Chemical composition, antibacterial and antioxidant activities of leaf essential oil and extracts of Metasequioa glyptostroboides Miki ex Hu

Transcriptomic and Molecular Docking Analysis Reveal Virulence Gene Regulation-Mediated Antibacterial Effects of Benzyl Isothiocyanate Against Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a common pathogen that can cause many serious infections. Thus, efficient and practical techniques to fight S. aureus are required. In this study, transcriptomics was used to evaluate changes in S. aureus following treatment with benzyl isothiocyanate (BITC) to determine its antibacterial action. The results revealed that the BITC at subinhibitory concentrations (1/8th MIC) treated group had 94 differentially expressed genes compared to the control group, with 52 downregulated genes. Moreover, STRING analyses were used to reveal the protein interactions encoded by 36 genes. Then, we verified three significant virulence genes by qRT-PCR, including capsular polysaccharide synthesis enzyme (cp8F), capsular polysaccharide biosynthesis protein (cp5D), and thermonuclease (nuc). Furthermore, molecular docking analysis was performed to investigate the action site of BITC with the encoded proteins of cp8F, cp5D, and nuc. The results showed that the docking fraction of BITC with selected proteins ranged from - 6.00 to - 6.60 kcal/mol, predicting the stability of these complexes. BITC forms hydrophobic, hydrogen-bonded, π-π conjugated interactions with amino acids TRP (130), GLY (10), ILE (406), LYS (368), TYR (192), and ARG (114) of these proteins. These findings will aid future research into the antibacterial effects of BITC against S. aureus.

Chemical Composition, Antibacterial Activity and Mechanism of Action of Fermentation Products from Aspergillus Niger xj

Six compounds were isolated and purified from the crude acetone extract of Aspergillus niger xj. Characterization of all compounds was done by NMR and MS. On the basis of chemical and spectral analysis structure, six compounds were elucidated as metazachlor (1), nonacosane (2), palmitic acid (3), 5,5'-oxybis(5-methylene-2-furaldehyde) (4), dimethyl 5-nitroisophthalate (5) and cholesta-3,5-dien-7-one (6), respectively, and compounds 1, 4, 5 and 6 were isolated for the first time from A. niger. To evaluate the antibacterial activity of compounds 1-6 against three plant pathogenic bacteria (Agrobacterium tumefaciens T-37, Erwinia carotovora EC-1 and Ralstonia solanacearum RS-2), and the minimum inhibitory concentrations (MICs) were determined by broth microdilution method in 96-well microtiter plates. Results of the evaluation of the antibacterial activity showed that T-37 strain was more susceptible to metazachlor with the lowest MIC of 31.25 µg/mL. The antibacterial activity of metazachlor has rarely been reported, thus the antibacterial mechanism of metazachlor against T-37 strain were investigated. The permeability of cell membrane demonstrated that cells membranes were broken by metazachlor, which caused leakage of ions in cells. SDS-PAGE of T-37 proteins indicated that metazachlor could damage bacterial cells through the destruction of cellular proteins. Scanning electron microscopy results showed obvious morphological and ultrastructural changes in the T-37 cells, further confirming the cell membrane damages caused by metazachlor. Overall, our findings demonstrated that the ability of metazachlor to suppress the growth of T-37 pathogenic bacteria makes it potential biocontrol agents.

Sodium alginate emulsion loaded with linalool: Preparation, characterization and antibacterial mechanism against Shigella sonnei

This study aimed to prepare sodium alginate-linalool emulsion (SA-LE) to overcome the low solubility of linalool and explore its inhibitory activity against Shigella sonnei. The results indicated that linalool significantly reduced the interfacial tension between SA and oil phase (p < 0.05). Droplet sizes of fresh emulsions were uniform with sizes from 2.54 to 2.58 μm. The ζ-potential was between -23.94 and -25.03 mV, and the viscosity distribution was 973.62 to 981.03 mPa·s at pH 5-8 (near neutral pH) without significant difference. In addition, linalool could be effectively released from SA-LE in accordance with the Peppas-Sahlin model, mainly described by Fickian diffusion. In particular, SA-LE can inhibit S. sonnei with a minimum inhibitory concentration of 3 mL/L, which was lower than free linalool. The mechanism can be described as damaging the membrane structure and inhibiting respiratory metabolism accompanied by oxidative stress based on FESEM, SDH activity, ATP and ROS content. These results suggest that SA is an effective encapsulation strategy to enhance the stability of linalool and its inhibitory effect on S. sonnei at near neutral pH. Moreover, the prepared SA-LE has the potential to be developed as a natural antibacterial agent to address the growing food safety challenges.

In vitro effects of cinnamon, oregano, and thyme essential oils against Escherichia coli and Trueperella pyogenes isolated from dairy cows with clinical endometritis

Clinical endometritis causes serious economic losses in dairy farms, mainly due to its negative health impact on fertility and milk production, as well as the additional costs of medicines used to treat the affected animals. The therapy for uterine diseases is principally performed with antibiotic treatment; however, its indiscriminate use in dairy herds can favor the increase in the resistance of pathogenic bacteria, leading to treatment failures. In this regard, the use of unconventional treatment may be a good option to reduce the use of antimicrobials in milk production. The objective of the present study was to evaluate the antibacterial activity of cinnamon, oregano, and thyme essential oils, and their combinations, against bovine uterine pathogens. The antibacterial activities of these essential oils were evaluated by the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC), and Fractional Inhibitory Concentration (FIC) indices against Escherichia coli and Trueperella pyogenes, which were isolated from dairy cows with clinical endometritis. Among the essential oils evaluated, the lowest MIC and MBC values observed were obtained with cinnamon essential oil alone. The association among essential oils showed different kinds of interactions, and in some situations, antagonism was observed. This study demonstrated a promising antimicrobial activity of cinnamon's essential oil, indicating that it has excellent potential to be explored as a possible alternative in the treatment of clinical endometritis in dairy cows.

Bioactive Properties of Instant Chicory Melanoidins and Their Relevance as Health Promoting Food Ingredients

Instant chicory is a caffeine-free brew worldwide consumed as a coffee substitute. Like coffee grounds processing, chicory roots suffer a roasting process, which may lead to the formation of high-molecular weight nitrogen-brown compounds, the melanoidins. It is hypothesized that similarly to coffee, chicory melanoidins have health promoting potential. In this work, the chemical composition and biological activity of chicory high molecular weight material (HMWM) was evaluated. The chicory HMWM is composed by 28.9% (w/w) of carbohydrates, mainly fructose-rich polysaccharides (18.7% w/w) and 5.7% (w/w) of protein, distinct from coffee. The phenolic compounds constituent of the HMWM were mainly present in glycosidically linked and condensed structures (0.9 g/100 g and 5.8 g/100 g), showing in vitro ABTS^•+ scavenging (IC₅₀ = 0.28 mg/mL) and ferric ion reducing capacity (ca. 11 µg Fe²⁺ eq/mg). Chicory HMWM revealed to be effective against Gram-positive bacteria, mainly Staphylococcus aureus and Bacillus cereus, although not so efficient as coffee. It also showed potential to inhibit α-glucosidase activity (15% of inhibition), higher than coffee HMWM, approaching acarbose activity that is used in type 2 diabetes mellitus treatment. Thus, chicory melanoidins, when used as a food ingredient, may contribute to an antioxidant diet and to prevent diabetes, while increasing the protective effects against pathogenic bacteria.

The improvement of Coreopsis tinctoria essential oil on learning and memory impairment of d-galactose-induced mice through Nrf2/NF-κB pathway

Essential oil of Coreopsis tinctoria (EOC) is a essential substance extracted from Coreopsis tinctoria with the excellent anti-oxidant effect. However, it is still unclear whether EOC can improve learning and memory impairment and its mechanism. The purpose of this study was to investigate the effect of EOC on learning and memory impairment induced by D-galactose (D-gal) in mice and reveal its mechanism. The composition of EOC was analyzed by GC-MS, and the results showed that the highest content was D-limonene. The follow-up experiments were conducted by comparing EOC with D-limonene. The aging model was established by subcutaneous injection of D-gal, and donepezil, D-limonene and EOC were given by intragastric administration. It was found that EOC and D-limonene significantly improved learning and memory impairment induced by D-gal through the Morris water maze and step-through tests. Pathological and biochemical analysis showed that the hippocampal morphologic of mice was damage and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) induced by D-gal were decreased, while the content of malondialdehyde (MDA) was increased, while EOC and D-limonene could reverse the morphological changes and reduce oxidative damage. In addition, EOC and D-limonene significantly increased body weight and organ coefficients, including liver, spleen and kidney. Moreover, EOC and D-limonene improved the expression of nuclear factor E2 related factor 2 (Nrf2) pathway and inhibited nuclear transcription factors-κB (NF-κB) pathway. In summary, the results showed that EOC and D-limonene could improve learning and memory impairment induced by D-gal through Nrf2/ NF-κB pathway. It was clear that as a mixture, EOC was better than D-limonene on improving learning and memory impairment.

Guaiacol augments quorum quenching potential of Ciprofloxacin against Pseudomonas aeruginosa

AIM

The present study aims to investigate the antimicrobial as well as antivirulence potential and the principle mechanism of action of guaiacol against Pseudomonas aeruginosa.

METHODS AND RESULTS

Quorum sensing inhibition and membrane disruption studies were performed to check effect of guaiacol on the virulence of P. aeruginosa. Production of various virulence factors and biofilm formation were studied at sub-MIC concentration of guaiacol alone (1/8 MIC) and in combination with ciprofloxacin (1/2 FIC). Guaiacol exhibited synergistic interactions with ciprofloxacin and further reduced production of all virulence factors and biofilm formation. Using crystal violet (CV) assay and quantification of exopolysaccharide we observed weak biofilm formation, together with reduced motilities at sub MIC which was further visualized by confocal laser microscopy and Field Emission Scanning Electron Microscopy (FESEM).The antibacterial activity of guaiacol against P. aeruginosa upon 2×MIC exposure coincided with enhanced membrane permeability leading to disruption and release of cellular material as quantified by CV uptake assay and Sodium dodecyl suphate-polyacrylamide gel electrophoresis (SDS-PAGE). The results demonstrated that sub MICs of guaiacol in combination with ciprofloxacin can act as a potent alternate compound for attenuation of quorum sensing in P. aeruginosa.

CONCLUSION

Study reports that guaiacol in combination with ciprofloxacin at 1/2 FIC significantly compromised the bacterial growth and motilities alongside inducing quorum quenching potential. This was accompanied by inhibition of biofilm which subsequently decreased EPS production at sub MIC concentration. Furthermore, guaiacol in combination displayed a severe detrimental effect on bacterial membrane disruption, thereby enhancing cellular material release.

SIGNIFICANCE AND IMPACT OF STUDY

For the first time, the potential of guaiacol in combination with ciprofloxacin in attenuation of virulence factors and biofilm formation in P. aeruginosa were described. Results corroborate on how plant bioactive in synergism with antibiotics can act as alternate treatment regime to tackle the menace of drug resistance.

Antimicrobial mechanism of linalool against Brochothrix thermosphacta and its application on chilled beef

This work aimed to explore the antibacterial ability and potential mechanism of linalool against Brochothrix thermosphacta (B. thermosphacta), providing knowledge of the preservation of chilled beef with linalool. The results found that linalool had an encouraging inhibitory effect on B. thermosphacta with a minimum inhibitory concentration (MIC) of 1.5 mL/L. Results of FESEM and zeta potential combined with probe labeling confirmed that linalool destroyed the cell structure thereby causing the leakage of intracellular components (AKP, protein, nucleic acid and ion). In addition, linalool caused respiratory disturbance by measuring the key enzyme activities including PK, SDH, MDH and ATPase. Energy limitation also appeared under linalool stress as seen from changes in ATP content (decreased by 56.06% and 69.24% in MIC and 2MIC groups, respectively). The respiratory inhibition rate of linalool to B. thermosphacta was 23.58% and the superposing rate with malonic acid was minimal (35.52%), suggesting that respiratory depression was mainly caused by the TCA cycle. Furthermore, accumulation of ROS and increase in MDA content (increased by 71.17% and 78.03% in MIC and 2MIC groups, respectively) accompanied by decreased activities of detoxification enzymes CAT and POD suggested that oxidative stress contributed to the bactericidal mechanism. Finally, linalool has been shown to effectively inhibit quality deterioration of chilled beef during storage by measuring pH, TVB-N and TVC without affecting sensory acceptability. All these highlight the great promise of using linalool as natural preservative for food industry.

Bactericidal activity of some plant essential oils against Ralstonia solanacearum infection

Potato plants and their tubers in Egypt are affected by one of the most renowned soil-borne pathogen, Ralstonia solanacearum, that caused brown rot in potato tubers and wilt in plants. There is no efficient therapeutic bactericide so; control of bacterial wilt is very rough. The study investigated three different concentrations of seven essential plant oils under in vitro and in vivo conditions as a result of their effects on Ralstonia solanacearum growth and their possibility use as potato seed pieces dressing for controlling bacterial wilt disease incidence. In vitro, anise oil at the three tested different concentrations (0.04, 0.07, and 0.14% vol/vol) was the most effective one inhibiting the growth of T4 and W9 isolates of Ralstonia solanacearum then pursued by thyme, lemongrass, and clove oils. On the other hand, rocket oil at the tested concentration was the least effective one followed by fennel oil. However, wheat germ oil was not completely effective. In vivo, experiment revealed that anise oil at the three concentrations significantly reduced disease incidence and severity in sponta and hermes potato cultivars and their effect was associated with increase of peroxidase, polyphenoloxidase, phenols and the foliar fresh weight of treated plants as well as the weight of tubers/plant followed by thyme and lemongrass oils compared to the infected untreated control. Morphological differences in bacterial cell structure have been observed using a transmission electron microscope (TEM). Anise oil at higher concentration caused of cell wall rupture and degraded cellular components.

Transcriptome analysis reveals the molecular mechanisms of the novel Lactobacillus pentosus pentocin against Bacillus cereus

The objective of this study was to investigate the antibacterial effect and mechanism of Lactobacillus pentosus pentocin against Bacillus cereus. The dynamic growth of B. cereus showed that the pentocin had strong antibacterial activity against the strain. The antibacterial mechanism focused on cytomembrane destruction, biofilms formation, DNA replication and protein synthesis of B. cereus. The scanning electron microscopy, transmission electron microscopy and flow cytometry analysis illustrated that the cytomembranes were destroyed, causing the leakage of internal cellular components. Transcriptome sequencing indicated that the genes (KinB, KinC and Spo0B) in two component systems signal pathway were down-regulated, which resulted in the inhibition of the spores and biofilms formation of B. cereus. The phosphorylation and autoinducer-2 import were inhibited by down-regulating the expression levels of LuxS and LsrB genes in quorum sensing signal pathway, which also suppressed biofilms formation of B. cereus. The K⁺ leakage activated the K⁺ transport channels by up-relating the genes (KdpA, KdpB and KdpC), promoting the entry of K⁺ from the extracellular. In addition, the pentocin interfered DNA replication and protein synthesis by regulating the genes associated with DNA replication (dnaX and holB), RNA degradation (cshA, rho, rnj, deaD, rny, dnaK, groEL and hfq) and ribosome function (rpsA, rpsO and rplS). In this article, we provide some novel insights into the molecular mechanism responsible for high antibacterial activity of the L. pentosus pentocin against B. cereus. And the pentocin might be a very promising natural preservative for controlling the B. cereus contaminations in foods.

Analysis of the Chemical Profiles and Anti-S. aureus Activities of Essential Oils Extracted from Different Parts of Three Oregano Cultivars

The use of antibiotics in the food industry is highly regulated owing to the potential harmful effects of antibiotics on human health. Therefore, it is crucial to seek alternatives for ensuring food safety. Essential oils (EOs) extracted from plants of the genus Origanum exhibit a wide range of chemical and antibacterial activities. Species and tissue factors shape the production and accumulation processes of EOs in Origanum plants, thereby affecting their bactericidal activity. In this study, the morphologies and EO yields from the inflorescences, leaves, and stems of three oregano cultivars were evaluated. In addition, the chemical compositions and antibacterial abilities of oregano EOs (OEOs) were assessed. The results showed that OEOs from the different parts of the plant displayed only minor differences in chemical composition, whereas the yield of EOs varied considerably. Additionally, the chemical profiles of OEOs differed significantly among cultivars. The carvacrol content in the OEOs was closely related to its activity against Staphylococcus aureus; the antibacterial properties of the OEOs were further verified using carvacrol. These findings suggested that OEOs possessing high antibacterial activity may have the potential to be developed as bactericides in the food industry.

Design, synthesis, molecular docking and in silico ADMET profile of pyrano[2,3-d]pyrimidine derivatives as antimicrobial and anticancer agents

Pyrano[2,3-d]pyrimidine derivatives were synthesized by treating cyclic compounds containing active methylene group with aldehyde and malononitrile in butanol. The behavior of pyrano[2,3-d]pyrimidine towards some electrophlies namely triethylorthoformate followed by nitrogen nucleophiles as isobutylamine, urea, phenylthiourea, p-toluidine, o-phenylenediamine, o-aminophenol, 2-amino-4-methyl-pyridine and acetic acid with the aim of obtaining some interesting non-mixed heterocyclic compounds. All synthesized compounds to some extent have shown good antimicrobial activity against different microbial strains that had been extracted by inhibiting cell wall synthesis. Compound 5b showed the highest antibacterial activities against B. subtilis, S. aureus and E. coli. On the other hand compound 5 g exhibited the highest antibacterial and antifungal activities against P. aeruginosa and A. niger respectively. In addition, they explore cytotoxic potentialities against different cell lines via DNA intercalation and Top-II inhibition. The cytotoxic activities clarify the strong inhibitory activity of derivative 5a against HepG2 cells with IC₅₀ = 2.09 μM, while HCT-116 cells were highly susceptible to derivative 5c with IC₅₀ = 2.61 μM, in the meantime, derivative 5f showed pronounced negative impact against MCF-7 (IC₅₀ = 2.43 μM) when compared with other prepared compounds. All derivatives exhibited higher anticancer activities than doxorubicin against the three cell lines except compound 2 against both HepG2 and MCF-7 and compound 5e against HepG2 cell lines. Compounds 5a, 5c and 5f potently intercalate DNA at IC₅₀ values of 26.96, 27.13 and 29.86 µM respectively, which were more potent than doxorubicin (IC₅₀ value of 31.27 µM). Moreover, compounds 5a, 5c and 5f exhibited very good Topoisomerase II inhibitory activities with IC₅₀ values of 0.752, 0.791 and 0.776 µM respectively, that were more potent than that of doxorubicin (IC₅₀ = 0.94 µM). For a great extent, the molecular modeling studies were in agreement with that of in vitro cytotoxicity activity, DNA binding and Top-II inhibition results.

Global transcriptomic response of Listeria monocytogenes exposed to Fingered Citron (Citrus medica L. var. sarcodactylis Swingle) essential oil

Listeria monocytogenes, which could cause severe disease of listeriosis, is one of the most concerned foodborne pathogens worldwide. Citrus medica L. var. sarcodactylis Swingle (Fingered Citron) is one of the citrus species cultivated in south China. Here, we investigated the efficacy of Fingered Citron essential oil (FCEO) against L. monocytogenes and explored the response of L. monocytogenes in the presence of FCEO using genome-wide transcriptome analysis. FCEO exhibited strong anti-listeria activity and obvious alterations of cell morphology were observed by scanning electron microscopy and transmission electron microscopy. Moreover, GO analysis demonstrated many potential cell responses, including metabolic process, cellular process, single-organism process, cell part, membrane, catalytic activity, binding, and transporter activity. KEGG analysis suggests that L. monocytogenes respond and adapt by (1) increasing motility through the enhancement of flagella rotation; (2) promoting cell tumbles and re-orientating to escape from FCEO; (3) enhancing the uptake of carbohydrates from environment to gain more energy; (4) changing the uptake of several metallic cations, including iron, zinc, cobalt, and nickel. Our research contributes to the understanding of the adaptive responses of L. monocytogenes exposed to FCEO and provides novel insights for finding new targets of anti-listeria therapy.

Modulation of the antioxidant defense system in liver, kidney, and pancreas tissues of alloxan-induced diabetic rats by camphor

Excess production of reactive oxygen species and the loss of antioxidant efficiency systems play an important role in the development of diabetes. Thus, using antioxidant compounds is an important strategy to reduce these complications. This study aimed to investigate the possible effect of camphor on the serum biochemical parameters and oxidative parameters in the pancreas, liver, and kidney tissues of alloxan-induced diabetic rats. In this study, 40 male Wistar rats were divided into five groups, including normal group, diabetic group, the diabetic group treated with glibenclamide, the diabetic group treated with 30 mg/kg camphor, and the diabetic group receiving the camphor solvent. Intragastric administration of camphor and glibenclamide, as the control drug, to diabetic rats for 21 days lowered their blood glucose, total cholesterol, triglyceride, and LDL-cholesterol, while the blood high-density lipoprotein -cholesterol level was increased. In addition, our results indicated that treatment of diabetic rats with camphor increased the activity of glutathione peroxidase, catalase, and superoxide dismutase enzymes as well as reduced glutathione content in the liver, pancreas, and kidney tissues as compared to the diabetic rats. Based on our data, it can be concluded that camphor has a hypoglycemic activity, and this effect may be attributed, in part, to its antioxidant ability. PRACTICAL APPLICATIONS: Camphor is a terpenoid natural compound derived from the wood present in the camphor laurel's stem and roots (Cinnamomum camphora L.) trees. The synthetic form of camphor is currently being produced for medical, health, and industrial applications. In addition, this compound is present in Rosmarinus officinalis, Cinnamomum zeylanicum, Salvia officinalis, Artemisia Annua, and Ocimum basilicum. Numerous researches have shown its beneficial effects on various diseases. In this study, it has been shown that camphor possesses antidiabetic effects in alloxan-induced diabetic rats. Treatment of diabetic rats with camphor increased the antioxidant capacity and reduces the oxidative stress markers in the liver, pancreas, and kidney tissues as compared to the diabetic rats. Given the favorable effect of camphor on some oxidative parameters in diabetic rats in our study, its antihyperglycemic property is probably due to its antioxidant effects.

Antibacterial Activity and Mechanism of Ginger Essential Oil against Escherichia coli and Staphylococcus aureus

Though essential oils exhibit antibacterial activity against food pathogens, their underlying mechanism is understudied. We extracted ginger essential oil (GEO) using supercritical CO2 and steam distillation. A chemical composition comparison by GC-MS showed that the main components of the extracted GEOs were zingiberene and α-curcumene. Their antibacterial activity and associated mechanism against Staphylococcus aureus and Escherichia coli were investigated. The diameter of inhibition zone (DIZ) of GEO against S. aureus was 17.1 mm, with a minimum inhibition concentration (MIC) of 1.0 mg/mL, and minimum bactericide concentration (MBC) of 2.0 mg/mL. For E. coli, the DIZ was 12.3 mm with MIC and MBC values of 2.0 mg/mL and 4.0 mg/mL, respectively. The SDS-PAGE analysis revealed that some of the electrophoretic bacterial cell proteins bands disappeared with the increase in GEO concentration. Consequently, the nucleic acids content of bacterial suspension was raised significantly and the metabolic activity of bacteria was markedly decreased. GEO could thus inhibit the expression of some genes linked to bacterial energy metabolism, tricarboxylic acid cycle, cell membrane-related proteins, and DNA metabolism. Our findings speculate the bactericidal effects of GEO primarily through disruption of the bacterial cell membrane indicating its suitability in food perseveration.

Comparative and Correlational Evaluation of the Phytochemical Constituents and Antioxidant Activity of Musa sinensis L. and Musa paradisiaca L. Fruit Compartments (Musaceae)

Secondary metabolites and their biological activity have pharmacological relevance in the prevention and therapeutic management of disease, including the facilitation of normal physiological processes through biochemical mechanisms. In this study, phytochemical constituents and antioxidant activity were evaluated quantitatively on the acetone, ethanol, and aqueous extracts of the flesh, and peel, as well as the boiled peel extract compartments of Musa sinensis L. and Musa paradisiaca L. fruits. Total phenol, proanthocyanidin, and flavonoid contents were estimated and measured spectrophotometrically. The free radical scavenging antioxidant capacity of the extracts was tested on DPPH (2,2-diphenyl-1-picrylhydrazyl ethanol), ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)), and FRAP (ferric reducing antioxidant power) assay models. Correlation between phytoconstituents and antioxidant activity was analysed using Pearson's coefficient. The results showed varying amounts of phytochemicals in the solvent extracts of the flesh and peel, including the boiled peel extract of M. sinensis and M. paradisiaca. All acetone extracts of M. sinensis flesh, M. paradisiaca flesh, and M. paradisiaca peel had the highest phytochemical contents, with the exception of the ethanol extract of M. sinensis peel which had the highest phenol content; just as on the overall scale, the peel compartments had generally higher phytochemical profiles than the soft flesh in both fruits. The boiled peel extracts of M. sinensis and M. paradisiaca had the highest ABTS (0.03 mg/mL) and DPPH (0.03 mg/mL) activity. Ferric reducing power (FRAP) was the highest in the ethanol extracts of M. sinensis flesh and peel, and M. paradisiaca flesh, while it was the highest in the acetone extract of M. paradisiaca at the peak concentration used (0.1 mg/mL). There was a significant negative correlation between the total phenol and flavonoid contents of M. sinensis flesh with its DPPH radical scavenging activity and proanthocyanidin content of M. paradisiaca flesh with its DPPH radical scavenging activity. The correlation outcomes indicate that none of the phytochemical constituents solely affected antioxidant activity; instead, a combination of the polyphenolic constituents contributed to antioxidant activity. This study shows the therapeutic potentials of the flesh and, importantly, the peel of M. sinensis and M. paradisiaca fruits on the basis of the polyphenolic constitution against free radicals and oxidative stress.

Glycosmis pentaphylla (Rutaceae): A Natural Candidate for the Isolation of Potential Bioactive Arborine and Skimmianine Compounds for Controlling Multidrug-Resistant Staphylococcus aureus

Several multidrug-resistant organisms have emerged, which increases the threat to public health around the world and a limited number of therapeutics were available to counteract these issues. Thus, researchers are trying to find out novel antimicrobials to overcome multidrug-resistant issues. The present study aimed to isolate antibacterial principles against the clinical isolates of multidrug-resistant (MDR) Staphylococcus aureus from the ethyl acetate extract of Gycosmis pentaphylla. The isolation and structural characterization of bioactive compounds were carried out using various chromatographic techniques (TLC, column, HPLC, and LC-MS) and spectral studies such as FT-IR, CHNS analysis, ¹H-NMR, and ¹³C-NMR. The antimicrobial potential of isolated compounds was assessed according to the standard methods. The isolated compounds were identified as arborine and skimmianine, which exhibited a significant antibacterial effect with the lowest MIC and MBC values against MDR S. aureus and in vitro kinetic and protein leakage assays supported the antimicrobial activity. Significant morphological changes such as uneven cell surfaces and morphology, cell shrinkage, and cell membrane damages were observed in the MDR S. aureus upon the treatment of arborine and skimmianine. The present investigation concludes that the isolated arborine and skimmianine compounds from G. pentaphylla harbor a strong antibacterial activity against MDR S. aureus and may be used as alternative natural drugs in the treatment of MDR S. aureus.

Antibacterial activity and mechanism of linalool against Pseudomonas aeruginosa

The purpose of this study was to evaluate the antibacterial activity and mechanism of linalool against Pseudomonas aeruginosa. The determination of antibacterial activity was based on the minimum inhibitory concentration (MIC) and the minimum bactericide concentration (MBC). Further, the antibacterial mechanism was explored by a growth curve assay, scanning electron microscopy (SEM), cell membrane permeability, membrane potential and respiratory chain dehydrogenase determination. The MIC and the MBC of linalool were 431 μg/mL and 862 μg/mL, respectively. The growth curve assay showed that the growth of P. aeruginosa was inhibited. The results of SEM revealed that linalool disrupted the normal morphology of the cell. The release of nucleic acids as well as the decrease in the membrane potential proved that the membrane integrity of P. aeruginosa was destroyed. Moreover, the respiratory chain was damaged by respiratory chain dehydrogenase determination as the absorbance at 490 nm decreased. This research suggested that it was possible for linalool to become a preservative of food by destroying the cell membrane, resulting in cell death.

Cu/H3BTC MOF as a potential antibacterial therapeutic agent against Staphylococcus aureus and Escherichia coli

The objective of this study was to design a more effective antibacterial agent to overcome the problem of fast-growing bacterial resistance.

Biocontrol of Citrus Canker Disease Caused by Xanthomonas citri subsp. citri Using an Endophytic Bacillus thuringiensis

Citrus canker is a devastating disease of citrus caused by Xanthomonas citri subsp. citri (Xcc). A total of 134 endophytic bacteria were isolated from various gymnospermic and angiospermic plants. They were screened for their antagonistic activities against three wild-type and six streptomycin-resistant Xcc strains. TbL-22 and TbL-26, both later identified as Bacillus thuringiensis, inhibited all the wild and resistant Xcc strains. TbL-22 exerted the highest antagonistic activity against XccW3 and XccM6 with inhibition zones of 20.64 ± 0.69 and 19.91 ± 0.87 mm, respectively. Similarly ethyl acetate extract of TbL-22 showed highest inhibition zones 15.31 ± 2.08 and 19.37 ± 3.17 mm against XccW3 and XccM6, respectively. TbL-22 reduced canker incidence on infected leaves by 64.05% relative to positive controls. Scanning electron microscopy revealed that the cell membranes of Xcc treated with ethyl acetate extract of TbL-22 were ruptured, lysed, and swollen. B. thuringiensis TbL-22 can effectively and sustainably controls streptomycin-resistant citrus canker.

Control of Foodborne Pathogenic Bacteria by Endophytic Bacteria Isolated from Ginkgo biloba L

Endophytic bacteria (EB) are a prospective source of natural and novel bioactive compounds with pharmaceutical relevance. In the present study, a total of 50 EB were isolated from the fruits and leaves of ginkgo tree (Ginkgo biloba L.), the only living species in the division Ginkgophyta and popularly known as a living fossil. All the isolated EB were screened for their antibacterial activity against five deleterious foodborne pathogenic bacteria namely Escherichia coli ATCC 43890, Salmonella Typhimurium ATCC 19586, Bacillus cereus ATCC 10876, Listeria monocytogenes ATCC19115, and Staphylococcus aureus ATCC 12600. Among the isolated EB, GbF-96, GbF-97, and GbF-98 exhibited antibacterial activity against all the pathogenic bacteria tested, with inhibition zone ranging from 33.47 to 9.55 mm. GbF-96, identified as Bacillus subtilis, exerted the highest antibacterial activity against all the tested bacteria. In contrast, the ethyl acetate extract of GbF-96 showed antibacterial activity against only B. cereus, E. coli, and Salmonella Typhimurium. Scanning electron microscopy results indicated cracked and irregular, swollen, shrunken, and lysed cell surfaces of the pathogenic bacteria treated with ethyl acetate extract of GbF-96 or B. subtilis, indicating that the metabolites of GbF-96 might penetrate the bacterial cell membranes and evoke pathways inducing cell lysis. Together, the data suggest that B. subtilis from G. biloba can be a potential candidate for controlling dreadful foodborne pathogenic bacteria, either by itself or by its metabolites.

Variation in essential oil composition of Rydingia michauxii at the three developmental stages

In this study, the essential oil composition of Rydingia michauxii was evaluated during the dormant, vegetative and flowering stages. The major chemical constituents of R. michauxii at the dormant stage were eugenol (36.81%), eugenol acetate (21.02%), and carvacrol (9.35%). While the main chemical constituents for the vegetative stage were carvacrol (16.08%), eugenol (13.23%), cumin aldehyde (9.63%), and linalool (8.28%). In addition, carvacrol (14.20%), eugenol (8.98%), δ-cadinene (8.90%), caryophyllene oxide (8.43%) and n-hexadecanoic acid (7.07%) were the major volatile components during the flowering stage. Variation in chemical compositions of R. michauxii during the various developmental stages might be affected by environmental and climatic factors.

Antibiofouling polysulfone ultrafiltration membranes via surface grafting of capsaicin derivatives

Biofouling is a critical issue in the membrane separation process as it can increase the operational cost by lower down membrane permeability. Covalent binding of an antibacterial agent on the membrane surface to kill microorganisms to hinder biofouling formation process draws great attention. In this study, we used three kinds of capsaicin derivatives, MBHBA, HMBA, and HMOBA, to fabricate antibiofouling membrane via UV-assisted photo grafting method. The influence of these capsaicin derivatives on membrane properties was investigated and compared. The results suggest that HMBA showed the best UV activity, followed by HMOBA and MBHBA successively. Due to the difference of functional groups among capsaicin derivatives, there is an increase in membrane wettability of HMBA and HMOBA-modified membranes, while there is a decrease for MBHBA-modified membrane. MBHBA-modified membrane showed enhanced irreversible fouling, which is in contrast to that of HMBA- and HMOBA-modified membranes. The modified membranes showed similar antibacterial activity against Escherichia coli. The practicability of the modified membranes was examined by dipping them into tap water and seawater for 30 days, and the results displayed the modified surfaces have the potential to relieve biofouling for separation membranes.

Antimicrobial Effects of Egyptian Local Chicory, Cichorium endivia subsp. pumilum

The discovery of novel and more efficient antimicrobial agents from natural sources like plants is one of the most important ways through which the growing threat of antibiotic-resistant pathogens can be overcome. Herein, we report the potential antimicrobial activity of Cichorium endivia L. subsp. pumilum. Different concentrations of various solvent extracts prepared from several parts of chicory were tested for their antimicrobial effect against a panel of microorganisms. The antimicrobial activity was analyzed using the well diffusion method, where zones of inhibition were used as indicators of antimicrobial activity. The results indicated the superiority of seed extracts over both leaf and root extracts. Methanol extracts showed higher activity compared with chloroform and water extracts. Increased solvent extract concentration was accompanied by a parallel increase in the diameter of the inhibition zone. Gram-positive bacteria were found to be more sensitive than Gram-negative bacteria and fungi. On a whole, the highest observed inhibition zones (21.3 ± 0.6 and 20.1 ± 0.4 mm) were recorded with the methanolic extract of chicory seeds against S. aureus and B. cereus, respectively. These results offer insights into the antimicrobial potency of this Egyptian local plant and provide a basis for further phytochemical and pharmacological research.

Time-Kill Kinetics of Lipid Fractions Isolated from Condiments against Foodborne Pathogens

Lipid fractions that are extracted from condiments have a wide array of biological potential and are commonly utilized for medicinal and culinary applications. This investigation aims at determining the antimicrobial potential of lipid fractions isolated using two different solvent systems against five foodborne pathogens. The antibacterial efficacy was tested after 0, 1, 2, 3 and 24 h of incubation with the active agent. The leakage of cellular content was assessed at 1 and 2 h of incubation. Scanning electron microscope (SEM) images were obtained after 18 h of contact time with lipid fractions at their minimum inhibitory concentration (MIC). From the results obtained from time-kill and cell constituents release tests, it could be concluded that during 3 and 1 h of incubation, the lipid fractions were more potent against Gram-negative isolates (Escherichia coli ATCC 8739). However, prolonged incubation with the active agent inhibited Gram-positive isolate, i.e. Listeria monocytogenes ATCC 13932. SEM images of treated microorganisms also confirmed the inhibitory action of selected lipid fractions against all the tested pathogens. The cellular morphology of the bacteria was completely altered after 18 h of incubation with the lipid fractions. The results of the present study corroborate significant inhibitory effects and disruption in bacterial cell integrity following prolonged incubation with these lipid fractions. The results also affirm the use of the tested lipid fractions in food systems.

The Influence of Microwave Sterilization on the Ultrastructure, Permeability of Cell Membrane and Expression of Proteins of Bacillus Cereus

Bacillus cereus was isolated from ready-to-serve brine goose, identified by 16S rRNA gene sequencing analysis and treated with a commercial microwave sterilization condition (a power of 1,800 W at 85°C for 5 min). The influence of microwaves on the morphology, the permeability of membrane and the expression of total bacterial proteins was observed. Microwave induced the clean of bacterial nuclear chromatin, increased the permeability and disrupted the integrity of membrane. Twenty-three proteins including 18 expressed down-regulated proteins and 5 expressed up-regulated proteins were identified by HPLC-MS/MS in the samples treated with microwave. The frequencies of proteins changed after microwaves treatment were labeled as 39.13% (synthesis and metabolism of amino acid or proteins), 21.74% (carbohydrate metabolism), 8.70% (anti-oxidant and acetyl Co-A synthesis), and 4.35% (the catalyst of catabolism of bacterial acetoin, ethanol metabolism, glyoxylate pathway, butyrate synthesis and detoxification activity), respectively. This study indicates that microwaves result in the inactivation of Bacillus cereus by cleaning nuclear chromatin, disrupting cell membrane and disordering the expression of proteins.

Time-Kill Kinetics of Lipid Fractions Isolated from Condiments against Foodborne Pathogens

Lipid fractions that are extracted from condiments have a wide array of biological potential and are commonly utilized for medicinal and culinary applications. This investigation aims at determining the antimicrobial potential of lipid fractions isolated using two different solvent systems against five foodborne pathogens. The antibacterial efficacy was tested after 0, 1, 2, 3 and 24 h of incubation with the active agent. The leakage of cellular content was assessed at 1 and 2 h of incubation. Scanning electron microscope (SEM) images were obtained after 18 h of contact time with lipid fractions at their minimum inhibitory concentration (MIC). From the results obtained from time-kill and cell constituents release tests, it could be concluded that during 3 and 1 h of incubation, the lipid fractions were more potent against Gram-negative isolates (Escherichia coli ATCC 8739). However, prolonged incubation with the active agent inhibited Gram-positive isolate, i.e. Listeria monocytogenes ATCC 13932. SEM images of treated microorganisms also confirmed the inhibitory action of selected lipid fractions against all the tested pathogens. The cellular morphology of the bacteria was completely altered after 18 h of incubation with the lipid fractions. The results of the present study corroborate significant inhibitory effects and disruption in bacterial cell integrity following prolonged incubation with these lipid fractions. The results also affirm the use of the tested lipid fractions in food systems.

A chitosan-coated liposome encapsulating antibacterial peptide, Apep10: characterisation, triggered-release effects and antilisterial activity in thaw water of frozen chicken

Contamination of Listeria monocytogenes in food and their processing environment is a focus of attention in the food industry. To achieve the controlled release of antibacterial agents to a food processing environment contaminated by L. monocytogenes, chitosan-stabilised liposomes encapsulating Apep10 (GLARCLAGTL), an antibacterial peptide derived from boiled-dried anchovies, were prepared by utilising listeria toxins to activate the peptide release. Characteristics including the particle size, polydispersity index (PDI), encapsulation efficiency (EE), and morphology of the chitosan-coated Apep10 liposomes were investigated. The chitosan liposomes were more stable than their uncoated counterparts, which indicated that the coating of chitosan on the surface of the liposomes inhibited undesirable vesicle fusion and payload release during storage. However, once the chitosan-stabilised liposomes encountered L. monocytogenes, which secretes pore-forming toxins, the encapsulated antibacterial peptide was released and it exerted antimicrobial effects on the strain. The results of time-kill inhibition, scanning electron microscopy (SEM), crystal violet staining and confocal laser scanning microscopy (CLSM) images demonstrated that these liposomes have favourable antibacterial and anti-biofilm activities against L. monocytogenes in the thaw water of frozen chicken. This bacterial toxin-enabled release of the encapsulated antibacterial peptide from chitosan-coated liposomes provides an effective approach for the control of listerial contamination. This technique can be broadly applied to treat contamination by a variety of pathogens that secrete pore-forming toxins.

Antibacterial activity and mode of action of totarol against Staphylococcus aureus in carrot juice

Food contaminated with pathogenic bacteria such as Staphylococcus aureus (S. aureus), represents a serious health risk to human beings. Totarol is an antibacterial novel phenolic diterpenes. In present study, the antibacterial activity of totarol against S. aureus was investigated in a food system. The antibacterial activity of totarol was determined by measuring the zones of inhibition and minimum inhibitory concentrations (MICs). The MICs for S. aureus strains were in the range of 2-4 μg/ml. The probable antibacterial mechanism of totarol was the alteration in cell membranes integrity and permeability, which leading to the leakage of cellular materials. The electric conductivity showed a time- and dose-dependent increasing manner, and we utilized totarol to induce the production of cytoplasmic β-galactosidase in S. aureus. Scanning electron microscopy and transmission electron microscopy analysis further confirmed that S. aureus cell membranes were damaged by totarol. The time-kill assay and detection of the kinetics of S. aureus deactivation in situ indicated that totarol has good preservative activities in a food model. Totarol successfully inhibited S. aureus development in carrot juice, at room temperature (25 °C) and in refrigerator (4 °C) respectively. Our works provided not only additional evidences in support of totarol being regarded as a natural antibacterial food preservative but also fundamental understanding on the mode of antibacterial action. It is necessary to consider that totarol will become a promising antibacterial additive for food preservative.

The Influence of Microwave Sterilization on the Ultrastructure, Permeability of Cell Membrane and Expression of Proteins of Bacillus Cereus

Bacillus cereus was isolated from ready-to-serve brine goose, identified by 16S rRNA gene sequencing analysis and treated with a commercial microwave sterilization condition (a power of 1,800 W at 85°C for 5 min). The influence of microwaves on the morphology, the permeability of membrane and the expression of total bacterial proteins was observed. Microwave induced the clean of bacterial nuclear chromatin, increased the permeability and disrupted the integrity of membrane. Twenty-three proteins including 18 expressed down-regulated proteins and 5 expressed up-regulated proteins were identified by HPLC-MS/MS in the samples treated with microwave. The frequencies of proteins changed after microwaves treatment were labeled as 39.13% (synthesis and metabolism of amino acid or proteins), 21.74% (carbohydrate metabolism), 8.70% (anti-oxidant and acetyl Co-A synthesis), and 4.35% (the catalyst of catabolism of bacterial acetoin, ethanol metabolism, glyoxylate pathway, butyrate synthesis and detoxification activity), respectively. This study indicates that microwaves result in the inactivation of Bacillus cereus by cleaning nuclear chromatin, disrupting cell membrane and disordering the expression of proteins.

Antimicrobial Potential of Carvacrol against Uropathogenic Escherichia coli via Membrane Disruption, Depolarization, and Reactive Oxygen Species Generation

Bacterial resistance to antibiotics poses a serious threat to cure diseases associated with microbial infection. Among the resistant bacteria, extended-spectrum β-lactamase (ESBL)-producing bacteria are the most concerned one as they encode the enzyme β-lactamase that confers resistance to most β-lactam antibiotics. The present study was carried out to determine the antimicrobial potential and the principle mechanism of action of carvacrol against ESBL Escherichia coli isolated from ascitic fluid of a patient having a urinary tract infection. Carvacrol exhibited a minimum inhibitory concentration (MIC) of 450 μg/ml at which it reduced E. coli cell counts significantly in a time-dependent manner. Carvacrol completely diminished the growth of E. coli after 2 h of incubation at its MIC. Fluorescent imaging displayed the elevated reactive oxygen species level and bacterial membrane depolarization leading to E. coli cell death in presence of carvacrol at its MIC. Furthermore, carvacrol displayed a severe detrimental effect on bacterial membrane disruption and cellular material release. In addition, a significant effect of carvacrol at sub-inhibitory concentration was observed on motility of E. coli cells and invasion of human colon HCT-116 cells in an ex vivo model. Based on the results, we conclude a potential antimicrobial role of carvacrol against ESBL E. coli.

Antimicrobial Effects of 7,8-Dihydroxy-6-Methoxycoumarin and 7-Hydroxy-6-Methoxycoumarin Analogues against Foodborne Pathogens and the Antimicrobial Mechanisms Associated with Membrane Permeability

The antimicrobial effects of 7,8-dihydroxy-6-methoxycoumarin and 7-hydroxy-6-methoxycoumarin isolated from Fraxinus rhynchophylla bark and of their structural analogues were determined in an attempt to develop natural antimicrobial agents against the foodborne pathogens Escherichia coli, Bacillus cereus, Staphylococcus intermedius, and Listeria monocytogenes. To elucidate the relationship between structure and antimicrobial activity for the coumarin analogues, isolated constituents and their structural analogues were evaluated against foodborne pathogens. Based on the culture plate inhibition zones and MICs, 6,7-dimethoxycoumarin, 7,8-dihydroxy-6-methoxycoumarin, 7-hydroxy-6-methoxycoumarin, and 7-methoxycoumarin, containing a methoxy functional group on the coumarin skeleton, had the notable antimicrobial activity against foodborne pathogens. However, 7-hydroxycoumarin and 6,7-dihydroxycoumarin, which contained a hydroxyl functional group on the coumarin skeleton, had no antimicrobial activity against these pathogens. An increase in cell membrane permeability was confirmed by electron microscopy observations, and release of extracellular ATP and cell constituents followed treatment with the ethyl acetate fraction of F. rhynchophylla extract. These findings indicate that F. rhynchophylla extract and coumarin analogues have potential for use as antimicrobial agents against foodborne pathogens and that the antimicrobial mechanisms are associated with the loss of cell membrane integrity.