Tea polyphenol epigallocatechin gallate inhibits Escherichia coli by increasing endogenous oxidative stress

Formation mechanism of injured bacteria after disinfection with epigallocatechin gallate (EGCG) as a disinfectant

This study explored the effects of epigallocatechin gallate (EGCG), the main antibacterial component of tea polyphenols, on Escherichia coli in terms of disinfection damage and the underlying mechanisms. The researchers assessed inactivation and injury rates, cell morphology, and antioxidant indicators of E. coli when subjected to different concentrations of EGCG. The results showed that varying EGCG concentrations produced damaged bacteria, with the extent of damage depending on EGCG dosage and treatment duration. The disinfection process involving EGCG resulted in oxidative damage in E. coli, evoking alterations in the antioxidant system of the affected bacteria. During disinfection-induced bacterial injury, E. coli showed the active regulation of metabolism and redox activities in response to EGCG-induced environmental stimuli. Transcriptomic analysis was conducted to investigate the damage mechanism at the gene level. The damaged E. coli countered oxidative stress by adjusting gene expression related to peroxidase and glutathione metabolism processes. In this way, E. coli adjusts its gene expression to alleviate the detrimental effects of EGCG-induced oxidative stress and maintain cellular homeostasis. These findings contribute to our understanding of tea polyphenols' disinfection effects and provide insights into EGCG's mechanisms of damaging bacteria such as E. coli.

Antibiofilm Effects of Plant Extracts Against Staphylococcus aureus

The global rise in antimicrobial resistance poses a significant threat to public health, necessitating alternative therapeutic options. One critical challenge is treating infections caused by biofilm-forming bacteria, which are notably resistant to conventional antibiotics. Staphylococcus aureus, including methicillin-resistant strains (MRSA), is a major pathogen in biofilm-related infections, complicating treatment and leading to chronic cases. Plant extracts have emerged as promising alternatives, offering new avenues for effective treatment. This study evaluated the antibacterial and antibiofilm activities of commercial extracts of Vitis vinifera L. (grape), Camellia sinensis L. (green tea), Olea europaea L. (olive), Quercus robur (oak), and Coffea arabica L. (coffee) against S. aureus strains from ATCC collections and clinical isolates. Preliminary screening using the disk diffusion test assessed the zones of inhibition, which was followed by minimum inhibitory concentration (MIC) determination via broth microdilution, with Quercus robur L. showing the best overall MIC results. The results obtained demonstrate the strong antibacterial activity of the extracts, with the MIC values ranging from 0.2 to 12.4 mg/mL. Using the XTT reduction assay, the extracts inhibited biofilm growth by 80-85% after 24 h of incubation, with Coffea arabica L. achieving interesting antibiofilm activities. These findings suggest that the investigated plant extracts hold potential as antimicrobial agents and biofilm inhibitors, offering an alternative approach to tackling antimicrobial resistance. Further research is needed to explore their potential applications in developing novel adjuvant therapies.

Advances and mechanisms of traditional Chinese medicine and its active ingredients against antibiotic-resistant Escherichia coli infections

In clinical practice, antibiotics have historically been utilized for the treatment of pathogenic bacteria. However, the gradual emergence of antibiotic resistance among bacterial strains has posed a significant challenge to this approach. In 2022, Escherichia coli, a Gram-negative bacterium renowned for its widespread pathogenicity and high virulence, emerged as the predominant pathogenic bacterium in China. The rapid emergence of antibiotic-resistant E. coli strains has rendered antibiotics insufficient to fight E. coli infections. Traditional Chinese medicine (TCM) has made remarkable contributions to the health of Chinese people for thousands of years, and its significant therapeutic effects have been proven in clinical practice. In this paper, we provide a comprehensive review of the advances and mechanisms of TCM and its active ingredients against antibiotic-resistant E. coli infections. First of all, this review introduces the classification, antibiotic resistance characteristics and mechanisms of E. coli. Then, the TCM formulas and extracts are listed along with their active ingredients against E. coli, including extraction solution, minimum inhibitory concentration (MIC), and the antibacterial mechanisms. In addition, there is growing evidence supporting the synergistic therapeutic strategy of combining TCM with antibiotics for the treatment of antibiotic-resistant E. coli infections, and we provide a summary of this evidence and its underlying mechanisms. In conclusion, we present a comprehensive review of TCM and highlight its potential and advantages in the prevention and treatment of E. coli infections. We hold the opinion that TCM will play an important role in global health, pharmaceutical development, and livestock farming in the future.

Injectable hydrogel microsphere-bomb for MRSA-infected chronic osteomyelitis

Biofilm and bone tissue defect induced by the bacterial infection severely impede chronic osteomyelitis treatment. It is critical to break though the densely and obstinate biofilm so that the target drugs can deliver to the infected bone more effectively. Herein, an acoustically responsive multifunctional hydrogel microsphere-bomb (EMgel) was designed and prepared by microfluidic technology, which could be injected to the focus of bone infection, and blasted into the nidus deeply to destroy the bacterial biofilm matrix barrier under penetrating ultrasound, so the encapsulated natural polyphenolic EGCG and bioactive MoS2 released to repair the damaged bone. The results proved the hydrogel microsphere-bomb exhibited controlling drug release, favorable antibacterial (as high as 99 %), high biofilm resistance, fascinating antioxidation, good cytocompatibility, and osteogenic differentiation. The acoustically responsive microsphere-bomb further proved their fantastic ability to eradicate biofilm and promote bone regeneration in the Methicillin-resistant Staphylococcus aureus (MRSA) infected chronic osteomyelitis model due to the synergy effects of EGCG and bioactive MoS2. Especially, immunohistochemical staining showed lower inflammatory reaction and higher expression of OCN in EMgel group treated with ultrasound wave. This study presents a new design of hydrogel microsphere-based intelligence drug delivery for osteomyelitis treatment, which exhibit great promising potential for dealing with chronic orthopedic infections, drug delivery system and tissue engineering.

Proteomic Profiling in Pediococcus pentosaceus SF11 Exposed to Condensed Tannins from Sainfoin

The antibacterial mechanism of condensed tannins (CTs) obtained from tea has been elucidated, but the mechanism of legume-derived CTs remains unclear. The mechanisms of legume- and tea-derived CTs probably differ due to the diverse compositions of CTs. Previous research found that sainfoin CTs directly inhibited the growth of Pediococcus. The present study investigated the inhibition mechanism of CTs against Pediococcus pentosaceus SF11 (SF11) through proteomic analysis. The results showed that the minimum inhibitory concentration (MIC) of CTs against SF11 was 1500 mg/L and that CTs increased cell membrane permeability in a dose-dependent manner. In total, 418 differentially expressed proteins (DEPs) were identified between the CT treatment and the control, among which 341 were down-regulated and 77 were up-regulated in the CT treatment. The protein interaction network showed that the expression of only two DEPs was highly different between CT treated and control (|log2FC|> 2); the atpD protein was up-regulated in the CT-treated group, which was involved in ATP synthesis; down-regulated DEPs were most involved in lipoteichoic acid synthesis, peptidoglycan synthesis, and glycine metabolism. Twenty-seven proteins were not detected after CT treatment, which were involved in functions including fatty acid synthesis, RNA synthesis and translation, drug resistance, and cell membrane permeability in SF11. Therefore, the findings suggest that the inhibition mechanism of CTs may be related to cell membrane damage and inhibition of cell reproduction.

Effects of Differently Processed Tea on the Gut Microbiota

Tea is a highly popular beverage, primarily due to its unique flavor and aroma as well as its perceived health benefits. The impact of tea on the gut microbiome could be an important means by which tea exerts its health benefits since the link between the gut microbiome and health is strong. This review provided a discussion of the bioactive compounds in tea and the human gut microbiome and how the gut microbiome interacts with tea polyphenols. Importantly, studies were compiled on the impact of differently processed tea, which contains different polyphenol profiles, on the gut microbiota from in vivo animal feeding trials, in vitro human fecal fermentation experiments, and in vivo human feeding trials from 2004-2024. The results were discussed in terms of different tea types and how their impacts are related to or different from each other in these three study groups.

By-product hazelnut seed skin characteristics and properties in terms of use in food processing and human nutrition

The hazelnut seed skins (HSS) are by-products from roasting or blanching hazelnuts without direct second utilization. The generation of HSS creates an economic and environmental problem. The object of the study was a comprehensive analysis of the properties for reuse of HSS. Water extraction of industrial HSS was applied (water with sonication of the HSS for 10 min at 90 ℃). The extracts obtained were freeze-dried to facilitate analysis and future application. The HSS and their extracts were analysed. Polyphenols, antioxidants, allergens, antimicrobial properties and instrumental sensory analysis were examined. The total polyphenol content in the samples was 37.8-44.0 mg gallic acid equivalent g-1. Gallic acid was the major phenolic compound. The antioxidant capacity of the samples was 198.9-250.6 mg VCEAC g-1 (vitamin C equivalent) according to the ABTS method and 98.4-106.8 mg VCEAC g-1 in the DPPH method. The extracts inhibited all tested strains of pathogenic bacteria. Allergen content was reduced in HSS and the extracts. Instrumental sensory analysis showed differences between taste parameters and odour profile samples. HSS can be reused in food production as a bacteriostatic, antioxidant additive and sensory-creating factor due to various chemical compounds corresponding with taste and odour.

Intelligent active films of sodium alginate and konjac glucomannan mixed by Lycium ruthenicum anthocyanins and tea polyphenols for milk preservation and freshness monitoring

To achieve real-time monitoring of food freshness, a pH-responsive film based on sodium alginate-konjac glucomannan loaded with Lycium ruthenicum anthocyanins (LRA) was prepared, with the addition of tea polyphenols (TP) to enhance the stability of LRA. The surface structure of the films was observed by AFM. The results of FTIR and molecular docking simulation showed that LRA and TP were bound to polysaccharide by hydrogen bonds. The mechanical properties, barrier properties, and antioxidant/antibacterial properties of the films were significantly improved and the films showed obvious color response to pH. Notably, the AFM images showed TP and LRA could lead to more severe damage to the bacterial structure. The results of molecular docking simulation suggested that TP and LRA could act on different components of the bacterial cell wall, indicating their synergistic mechanism in antimicrobial activity. Moreover, the stability of LRA was improved due to the interactions of TP and polysaccharides with LRA. The aggregates formed by TP and LRA were clearly observed by AFM. Finally, the film showed excellent preservation and freshness monitoring effect in milk. In conclusion, TP-LRA-SA-KGM intelligent film exhibited excellent performance and represented a promising novel food packaging material with potential applications.

Tea Polyphenols Inhibit the Activity and Toxicity of Staphylococcus aureus by Destroying Cell Membranes and Accumulating Reactive Oxygen Species

Staphylococcus aureus can cause bacterial food intoxication and seriously affect human health. Tea polyphenols (TP) are a kind of natural, safe, and broad-spectrum bacteriostatic substances, with a wide range of bacteriostatic effects. In the study, we explored the possible bacteriostatic mode of TP. The minimum inhibitory concentration of TP against S. aureus was 64 μg/mL. Protein, DNA, and K+ leak experiments, fluorescence microscopy, and transmission electron microscopy suggested that TP disrupt cell membranes, leading to intracellular component loss. By studying the effect of TP on the toxicity of S. aureus, it was found that the expression levels of two toxin genes, coa and spa, were downregulated by 2.37 and 32.6, respectively. Furthermore, after treatment with TP, a large number of reactive oxygen species (ROS) were propagated and released, leading to oxidative stress in cells. We speculated that the bacteriostatic mechanism of TP may be through the destruction of the cell membrane and ROS-mediated oxidative stress. Meanwhile, the hemolysis activity proved the safety of TP. Our results suggested that TP may be a potential antimicrobial agent for food.

Plant Antimicrobials for Food Quality and Safety: Recent Views and Future Challenges

The increasing demand for natural, safe, and sustainable food preservation methods drove research towards the use of plant antimicrobials as an alternative to synthetic preservatives. This review article comprehensively discussed the potential applications of plant extracts, essential oils, and their compounds as antimicrobial agents in the food industry. The antimicrobial properties of several plant-derived substances against foodborne pathogens and spoilage microorganisms, along with their modes of action, factors affecting their efficacy, and potential negative sensory impacts, were presented. The review highlighted the synergistic or additive effects displayed by combinations of plant antimicrobials, as well as the successful integration of plant extracts with food technologies ensuring an improved hurdle effect, which can enhance food safety and shelf life. The review likewise emphasized the need for further research in fields such as mode of action, optimized formulations, sensory properties, safety assessment, regulatory aspects, eco-friendly production methods, and consumer education. By addressing these gaps, plant antimicrobials can pave the way for more effective, safe, and sustainable food preservation strategies in the future.

Dietary Polyphenols as a Protection against Cognitive Decline: Evidence from Animal Experiments; Mechanisms and Limitations

Emerging evidence suggests that cognitive impairments may result from various factors, such as neuroinflammation, oxidative stress, mitochondrial damage, impaired neurogenesis, synaptic plasticity, blood-brain barrier (BBB) disruption, amyloid β protein (Aβ) deposition, and gut dysbiosis. Meanwhile, dietary polyphenol intake in a recommended dosage has been suggested to reverse cognitive dysfunction via various pathways. However, excessive intake of polyphenols could trigger unwanted adverse effects. Thus, this review aims to outline possible causes of cognitive impairments and how polyphenols alleviate memory loss via various pathways based on in vivo experimental studies. Thus, to identify potentially relevant articles, the keywords (1) nutritional polyphenol intervention NOT medicine AND neuron growth OR (2) dietary polyphenol AND neurogenesis AND memory impairment OR (3) polyphenol AND neuron regeneration AND memory deterioration (Boolean operators) were used in the Nature, PubMed, Scopus, and Wiley online libraries. Based on the inclusion and exclusion criteria, 36 research papers were selected to be further reviewed. The outcome of all the studies included supports the statement of appropriate dosage by taking into consideration gender differences, underlying conditions, lifestyle, and causative factors for cognitive decline, which will significantly boost memory power. Therefore, this review recapitulates the possible causes of cognitive decline, the mechanism of polyphenols involving various signaling pathways in modulating the memory, gut dysbiosis, endogenous antioxidants, bioavailability, dosage, and safety efficacy of polyphenols. Hence, this review is expected to provide a basic understanding of therapeutic development for cognitive impairments in the future.

Natural Bioactive Epigallocatechin-Gallate Promote Bond Strength and Differentiation of Odontoblast-like Cells

The (-)-Epigallocatechin-gallate (EGCG) metabolite is a natural polyphenol derived from green tea and is associated with antioxidant, biocompatible, and anti-inflammatory effects.

OBJECTIVE

To evaluate the effects of EGCG to promote the odontoblast-like cells differentiated from human dental pulp stem cells (hDPSCs); the antimicrobial effects on Escherichia coli, Streptococcus mutans, and Staphylococcus aureus; and improve the adhesion on enamel and dentin by shear bond strength (SBS) and the adhesive remnant index (ARI).

MATERIAL AND METHODS

hDSPCs were isolated from pulp tissue and immunologically characterized. EEGC dose-response viability was calculated by MTT assay. Odontoblast-like cells were differentiated from hDPSCs and tested for mineral deposition activity by alizarin red, Von Kossa, and collagen/vimentin staining. Antimicrobial assays were performed in the microdilution test. Demineralization of enamel and dentin in teeth was performed, and the adhesion was conducted by incorporating EGCG in an adhesive system and testing with SBS-ARI. The data were analyzed with normalized Shapiro-Wilks test and ANOVA post hoc Tukey test.

RESULTS

The hDPSCs were positive to CD105, CD90, and vimentin and negative to CD34. EGCG (3.12 µg/mL) accelerated the differentiation of odontoblast-like cells. Streptococcus mutans exhibited the highest susceptibility < Staphylococcus aureus < Escherichia coli. EGCG increased (p < 0.05) the dentin adhesion, and cohesive failure was the most frequent.

CONCLUSION

(-)-Epigallocatechin-gallate is nontoxic, promotes differentiation into odontoblast-like cells, possesses an antibacterial effect, and increases dentin adhesion.

Crosstalk between Gut Microbiota and Host Immunity: Impact on Inflammation and Immunotherapy

Gut microbes and their metabolites are actively involved in the development and regulation of host immunity, which can influence disease susceptibility. Herein, we review the most recent research advancements in the gut microbiota-immune axis. We discuss in detail how the gut microbiota is a tipping point for neonatal immune development as indicated by newly uncovered phenomenon, such as maternal imprinting, in utero intestinal metabolome, and weaning reaction. We describe how the gut microbiota shapes both innate and adaptive immunity with emphasis on the metabolites short-chain fatty acids and secondary bile acids. We also comprehensively delineate how disruption in the microbiota-immune axis results in immune-mediated diseases, such as gastrointestinal infections, inflammatory bowel diseases, cardiometabolic disorders (e.g., cardiovascular diseases, diabetes, and hypertension), autoimmunity (e.g., rheumatoid arthritis), hypersensitivity (e.g., asthma and allergies), psychological disorders (e.g., anxiety), and cancer (e.g., colorectal and hepatic). We further encompass the role of fecal microbiota transplantation, probiotics, prebiotics, and dietary polyphenols in reshaping the gut microbiota and their therapeutic potential. Continuing, we examine how the gut microbiota modulates immune therapies, including immune checkpoint inhibitors, JAK inhibitors, and anti-TNF therapies. We lastly mention the current challenges in metagenomics, germ-free models, and microbiota recapitulation to a achieve fundamental understanding for how gut microbiota regulates immunity. Altogether, this review proposes improving immunotherapy efficacy from the perspective of microbiome-targeted interventions.

Current understanding on antibacterial mechanisms and research progress of tea polyphenols as a supplementary disinfectant for drinking water

Disinfection by-products (DBPs) generated during the disinfection of drinking water have become an urgent problem. So, tea polyphenol, a natural green disinfectant, has attracted widespread attention in recent years. This review summarizes the antibacterial mechanism of tea polyphenols and the recent findings on tea polyphenols as disinfectants for drinking water. These studies show that tea polyphenol is an antibacterial agent that works through different mechanisms and can be used as a supplementary disinfectant because of its higher lasting effect and economical cost. The dosage of tea polyphenols as a disinfectant of ultrafiltration effluent is the lowest among all the tea polyphenols disinfection methods, which can ensure the microbial safety of drinking water. This application of tea polyphenols is deemed a practical solution to solving the issue of disinfecting drinking water and reducing DBPs. However, it is necessary to further explore the influence of factors such as pipeline materials on the disinfection process and efficacy to expand the application scope of tea polyphenols. The large-scale application of tea polyphenols still needs to be fine-tuned but with new developments in tea polyphenol purification technology and the long-term need for drinking water that is safe for human consumption, tea polyphenols have good prospects for further development.

Redox Impact on Bacterial Macromolecule: A Promising Avenue for Discovery and Development of Novel Antibacterials

Antibiotic resistance in bacteria has remained a serious public health concern, resulting in substantial deaths and morbidity each year. Factors such as mutation and abuse of currently available antibiotics have contributed to the bulk of the menace. Hence, the introduction and implementation of new therapeutic strategies are imperative. Of these strategies, data supporting the role of reactive oxygen species (ROS) in bacterial lethality are intriguing, with several antimicrobials, including antibiotics such as fluoroquinolones, β-lactams, and aminoglycosides, as well as natural plant compounds, being remarkably implicated. Following treatment with ROS-inducing antimicrobials, ROS such as O₂^•-, ^•OH, and H₂O₂ generated in bacteria, which the organism is unable to detoxify, damage cellular macromolecules such as proteins, lipids, and nucleic acids and results in cell death. Despite the unique mechanism of action of ROS-inducing antibacterials and significant studies on ROS-mediated means of bacterial killing, the field remains a topical one, with contradicting viewpoints that require frequent review. Here, we appraised the antibacterial agents (antibiotics, natural and synthetic compounds) implicated in ROS generation and the safety concerns associated with their usage. Further, background information on the sources and types of ROS in bacteria, the mechanism of bacterial lethality via oxidative stress, as well as viewpoints on the ROS hypothesis undermining and solidifying this concept are discussed.

Metabolomics and proteomics analyses revealed mechanistic insights on the antimicrobial activity of epigallocatechin gallate against Streptococcus suis

Streptococcus suis (S. suis) is a highly virulent zoonotic pathogen and causes severe economic losses to the swine industry worldwide. Public health security is also threatened by the rapidly growing antimicrobial resistance in S. suis. Therefore, there is an urgent need to develop new and safe antibacterial alternatives against S. suis. The green tea polyphenol epigallocatechin gallate (EGCG) with a number of potential health benefits is known for its antibacterial effect; however, the mechanism of its bactericidal action remains unclear. In the present, EGCG at minimal inhibitory concentration (MIC) showed significant inhibitory effects on S. suis growth, hemolytic activity, and biofilm formation, and caused damage to S. suis cells in vitro. EGCG also reduced S. suis pathogenicity in Galleria mellonella larvae in vivo. Metabolomics and proteomics analyses were performed to investigate the underlying mechanism of antibacterial activity of EGCG at MIC. Many differentially expressed proteins involved in DNA replication, synthesis of cell wall, and cell membrane, and virulence were down-regulated after the treatment of S. suis with EGCG. EGCG not only significantly reduced the hemolytic activity of S. suis but also down-regulated the expression of suilysin (Sly). The top three shared KEGG pathways between metabolomics and proteomics analysis were ABC transporters, glycolysis/gluconeogenesis, and aminoacyl-tRNA biosynthesis. Taken together, these data suggest that EGCG could be a potential phytochemical compound for treating S. suis infection.

Systemic H2O2 signaling mediates epigallocatechin-3-gallate-induced cadmium tolerance in tomato

Toxic heavy metal cadmium (Cd) reduces crop yield and threatens human health via the food chain. The bioactive flavonoid 'Epigallocatechin-3-gallate' (EGCG) affects plant stress response; however, the function of EGCG in Cd tolerance and the molecular pathways remain largely unknown. Here, we revealed that root application of EGCG alleviated Cd stress in tomato plants. While Cd stress decreased Fv/Fm, Ф_PSII, photosynthetic rate, root growth, root vitality and biomass accumulation by increasing reactive oxygen species (ROS) accumulation and lipid peroxidation, exogenous EGCG minimized excessive ROS accumulation and oxidative stress by promoting the activity of antioxidant enzymes and redox poise in roots and leaves. Moreover, EGCG induced the transcript of RESPIRATORY BURST OXIDASE HOMOLOG1 (RBOH1) and decreased Cd content and photoinhibition in leaves. Interestingly, similar to EGCG, exogenous H₂O₂ application also enhanced Cd tolerance; however, the application of an NADPH oxidase inhibitor, diphenyleneiodonium (DPI), aggravated Cd phytotoxicity and attenuated the beneficial effects of EGCG on plant tolerance to Cd stress, suggesting that root applied EGCG-induced expression of RBOH1 and associated H₂O₂ signaling mediate the EGCG-induced enhanced Cd tolerance. This work elucidates a fundamental mechanism behind EGCG-mediated Cd tolerance and contributes to our existing knowledge of stress resistance properties of EGCG in plants.

Antimicrobial Effect of Epigallocatechin Gallate Against Shewanella putrefaciens ATCC 8071: A Study Based on Cell Membrane and Biofilm

The study was to evaluate the antimicrobial impacts and biofilm influences on epigallocatechin gallate (EGCG) against Shewanella putrefaciens ATCC 8071. The minimum inhibitory concentration (MIC) of EGCG on S. putrefaciens was 160 μg mL^-1. The growth curve exhibited that EGCG had a good antimicrobial activity. EGCG caused damages to the bacterial cell wall and membrane based the intracellular component leakage and cell viability analysis. The damage to the membrane integrity by EGCG has been confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM shows deformation of shape, TEM shows cell membrane and wall damage, and the leakage of cytoplasmic material. The treatment with EGCG at 0.25× and 0.5× MIC resulted in decreased motility and elevated levels of oxidative stress, leading to an increase in biofilm formation. These results demonstrated that EGCG may be used as a natural preservative to reduce S. putrefaciens in fish during cold storage.

GREEN TEA ETHANOL EXTRACT EFFICACY AGAINST PSEUDOMONAS AERUGINOSA

Research about green tea ethanol extract efficacy against Pseudomonas aeruginosa has been done. The green tea leaves were sourced from tea distributor in Sidamanik District, North Sumatra, Indonesia. Green tea leaves extract was obtained by maceration technique in which green tea leaves were soaked with ethanol 96% for 24 hours. After that, the filtrate was concentrated to be thick extract with no liquid content again.  After that, the concentrated extract was made by 5%, 10% and 15% as extract variations. The efficacy of green tea ethanol extract against Pseudomonas aeruginosa  was signed by increasing the inhibitory diameter that using disc method, in which the distilled water was used as negative blank. The results obtained for blanks, 5%, 10% and 15% extracts were 0; 1.85; 2.9 and 4.45 mm. The conclusion of this study is that the concentration of the extract is increasing proportionally to its inhibitory power, the higher of extract concentration is higher of its inhibitory activity against Pseudomonas aeruginosa. The conclusion described the green tea ethanol extract was effective to be antibacterial agent against Pseudomonas aeruginosa.

EGCG-coated silver nanoparticles self-assemble with selenium nanowires for treatment of drug-resistant bacterial infections by generating ROS and disrupting biofilms

Bacterial infections pose a serious threat to human health, and the development of new antibiotics has not kept pace with the development of bacterial resistance. Therefore, there is an urgent need to design antibiotic-like nano-formulations that break through bacterial resistance mechanisms. In this work, we successfully synthesized a safe and effective antibacterial nano-formulation of Se@Ag@EGCG by self-assembly of epigallocatechin gallate (EGCG)-coated silver nanoparticles (Ag) on the surface of selenium nanowires (Se). Thein vitrobacteriostatic results showed that 40μg ml^-1Se@Ag@EGCG had significant antibacterial activity against drug-resistantStaphylococcus aureus(S. aureus) andEscherichia coli(E. coli) by destroying the formation of bacterial biofilm, promoting the production of high concentration reactive oxygen species and destroying bacterial cell wall. In addition, the results ofin vivoantibacterial experiments showed that subcutaneous administration of 10 mg kg^-1of Se@Ag@EGCG could promote wound healing by reducing apoptosis and inflammatory responses in infected wounds. It is worth mentioning that the reduced and modified Se@Ag@EGCG by this natural product has negligiblein vivotoxicity. This development strategy of nano-antibacterial materials, which breaks through the drug resistance mechanism, provides new ideas for the development of drugs for drug-resistant bacterial infections.

Effects of Dietary Nutrients on Fatty Liver Disease Associated With Metabolic Dysfunction (MAFLD): Based on the Intestinal-Hepatic Axis

Non-alcoholic fatty liver disease (NAFLD) has recently become the most common liver disease with a global prevalence of over 25% and is expected to increase. Recently, experts have reached a consensus that “fatty liver disease associated with metabolic dysfunction or MAFLD” may be a more appropriate and inclusive definition than NAFLD. Like the former name NAFLD, MAFLD, as a manifestation of multiple system metabolic disorders involving the liver, has certain heterogeneity in its pathogenesis, clinical manifestations, pathological changes and natural outcomes. We found that there is a delicate dynamic balance among intestinal microflora, metabolites and host immune system to maintain a healthy intestinal environment and host health. On the contrary, this imbalance is related to diseases such as MAFLD. However, there are no clear studies on how dietary nutrients affect the intestinal environment and participate in the pathogenesis of MAFLD. This review summarizes the interactions among dietary nutrients, intestinal microbiota and MAFLD in an attempt to provide evidence for the use of dietary supplements to regulate liver function in patients with MAFLD. These dietary nutrients influence the development and progression of MAFLD mainly through the hepatic-intestinal axis by altering dietary energy absorption, regulating bile acid metabolism, changing intestinal permeability and producing ethanol. Meanwhile, the nutrients have the ability to combat MAFLD in terms of enriching abundance of intestinal microbiota, reducing Firmicutes/Bacteroidetes ratio and promoting abundance of beneficial gut microbes. Therefore, family therapy with MAFLD using a reasonable diet could be considered.

Preparation of epigallocatechin gallate decorated Au-Ag nano-heterostructures as NIR-sensitive nano-enzymes for the treatment of osteoarthritis through mitochondrial repair and cartilage protection

Osteoarthritis (OA), a widespread degenerative disease characterized by cartilage destruction, has emerged as a public health challenge in the current aging society. In addition to applied steroids and surgery, near-infrared (NIR) sensitive nano-enzyme for the treatment of osteoarthritis through mitochondrial repair and cartilage protection is attractive and promising. In this study, a NIR sensitive multifunctional heterostructure (EGCG (Epigallocatechin gallate) decorated Au-Ag nano-jars (E@Au-Ag)) was introduced as an enzyme-sensitive active nanoplatform for the treatment of osteoarthritis. Molecular biology results indicated that E@Au-Ag possesses intrinsic properties of anti-oxidative stress and was able to reduce the apoptosis rate of chondrocytes by 83.3%. The area of the intra-articular joint cavity injected with E@Au-Ag can be elevated to 46.6 °C under NIR to promote the release of EGCG further to induce cartilage regeneration. X-ray radiography and section staining showed that E@Au-Ag reduced cartilage damage and decreased OARSI scores by approximately 52% after 8 weeks of treatment in a surgically induced OA model. The results demonstrated that this multifunctional enzyme-like nanoplatform with a synergistic NIR sensitive property to facilitate cartilage migration and regeneration repair provides a promising OA treatment strategy. STATEMENT OF SIGNIFICANCE: 1. NIR-sensitive nano-enzyme is gaining much attention in the field of biomedical materials. 2. EGCG decorated Au-Ag nano-heterostructures were utilized as NIR-sensitive nano-enzymes for the treatment of osteoarthritis through mitochondrial repair and cartilage protection. 3. The obtained multifunctional Au-Ag nano-heterostructures are promising for osteoarthritis treatment.

Amidoxime Group-Anchored Single Cobalt Atoms for Anti-Biofouling during Uranium Extraction from Seawater

Marine biofouling is one of the most significant challenges hindering practical uranium extraction from seawater. Single atoms have been widely used in catalytic applications because of their remarkable redox property, implying that the single atom is highly capable of catalyzing the generation of reactive oxygen species (ROS) and acts as an anti-biofouling substance for controlling biofouling. In this study, the Co single atom loaded polyacrylamidoxime (PAO) material, PAO-Co, is fabricated based on the binding ability of the amidoxime group to uranyl and cobalt ions. Nitrogen and oxygen atoms from the amidoxime group stabilize the Co single atom. The fabricated PAO-Co exhibits a broad range of antimicrobial activity against diverse marine microorganisms by producing ROS, with an inhibition rate up to 93.4%. The present study is the first to apply the single atom for controlling biofouling. The adsorbent achieves an ultrahigh uranium adsorption capacity of 9.7 mg g-1 in biofouling-containing natural seawater, which decreased only by 11% compared with that in biofouling-removed natural seawater. These findings indicate that applying single atoms would be a promising strategy for designing biofouling-resistant adsorbents for uranium extraction from seawater.

Inhibition effect of epigallocatechin gallate on the growth and biofilm formation of Vibrio parahaemolyticus

Vibrio parahaemolyticus (V. parahaemolyticus) is a common marine foodborne pathogen that causes gastroenteritis. With the long-term use of antibiotics, many bacteria become resistant strains, therefore, developing antibiotic-free antimicrobial strategies is urgent. Epigallocatechin gallate (EGCG) as the abundant constituent of polyphenols in tea extract has broad-spectrum antibacterial activity and non-toxicity. Here, we took advantage of EGCG to evaluate its inhibition effect on the growth of V. parahaemolyticus 17802 and the biofilm formation, and explore its antibacterial mechanism. It was found that EGCG showed antibacterial activity to V. parahaemolyticus 17802, and the minimum inhibitory concentration (MIC) is 128 μg mL^-1 , crystal violet staining and confocal laser scanning microscope (CLSM) evidenced EGCG hindered its biofilm formation. Moreover, the swimming motility and extracellular polysaccharides were also notably inhibited. The antibacterial mechanism was further confirmed by several assays, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), live/dead staining assay, together with membrane permeability assay, which all suggested that EGCG caused damage to cell membrane and made it lose integrity, eventually resulting in the death of V. parahaemolyticus 17802. The bactericidal activity of EGCG verified its potential as a promising candidate to combat foodborne pathogen.

Tea polyphenols-loaded nanocarriers: preparation technology and biological function

Tea polyphenols (TP) have various biological functions including anti-oxidant, anti-bacterial, anti-apoptotic, anti-inflammatory and bioengineered repair properties. However, TP exhibit poor stability and bioavailability in the gastrointestinal tract. Nanoencapsulation techniques can be used to protect TP and to uphold their original characteristics during processing, storage and digestion, improve their physiochemical properties and enhance their health promoting effects. Nano-embedded TP show higher antioxidant, antibacterial and anticancer properties than TP, allowing TP to play a better role in bioengineering restoration after embedding. In this review, recent advances in nanoencapsulation of TP with biopolymeric nanocarriers (polysaccharides and proteins), lipid-based nanocarriers and innovative developments in preparation strategies were mainly discussed. Additionally, the strengthening biological functions of stability and bioavailability, antioxidant, antibacterial, anticancer activities and bioengineering repair properties activities after the nano-embedding of TP have been considered. Finally, further studies could be conducted for exploring the application of nanoencapsulated systems in food for industrial applications.

Enhanced antibacterial efficacy and mechanism of octyl gallate/beta-cyclodextrins against Pseudomonas fluorescens and Vibrio parahaemolyticus and incorporated electrospun nanofibers for Chinese giant salamander fillets preservation

A series of alkyl gallates were evaluated for the antibacterial activity against two common Gram-negative foodborne bacteria (Pseudomonas fluorescens and Vibrio parahaemolyticus) associated with seafood. The length of the alkyl chain plays a pivotal role in eliciting their antibacterial activities and octyl gallate (OG) exerted an excellent inhibitory efficacy. To extend the aqueous solubility, stability, and bactericidal properties of octyl gallate (OG), an inclusion complex between OG and β-cyclodextrin (βCD), OG/βCD, was prepared and identified with various methods including X-ray diffraction (XRD), differential scanning calorimeter (DSC) and Fourier transform infrared spectroscopy (FTIR). Furthermore, the enhanced inhibitory effect and potential antibacterial mechanism of OG/βCD against two Gram-negative and Gram-positive foodborne bacteria were comprehensively investigated. The results show that OG/βCD could function against bacteria through effectively damaging the membrane, permeating into cells, and then disturbing the activity of the respiratory electron transport chain to cause the production of high-level intracellular hydroxyl radicals. Moreover, the reinforced OG/βCD-incorporated polylactic acid (PLA) nanofibers were fabricated using the electrospinning technique as food packaging to extend the Chinese giant salamander fillet's shelf life at 4 °C. This research highlights the antibacterial effectiveness of OG/βCD in aqueous media, which can be used as a safe multi-functionalized food additive combined with the benefits of electrospun nanofibers to extend the Chinese giant salamander fillets shelf life by 15 d at 4 °C.

Antimicrobial Activity and Action Mechanism of Thymoquinone against Bacillus cereus and Its Spores

In this study, thymoquinone (TQ), a natural active substance, was investigated for its antibacterial activity against Bacillus cereus, and its inhibitory effect on B. cereus in reconstituted infant formula (RIF) was evaluated. In addition, the inhibitory effect of TQ on B. cereus spore germination was explored. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of TQ against eight B. cereus strains ranged from 4.0 to 8.0 μg/mL, whereas B. cereus treated with TQ displayed a longer lag phase than the untreated control. TQ exerted a good bactericidal effect on B. cereus in Luria–Bertani broth. In addition, TQ obviously reduced the intracellular ATP concentration of B. cereus, which caused depolarization of the cell membrane, increased the intracellular reactive oxygen species level, impaired the cell morphology, and destroyed proteins or inhibited proteins synthesis. This provides a mechanism for its bacteriostatic effect. TQ also inactivated B. cereus growth in RIF. Moreover, reverse transcription–quantitative polymerase chain reaction illustrated that TQ downregulated the transcription of genes related to hemolysin, non-hemolytic enterotoxin, enterotoxin, and cytotoxin K. Meanwhile, TQ displayed the ability to inhibit the germination of B. cereus spores. These findings indicate that TQ, as an effective natural antimicrobial preservative, has potential applications in controlling food contamination and foodborne diseases caused by B. cereus.

An NIR-Triggered Au Nanocage Used for Photo-Thermo Therapy of Chronic Wound in Diabetic Rats Through Bacterial Membrane Destruction and Skin Cell Mitochondrial Protection

Bacterial infection and its severe oxidative stress reaction will cause damage to skin cell mitochondria, resulting in long-lasting wound healing and great pain to patients. Thus, delayed wound healing in diabetic patients with Staphylococcus aureus infection is a principal challenge worldwide. Therefore, novel biomaterials with multifunction of bacterial membrane destruction and skin cell mitochondrial protection are urgently needed to be developed to address this challenge. In this work, novel gold cage (AuNCs) modified with epigallocatechin gallate (EGCG) were prepared to treat delayed diabetic wounds. The results showed that Au-EGCG had a high and stable photothermal conversion efficiency under near-infrared irradiation, and the scavenging rate of Au-EGCG for S. aureus could reach 95%. The production of large amounts of reactive oxygen species (ROS) leads to the disruption of bacterial membranes, inducing bacterial lysis and apoptosis. Meanwhile, Au-EGCG fused into hydrogel (Au-EGCG@H) promoted the migration and proliferation of human umbilical cord endothelial cells, reduced cellular mitochondrial damage and oxidative stress in the presence of infection, and significantly increased the basic fibroblast growth factor expression and vascular endothelial growth factor. In addition, animal studies showed that wound closure was 97.2% after 12 days of treatment, and the healing of chronic diabetic wounds was significantly accelerated. Au-EGCG nanoplatforms were successfully prepared to promote cell migration and angiogenesis in diabetic rats while removing S. aureus, reducing oxidative stress in cells, and restoring impaired mitochondrial function. Au-EGCG provides an effective, biocompatible, and multifunctional therapeutic strategy for chronic diabetic wounds.

Molecular mechanisms and applications of tea polyphenols: A narrative review

Tea is a worldwide popular drink with high nutritional and medicinal values as it is rich in nutrients, such as polyphenols, amino acids, vitamins, glycosides, and so on. Among them, tea polyphenols (TPs) are the current research hotspot. TPs are known to have multiple biological activities such as anti-oxidation, anti-tumor, anti-inflammation, anti-bacteria, lowering lipid, and liver protection. By reviewing a large number of literatures, we explained the mechanism of TPs exerting biological activity and a wide range of applications. We also discussed the deficiencies and development potential of TPs, in order to provide theoretical reference and scientific basis for the subsequent development and utilization of TPs. PRACTICAL APPLICATIONS: We summarized the bioactivity mechanisms of TPs in anti-tumor, anti-oxidation, antibacterial, anti-inflammatory, lipid-lowering, and liver protection, focused on its application fields in food and medicine, and discussed the deficiency and development potential of current research on TPs, so as to provide a certain convenient way for scholars studying TPs. It is expected to contribute to the subsequent discovery of biological activity and the broadening of the field of TPs.

Unraveling enterohemorrhagic Escherichia coli infection: the promising role of dietary compounds and probiotics in bacterial elimination and host innate immunity boosting

The innate immune system has developed sophisticated strategies to defense against infections. Host cells utilize the recognition machineries such as toll-like receptors and nucleotide binding and oligomerization domain-like receptors to identify the pathogens and alert immune system. However, some pathogens have developed tactics to evade host defenses, including manipulation of host inflammatory response, interference with cell death pathway, and highjack of phagocytosis signaling for a better survival and colonization in host. Enterohemorrhagic Escherichia coli (EHEC) is a notorious foodborne pathogen that causes severe tissue damages and gastrointestinal diseases, which has been reported to disturb host immune responses. Diverse bioactive compounds such as flavonoids, phenolic acids, alkaloids, saccharides, and terpenoids derived from food varieties and probiotics have been discovered and investigated for their capability of combating bacterial infections. Some of them serve as novel antimicrobial agents and act as immune boosters that harness host immune system. In this review, we will discuss how EHEC, specifically E. coli O157:H7, hijacks the host immune system and interferes with host signaling pathway; and highlight the promising role of food-derived bioactive compounds and probiotics in harnessing host innate immunity and eliminating E. coli O157:H7 infection with multiple strategies.

Overview of the Antioxidant and Anti-Inflammatory Activities of Selected Plant Compounds and Their Metal Ions Complexes

Numerous plant compounds and their metal-ion complexes exert antioxidative, anti-inflammatory, anticancer, and other beneficial effects. This review highlights the different bioactivities of flavonoids, chromones, and coumarins and their metal-ions complexes due to different structural characteristics. In addition to insight into the most studied antioxidative properties of these compounds, the first part of the review provides a comprehensive overview of exogenous and endogenous sources of reactive oxygen and nitrogen species, oxidative stress-mediated damages of lipids and proteins, and on protective roles of antioxidant defense systems, including plant-derived antioxidants. Additionally, the review covers the anti-inflammatory and antimicrobial activities of flavonoids, chromones, coumarins and their metal-ion complexes which support its application in medicine, pharmacy, and cosmetology.

Syzygium cumini leaf extract protects macrophages against the oxidized LDL-induced toxicity: A promising atheroprotective effect

Oxidized LDL (oxLDL) plays a pivotal role on atherosclerosis development, mainly in the formation of lipid-laden macrophage "foam cells". As a consequence, substances that can modulate LDL oxidation have a pharmacological and therapeutic relevance. Based in previous findings showing the ability of Syzigium cumini leaf extract (ScExt) in preventing LDL oxidation in vitro, this study was aimed to assess the effects of ScExt on oxLDL-mediated toxicity in murine J774 macrophages-like cells. For biochemical analyses, LDL isolated from fresh human plasma and oxidized with CuSO₄ was incubated with ScExt pre-treated macrophages. Our results demonstrated that ScExt was efficient in preventing the overproduction of reactive oxygen/nitrogen species (ROS/RNS), the loss of macrophage's viability and the foam cells formation induced by oxLDL. These protective effects of ScExt make it a promising antioxidant for future trials toward atherogenesis.

Physiological Dose of EGCG Attenuates the Health Defects of High Dose by Regulating MEMO-1 in Caenorhabditis elegans

EGCG, as a dietary-derived antioxidant, has been extensively studied for its beneficial health effects. Nevertheless, it induces the transient increase in ROS and leads to the hormetic extension of lifespan. How exactly biology-benefiting effects with the minimum severe adverse are realized remains unclear. Here, we showed that physiological dose of EGCG could help moderate remission in health side effects exposed to high doses, including shortened lifespan, reduced body size, decreased pharyngeal pumping rate, and dysfunctional body movement in C. elegans. Furthermore, we found this result was caused by the physiological dose of EGCG to block the continued ROS accumulation and triggered acclimation responses after stressor removal. Also, in this process, we observed that EGCG downregulated the key redox protein MEMO-1 to activate the feedback loop of NADPH oxidase-mediated redox signaling. Our data indicates that the feedback signal induced by NADPH oxidase may contribute to the health-protective mechanism of dietary polyphenols in vivo.

EGCG Induces Pro-inflammatory Response in Macrophages to Prevent Bacterial Infection through the 67LR/p38/JNK Signaling Pathway

Extensive studies focused on the therapeutic efficacy of epigallocatechin-3-gallate (EGCG) against bacterial infection. However, little is known about its prophylactic efficacy against bacterial infection. Herein, we found that EGCG showed an effective prophylactic efficacy against bacterial infection with a broad spectrum, including Gram-negative, Gram-positive, and drug-resistant bacteria. Pretreatment with EGCG through intraperitoneal injection, intravenous injection, or intragastric administration significantly reduced the bacterial load, inflammatory response, and mortality in mouse abdominal infection models induced by bacterial inoculation or cecal ligation and puncture. Pretreatment with EGCG by intraperitoneal injection significantly increased the numbers of neutrophils and monocytes/macrophages in the abdominal cavity and peripheral blood of mice, and depletion of neutrophils and monocytes/macrophages by specific antibodies or chemical drugs obviously increased the bacterial load in mice. Of note, EGCG did not directly induce neutrophil and macrophage migration, and it just induced phagocyte migration in the presence of macrophages in a co-cultured system, implying that EGCG-induced phagocyte migration relies on its immunoregulatory effects on macrophages. EGCG markedly induced the production of cytokines and chemokines in macrophages and mouse peritoneal lavage, including tumor necrosis factor-α (TNF-α), interleukin-1 β (IL-1β), IL-6, CXC chemokine ligands 1 and 2 (CXCL1 and 2), and monocyte chemotactic protein-1 (MCP-1). EGCG significantly induced the phosphorylation of p38 and JNK mitogen-activated protein kinases (MAPKs) in macrophages, and inhibition of p38 and JNK MAPKs markedly reduced EGCG-induced chemokine and cytokine production. Anti-67-kDa laminin receptor (67LR) antibody treatment significantly reduced EGCG-induced chemokine production and p38 and JNK phosphorylation in macrophages. Together, EGCG showed an obvious prophylactic efficacy against bacterial infection by inducing a pro-inflammatory response in macrophages through the 67LR/p38/JNK signaling pathway, supporting the further development of EGCG as a potent prophylaxis for bacterial infection and providing new clues to understand the healthcare function of green tea.

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.

EGCG-Mediated Potential Inhibition of Biofilm Development and Quorum Sensing in Pseudomonas aeruginosa

Pseudomonas aeruginosa (P. aeruginosa), one of the dangerous multidrug resistance pathogens, orchestrates virulence factors production through quorum sensing (QS). Since the exploration of QS inhibitors, targeting virulence to circumvent bacterial pathogenesis without causing significant growth inhibition is a promising approach to treat P. aeruginosa infections. The present study has evaluated the anti-QS and anti-infective activity of epigallocatechin-3-gallate (EGCG), a bioactive ingredient of the traditional green tea, against P. aeruginosa. EGCG showed significant inhibitory effects on the development of biofilm, protease, elastase activity, swimming, and swarming motility, which was positively related to the production of C4-AHL. The expression of QS-related and QS-regulated virulence factors genes was also evaluated. Quantitative PCR analysis showed that EGCG significantly reduced the expression of las, rhl, and PQS genes and was highly correlated with the alterations of C4-AHL production. In-vivo experiments demonstrated that EGCG treatment reduced P. aeruginosa pathogenicity in Caenorhabditis elegans (C. elegans). EGCG increased the survival of C. elegans by 23.25%, 30.04%, and 36.35% in a dose-dependent manner. The findings of this study strongly suggest that EGCG could be a potential candidate for QS inhibition as an anti-virulence compound against bacterial infection.

On the mechanism behind enhanced antibacterial activity of alkyl gallate esters against foodborne pathogens and its application in Chinese icefish preservation

The objective of this study was to investigate antibacterial activities and action mode of alkyl gallates against three food-related bacteria. Results show that the length of the alkyl chain plays a critical role in eliciting their antibacterial activities and octyl gallate (GAC8) exhibited an outstanding bactericidal effect against these strains. A possible bactericidal mechanism of GAC8 against E. coli was fully elucidated by analyzing associated changes in cellular functions of E. coli, including assessments of membrane modification and intracellular oxidation state. Our data strongly suggested that GAC8 functions outside and inside the bacterial membrane and causes increased intracellular reactive oxygen species (hydroxyl radicals) and subsequent oxidative damage. We demonstrated that the hydroxyl radical formation induced by GAC8 is the end product of an oxidative damage cellular death pathway involving a transient depletion of NADH, the tricarboxylic acid cycle, intrinsic redox cycling activities, and stimulation of the Fenton reaction. Also, chitosan-based edible films containing GAC8 have unique superiorities for icefish preservation at 4 °C. This research highlights the effectiveness of GAC8 as an attractive antibacterial, which possesses both antioxidant and antibacterial activities and can be used as a multifunctional food additive combined with the benefit of active packaging for food preservations.

Controlled bacteriostasis of tea polyphenol loaded ultrahigh molecular weight polyethylene with high crosslink density and oxidation resistance for total joint replacement

To avoid catastrophic bacterial infection in prosthesis failure, ultrahigh molecular weight polyethylene (UHMWPE), a common bearing material of artificial joints, has been formulated with antibiotics to eliminate bacteria locally at the implant site. However, the pressing issues regarding cytotoxic effects and evolution of drug resistant bacteria necessitates the development of bio-friendly bacteriostat with long bacteriostatic efficacy. Herein, tea polyphenol extracted from nature source was introduced in UHMWPE as a biogenic antimicrobial. Controlled antimicrobial activity was achieved by chemical crosslinking to regulate the release of the tea polyphenol. In addition, the crosslinking efficiency of UHMWPE blends with high loaded tea polyphenol was significantly improved in comparison to radiation crosslinking. The immobilized tea polyphenols also enhanced the oxidation stability of the UHMWPE, which is essential to prolong the service life in vivo and the storage time in vitro. The blends presented good biocompatibility, despite cell repellent on the highly crosslinked surface. Chemically crosslinked tea polyphenol/UHMWPE exhibited feasible properties for total joint implants, which is promising for clinical application.

The application of polyphenols in food preservation

Polyphenols are a kind of complex secondary metabolites in nature, widely exist in the flowers, bark, roots, stems, leaves, and fruits of plants. Numerous studies have shown that plant-derived polyphenols have a variety of bioactivities due to their unique chemical structure, such as antioxidant, antimicrobial, and prevention of chronic diseases, cardiovascular disease, cancer, osteoporosis, and neurodegeneration. With the gradual rise of natural product development, plant polyphenols have gradually become one of the research hotspots in the field of food science due to their wide distribution in the plants, and the diversity of physiological functions. Owing to the extraordinary antioxidant and antibacterial activity of polyphenols, plant-derived polyphenols offer an alternative to chemical additives used in the food industry, such as oil, seafood, meat, beverages, and food package materials. Based on this, this chapter provides an overview of the potential antioxidant and antibacterial mechanisms of plant polyphenols and their application in food preservation, it would be providing a reference for the future development of polyphenols in the food industry.

Antibacterial mechanisms of Aronia melanocarpa (Michx.), Chaenomeles superba Lindl. and Cornus mas L. leaf extracts

The aim of this study was to investigate the in vitro antibacterial mechanisms of Aronia melanocarpa, Chaenomeles superba, and Cornus mas leaf extracts towards meat spoilage and pathogenic bacteria. The extracts decreased bacterial viability after 24 h and 48 h of incubation. Acting as prooxidants, the extracts induced intracellular ROS (reactive oxygen species) generation in bacteria cells, with C. mas having the strongest influence. The leaf extracts increased the release of UV intracellular absorbing components, suggesting a reduction in membrane integrity. They also increased the outer-membrane permeability of the Gram-negative bacteria, with C. superba extract being the most active. Following exposure to the leaf extracts, morphological changes in the bacteria were observed, including the formation of aggregates, EPS synthesis, irregular forms, wrinkled cell surfaces, pores in the cell wall, and shriveling of cells. The leaf extracts inhibited DNA synthesis in E. coli cells by suppressing DNA gyrase activity.

Catechins as Model Bioactive Compounds for Biomedical Applications

Research regarding polyphenols has gained prominence over the years because of their potential as pharmacological nutrients. Most polyphenols are flavanols, commonly known as catechins, which are present in high amounts in green tea. Catechins are promising candidates in the field of biomedicine. The health benefits of catechins, notably their antioxidant effects, are related to their chemical structure and the total number of hydroxyl groups. In addition, catechins possess strong activities against several pathogens, including bacteria, viruses, parasites, and fungi. One major limitation of these compounds is low bioavailability. Catechins are poorly absorbed by intestinal barriers. Some protective mechanisms may be required to maintain or even increase the stability and bioavailability of these molecules within living organisms. Moreover, novel delivery systems, such as scaffolds, fibers, sponges, and capsules, have been proposed. This review focuses on the unique structures and bioactive properties of catechins and their role in inflammatory responses as well as provides a perspective on their use in future human health applications.