A study of the antibacterial mechanism of catechins: Isolation and identification of Escherichia coli cell surface proteins that interact with epigallocatechin gallate

Effect of ultra-high pressure combined with heat-assisted treatment on the characterization, moisture absorption, and antioxidant activity properties of walnut peptide

In this study, ultra-high pressure (UHP) and heat-assisted technology (HT) were used to process walnut peptides (WP) and investigate their combined effects (UHP-HT) on the characterization, moisture absorption, and antioxidant activity of WP. The results indicated that UHP (300 Mpa, 10 min) combined with HT treatment (55 °C, 30 min) significantly increased the surface hydrophobicity and disulfide bonds of WP. UHP-HT-treated WP exhibited lower moisture absorption and more stable water molecule migration. Additionally, the moisture absorption capacity of the WP (48.78 %) was significantly decreased in WP-UHP, WP-HT and WP-UHP (45.37 %, 43.15 %, and 40.19 %, respectively) because of increasing the surface hydrophobicity. UHP-HT combined improved structural characteristics, including particle size, zeta potential, and functional group stability, and significantly enhanced the antioxidant activity of WP under high humidity conditions. Overall, these findings suggest that UHP-HT can effectively reduce the moisture absorption of WP, thus enhancing its storage stability and extending its shelf life.

Depolymerized peanut skin-derived proanthocyanidins alleviate cognitive dysfunction by inhibiting Aβ42 aggregation in Alzheimer's disease

Peanut skin proanthocyanidins (PSP) are natural polyphenols with antioxidant properties that mitigate Alzheimer's disease (AD), a complex progressive neurodegenerative disorder whose underlying biological mechanisms includes the aggregation of insoluble amyloid plaques. However, the high degree of polymerization of PSP, extracted using conventional methods, limits its bioavailability. This study established the optimal processes for ultrasound-assisted alkaline depolymerization to produce oligomeric proanthocyanidins (OPSP) from PSP content (2.7 mg/mL), depolymerization temperature (54.8 °C), ultrasonic power (480 W, 28 Hz), ultrasonic duration (28.7 min), and pH (12.1). Under these conditions, the degree of polymerization of the proanthocyanidins decreased from 6.74 to 2.87. Physicochemical characteristics of PSP and OPSP were analyzed. Both PSP and OPSP exhibited shared structural bonding and a repeating 288 Da unit, with Proanthocyanidin A identified as the predominant type. Furthermore, compared with PSP, OPSP demonstrated enhanced stability and antioxidant activity. Using in vitro detection of amyloid-beta (Aβ42) inhibition, this study demonstrated that OPSP exhibited greater inhibition of Aβ42 fibrillogenicity than underpolymerized PSP, and OPSP significantly inhibited Aβ42-induced cytotoxicity. In addition, the effect of OPSP was investigated in a rat model of Alzheimer's disease. The results indicated that OPSP improved the memory performance of AD rats in the water maze and decreased the levels of inflammatory factors IL-6, IL-1β, and TNF-α. Moreover, OPSP ameliorated histopathological changes and reduced Aβ42 plaque deposition in the brains of AD rats. These findings regarding OPSP are anticipated to facilitate high-value utilization of peanut by-products, expand their applications, and provide guidance for the use of OPSP in the development of natural healthcare pharmaceuticals and mitigation and treatment of Alzheimer's disease.

Dietary anti-inflammatory and anti-bacterial medicinal plants and its compounds in bovine mastitis associated impact on human life

Bovine mastitis (BM) is the most common bacterial mediated inflammatory disease in the dairy cattle that causes huge economic loss to the dairy industry due to decreased milk quality and quantity. Milk is the essential food in the human diet, and rich in crucial nutrients that helps in lowering the risk of diseases like hypertension, cardiovascular diseases and type 2 diabetes. The main causative agents of the disease include various gram negative, and positive bacteria, along with other risk factors such as udder shape, age, genetic, and environmental factors also contributes much for the disease. Currently, antibiotics, immunotherapy, probiotics, dry cow, and lactation therapy are commonly recommended for BM. However, these treatments can only decrease the rise of new cases but can't eliminate the causative agents, and they also exhibit several limitations. Hence, there is an urgent need of a potential source that can generate a typical and ideal treatment to overcome the limitations and eliminate the pathogens. Among the various sources, medicinal plants and its derived products always play a significant role in drug discovery against several diseases. In addition, they are also known for its low toxicity and minimum resistance features. Therefore, plants and its compounds that possess anti-inflammatory and anti-bacterial properties can serve better in bovine mastitis. In addition, the plants that are serving as a food source and possessing pharmacological properties can act even better in bovine mastitis. Hence, in this evidence-based study, we particularly review the dietary medicinal plants and derived products that are proven for anti-inflammatory and anti-bacterial effects. Moreover, the role of each dietary plant and its compounds along with possible role in the management of bovine mastitis are delineated. In this way, this article serves as a standalone source for the researchers working in this area to help in the management of BM.

A novel approach has been developed to produce pure plant-based gel soy yogurt by combining soy proteins (7S/11S), high pressure homogenization, and glycation reaction

This research sought to examine how the physicochemical characteristics of soy globulins and different processing techniques influence the gel properties of soy yogurt. The goal was to improve these gel properties and rectify any texture issues in soy yogurt, ultimately aiming to produce premium-quality plant-based soy yogurt. In this research study, the investigation focused on examining the impact of 7S/11S, homogenization pressure, and glycation modified with glucose on the gel properties of soy yogurt. A plant-based soy yogurt with superior gel and texture properties was successfully developed using a 7S/11S globulin-glucose conjugate at a 1:3 ratio and a homogenization pressure of 110 MPa. Compared to soy yogurt supplemented with pectin or gelatin, this yogurt demonstrated enhanced characteristics. These findings provide valuable insights into advancing plant protein gels and serve as a reference for cultivating new soybean varieties by soybean breeding experts.

Mechanisms of polyphenols on quality control of aquatic products in storage: A review

Aquatic products are easily spoiled during storage due to oxidation, endogenous enzymes, and bacteria. At the same time, compared with synthetic antioxidants, based on the antibacterial and antioxidant mechanism of biological agents, the development of natural, nontoxic, low-temperature, better-effect green biological preservatives is more acceptable to consumers. The type and molecular structure of polyphenols affect their antioxidant and antibacterial effectiveness. This review will describe how they achieve their antioxidant and antibacterial effects. And the recent literature on the mechanism and application of polyphenols in the preservation of aquatic products was updated and summarized. The conclusion is that in aquatic products, polyphenols alleviate lipid oxidation, protein degradation and inhibit the growth and reproduction of microorganisms, so as to achieve the effect of storage quality control. And put forward suggestions on the application of the research results in aquatic products. We hope to provide theoretical support for better exploration of the application of polyphenols and aquatic product storage.

Natural phenolic compounds: Antimicrobial properties, antimicrobial mechanisms, and potential utilization in the preservation of aquatic products

Natural antibacterials have stood out in the last decade due to the growing demand for reducing chemical preservatives in food. In particular, natural phenolic compounds are secondary metabolites produced by plants for numerous functions including antimicrobial defence. Polyphenol has significant antimicrobial activity, but its antimicrobial properties are affected by the cell structure difference of bacteria, the concentration, type, and extraction method of polyphenol, and the treatment time of bacteria exposed to polyphenol. Therefore, this paper analyzed the antibacterial activity and mechanism of polyphenol as an antimicrobial agent. However, there remained significant considerations, including the interaction of polyphenols and food matrix, environmental temperature, and the effect of color and odor of some polyphenols on sensory properties of aquatic products, and the additive amount of polyphenols. On this basis, the application strategies of polyphenols as the antimicrobial agent in aquatic products preservation were reviewed.

Mechanisms of bacterial resistance to environmental silver and antimicrobial strategies for silver: A review

The good antimicrobial properties of silver make it widely used in food, medicine, and environmental applications. However, the release and accumulation of silver-based antimicrobial agents in the environment is increasing with the extensive use of silver-based antimicrobials, and the prevalence of silver-resistant bacteria is increasing. To prevent the emergence of superbugs, it is necessary to exercise rational and strict control over drug use. The mechanism of bacterial resistance to silver has not been fully elucidated, and this article provides a review of the progress of research on the mechanism of bacterial resistance to silver. The results indicate that bacterial resistance to silver can occur through inducing silver particles aggregation and Ag+ reduction, inhibiting silver contact with and entry into cells, efflux of silver particles and Ag+ in cells, and activation of damage repair mechanisms. We propose that the bacterial mechanism of silver resistance involves a combination of interrelated systems. Finally, we discuss how this information can be used to develop the next generation of silver-based antimicrobials and antimicrobial therapies. And some antimicrobial strategies are proposed such as the "Trojan Horse" - camouflage, using efflux pump inhibitors to reduce silver efflux, working with "minesweeper", immobilization of silver particles.

Identification of Escherichia coli multidrug resistance transporters involved in anthocyanin biosynthesis

The anthocyanin compound cyanidin 3-O-glucoside (C3G) is a natural pigment widely used in food and nutraceutical industries. Its microbial synthesis by E. coli is a promising alternative to the traditional extraction methods. However, part of the synthesized C3G accumulates in the cytoplasm, thus potentially causing growth inhibition and product degradation. Therefore, it is necessary to enhance C3G secretion via exploration of native transporters facilitating C3G export. In this study, we report the screening and verification of native multidrug resistance transporters from 40 candidates in E. coli that can improve the extracellular C3G production when using catechin as the substrate. Overexpression of single transporter genes including fsr, yebQ, ynfM, mdlAB, and emrKY were found to increase C3G production by 0.5- to 4.8-fold. Genetic studies indicated that mdlAB and emrKY are vital transporters in the secretion of C3G. Our study reveals a set of new multidrug resistance transporters for the improvement of microbial biosynthesis of C3G and other anthocyanins.

Antibacterial and Anti-Inflammatory Properties of Flavonoids from Streptomyces chartreusis RH3.5

<b>Background and Objective:</b> The RH3.5 was isolated from the rhizosphere of <i>Boesenbergia rotunda</i> (L.) Mansf. and identified to be <i>Streptomyces chartreusis</i> via analysis of its 16S rDNA sequence, chemotaxonomy and morphology. The aim of this study was to identify the major compounds of RH3.5 and assess their biological activities. <b>Materials and Methods:</b> Silica gel column chromatography and thin-layer chromatography were used to purify major compounds, elucidate 5,7,2'-trihydroxy-8-methoxyflavanone (compound <b>1</b>) and 5',2',5'-trihydroxy-7,8-dimethoxyflavanone (compound <b>2</b>). Subsequently, mass spectrometry and NMR techniques were used to identify the structure of these compounds. Antimicrobial, anti-inflammatory and cytotoxic properties were carried out using <i>in vitro</i> assays. <b>Results:</b> The bioassays revealed the antimicrobial effect of compounds <b>1</b> and <b>2</b> on MRSA and <i>Staphylococcus aureus</i>. The minimum inhibitory concentration and minimum bactericidal concentration was calculated in the range of 32-64 and 128-256 μg/mL, respectively. The compounds <b>1</b> and <b>2</b> also exhibited anti-inflammatory potential by inhibiting NO, IL-1β and TNF-α production in LPS-stimulated RAW264.7 cells in a dose-dependent manner. Additionally, they had mild cytotoxic action against Vero and L929 cell lines with IC₅₀ values greater than 512 μg/mL. <b>Conclusion:</b> These findings showed that flavonoids of <i>Streptomyces</i> <i>chartreusis</i> RH3.5 exhibited antibacterial and anti-inflammatory activities with low cytotoxicity against healthy cells. Thorough research on these compounds could result in the creation of useful methods for treating microbial infections and acute inflammatory responses.

On the road to colorectal cancer development: crosstalk between the gut microbiota, metabolic reprogramming, and epigenetic modifications

An increasing number of studies have reported the role of gut microbes in colorectal cancer (CRC) development, as they can be influenced by dietary metabolism and mediate alterations in host epigenetics, ultimately affecting CRC. Intake of specific dietary components can affect gut microbial composition and function, and their metabolism regulates important epigenetic functions that may influence CRC risk. Gut microbes can regulate epigenetic modifications through nutrient metabolism, including histone modification, DNA methylation, and noncoding RNAs. Epigenetics, in turn, determines the gut microbial composition and thus influences the risk of developing CRC. This review discusses the complex crosstalk between metabolic reprogramming, gut microbiota, and epigenetics in CRC and highlights the potential applications of the gut microbiota as a biomarker for the prevention, diagnosis, and therapy of CRC.

Interactions between gut microbiota and polyphenols: A mechanistic and metabolomic review

BACKGROUND

Polyphenols are a class of naturally sourced compounds with widespread distribution and an extensive array of bioactivities. However, due to their complex constituents and weak absorption, a convincing explanation for their remarkable bioactivity remains elusive for a long time. In recent years, interaction with gut microbiota is hypothesized to be a reasonable explanation of the potential mechanisms for natural compounds especially polyphenols.

OBJECTIVES

This review aims to present a persuasive explanation for the contradiction between the limited bioavailability and the remarkable bioactivities of polyphenols by examining their interactions with gut microbiota.

METHODS

We assessed literatures published before April 10, 2023, from several databases, including Scopus, PubMed, Google Scholar, and Web of Science. The keywords used include "polyphenols", "gut microbiota", "short-chain fatty acids", "bile acids", "trimethylamine N-oxide", "lipopolysaccharides" "tryptophan", "dopamine", "intestinal barrier", "central nervous system", "lung", "anthocyanin", "proanthocyanidin", "baicalein", "caffeic acid", "curcumin", "epigallocatechin-3-gallate", "ferulic acid", "genistein", "kaempferol", "luteolin", "myricetin", "naringenin", "procyanidins", "protocatechuic acid", "pterostilbene", "quercetin", "resveratrol", etc. RESULTS: The review first demonstrates that polyphenols significantly alter gut microbiota diversity (α- and β-diversity) and the abundance of specific microorganisms. Polyphenols either promote or inhibit microorganisms, with various factors influencing their effects, such as dosage, treatment duration, and chemical structure of polyphenols. Furthermore, the review reveals that polyphenols regulate several gut microbiota metabolites, including short-chain fatty acids, dopamine, trimethylamine N-oxide, bile acids, and lipopolysaccharides. Polyphenols affect these metabolites by altering gut microbiota composition, modifying microbial enzyme activity, and other potential mechanisms. The changed microbial metabolites induced by polyphenols subsequently trigger host responses in various ways, such as acting as intestinal acid-base homeostasis regulators and activating on specific target receptors. Additionally, polyphenols are transformed into microbial derivatives by gut microbiota and these polyphenols' microbial derivatives have many potential advantages (e.g., increased bioactivity, improved absorption). Lastly, the review shows polyphenols maintain intestinal barrier, central nervous system, and lung function homeostasis by regulating gut microbiota.

CONCLUSION

The interaction between polyphenols and gut microbiota provides a credible explanation for the exceptional bioactivities of polyphenols. This review aids our understanding of the underlying mechanisms behind the bioactivity of polyphenols.

Dietary (poly)phenols mitigate inflammatory bowel disease: Therapeutic targets, mechanisms of action, and clinical observations

Inflammatory bowel diseases (IBD), which include Crohn's disease and ulcerative colitis, are a rapidly growing public health concern worldwide. These diseases are heterogeneous at the clinical, immunological, molecular, genetic, and microbial level, but characteristically involve a disrupted immune-microbiome axis. Shortcomings in conventional treatment options warrant the need for novel therapeutic strategies to mitigate these life-long and relapsing disorders of the gastrointestinal tract. Polyphenols, a diverse group of phytochemicals, have gained attention as candidate treatments due to their array of biological effects. Polyphenols exert broad anti-inflammatory and antioxidant effects through the modulation of cellular signaling pathways and transcription factors important in IBD progression. Polyphenols also bidirectionally modulate the gut microbiome, supporting commensals and inhibiting pathogens. One of the primary means by which gut microbiota interface with the host is through the production of metabolites, which are small molecules produced as intermediate or end products of metabolism. There is growing evidence to support that modulation of the gut microbiome by polyphenols restores microbially derived metabolites critical to the maintenance of intestinal homeostasis that are adversely disrupted in IBD. This review aims to define the therapeutic targets of polyphenols that may be important for mitigation of IBD symptoms, as well as to collate evidence for their clinical use from randomized clinical trials.

Variation in Phenolic Compounds, Antioxidant and Antibacterial Activities of Extracts from Different Plant Organs of Meadowsweet (Filipendula ulmaria (L.) Maxim.)

Meadowsweet (Filipendula ulmaria (L.) Maxim.) has been widely used in the treatment of various diseases. The pharmacological properties of meadowsweet are derived from the presence of phenolic compounds of a diverse structure in sufficiently large quantities. The purpose of this study was to examine the vertical distribution of individual groups of phenolic compounds (total phenolics, flavonoids, hydroxycinnamic acids, catechins, proanthocyanidins, and tannins) and individual phenolic compounds in meadowsweet and to determine the antioxidant and antibacterial activity of extracts from various meadowsweet organs. It was found that the leaves, flowers, fruits, and roots of meadowsweet are characterized by a high total phenolics content (up to 65 mg g^-1). A high content of flavonoids was determined in the upper leaves and flowers (117-167 mg g^-1), with high contents of hydroxycinnamic acids in the upper leaves, flowers, and fruits (6.4-7.8 mg g^-1); high contents of catechins and proanthocyanidins in the roots (45.1 and 3.4 mg g^-1, respectively); and high tannin content in the fruits (38.3 mg g^-1). Analysis of extracts by high-performance liquid chromatography (HPLC) showed that the qualitative and quantitative composition of individual phenolic compounds in various parts of the meadowsweet varied greatly. Among the flavonoids identified in meadowsweet, quercetin derivatives dominate, namely quercetin 3-O-rutinoside, quercetin 3-β-d-glucoside, and quercetin 4'-O-glucoside. Quercetin 4'-O-glucoside (spiraeoside) was found only in the flowers and fruits. Catechin was identified in the leaves and roots of meadowsweet. The distribution of phenolic acids across the plant was also uneven. In the upper leaves, a higher content of chlorogenic acid was determined, and in the lower leaves, a higher content of ellagic acid determined. In flowers and fruits, a higher contents of gallic, caftaric, ellagic, and salicylic acids were noted. Ellagic and salicylic acids were also dominant among phenolic acids in the roots. Based on the results of the analysis of antioxidant activity in terms of the ability to utilize the radicals of 2,2-diphenyl-1-picrylhydrazine (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazolino-6-sulfonic acid) (ABTS) and in terms of iron-reducing ability (FRAP), the upper leaves, flowers, and fruits of meadowsweet can be considered plant raw materials suitable to obtain extracts with high antioxidant activity. Extracts of plant fruits and flowers also showed high antibacterial activity against the bacteria Bacillus subtilis and Pseudomonas aeruginosa.

Facile fabrication of robust bilayer film loaded with chitosan active microspheres for potential multifunctional food packing

The utilization of microcarriers is an effective technique to protect and slow down the release of active ingredients, while the combination of microcarriers and film materials is an important way to expand the application scenario of active ingredients. The aim of this study was to develop a simple and facile strategy for designing a multifunctional bilayer bioactive film that combines stable mechanical properties, sustained-release characteristics for active ingredients with good antioxidant and antibacterial properties. The EGCG-loaded chitosan active microspheres were prepared by sol-gel method, and then the carboxymethyl cellulose solution containing the active microspheres was assembled onto the carboxymethyl chitosan gel substrate based on intermolecular hydrogen bonding to construct a film with a stable bilayer structure. The results indicated that the bilayer film had dense microstructure and excellent mechanical strength (37.05 MPa), and exhibited UV-blocking properties and excellent gas barrier performance. Meanwhile, the loading of active ingredients (EGCG) in the microspheres enabled the bilayer film to exhibit excellent antioxidant and antibacterial properties, and the controlled release of EGCG by the film was sustainable and showed pH responsiveness. The results of this work provide a new perspective for the design and development of bio-based active packaging film with tunable functional characteristics.

Three Phenolic Extracts Regulate the Physicochemical Properties and Microbial Community of Refrigerated Channel Catfish Fillets during Storage

It has been demonstrated that polyphenols have the potential to extend the shelf life of fish products. Thus, the effects of phenolic extracts from grape seed (GSE), lotus seedpod (LSPC), and lotus root (LRPE) were investigated in this study, focusing on the physicochemical changes and bacterial community of refrigerated channel catfish fillets during storage at 4 °C, using ascorbic acid (AA) as reference. As a result, GSE, LSPC, LRPE and AA inhibit the reproduction of microbials in catfish fillets during storage. According to the microbial community analysis, the addition of polyphenols significantly reduced the relative abundance of Proteobacterial in the early stage and changed the distribution of the microbial community in the later stage of storage. After 11 days of storage, the increase in total volatile base nitrogen (TVB-N) in fish was significantly reduced by 25.85%, 25.70%, 22.41%, and 39.31% in the GSE, LSPC, LRPE, and AA groups, respectively, compared to the control group (CK). Moreover, the lipid oxidation of samples was suppressed, in which thiobarbituric acid-reactive substances (TBARS) decreased by 28.77% in the GSE group, compared with the CK. The centrifugal loss, LF-NMR, and MRI results proved that GSE significantly delayed the loss of water and the increase in immobilized water flowability in catfish fillets. The polyphenol-treated samples also showed less decrease in shear force and muscle fiber damage in histology, compared to the CK. Therefore, the dietary polyphenols including GSE, LSPC, and LRPE could be developed as natural antioxidants to protect the quality and to extend the shelf life of freshwater fish.

Anthocyanins from Malus spp. inhibit the activity of Gymnosporangium yamadae by downregulating the expression of WSC, RLM1, and PMA1

Malus plants are frequently devastated by the apple rust caused by Gymnosporangium yamadae Miyabe. When rust occurs, most Malus spp. and cultivars produce yellow spots, which are more severe, whereas a few cultivars accumulate anthocyanins around rust spots, forming red spots that inhibit the expansion of the affected area and might confer rust resistance. Inoculation experiments showed that Malus spp. with red spots had a significantly lower rust severity. Compared with M. micromalus, M. 'Profusion', with red spots, accumulated more anthocyanins. Anthocyanins exhibited concentration-dependent antifungal activity against G. yamadae by inhibiting teliospores germination. Morphological observations and the leakage of teliospores intracellular contents evidenced that anthocyanins destroyed cell integrity. Transcriptome data of anthocyanins-treated teliospores showed that differentially expressed genes were enriched in cell wall and membrane metabolism-related pathways. Obvious cell atrophy in periodical cells and aeciospores was observed at the rust spots of M. 'Profusion'. Moreover, WSC, RLM1, and PMA1 in the cell wall and membrane metabolic pathways were progressively downregulated with increasing anthocyanins content, both in the in vitro treatment and in Malus spp. Our results suggest that anthocyanins play an anti-rust role by downregulating the expression of WSC, RLM1, and PMA1 to destroy the cell integrity of G. yamadae.

Characterization and Isolation of the Major Biologically Active Metabolites Isolated from Ficus retusa and Their Synergistic Effect with Tetracycline against Certain Pathogenic-Resistant Bacteria

Globally, pathogenic microbes have reached a worrisome level of antibiotic resistance. Our work aims to identify and isolate the active components from the bioactive Ficus retusa bark extract and assess the potential synergistic activity of the most major compounds' constituents with the antibiotic tetracycline against certain pathogenic bacterial strains. The phytochemical screening of an acetone extract of F. retusa bark using column chromatography led to the identification of 10 phenolic components. The synergistic interaction of catechin and chlorogenic acid as the most major compounds with tetracycline was evaluated by checkerboard assay followed by time-kill assay, against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, and Salmonella typhi with fraction inhibitory concentration index values (FICI) of 0.38, 0.43, 0.38, 0.38, 0.38, and 0.75 for catechin and 0.38, 0.65, 0.38, 0.63, 0.38, and 0.75 for chlorogenic acid. The combination of catechin and chlorogenic acid with tetracycline significantly enhanced antibacterial action against gram-positive and gram-negative microorganisms; therefore, catechin and chlorogenic acid combinations with tetracycline could be employed as innovative and safe antibiotics to combat microbial resistance.

Breaking down the cell wall: Still an attractive antibacterial strategy

Since the advent of penicillin, humans have known about and explored the phenomenon of bacterial inhibition via antibiotics. However, with changes in the global environment and the abuse of antibiotics, resistance mechanisms have been selected in bacteria, presenting huge threats and challenges to the global medical and health system. Thus, the study and development of new antimicrobials is of unprecedented urgency and difficulty. Bacteria surround themselves with a cell wall to maintain cell rigidity and protect against environmental insults. Humans have taken advantage of antibiotics to target the bacterial cell wall, yielding some of the most widely used antibiotics to date. The cell wall is essential for bacterial growth and virulence but is absent from humans, remaining a high-priority target for antibiotic screening throughout the antibiotic era. Here, we review the extensively studied targets, i.e., MurA, MurB, MurC, MurD, MurE, MurF, Alr, Ddl, MurI, MurG, lipid A, and BamA in the cell wall, starting from the very beginning to the latest developments to elucidate antimicrobial screening. Furthermore, recent advances, including MraY and MsbA in peptidoglycan and lipopolysaccharide, and tagO, LtaS, LspA, Lgt, Lnt, Tol-Pal, MntC, and OspA in teichoic acid and lipoprotein, have also been profoundly discussed. The review further highlights that the application of new methods such as macromolecular labeling, compound libraries construction, and structure-based drug design will inspire researchers to screen ideal antibiotics.

Flavonoids-Rich Plant Extracts Against Helicobacter pylori Infection as Prevention to Gastric Cancer

Gastric cancer is the fifth most common and fourth type to cause the highest mortality rates worldwide. The leading cause is related to Helicobacter pylori (H. pylori) infection. Unfortunately, current treatments have low success rates, highlighting the need for alternative treatments against carcinogenic agents, specifically H. pylori. Noteworthy, natural origin products contain pharmacologically active metabolites such as flavonoids, with potential antimicrobial applications.

Objective: This article overviews flavonoid-rich extracts’ biological and pharmacological activities. It focuses on using these substances against Helicobacter pylori infection to prevent gastric cancer. For this, PubMed and Science Direct databases were searched for studies that reported the activity of flavonoids against H. pylori, published within a 10-year time frame (2010 to August 2020). It resulted in 1,773 publications, of which 44 were selected according to the search criteria. The plant family primarily found in publications was Fabaceae (9.61%). Among the flavonoids identified after extraction, the most prevalent were quercetin (19.61%), catechin (13.72), epicatechin (11.76), and rutin (11.76). The potential mechanisms associated with anti-H. pylori activity to the extracts were: inhibition of urease, damage to genetic material, inhibition of protein synthesis, and adhesion of the microorganism to host cells.

Conclusion: Plant extracts rich in flavonoids with anti-H. pylori potential proved to be a promising alternative therapy source, reinforcing the relevance of studies with natural products.

Natural Antioxidant, Antibacterial, and Antiproliferative Activities of Ethanolic Extracts from Punica granatum L. Tree Barks Mediated by Extracellular Signal-Regulated Kinase

The nonedible parts of the pomegranate plant, such as tree barks and fruit peels, have pharmacological properties that are useful in traditional medicine. To increase their value, this study aimed to compare the antioxidative and antibacterial effects of ethanolic extracts from pomegranate barks (PBE) and peels (PPE). The antiproliferative effects on HeLa and HepG2 cells through the extracellular signal-regulated kinase pathway were also evaluated. The results indicated that the total amounts of phenolics and flavonoids of PBE and PPE were 574.64 and 242.60 mg equivalent gallic acid/g sample and 52.98 and 23.08 mg equivalent quercetin/g sample, respectively. Gas chromatography−mass spectrometry revealed that 5-hdroxymethylfurfural was the major component of both PBE (23.76%) and PPE (33.19%). The 2,2-diphenyl-1-picryl-hydrazyl-hydrate free radical scavenging capacities of PBE and PPE, in terms of the IC50 value, were 4.1 and 9.6 µg/mL, respectively. PBE had a greater potent antibacterial effect against Escherichia coli, Staphylococcus aureus, Salmonella Enteritidis, and S. Typhimurium. PBE and PPE (1000 µg/mL) had exhibited no cytotoxic effects on LLC-MK2. PBE and PPE (250 and 1000 µg/mL, respectively) treatments were safe for BHK-21. Both extracts significantly inhibited HepG2 and HeLa cell proliferations at 10 and 50 µg/mL, respectively (p < 0.001). The results indicated that PBE and PPE have remarkable efficiencies as free radical scavengers and antibacterial agents, with PBE exhibiting greater efficiency. The inhibitory effects on HepG2 might be through the modulation of the ERK1/2 expression. PBE and PPE have the potential for use as optional supplementary antioxidative, antibacterial, and anticancer agents.

Antibacterial effect and mechanism against Escherichia coli of polysaccharides from Armillariella tabescens mycelia

The objectives of this study were (1) to prepare Armillariella tabescens mycelia polysaccharides (PAT) with remarkably growth inhibitory effect on typical food-borne pathogenic bacteria using a green and efficient polyamide method and (2) to explore the antibacterial mechanism of PAT for use as a natural antibacterial agent. The sugar and uronic acid contents of PAT were 93.41% and 12.24%, respectively. PAT could inhibit the growth of Escherichia coli, Proteus vulgaris, Bacillus subtilis, and Staphylococcus aureus cells, with minimum inhibitory concentrations of 0.5, 1.0, 4.0, and 4.0 mg/mL, respectively. Ultra-high-resolution field emission scanning electron microscopy and high-resolution transmission electron microscopy analysis revealed cell wall and membrane rupture of E. coli treated with PAT. Further, 0.5-4.0 mg/mL PAT was found to significantly (P < 0.01) and concentration-dependently increase the conductivity of the broth, exudation of the intracellular protein, and alkaline phosphatase and β-galactosidase activities. Confocal laser scanning microscopy revealed morphological changes in E. coli DNA after PAT treatment and intracellular reactive oxygen species accumulation; flow cytometry revealed E. coli cell apoptosis. Our findings provide a theoretical basis and technical support for the development of PAT as a natural antibacterial product.

Beneficial Effects of Green Tea EGCG on Skin Wound Healing: A Comprehensive Review

Epigallocatechin gallate (EGCG) is associated with various health benefits. In this review, we searched current work about the effects of EGCG and its wound dressings on skin for wound healing. Hydrogels, nanoparticles, micro/nanofiber networks and microneedles are the major types of EGCG-containing wound dressings. The beneficial effects of EGCG and its wound dressings at different stages of skin wound healing (hemostasis, inflammation, proliferation and tissue remodeling) were summarized based on the underlying mechanisms of antioxidant, anti-inflammatory, antimicrobial, angiogenesis and antifibrotic properties. This review expatiates on the rationale of using EGCG to promote skin wound healing and prevent scar formation, which provides a future clinical application direction of EGCG.

Antimicrobial Effect of Tea Polyphenols against Foodborne Pathogens: A Review

ABSTRACT

Food contamination by foodborne pathogens is still widespread in many countries around the world, and food safety is a major global public health issue. Therefore, novel preservatives that can guarantee safer food are in high demand. Contrary to artificial food preservatives, tea polyphenols (TPs) are getting wide attention as food additives for being "green," "safe," and "healthy." TPs come from many sources, and the purification technology is sophisticated. Compared with other natural antibacterial agents, the antibacterial effect of TPs is more stable, making them excellent natural antibacterial agents. This review includes a systematic summary of the important chemical components of TPs and the antibacterial mechanisms of TPs against various foodborne pathogens. The potential applications of TPs are also discussed. These data provide a theoretical basis for the in-depth study of TPs.

HIGHLIGHTS

An Iron Shield to Protect Epigallocatehin-3-Gallate from Degradation: Multifunctional Self-Assembled Iron Oxide Nanocarrier Enhances Protein Kinase CK2 Intracellular Targeting and Inhibition

Protein kinase CK2 is largely involved in cell proliferation and apoptosis and is generally recognized as an Achilles’ heel of cancer, being overexpressed in several malignancies. The beneficial effects of (−)-epigallocatechin-3-gallate (EGCG) in the prevention and treatment of several diseases, including cancer, have been widely reported. However, poor stability and limited bioavailability hinder the development of EGCG as an effective therapeutic agent. The combination of innovative nanomaterials and bioactive compounds into nanoparticle-based systems demonstrates the synergistic advantages of nanocomplexes as compared to the individual components. In the present study, we developed a self-assembled core-shell nanohybrid (SAMN@EGCG) combining EGCG and intrinsic dual-signal iron oxide nanoparticles (Surface Active Maghemite Nanoparticles). Interestingly, nano-immobilization on SAMNs protects EGCG from degradation, preventing its auto-oxidation. Most importantly, the nanohybrid was able to successfully deliver EGCG into cancer cells, displaying impressive protein kinase CK2 inhibition comparable to that obtained with the most specific CK2 inhibitor, CX-4945 (5.5 vs. 3 µM), thus promoting the phytochemical exploitation as a valuable alternative for cancer therapy. Finally, to assess the advantages offered by nano-immobilization, we tested SAMN@EGCG against Pseudomonas aeruginosa, a Gram-negative bacterium involved in severe lung infections. An improved antimicrobial effect with a drastic drop of MIC from 500 to 32.7 μM was shown.

Synergistic antimicrobial activities of epigallocatechin gallate, myricetin, daidzein, gallic acid, epicatechin, 3-hydroxy-6-methoxyflavone and genistein combined with antibiotics against ESKAPE pathogens

AIM

To verify synergistic effects, we investigated the antimicrobial activity of seven phenolic phytochemicals (gallic acid; epicatechin; epigallocatechin gallate; daidzein; genistein; myricetin; 3-hydroxy-6-methoxyflavone) in combination with six antibiotics against multidrug-resistant isolates from the ESKAPE group.

METHODS AND RESULTS

To investigate single phytochemicals and combinations, initial microdilution and checkerboard assays were used, followed by time-kill assays to evaluate the obtained results. The research revealed that phenolic compounds on their own resulted in little or no inhibitory effects. During preliminary tests, most of the combinations resulted in indifference (134 [71.3%]). In all, 30 combinations led to antagonism (15.9%); however, 24 showed synergistic effects (12.8%). The main tests resulted in nine synergistic combinations for the treatment of four different bacteria strains, including two substances (3-hydroxy-6-methoxyflavone, genistein) never tested before in such setup. Time-kill curves for combinations with possible synergistic effects confirmed the results against Acinetobacter baumannii as the one with the greatest need for research.

CONCLUSIONS

The results highlight the potential use of antibiotic-phytocompound combinations for combating infections with multi-resistant pathogens. Synergistic combinations could downregulate the resistance mechanisms of bacteria.

SIGNIFICANCE AND IMPACT OF THE STUDY

The aim of this study is to demonstrate the potential use of phenolic natural compounds in combination with conventional antibiotics against multidrug-resistant bacteria of the ESKAPE group. Due to synergistic effects of natural phenolic compounds combined with antibiotics, pathogens that are already resistant to antibiotics could be resensitized as we were able to reduce their MICs back to sensitive. In addition, combination therapies could prevent the development of resistance by reducing the dose of antibiotics. This approach opens up the basis for future development of antimicrobial therapy strategies, which are so urgently needed in the age of multidrug-resistant pathogens.

Synergic interactions between polyphenols and gut microbiota in mitigating inflammatory bowel diseases

Inflammatory bowel diseases (IBD) are a group of chronic and recurring inflammatory conditions in the colon and intestine. Their etiology is not fully understood but involves the combination of gut dysbiosis, genetics, immune functions, and environmental factors including diet. Polyphenols from plant-based food synergistically interact with gut microbiota to suppress inflammation and alleviate symptoms of IBD. Polyphenols increase the diversity of gut microbiota, improve the relative abundance of beneficial bacteria, and inhibit the pathogenic species. Polyphenols not absorbed in the small intestine are catabolized in the colon by microbiota into microbial metabolites, many of which have higher anti-inflammatory activity and bioavailability than their precursors. The polyphenols and their microbial metabolites alleviate IBD through reduction of oxidative stress, inhibition of inflammatory cytokines secretion (TNF-α, IL-6, IL-8, and IL-1β), suppression of NF-κB, upregulation of Nrf2, gut barrier protection, and modulation of immune function. Future studies are needed to discover unknown microbial metabolites of polyphenols and correlate specific gut microbes with microbial metabolites and IBD mitigating activity. A better knowledge of the synergistic interactions between polyphenols and gut microbiota will help to devise more effective prevention strategies for IBD. This review focuses on the role of polyphenols, gut microbiota and their synergistic interactions on the alleviation of IBD as well as current trends and future directions of IBD management.

Antibacterial green tea catechins from a molecular perspective: mechanisms of action and structure-activity relationships

This review summarizes the mechanisms of antibacterial action of green tea catechins, discussing the structure-activity relationship (SAR) studies for each mechanism. The antibacterial activity of green tea catechins results from a variety of mechanisms that can be broadly classified into the following groups: (1) inhibition of virulence factors (toxins and extracellular matrix); (2) cell wall and cell membrane disruption; (3) inhibition of intracellular enzymes; (4) oxidative stress; (5) DNA damage; and (6) iron chelation. These mechanisms operate simultaneously with relative importance differing among bacterial strains. In all SAR studies, the highest antibacterial activity is observed for galloylated compounds (EGCG, ECG, and theaflavin digallate). This observation, combined with numerous experimental and theoretical evidence, suggests that catechins share a common binding mode, characterized by the formation of hydrogen bonds and hydrophobic interactions with their target.

Characterization of Epigallocatechin-Gallate-Grafted Chitosan Nanoparticles and Evaluation of Their Antibacterial and Antioxidant Potential

Nanoparticles based on chitosan modified with epigallocatechin gallate (EGCG) were synthetized by nanoprecipitation (EGCG-g-chitosan-P). Chitosan was modified by free-radical-induced grafting, which was verified by Fourier transform infrared (FTIR). Furthermore, the morphology, particle size, polydispersity index, and zeta potential of the nanoparticles were investigated. The grafting degree of EGCG, reactive oxygen species (ROS) production, antibacterial and antioxidant activities of EGCG-g-chitosan-P were evaluated and compared with those of pure EGCG and chitosan nanoparticles (Chitosan-P). FTIR results confirmed the modification of the chitosan with EGCG. The EGCG-g-chitosan-P showed spherical shapes and smoother surfaces than those of Chitosan-P. EGCG content of the grafted chitosan nanoparticles was 330 μg/g. Minimal inhibitory concentration (MIC) of EGCG-g-chitosan-P (15.6 μg/mL) was lower than Chitosan-P (31.2 μg/mL) and EGCG (500 μg/mL) against Pseudomonas fluorescens (p < 0.05). Additionally, EGCG-g-chitosan-P and Chitosan-P presented higher Staphylococcus aureus growth inhibition (100%) than EGCG at the lowest concentration tested. The nanoparticles produced an increase of ROS (p < 0.05) in both bacterial species assayed. Furthermore, EGCG-g-chitosan-P exhibited higher antioxidant activity than that of Chitosan-P (p < 0.05) in 2,2'-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and ferric-reducing antioxidant power assays. Based on the above results, EGCG-g-chitosan-P shows the potential for food packaging and biomedical applications.

Efflux pumps in multidrug-resistant Acinetobacter baumannii: Current status and challenges in the discovery of efflux pumps inhibitors

Acinetobacter baumannii is an ESKAPE pathogen known to cause fatal nosocomial infections. With the surge of multidrug resistance (MDR) in the bacterial system, effective treatment measures have become very limited. The MDR in A. baumannii is contributed by various factors out of which efflux pumps have gained major attention due to their broad substrate specificity and wide distribution among bacterial species. The efflux pumps are involved in the MDR as well as contribute to other physiological processes in bacteria, therefore, it is critically important to inhibit efflux pumps in order to combat emerging resistance. The present review provides insight about the different efflux pump systems in A. baumannii and their role in multidrug resistance. A major focus has been put on the different strategies and alternate therapeutics to inhibit the efflux system. This includes use of different efflux pump inhibitors-natural, synthetic or combinatorial therapy. The use of phage therapy and nanoparticles for inhibiting efflux pumps have also been discussed here. Moreover, the present review provides the knowledge of barriers in development of efflux pump inhibitors (EPIs) and their approval for commercialization. Here, different prospectives have been discussed to improve the therapeutic development process and make it more compatible for clinical use.

Tea bioactive components prevent carcinogenesis via anti-pathogen, anti-inflammation, and cell survival pathways

Cancer seriously impairs human health and survival. Many perturbations, such as increased oxidative stress, pathogen infection, and inflammation, promote the accumulation of DNA mutations, and ultimately lead to carcinogenesis. Tea is one of the most highly consumed beverages worldwide and has been linked to improvements in human health. Tea contains many active components, including tea polyphenols, tea polysaccharides, L-theanine, tea pigments, and caffeine among other common components. Several studies have identified components in tea that can directly or indirectly reduce carcinogenesis with some being used in a clinical setting. Many previous studies, in vitro and in vivo, have focused on the mechanisms that functional components of tea utilized to protect against cancer. One particular mechanism that has been well described is an improvement in antioxidant capacity seen with tea consumption. However, other mechanisms, including anti-pathogen, anti-inflammation and alterations in cell survival pathways, are also involved. The current review focuses on these anti-cancer mechanisms. This will be beneficial for clinical utilization of tea components in preventing and treating cancer in the future.

The Interactions between Polyphenols and Microorganisms, Especially Gut Microbiota

This review presents the comprehensive knowledge about the bidirectional relationship between polyphenols and the gut microbiome. The first part is related to polyphenols' impacts on various microorganisms, especially bacteria, and their influence on intestinal pathogens. The research data on the mechanisms of polyphenol action were collected together and organized. The impact of various polyphenols groups on intestinal bacteria both on the whole "microbiota" and on particular species, including probiotics, are presented. Moreover, the impact of polyphenols present in food (bound to the matrix) was compared with the purified polyphenols (such as in dietary supplements) as well as polyphenols in the form of derivatives (such as glycosides) with those in the form of aglycones. The second part of the paper discusses in detail the mechanisms (pathways) and the role of bacterial biotransformation of the most important groups of polyphenols, including the production of bioactive metabolites with a significant impact on the human organism (both positive and negative).

Polyphenol-Assisted Chemical Crosslinking: A New Strategy to Achieve Highly Crosslinked, Antioxidative, and Antibacterial Ultrahigh-Molecular-Weight Polyethylene for Total Joint Replacement

Highly crosslinked ultrahigh-molecular-weight polyethylene (UHMWPE) bearings are wear-resistant to reduce aseptic loosening but are susceptible to oxidize in vivo/in vitro, as reported in clinical studies. Despite widespread acceptance of antioxidants in preventing oxidation, the crosslinking efficiency of UHMWPE is severely impacted by antioxidants, the use of which was trapped in a trace amount. Herein, we proposed a new strategy of polyphenol-assisted chemical crosslinking to facilitate the formation of a crosslinking network in high-loaded tea polyphenol/UHMWPE blends. Epigallocatechin gallate (EGCG), a representative of tea polyphenol, was mixed with UHMWPE and peroxide. Multiple reactive phenolic hydroxyl groups of tea polyphenol coupled with the nearby free radicals to form extra crosslinking sites. The crosslinking efficiency was remarkably enhanced with increasing tea polyphenol content, even at a concentration of 8 wt %. Given by the hydrogen donation principle, the high-loaded tea polyphenol also enhanced the oxidation stability of the crosslinked UHMWPE. The antioxidative performance was preserved even after tea polyphenol elution. Moreover, superior antibacterial performance was achieved by the in situ tea polyphenol release from the interconnected pathways in the present design. The strategy of polyphenol-assisted chemical crosslinking is applicable for producing highly crosslinked, antioxidative, and antibacterial UHMWPE, which has promising prospects in clinical applications.

Antibacterial and anti-inflammatory ultrahigh molecular weight polyethylene/tea polyphenol blends for artificial joint applications

Periprosthetic joint infection (PJI) is one of the main causes for the failure of joint arthroplasty. In view of the limited clinical effect of oral/injectable antibiotics and the drug resistance problem, there is a pressing need to develop antibacterial implants with therapeutic antimicrobial properties. In this work, we prepared a highly antibacterial ultrahigh molecular weight polyethylene (UHMWPE) implant by incorporating tea polyphenols. The presence of tea polyphenols not only improved the oxidation stability of irradiated UHMWPE, but also gave it the desirable antibacterial property. The potent antibacterial activity was attributed to the tea polyphenols that produced excess intracellular reactive oxygen species and destroyed the bacterial membrane structure. The tea polyphenol-blended UHMWPE had no biological toxicity to human adipose-derived stem cells and effectively reduced bacteria-induced inflammation in vivo. These results indicate that tea polyphenol-blended UHMWPE is promising for joint replacement prostheses with multifunctionality to meet patient satisfaction.

Fabrication of Functional Bioelastomer for Food Packaging from Aronia (Aronia melanocarpa) Juice Processing By-Products

Carbon-neutral and eco-friendly biomass-based processes are recognized as a frontier technology for sustainable development. In particular, biopolymers are expected to replace petrochemical-based films that are widely used in food packaging. In this study, the fabrication conditions of functional (antioxidant and antibacterial) bioelastomers were investigated using by-products from the juice processing (experimental group) and freeze-dried whole fruit (control group). Bioelastomer was fabricated by a casting method in which polydimethylsiloxane (PDMS) was mixed with 25 or 50 wt% aronia powder (juice processing by-products and freeze-dried whole fruit). The mechanical properties of the bioelastomers were measured based on tensile strength and Young's modulus. When the mixture contained 50 wt% aronia powder, the strength was not appropriate for the intended purpose. Next, the surface and chemical properties of the bioelastomer were analyzed; the addition of aronia powder did not significantly change these properties when compared to PDMS film (no aronia powder). However, the addition of aronia powder had a significant effect on antioxidant and antimicrobial activities and showed higher activity with 50 wt% than with 25 wt%. In particular, bioelastomers fabricated from aronia juice processing by-products exhibited approximately 1.4-fold lower and 1.5-fold higher antioxidant and antimicrobial activities, respectively, than the control group (bioelastomers fabricated from freeze-dried aronia powder).

Role of symbiosis in the discovery of novel antibiotics

Antibiotic resistance has been an ongoing challenge that has emerged almost immediately after the initial discovery of antibiotics and requires the development of innovative new antibiotics and antibiotic combinations that can effectively mitigate the development of resistance. More than 35,000 people die each year from antibiotic resistant infections in just the United States. This signifies the importance of identifying other alternatives to antibiotics for which resistance has developed. Virtually, all currently used antibiotics can trace their genesis to soil derived bacteria and fungi. The bacteria and fungi involved in symbiosis is an area that still remains widely unexplored for the discovery and development of new antibiotics. This brief review focuses on the challenges and opportunities in the application of symbiotic microbes and also provides an interesting platform that links natural product chemistry with evolutionary biology and ecology.

Antibacterial Activity of Four Plant Extracts Extracted from Traditional Chinese Medicinal Plants against Listeria monocytogenes, Escherichia coli, and Salmonella enterica subsp. enterica serovar Enteritidis

The worldwide ethnobotanical use of four investigated plants indicates antibacterial properties. The aim of this study was to screen and determine significant antibacterial activity of four plant extracts in vitro and in a poultry digest model. Using broth microdilution, the concentrations at which four plant extracts inhibited Listeria monocytogenes, Salmonella enteritidis, and Escherichia coli over 24 h was determined. Agrimonia pilosa Ledeb, Iris domestica (L.) Goldblatt and Mabb, Anemone chinensis Bunge, and Smilax glabra Roxb all exhibited a minimum inhibitory concentration (MIC) of 62.5 mg/L and a minimum bactericidal concentration (MBC) of 500 mg/L against one pathogen. A. pilosa Ledeb was the most effective against L. monocytogenes and E. coli with the exception of S. enteritidis, for which A. chinensis Bunge was the most effective. Time–kills of A. pilosa Ledeb and A. chinensis Bunge against L. monocytogenes, E. coli and S. enteritidis incubated in poultry cecum were used to determine bactericidal activity of these plant extracts. A. chinensis Bunge, significantly reduced S. enteritidis by ≥ 99.99% within 6 h. A. pilosa Ledeb exhibited effective significant bactericidal activity within 4 h against L. monocytogenes and E. coli. This paper highlights the potential of these plant extracts to control pathogens commonly found in the poultry gastrointestinal tract.

A transcriptome analysis of the antibacterial mechanism of flavonoids from Sedum aizoon L. against Shewanella putrefaciens

Flavonoids from Sedum aizoon L. (FSAL) possess prominent antibacterial activity against Shewanella putrefaciens isolated from sea food. In the current study, the involved molecular mechanisms were investigated using transcriptome analyses combined with bioinformatics analysis in vitro for the first time. Results showed that treatment of FSAL (1.0 MIC) damaged the permeability and integrity of cell membrane and induced 721 differentially expressed genes (DEGs) in tested bacteria at transcriptional levels, including 107 DEGs were up-regulated and 614 DEGs were down-regulated. In addition, the RNA-Seq analysis revealed that the majority of DEGs mainly involved in pathways of lipopolysaccharide biosynthesis, glycerophospholipid metabolism, biosynthesis of amino acids, purine metabolism, ABC transporters and response to stimulus. In summary, the integrated results indicated that the intervention of FSAL induced destruction of cell wall and membrane, disorder of the metabolic process and redox balance, and damage of nucleic acids in S. putrefaciens, at last resulted in the death of cells. This study provided new insights into the anti- S. putrefaciens molecular mechanism underlying the treatment of FSAL, which may be served as the basis guide for identifying potential antimicrobial targets and application of FSAL in food safety.

Fabrication of polyphenol-incorporated anti-inflammatory hydrogel via high-affinity enzymatic crosslinking for wet tissue adhesion

Epigallocatechin gallates (EGCGs), isolated from green tea, have intrinsic properties such as anti-oxidant, anti-inflammation, and radical scavenger effects. In this study, we report a tissue adhesive and anti-inflammatory hydrogel formed by high-affinity enzymatic crosslinking of polyphenolic EGCGs. A mixture of EGCG conjugated hyaluronic acids (HA_E) and tyramine conjugated hyaluronic acids (HA_T) was reacted with tyrosinase isolated from Streptomyces avermitillis (SA_Ty) to form that displayed fast enzyme kinetic to form a crosslinked adhesive hydrogel. A 1,2,3-trihydroxyphenyl group in EGCG displayed a high affinity to SA_Ty that allowed HA_E to be quickly oxidized and crosslinked with HA_T to form HA_T and HA_E mixed hydrogel (HA_TE). We then compared the HA_TE hydrogel with commercially available tissue adhesives, such as cyanoacrylate and fibrin glue. We report that the HA_TE exhibited the highest tissue adhesiveness both in wet and dry conditions. Furthermore, HA_TE successfully closed a skin wound and displayed insignificant host tissue responses. This demonstrates that polyphenol-incorporated anti-inflammatory hydrogel may provide a robust tissue adhesive platform for clinical applications.

Difference in the antibacterial action of epigallocatechin gallate and theaflavin 3,3'-di-O-gallate on Bacillus coagulans

AIMS

To study the mechanism of the antibacterial action of tea polyphenols such as catechins and theaflavins against Bacillus coagulans, and the interaction of epigallocatechin gallate (EGCg) or theaflavin 3,3'-di-O-gallate (TFDG) with the surface of B. coagulans cells was investigated.

METHODS AND RESULTS

The antibacterial activities of EGCg and TFDG against B. coagulans cells were measured by counting of the viable cells after the mixing with each polyphenol. Bactericidal effect of TFDG was shown at the concentration of greater than or equal to 62·5 mg l^-1 ; however, at the same concentration, EGCg did not. According to the results of two dimensional (2D)-electrophoresis analysis, TFDG seemed to interact with cytoplasmic membrane proteins. The activity of the glucose transporters of the cells decreased 40% following the treatment with TFDG of 62·5 mg l^-1 ; however, this decrease was only slight in case of EGCg. This result was in accordance with the strength of their bactericidal activities.

CONCLUSION

Our results suggest that the direct interaction between membrane proteins and TFDG is an important factor in the antibacterial activity of polymerized catechins, affecting their functions and leading to cell death.

SIGNIFICANCE AND IMPACT OF THE STUDY

Tea polyphenols can effectively use the prevention of product spoilage in the food and beverage industry.

Interactions of Tea-Derived Catechin Gallates with Bacterial Pathogens

Green tea-derived galloylated catechins have weak direct antibacterial activity against both Gram-positive and Gram-negative bacterial pathogens and are able to phenotypically transform, at moderate concentrations, methicillin-resistant Staphylococcus aureus (MRSA) clonal pathogens from full β-lactam resistance (minimum inhibitory concentration 256-512 mg/L) to complete susceptibility (~1 mg/L). Reversible conversion to susceptibility follows intercalation of these compounds into the bacterial cytoplasmic membrane, eliciting dispersal of the proteins associated with continued cell wall peptidoglycan synthesis in the presence of β-lactam antibiotics. The molecules penetrate deep within the hydrophobic core of the lipid palisade to force a reconfiguration of cytoplasmic membrane architecture. The catechin gallate-induced staphylococcal phenotype is complex, reflecting perturbation of an essential bacterial organelle, and includes prevention and inhibition of biofilm formation, disruption of secretion of virulence-related proteins, dissipation of halotolerance, cell wall thickening and cell aggregation and poor separation of daughter cells during cell division. These features are associated with the reduction of capacity of potential pathogens to cause lethal, difficult-to-treat infections and could, in combination with β-lactam agents that have lost therapeutic efficacy due to the emergence of antibiotic resistance, form the basis of a new approach to the treatment of staphylococcal infections.

The odour assessment of thyme essential oils in electrospun fibre mat with a virtual sensor array data and its relation to antibacterial activity

Aims: The ability of a single-sensor gas diagnosis device (SSGDD) as a virtual sensor array data to appraise thyme essential oils (TEO) based on its quantitatively release rate from nanofibres was aimed.Methods: To form nylon 6 fragrant electrospun nanofibre, TEO was added as a natural antibacterial substance under homogeniser to make a stable emulsion.Results: The optimised nanofibre inactivated against Escherichia Coli and Staphylococcus Aureus bacteria up to >75% at once and to > 41.9% over 2-weeks period. Moreover, large differences in sensor responses to samples with experimental variables (percent TEO and storage time) and different odour intensity exist which correctly classified by discriminant function analysis.Conclusions: Odour intensity as an accessible incubator evinces the nanofibres efficiency which correlated to the antibacterial activity. With applying SSGDD technique as a quantified subjective solution, carefully odour assessment is possible and prepared mats could be demonstrated as a face-masks' promising candidate.

Potential Natural Food Preservatives and Their Sustainable Production in Yeast: Terpenoids and Polyphenols

Terpenoids and polyphenols are high-valued plant secondary metabolites. Their high antimicrobial activities demonstrate their huge potential as natural preservatives in the food industry. With the rapid development of metabolic engineering, it has become possible to realize large-scale production of non-native terpenoids and polyphenols by using the generally recognized as safe (GRAS) strain, Saccharomyces cerevisiae, as a cell factory. This review will summarize the major terpenoid and polyphenol compounds with high antimicrobial properties, describe their native metabolic pathways as well as antimicrobial mechanisms, and highlight current progress on their heterologous biosynthesis in S. cerevisiae. Current challenges and perspectives for the sustainable production of terpenoid and polyphenol as natural food preservatives via S. cerevisiae will also be discussed.