dozens of essential oil (EO)-rich species that are appreciated worldwide for their various medicinal values. Additionally, they are renowned in traditional medicine for their antimicrobial, antifungal, and other skin-related activities. The current study investigated the chemical profile and skin-related activities of volatile constituents derived from M. subulata (Cheel) Craven (Synonym Callistemon subulatus) leaves cultivated in Egypt for the first time.MethodsThe volatile components were extracted using hydrodistillation (HD), headspace (HS), and supercritical fluid (SF). GC/MS and Kovat’s retention indices were implemented to identify the volatile compounds, while the variations among the components were assessed using Principal Component Analysis and Hierarchical Cluster Analysis. The radical scavenging activity was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC) and β-carotene assays. Moreover, the anti-aging effect was evaluated using anti-elastase, and anti-collagenase, while the antimicrobial potential was deduced from the agar diffusion and broth microdilution assays. Lastly, the molecular docking study was executed using C-docker protocol in Discovery Studio 4.5 to rationalize the binding affinity with targeted enzymes.ResultsThe SF extraction approach offered the highest EO yield, being 0.75%. According to the GC/MS analysis, monoterpene hydrocarbons were the most abundant volatile class in the HD oil sample (54.95%), with α-pinene being the most copious component (35.17%). On the contrary, the HS and SF volatile constituents were pioneered with oxygenated monoterpenes (72.01 and 36.41%) with eucalyptol and isopulegone being the most recognized components, representing 67.75 and 23.46%, respectively. The chemometric analysis showed segregate clustering of the three extraction methods with α-pinene, eucalyptol, and isopulegone serving as the main discriminating phytomarkers. Concerning the bioactivity context, both SF and HD-EOs exhibited antioxidant effects in terms of ORAC and β-carotene bleaching. The HD-EO displayed potent anti-tyrosinase activity, whereas the SF-EO exhibited significant anti-elastase properties. Moreover, SF-EO shows selective activity against gram-positive skin pathogens, especially S. aureus. Ultimately, molecular docking revealed binding scores for the volatile constituents; analogous to those of the docked reference drugs.ConclusionsM. subulata leaves constitute bioactive volatile components that may be indorsed as bioactive hits for managing skin aging and infection, though further in vivo studies are recommended.

In-silico and in-vitro evaluation of antifungal bioactive compounds from Streptomyces sp. strain 130 against Aspergillus flavus

Streptomyces spp. are considered excellent reservoirs of natural bioactive compounds. The study evaluated the bioactive potential of secondary metabolites from Streptomyces sp. strain 130 through PKS-I and NRPS gene-clusters screening. GC-MS analysis was done for metabolic profiling of bioactive compounds from strain 130 in the next set of experiments. Identified antifungal compounds underwent ADMET analyses to screen their toxicity. All compounds’ molecular docking was done with the structural gene products of the aflatoxin biosynthetic pathway of Aspergillus flavus. MD simulations were utilized to evaluate the stability of protein-ligand complexes under physiological conditions. Based on the in-silico studies, compound 2,4-di-tert butyl-phenol (DTBP) was selected for in-vitro studies against Aspergillus flavus. Simultaneously, bioactive compounds were extracted from strain 130 in two different solvents (ethyl-acetate and methanol) and used for similar assays. The MIC value of DTBP was found to be 314 µg/mL, whereas in ethyl-acetate extract and methanol-extract, it was 250 and 350 µg/mL, respectively. A mycelium growth assay was done to analyze the effect of compounds/extracts on the mycelium formation of Aspergillus flavus. In agar diffusion assay, zone of inhibitions in DTBP, ethyl-acetate extract, and methanol extract were observed with diameters of 11.3, 13.3, and 7.6 mm, respectively. In the growth curve assay, treated samples have delayed the growth of fungi, which signified that the compounds have a fungistatic nature. Spot assay has determined the fungal sensitivity to a sub-minimum inhibitory concentration of antifungal compounds. The study’s results suggested that DTBP can be exploited for antifungal-drug development. Communicated by Ramaswamy H. Sarma

Phytochemical Constituents and Potential of Different Extracts from Eleutherine bulbosa on Skin Infectious Treatment : Anti-fungal, Anti-bacterial, Anti-inflammatory and Cytotoxic Activities

Eleutherine bulbosa is a plant commonly employed in traditional medicine across various tropical regions, including Thailand. The aim of this study was to identify the phytochemical constituents of E. bulbosa, evaluate the inhibitory effects on skin fungal and bacterial pathogens, and examine the anti-inflammatory and cytotoxic properties of extracts obtained from E. bulbosa bulbs through n-Hexane, EtOAc, and EtOH extraction methods. Agar diffusion, MIC, and MBC assays were employed to determine the fungistatic, bacteriostatic, and bactericidal activities. The EtOAc extract of E. bulbosa bulbs demonstrated the highest inhibition against fungal and bacterial strains when compared to other solvents. The results revealed that the EtOAc extract exhibited a potent anti-fungal effect on T. rubrum (the zones of inhibition = 35.00 ± 0.00 mm) comparable to Ketoconazole (the zones of inhibition = 34.33 ± 1.16 mm). The highest antibacterial activity against S. pyogenes was observed, with a zone diameter of 23.00 ± 1.00 mm, while the lowest MIC and MBC values were recorded at 19.53 and 78.12 μg/ml, respectively. Additionally, we demonstrated significant inhibitory properties of E. bulbosa bulbs extracted with n-Hexane on NO production in LPS-stimulated RAW 264.7 cells compared to other solvent extracts. This occurred without affecting cell viability across a concentration range of 6.25 to 25 μg/ml. Moreover, the less affected viability of fibroblasts suggests that the extract may be useful in preventing inflammatory diseases mediated by excessive production of NO with low toxicity to normal cells. Phytochemical screening indicated the presence of various compounds with biological activities including alkaloids, flavonoids, phenols, and tannins in all different solvent extracts. These findings suggest that E. bulbosa bulb extracts possess beneficial effects and hold potential for further development as a new natural source of multifunctional therapeutic agents, which are safe and effective for a broad spectrum of skin infectious microorganisms and also potentially reduce inflammation that is associated with an infection caused by microorganisms.

Antioxidant and antimicrobial activities of lignin-derived products from all steam-exploded palm oil mill lignocellulosic biomass waste

BackgroundSteam explosion pretreatment has been proven to be an effective treatment for breaking down the recalcitrant character of lignin–carbohydrate complexes (LCC) in lignocellulosic biomass. This study investigated the production of lignin-derived products from steam-exploded palm oil mill lignocellulosic biomass waste (POMLBW), that is, empty fruit bunches (EFB), kernel shells (KS), and kernel fibers (KF), also known as mesocarp fibers. Steam explosions cause lignin depolymerization, which forms various polyphenols. The low average molecular weight of the steam-exploded lignin-derived products and their antioxidant activities could potentially enhance their antimicrobial activities.MethodsPOMLBW was steam-exploded with various degrees of severity factors (R0: 4.03, 4.91, 5.12, 5.35, and 5.65). Steam-exploded POMLBW produces lignin-derived products such as low-molecular-weight lignin (LML) and water-soluble lignin (WSL). Antioxidant activity was evaluated using 0.5 mM 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. Polyphenol content was evaluated using the Folin–Ciocalteu method. The antimicrobial activity was evaluated using an agar diffusion assay with Gram-positive and Gram-negative bacteria, and the thermal characteristics were evaluated using differential scanning calorimetry and thermogravimetric analysis.ResultsWSL and LML resulted in high radical scavenging activity (RSA) of approximately 95% and 80%, with 0.25 g/L and 0.5 g/L of EC50, where the polyphenol amount was 242–448 mg/g (catechin eq.) and 20–117 mg/g (catechin eq.) under all LML and WSL conditions, respectively. The steam-exploded POMLBW had an average molecular weight of 1589–2832 Da, and this condition, including high RSA and polyphenol amounts, was responsible for the high antimicrobial activities of LML against both Gram-positive (Salmonella enterica, Pseudomonas aeruginosa, and Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. Additionally, the thermal properties investigations revealed that the glass transition temperature was 80–90 °C (Tg), the melting temperature (Tm) was 338–362 °C, and the start temperature was 101–128 °C at the beginning of mass loss.ConclusionsThese results show that the lignin-derived product from steam-exploded POMLBW has the potential for antioxidant (LML and WSL) and antimicrobial (LML) applications with good thermal resistance.Graphical

Antibacterial Activity of Hibiscus Flower Extracts

In Ayurveda and the traditional Chinese medicine system, it is well documented that the use of herbal extracts and nutritional supplements for the treatment of various diseases. The Hibiscus plant has been used as a diuretic, mild laxative, and treatment for cardiac and nerve diseases. This plant is used for mild laxative effect, the ability to increase urination, relief during hot weather, and treatment of cracks in the feet, bilious, sores, and wounds. The purpose of this study was to examine the evolution of antimicrobial activity of flower extract of Hibiscus against human pathogens. Fresh flowers and dried flower powder were used for extract production. Two types of extracts were prepared, viz. aqueous and solvent extracts. Their antibacterial activity was studied against different human pathogens. Well agar diffusion assay was used for antibacterial investigation.

Screening for Antimycobacterial Activity of Actinomycetes Collected in Vietnam – Isolation and Activity of Metabolites from Streptomyces alboniger (A121)

Objective Actinomycetes have been known to be the great natural sources to explore antibiotics for the treatment of tuberculosis (TB). The isolation of actinomycetes from the samples in Vietnam followed by the screening of their antimycobacterial activity was performed in this study. The metabolites isolated from the most active strain were further evaluated for their antimycobacterial, antimicrobial and cytotoxic activity. Methods Actinomycetes were growth in culture media, isolated and identified by colony, spore chain morphology and 16S rRNA gene sequencing. Agar diffusion assay was used for the screening of the isolated strains against Mycobacterium smegmatis, a safety surrogate for Mycobacterium tuberculosis. The metabolites produced from the most active strain were investigated by actinomycete fermentation, extraction and isolation from biomass and cultures. The structures of the isolated compound were elucidated by spectral data and comparison with the reported literatures. Results 181 strains were isolated from nine regions along the north to central Vietnam. The five most active strains against Mycobacterium smegmatis were detected. Following the bioassay-guided result, the strain A121 ( Streptomyces alboniger) was selected for further isolation of the bioactive metabolites. As a result, obscurolide B2β (1) and chartreusin (2) were obtained and evaluated for their antimycobacterial activity against M. smegmatis. Compound 2 displayed potential antimycobacterial activity, antimicrobial effect against the Gram positive bacteria Staphylococcus aureus, Bacillus subtilis, Lactobacillus fermentum and cytotoxicity against four cancer cell lines KB, HepG-2, Lu-1 and MCF-7. Conclusions Five strains possessing potential antimycobacterial activity were identified from the samples collected in Vietnam. Two compounds including obscurolide B2β (1) and chartreusin (2) were isolated from the most active strain A121 ( Streptomyces alboniger). This is the first time these compounds have been isolated from this strain. Chartreusin (2) exhibited notable antimycobacterial, antimicrobial and cytotoxic activity, making its worthy attention for further drug development, particularly for antituberculosis therapeutic agents.

Screening of Lactic Acid Bacteria from Oysters for Antibacterial Activity Against Selected Pathogens

Lactic acid bacteria (LAB) are among the important groups of bacteria and considered as probiotics development. LAB is mostly isolated from the gastrointestinal tract (GIT) from organism such as oyster. Oyster belongs in to class Bivalvia which live in estuaries area. The purpose of research was to isolate and screened for antibacterial activity against selected pathogens. The LAB was isolated by pour plate method using MRSA (De Man, Rogosa, Sharpe Agar) as selection media for LAB. Then, LAB was screened by an agar diffusion assay for antibacterial activity. The result showed that four isolates (TR-01; TR-02; TR-03 and TR-04) have inhibitory activity against pathogens including E. coli, Salmonella enterica, Staphylococcus aureus, Bacillus cereus. Therefore, it is needed further assay to selected 4 isolates as potential probiotics.