Carboxymethyl cellulose-based multifunctional film integrated with polyphenol-rich extract and carbon dots from coffee husk waste for active food packaging applications.

Sustainable carboxymethyl cellulose (CMC)-based active composite films were developed through the addition of polyphenol-rich extract from coffee husk (CHE) and carbon dots (CDs) prepared using the biowaste residue of CHE extraction. The influences of various CDs contents on the physicochemical and functional characteristics of composite films have been researched. The 6% (w/w) CHE and 3% (w/w) CDs were uniformly dispersed within the CMC matrix to produce a homogenous film with enhanced mechanical properties. The CMC/CHE/CDs3% film exhibited outstanding UV-light blocking, improved water and gas barriers, potent antioxidant activity with above 95% DPPH and ABTS scavenging rates, and effective antibacterial capabilities against L. monocytogenes and E. coli. The food packaging experiment demonstrated that this active composite film slowed the rotting of fresh-cut apples and extended their shelf-life to 7 days at 4 °C storage. Therefore, the obtained multifunctional film showed promise as an environmentally friendly food packaging material.

Logistic modeling to predict the minimum inhibitory concentration (MIC) of olive leaf extract (OLE) against Listeria monocytogenes.

Olive leaf extract (OLE) has been increasingly recognized as a natural and effective antimicrobial against a host of foodborne pathogens. This study attempts to predict the minimum inhibitory concentration (MIC) of OLE against Listeria monocytogenes F2365 by utilizing the asymptotic deceleration point (PDA) in a logistic model (LM), namely MIC-PDA. The experimental data obtained from the inhibitory rate (IR) versus OLE concentration against L. monocytogenes were sufficiently fitted (R2 = 0.88957). Five significant critical points were derived by taking the multi-order derivatives of the LM function: the inflection point (PI), the maximum acceleration point (PAM), the maximum deceleration point (PDM), the absolute acceleration point (PAA), and the asymptotic deceleration point (PDA). The PDA ([OLE] = 37.055 mg/mL) was employed to approximate the MIC-PDA. This MIC value was decreased by over 42% compared to the experimental MIC of 64.0 mg/mL, obtained using the conventional 2-fold dilution method (i.e., MIC-2fold). The accuracy of MIC-PDA was evaluated by an in vitro L. monocytogenes growth inhibition assay. Finally, the logistic modeling method was independently validated using our previously published inhibition data of OLE against the growths of Escherichia coli O157:H7 and Salmonella enteritidis. The MIC-PDA (for [OLE]) values were estimated to be 41.083 and 35.313 mg/mL, respectively, compared to the experimental value of 62.5 mg/mL. Taken together, MIC-PDA, as estimated from the logistic modeling, holds the potential to shorten the time and reduce cost when OLE is used as an antimicrobial in the food industry.

Antimicrobial activity of essential oils and natural plant extracts against Listeria monocytogenes in a dry-cured ham-based model.

BACKGROUND: Listeria monocytogenes is a widespread common contaminant in food production facilities during preparation, storage, and distribution, and minimally processed ready-to-eat products are considered at high risk of contamination by this bacterium. Increased antibiotic resistance has led researchers to search for plant-based natural alternatives to control pathogenic microorganisms. Among these products, essential oils and plant extracts have previously shown antimicrobial activity and are possible alternatives to manage food pathogens. In this study, commercial essential oils (cinnamon, clove, oregano, ginger, and thyme) and plant extracts (pomegranate, acorn, olive, strawberry tree, and dog rose) were tested against L. monocytogenes in a dry-cured ham-based model. RESULTS: Essential oils and plant extracts were screened by agar diffusion and minimum inhibitory concentration for anti-L. monocytogenes activity. Cinnamon, pomegranate, and strawberry trees returned the strongest results and were therefore evaluated in a dry-cured ham-based medium assay with water activity of 0.93 or 0.95. The 10% essential oil of cinnamon was capable of completely inhibiting bacterial growth, while strawberry tree and pomegranate extract also showed antilisterial activity (P > 0.05). Water activity influenced the bacterial count of L. monocytogenes in a dry-cured ham-based medium. CONCLUSIONS: There was a reduction in L. monocytogenes with the application of cinnamon essential oil but, because of the negative sensory impact of this particular compound in meat products, we suggest the use of pomegranate or strawberry tree for the biocontrol of Listeria in ready-to-eat products. © 2021 Society of Chemical Industry.

Protein extract of Bromelia karatas L. rich in cysteine proteases (ananain- and bromelain-like) has antibacterial activity against foodborne pathogens Listeria monocytogenes and Salmonella Typhimurium.

Bromelia karatas L. is a plant species from the Americas. The presence of proteases in fruits of B. karatas has been reported but scarcely studied in detail. Proteolytic enzymes from Ananas comosus have displayed antifungal and antibacterial activity. Thus, novel proteases present in B. karatas may be useful as a source of compounds against microorganisms in medicine and food production. In this work, the protein extract from the fruits of B. karatas was characterized and its antibacterial activity against Salmonella Typhimurium and Listeria monocytogenes was determined for the first time. Proteins highly similar to ananain and the fruit bromelain from A. comosus were identified as the main proteases in B. karatas fruits using liquid chromatography with tandem mass spectrometry (LC-MS/MS). The soluble protein extract (SPE) at a concentration of 2.0 mg/mL displayed up to 80% of antibacterial activity against S. Typhimurium. Complete inhibition of L. monocytogenes was reached with up to 1.65 mg/mL of SPE. Plant protease extract containing ananain-like enzyme inhibited up to 90% against S. Typhimurium and up to 85% against L. monocytogenes using only 10 µg/mL of the partial-purified enzyme.

Risk assessment of in vitro cytotoxicity, antioxidant and antimicrobial activities of Mentha piperita L. essential oil.

The objective of this study was to determine the chemical composition as well as antioxidant, antibacterial, and cytotoxic properties of the essential oil of Mentha piperita L. (peppermint). Fifteen chemical constituents were identified in the essential oil, for a total of 99.99% of the compounds. The essential oil exhibited antimicrobial activity against two Gram-positive bacteria Staphylococcus aureus and Listeria monocytogenes. The minimum inhibitory concentration (MIC) of essential oil of Mentha piperita L. for Staphylococcus aureus and Listeria monocytogenes was 1.84 µg/ml, whereas the minimum bactericidal concentration (MBC) values were 3.7 and 7.43 µg/ml, respectively. The oil displayed potent antioxidant activity inhibiting up to approximately73% of 2,2'-azinothiobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals. In the cytotoxicity assay, the highest essential oil concentration (100 µg/ml) resulted in viability of approximately 90% human epidermal keratinocyte (HaCaT) cells. With respect to antitumor activity in C6 rat glioma cells, there was significant reduction in cell viability: 56-74% in 24 hr, and 71-77% in 48 hr. Data suggest that in presence of the essential oil of Mentha piperita L. antioxidant, antibacterial, antitumor and non-cytotoxic properties were noted.

Listeria monocytogenes Sublethal Injury and Viable-but-Nonculturable State Induced by Acidic Conditions and Disinfectants.

The dormancy continuum hypothesis states that in response to stress, cells enter different stages of dormancy ranging from unstressed living cells to cell death, in order to ensure their long-term survival under adverse conditions. Exposure of Listeria monocytogenes cells to sublethal stressors related to food processing may induce sublethal injury and the viable-but-nonculturable (VBNC) state. In this study, exposure to acetic acid (AA), hydrochloric acid (HCl), and two disinfectants, peracetic acid (PAA) and sodium hypochlorite (SH), at 20°C and 4°C was used to evaluate the potential induction of L. monocytogenes strain Scott A into different stages of dormancy. To differentiate the noninjured subpopulation from the total population, tryptic soy agar with 0.6% yeast extract (TSAYE), supplemented or not with 5% NaCl, was used. Sublethally injured and VBNC cells were detected by comparing plate counts obtained with fluorescence microscopy and by using combinations of carboxyfluorescein and propidium iodide (viable/dead cells). Induction of sublethal injury was more intense after PAA treatment. Two subpopulations were detected, with phenotypes of untreated cells and small colony variants (SCVs). SCVs appeared as smaller colonies of various sizes and were first observed after 5 min of exposure to 5 ppm PAA at 20°C. Increasing the stress intensity from 5 to 40 ppm PAA led to earlier detection of SCVs. L. monocytogenes remained culturable after exposure to 20 and 30 ppm PAA for 3 h. At 40 ppm, after 3 h of exposure, the whole population was considered nonculturable, while cells remained metabolically active. These results corroborate the induction of the VBNC state. IMPORTANCE Sublethally injured and VBNC cells may evade detection, resulting in underestimation of a food product's microbial load. Under favorable conditions, cells may regain their growth capacity and acquire new resistant characteristics, posing a major threat for public health. Induction of the VBNC state is crucial for foodborne pathogens, such as L. monocytogenes, the detection of which relies almost exclusively on the use of culture recovery techniques. In the present study, we confirmed that sublethal injury is an initial stage of dormancy in L. monocytogenes that is followed by the VBNC state. Our results showed that PAA induced SCVs (a phenomenon potentially triggered by external factors) and the VBNC state in L. monocytogenes, indicating that tests of lethality based only on culturability may provide false-positive results regarding the effectiveness of an inactivation treatment.

Responses of Escherichia coli and Listeria monocytogenes to ozone treatment on non-host tomato: Efficacy of intervention and evidence of induced acclimation.

Because of the continuous rise of foodborne illnesses caused by the consumption of raw fruits and vegetables, effective post-harvest anti-microbial strategies are necessary. The aim of this study was to evaluate the anti-microbial efficacy of ozone (O3) against two common causes of fresh produce contamination, the Gram-negative Escherichia coli O157:H7 and Gram-positive Listeria monocytogenes, and to relate its effects to potential mechanisms of xenobiosis by transcriptional network modeling. The study on non-host tomato environment correlated the dose × time aspects of xenobiosis by examining the correlation between bacterial survival in terms of log-reduction and defense responses at the level of gene expression. In E. coli, low (1 µg O3/g of fruit) and moderate (2 µg O3/g of fruit) doses caused insignificant reduction in survival, while high dose (3 µg/g of fruit) caused significant reduction in survival in a time-dependent manner. In L. monocytogenes, moderate dose caused significant reduction even with short-duration exposure. Distinct responses to O3 xenobiosis between E. coli and L. monocytogenes are likely related to differences in membrane and cytoplasmic structure and components. Transcriptome profiling by RNA-Seq showed that primary defenses in E. coli were attenuated after exposure to a low dose, while the responses at moderate dose were characterized by massive upregulation of pathogenesis and stress-related genes, which implied the activation of defense responses. More genes were downregulated during the first hour at high dose, with a large number of such genes getting significantly upregulated after 2 hr and 3 hr. This trend suggests that prolonged exposure led to potential adaptation. In contrast, massive downregulation of genes was observed in L. monocytogenes regardless of dose and exposure duration, implying a mechanism of defense distinct from that of E. coli. The nature of bacterial responses revealed by this study should guide the selection of xenobiotic agents for eliminating bacterial contamination on fresh produce without overlooking the potential risks of adaptation.

HPLC-Analysis, Biological Activities and Characterization of Action Mode of Saudi Marrubium vulgare against Foodborne Diseases Bacteria.

The present study aims to evaluate the chemical composition, metabolites secondary and pharmacology activities of methanolic extract of Marrubium vulgare collected from King Saudi Arabia. Moreover, the primary mode of action of the tested extract was studied here for the first time against E. coli and L. monocytogenes. HPLC analysis shows that the major components in the tested extract are luteolin-7-O-d-glucoside, ferulic acid and premarrubiin. Obtained data demonstrated that the investigated extract was richer in phenol (26.8 ± 0.01 mg/GAE g) than in flavonoids (0.61 ± 0.05 mg EC/mL). In addition, the methanolic extract showed an important antioxidant capacity against the DPPH (IC50 = 35 ± 0.01 µg/mL) and ABTS (IC50 = 25 ± 0.2 µg/mL) radical scavenging and a strong inhibition of acetylcholinesterase enzyme with an IC50 value corresponding to 0.4 mg/mL. The antibacterial activity demonstrated that the evaluated extract had significant activity against both Gram-positive and Gram-negative bacteria. The effect of time on cell integrity on E. coli and L. monocytogenes determined by time-kill and bacteriolysis tests showed that the M. vulgare extract reduced the viability of both strains after 8 and 10 h and had a bacteriolytic effect against two different categories of bacteria, Gram-positive and negative, which are not of the same potency. Based on obtained data, it can be concluded that Saudi M. vulgare has a high pharmacological importance and can be used in preparation of food or drugs.

The Digestibility of Hibiscus sabdariffa L. Polyphenols Using an In Vitro Human Digestion Model and Evaluation of Their Antimicrobial Activity.

Hibiscus sabdariffa L. (H.s.) is a polyphenolic-rich plant commonly consumed either as a beverage or spice. The aim of the present study was to evaluate the in vitro digestibility of H.s. polyphenols using an in vitro model of digestion which simulates the human stomach and small intestine. The bioaccessible polyphenols released in the digested samples were analyzed by liquid chromatography coupled to photodiode array and mass spectrometry detection. H.s. anthocyanins (cyanidin-3-O-sambubioside and delphinidin-3-O-sambubioside) content drastically dropped during the digestion process from 2.91 ± 0.03 µg g-1 and 8.53 ± 0.08 µg g-1 (w/w) CG (Cyanidin-glucoside) in the raw extract, respectively, to 0.12 ± 0.01 µg g-1 0.12 ± 0.01 µg g-1 (w/w) CG at the end of duodenal digestion. Total polyphenols also have shown a decrease from 1192.65 ± 30.37 µg g-1 (w/w) in the raw extract to 282.24 ± 7.21 µg g-1 (w/w) by the end of gastric digestion, in contrast to their increase by the end of duodenal digestion 372.91 ± 3.97 µg g-1 (w/w). On the other hand, the decrease in certain compounds (e.g., caffeoylquinicandcoumaroylquinic acids) was observed during gastric digestion resulting in an increase of quinic acid in the duodenal aliquots, thus suggesting that this compound was derived from the degradation of the more complex hydroxycinnamic acids. H.s. extract also exhibited a bacteriostatic effect against Staphylococcus aureus ATCC 6538 (MIC of 2.5 mg mL-1) and a bactericidal effect against a food isolate of Listeria monocytogenes (MBC of 2.5 mg mL-1). The undigested polyphenols of H.s. in the upper gastrointestinal tract enters the colon, where they are metabolized by the gut microbiota. The present study results showed that resistance of H.s. polyphenols during gastrointestinal digestion might affect their uptake, resulting in a decrease in their digestibility.

Effects of Green Tea Powder, Pomegranate Peel Powder, Epicatechin and Punicalagin Additives on Antimicrobial, Antioxidant Potential and Quality Properties of Raw Meatballs.

Alternative technologies, which have been developed in order to meet the consumers' demand for nourishing and healthy meat and meat products, are followed by the food industry. In the present study, it was determined, using the HPLC method, that green tea contains a high level of epicatechin (EP) under optimal conditions and that pomegranate peel contains a high level of punicalagin (PN). Green tea, pomegranate peel, EP and PN were added to meatballs at different concentrations in eight groups. The antioxidant capacities of extracts were measured. The antimicrobial activity was examined for 72 h using three different food pathogens. The highest level of antimicrobial activity was achieved in the 1% punicalagin group, whereas the minimum inhibition concentration (L. monocytogenes, S. typhimurium) was found to be 1.87 mg/mL. A statistically significant decrease was found in FFA, POV and TBARS levels of meatballs on different days of storage (p < 0.05). When compared to the control group, the bioactive compounds preserved the microbiological and chemical properties of meatballs during storage at +4 °C (14 days). It was concluded that the extracts with high EP and PN concentrations can be used as bio-preservative agents for meat and meat products.

Oregano and Thyme Essential Oils Encapsulated in Chitosan Nanoparticles as Effective Antimicrobial Agents against Foodborne Pathogens.

The use of natural compounds with biocidal activity to fight the growth of bacteria responsible for foodborne illness is one of the main research challenges in the food sector. This study reports the preparation and physicochemical characterization of chitosan nanoparticles loaded with Thymus capitatus (Th-CNPs) and Origanum vulgare (Or-CNPs) essential oils. The nanosystems were obtained by ionotropic gelation technique with high encapsulation efficiency (80-83%) and loading capacity (26-27%). Nanoparticles showed a spherical shape, bimodal particle size distribution, and good stability (zeta potential values > 40 mV). The treatment of the nanosuspensions at different temperatures (4 and 40 °C) and storage times (7, 15, 21, and 30 days) did not affect their physicochemical parameters and highlights their reservoir ability for essential oils also under stressful conditions. Both Or-CNPs and Th-CNPs exhibited an enhanced bactericidal activity against foodborne pathogens (S. aureus, E. coli, L. monocytogenes) than pure essential oils. These ecofriendly nanosystems could represent a valid alternative to synthetic preservatives and be of interest for health and food safety.

Ensuring safety and improving keeping quality of meatballs by addition of sesame oil and sesamol as natural antimicrobial and antioxidant agents.

The antioxidant and antimicrobial effect of sesame oil (10, 30, and 50 g/kg) and sesamol (0.1, 0.3, and 0.5 g/kg) in meatballs during cold storage for 18 days at 3 ± 1 °C was investigated. Sesame oil and sesamol did not alter the sensory attributes of meatballs. Addition of either sesame oil or sesamol significantly delayed lipid oxidation when compared with control. Sesamol exhibited more potent antioxidant activities more than sesame oil. During storage, the aerobic plate counts (APCs) and Enterobacteriaceae counts (EBCs) were markedly (P < 0.01) decreased in meatballs treated with sesame oil or sesamol in comparison with untreated control samples. Control meatballs showed signs of quality deterioration at day 7 of storage, while treated meatballs exhibited longer shelf lifes ranged from 9-18 days according to sesame oil or sesamol concentrations. Both sesame oil and sesamol induced marked (P < 0.01) decline in the counts of E. coli O157:H7, Salmonella enterica serovar Typhimurium, Staphylococcus aureus and Listeria monocytogenes that artificially inoculated to meatballs. Sesamol was more effective than sesame oil in the reduction of APCs, EBCs as well as foodborne pathogens. The results suggest that both sesame oil and sesamol are potentially useful natural additives to fresh meat products for improving its microbial quality and extending its shelf life during cold storage.

Menaquinone-mediated regulation of membrane fluidity is relevant for fitness of Listeria monocytogenes.

Listeria monocytogenes is a food-borne pathogen with the ability to grow at low temperatures down to - 0.4 °C. Maintaining cytoplasmic membrane fluidity by changing the lipid membrane composition is important during growth at low temperatures. In Listeria monocytogenes, the dominant adaptation effect is the fluidization of the membrane by shortening of fatty acid chain length. In some strains, however, an additional response is the increase in menaquinone content during growth at low temperatures. The increase of this neutral lipid leads to fluidization of the membrane and thus represents a mechanism that is complementary to the fatty acid-mediated modification of membrane fluidity. This study demonstrated that the reduction of menaquinone content for Listeria monocytogenes strains resulted in significantly lower resistance to temperature stress and lower growth rates compared to unaffected control cultures after growth at 6 °C. Menaquinone content was reduced by supplementation with aromatic amino acids, which led to a feedback inhibition of the menaquinone synthesis. Menaquinone-reduced Listeria monocytogenes strains showed reduced bacterial cell fitness. This confirmed the adaptive function of menaquinones for growth at low temperatures of this pathogen.

Anti-listerial properties of chemical constituents of Eruca sativa (rocket salad): From industrial observation to in vitro activity.

The frequency of foodborne outbreaks epidemiologically associated with Listeria monocytogenes in fresh produce has increased in recent years. Although L. monocytogenes may be transferred from the environment to vegetables during farming, contamination of food products most commonly occurs in food processing facilities, where L. monocytogenes has the ability to establish and persist on processing equipment. The current study was undertaken to collect data on the occurrence of L. monocytogenes and the identity of the endogenous microbiota in a fresh produce processing facility, for which information has remained scarce. L. monocytogenes was not detected in the facility. Experiments simulating conditions in the processing environment were performed, including examination of bacterial growth in nutrients based on vegetables (salad juice) compared to in other types of nutrients (fish, meat). Results showed that the endogenous microbiota (dominated by Pseudomonas) grew well in iceberg lettuce and rocket salad juice at low temperatures, while growth inhibition of L. monocytogenes was observed, particularly in rocket salad juice. The anti-listerial activity in rocket salad juice was retained in a polar chromatographic fraction containing several metabolites. Characterization of this active fraction, using LC-MS/MS, led to identification of 19 compounds including nucleosides and amino acids. Further work is necessary to determine the molecular mechanism responsible for the inhibitory activity of rocket salad constituents. The study nevertheless suggests that the available nutrients, as well as a low temperature (3 °C) and the in-house bacterial flora, may influence the prevalence of L. monocytogenes in fresh produce processing facilities.

Inhibition of Listeria monocytogenes growth in turkey fillets by alginate edible coating with Trachyspermum ammi essential oil nano-emulsion.

The objective of this study was to determine the chemical composition and antibacterial activity of Trachyspermum ammi essential oil (TAEO). Moreover, the present study comparatively investigated TAEO in the forms of emulsion and Nano-emulsion in alginate-based edible coatings against inoculated Listeria monocytogenes in turkey fillets during 12 days in cold storage (at a temperature of 4 ± 1 °C). Alginate solutions with two levels of TAEO (in emulsion and Nano-emulsion forms) were prepared in this study. The bacterial count was performed on days 0, 1, 2, 4, 8, and 12. Based on the obtained results of the current study, a comparison of different treatments with the blank samples (without any coating) showed that the highest considerable result was observed in the samples with Nano-emulsion coating (P < 0.05). Nano-emulsion loaded alginate coating prevented the growth of listeria in turkey fillets even after 12 days of cold storage. According to the findings of this study, the application of alginate edible coatings containing TAEO, especially in Nano-form, can be very effective in controlling the growth of L. monocytogenes, as a foodborne pathogen, during storage; therefore, it is a good choice to be applied in the meat industry.

Interstrains comparison of the antimicrobial effect and mode of action of a Vietnamese Cinnamomum cassia essential oil from leaves and its principal component against Listeria monocytogenes.

The antibacterial activity of a Cinnamomum cassia essential oil (EO) and of its main component trans-cinnamaldehyde (90% w/w) was examined against five Listeria monocytogenes strains. The minimal inhibitory concentrations (MICs) of C. cassia EO against the five L. monocytogenes strains were identical (250 µg ml-1 ), while the minimal bactericidal concentrations (MBCs) ranged between 800 and 1200 µg ml-1 . In order to study if this EO and trans-cinnamaldehyde altered the five strains at the membrane level, fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) was measured in presence of different concentrations (1/2MIC, MIC, 2MIC) of these antibacterial agents. A concentration-dependent increase of fluorescence anisotropy of DPH in their presence reflecting a rigidification of the membrane was observed for the five strains. This modification of the membrane fluidity was associated with a perturbation of the selective membrane permeability, as a perturbation of the gradient between intracellular and extracellular pH was also observed.

Microwave-Assisted Rapid Green Synthesis of Gold Nanoparticles Using Seed Extract of Trachyspermum ammi: ROS Mediated Biofilm Inhibition and Anticancer Activity.

Green synthesis of metal nanoparticles using plant extracts as capping and reducing agents for the biomedical applications has received considerable attention. Moreover, emergence and spread of multidrug resistance among bacterial pathogens has become a major health concern and lookout for novel alternative effective drugs has gained momentum. In current study, we synthesized gold nanoparticles using the seed extract of Trachyspermum ammi (TA-AuNPs), assessed its efficacy against drug resistant biofilms of Listeria monocytogenes and Serratia marcescens, and evaluated its anticancer potential against HepG2 cancer cell lines. Microwave-assisted green synthesis of gold nanoparticles was carried out and characterization was done using UV-vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and dynamic light scattering (DLS). Most nanoparticles were observed as spherical and spheroidal with few anisotropies with an average crystalline size of 16.63 nm. Synthesized TA-AuNPs demonstrated significant biofilm inhibitory activity against L. monocytogenes (73%) as well as S. marcescens (81%). Exopolysaccharide (EPS), motility, and CSH, key elements that facilitate the formation and maintenance of biofilm were also inhibited significantly at the tested sub-minimum inhibitory concentrations (sub-MICs). Further, TA-AuNPs effectively obliterated preformed mature biofilms of S. marcescens and L. monocytogenes by 64% and 58%, respectively. Induction of intracellular ROS production in TA-AuNPs treated bacterial cells could be the plausible mechanism for the reduced biofilm formation in test pathogens. Administration of TA-AuNPs resulted in the arrest of cellular proliferation in a concentration-dependent manner. TA-AuNPs decrease the intracellular GSH in HepG2 cancer cell lines, cells become more prone to ROS generation, hence induce apoptosis. Thus, this work proposes a new eco-friendly and rapid approach for fabricating NPs which can be exploited for multifarious biomedical applications.

Quorum sensing modulatory and biofilm inhibitory activity of Plectranthus barbatus essential oil: a novel intervention strategy.

The essential oil (EO) from the roots of Plectranthus barbatus Andr. (Syn. Coleus forskohlii Briq.) was evaluated for quorum sensing (QS) inhibitory activity. P. barbatus EO was screened for inhibition of QS regulated violacein production in Chromobacterium violaceum (ATCC 12472) wild-type strain. At inhibitory (6.25% v/v) and sub-inhibitory concentrations (3.125% v/v) of the EO, dose-dependent response in the inhibition of violacein production was observed in C. violaceum. Similarly, sub-MIC (6.25% v/v) of P. barbatus EO disrupted QS regulated biofilm formation by 27.87% and inhibited swarming and twitching motility in Pseudomonas aeruginosa PA01 implying its anti-infective and QS modulatory activity. Fluorescence microscopy studies confirmed the disruption of biofilm formation by EO in P. aeruginosa PAO1. Promising antibacterial activity was recorded at concentrations as low as 3.12% v/v for Listeria monocytogenes (ATCC 13932) and at 6.25% v/v for both Salmonella enterica subsp. enterica serovar Typhimurium (ATCC 25241) and Escherichia coli (ATCC 11775). Furthermore, significant dose-dependent inhibition was observed for biofilm formation and motility in all the tested pathogens in different treated concentrations. GC-MS analysis revealed α-pinene, endo-borneol, bornyl acetate, 1-Hexyl-2-Nitrocyclohexane as the major phytoconstituents. P. barbatus EO or its constituent compounds with QS modulatory, antimicrobial and biofilm inhibitory property could be potential new-age dietary source based intervention and preservation technologies.

Stability and antibacterial activity of Thymus daenensis L. essential oil nanoemulsion in mayonnaise.

BACKGROUND: There is a growing demand in the food industry for the replacement of synthetic preservatives with their natural alternatives. This has led to the development of novel methods such as encapsulation of plants essential oil with appropriate physicochemical stability, and antibacterial and organoleptic properties. This study aimed to prepare an optimal nanoemulsion of Thymus daenensis L. essential oil for use as a natural preservative in mayonnaise. RESULTS: The analysis of droplet diameter, polydispersity index, zeta potential, encapsulation rate, and intrinsic stability showed that out of nine T. daenensis essential oil-containing nanoemulsions, two preparations of A and B had high stability scores. In vitro antibacterial tests showed the adverse effect of Tween 80 volume on the antibacterial properties of nanoemulsions. One nanoemulsion (essential oil:Tween 80, ratio 1:1, 15 min sonication) was considered to be optimal based on its long-term stability and antibacterial effects on Salmonella Typhimurium, Escherichia coli, and Listeria monocytogenes. However, compared to the optimal nanoemulsion, the pure essential oil showed more antibacterial effects. The bacterial control in mayonnaise was close to equal for sodium benzoate (in maximum limit 1 g kg-1 ) and the optimal nanoemulsion (½ MIC) for 24 h. The optimal nanoemulsion achieved significantly higher sensory scores (taste, appearance, and mouthfeel) than the pure essential oil in mayonnaise (P < 0.05). CONCLUSION: The results demonstrated similar antibacterial effects for the optimal nanoemulsion and sodium benzoate. The optimal nanoemulsion, due to its desirable sensorial attributes, long-term stability, and slow release of volatile compounds, can be considered an appropriate alternative to synthetic preservatives.

Fabrication of Carboxymethyl Cellulose/Agar-Based Functional Films Hybridized with Alizarin and Grapefruit Seed Extract.

Carboxymethyl cellulose/agar-based functional halochromic films were fabricated by adding alizarin and grapefruit seed extract (GSE). The fillers were evenly dispersed in the polymer matrix to form compatible composite films. The addition of alizarin has improved the film's mechanical strength (20%) and water resistance (40%) with potent antioxidant and excellent color indicating properties. In contrast, GSE has imparted strong antibacterial and antioxidant activities to the film. Also, the addition of alizarin and GSE slightly improved the water vapor barrier properties but did not affect the thermal stability of the film. The composite film also exhibited UV blocking properties with adequate transparency. The composite film showed an excellent pH-dependent color change with color reversibility and color stability and a volatile gas detection function. The film also showed potent antimicrobial activity against foodborne pathogenic bacteria, Escherichia coli and Listeria monocytogenes, and showed an intense antioxidant action.