Redox and Other Biological Activities of Tea Catechins That May Affect Health: Mechanisms and Unresolved Issues

Characterization of physicochemical properties of different epigallocatechin-3-gallate nanoparticles and their effect on bioavailability

Epigallocatechin-3-gallate (EGCG), a major catechin in green tea, exhibits potent antioxidant and disease-preventive properties, but its application is limited by poor stability and bioavailability. This study aimed to address these challenges by preparing and characterizing three EGCG-loaded nanoparticles: chitosan-EGCG-tripolyphosphate nanoparticles (CE-NPs), β-cyclodextrin-EGCG (BE-NPs), and EGCG-nanostructured lipid carriers (NE-NPs). BE-NPs exhibited the highest loading performance and retention rate under thermal environment (89.78 % after 10 h at 80 °C). NE-NPs had the highest EGCG stability in alkaline condition (45 % after 4 h at pH 7.4). Compared to free EGCG, all NPs significantly improved in vitro bioaccessibility following incubation in simulated gastrointestinal digestion for 4 h; BE-NPs enhanced oral bioavailability by 1.71 times in vivo. Additionally, CE-NPs and NE-NPs increased the relative abundance of Faecalibaculum, Erysipelotrichaceae, and Bifidobacterium in the colons of Sprague-Dawley rats. These findings suggest that BE-NPs are a promising nano-delivery system for enhancing EGCG stability and bioavailability in healthy organisms.

Protection of Green Tea Polyphenols against Neurodegenerative Diseases: Evidence and Possible Mechanisms

Aging is a major risk factor for neurodegenerative diseases. With aging of the global population, the prevalence of neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD), has increased worldwide. Unfortunately, the available therapeutic options for these neurodegenerative diseases are limited, most of which only provide symptomatic relief and have potentially serious side effects. Epidemiological studies have shown that green tea consumption is associated with a lower prevalence of cognitive decline and decreased risk of AD and PD, providing an attractive preventive and therapeutic option. Polyphenols are major bioactive components in green tea, which contribute to the beneficial effects of green tea. Accumulating data suggest that green tea polyphenols (GTPs) have neuroprotective properties that inhibit the pathological development of neurodegenerative diseases; however, the underlying mechanisms are not yet completely understood. This paper reviews both in vitro and in vivo evidence that demonstrates the neuroprotective effects of GTPs against neurodegenerative diseases, with the main focus on AD and PD, and summarizes the possible molecular mechanisms by which GTPs impede the progression of neurodegeneration. In particular, this review highlights the modulation of GTPs on the common mechanisms involved in pathogenesis of neurodegenerative diseases, including oxidative stress-mediated neuronal toxicity, impaired proteostasis, and metal ion dyshomeostasis. The potential of using GTPs in the intervention of neurodegenerative diseases is also discussed, hopefully, providing useful insights into novel preventive and therapeutic strategies for these diseases.

Antimicrobial Phenolic Materials: From Assembly to Function

Infectious diseases pose considerable challenges to public health, particularly with the rise of multidrug-resistant pathogens that globally cause high mortality rates. These pathogens can persist on surfaces and spread in public and healthcare settings. Advances have been made in developing antimicrobial materials to reduce the transmission of pathogens, including materials composed of naturally sourced polyphenols and their derivatives, which exhibit antimicrobial potency, broad-spectrum activity, and a lower likelihood of promoting resistance. This review provides an overview of recent advances in the fabrication of antimicrobial phenolic biomaterials, where natural phenolic compounds act as active antimicrobial agents or encapsulate other antimicrobial agents (e.g., metal ions, antimicrobial peptides, natural biopolymers). Various forms of phenolic biomaterials synthesized through these two strategies, including antimicrobial particles, capsules, hydrogels, and coatings, are summarized, with a focus on their application in wound healing, bone repair and regeneration, oral health, and antimicrobial coatings for medical devices. The potential of these advanced phenolic biomaterials provides a promising therapeutic approach for combating antimicrobial-resistant infections and reducing microbial transmission.

Research Progress on the Protective Effect of Green Tea Polyphenol (-)-Epigallocatechin-3-Gallate (EGCG) on the Liver

The liver, as the primary metabolic organ, is susceptible to an array of factors that can harm liver cells and give rise to different liver diseases. Epigallocatechin gallate (EGCG), a natural compound found in green tea, exerts numerous beneficial effects on the human body. Notably, EGCG displays antioxidative, antibacterial, antiviral, anti-inflammatory, and anti-tumor properties. This review specifically highlights the pivotal role of EGCG in liver-related diseases, focusing on viral hepatitis, autoimmune hepatitis, fatty liver disease, and hepatocellular carcinoma. EGCG not only inhibits the entry and replication of hepatitis B and C viruses within hepatocytes, but also mitigates hepatocytic damage caused by hepatitis-induced inflammation. Furthermore, EGCG exhibits significant therapeutic potential against hepatocellular carcinoma. Combinatorial use of EGCG and anti-hepatocellular carcinoma drugs enhances the sensitivity of drug-resistant cancer cells to chemotherapeutic agents, leading to improved therapeutic outcomes. Thus, the combination of EGCG and anti-hepatocellular carcinoma drugs holds promise as an effective approach for treating drug-resistant hepatocellular carcinoma. In conclusion, EGCG possesses hepatoprotective properties against various forms of liver damage and emerges as a potential drug candidate for liver diseases.

A comprehensive review on the promising purple leaf tea

Purple leaf tea products (PTPs) are processed from purple tea leaves (PTLs) and combine unique color, flavors, and superior health benefits, holding promising market potential. However, PTLs contain unique chemical compositions, and the lack of systematic generalization of PTPs processing techniques has led to the under-representation of their unique qualities. Compared to traditional green leaf tea products, knowledge about PTPs is extremely limited and lacks a systematic framework linking chemical composition, processing techniques, and health benefits, which has largely limited the exploitation of PTPs. This review summarizes the chemical composition of PTLs, highlights variations across tea processing techniques, and their effects on the flavor qualities of PTPs. It also explores the potential health benefits of PTPs and examines the challenges of incorporating PTPs into the food industry, offering insights into potential applications. The chemical composition of PTLs is characterized by its unique polyphenolic profile, rich in anthocyanins, catechins, O-methyl catechins, and aroma components such as α/β-ionone and linalool. This unique chemical composition requires suitable processing methods to maximize its flavor qualities and health-promoting effects. PTPs offer notable potential health benefits, including antioxidant, anti-inflammatory, anticancer, neuroprotective, and anti-obesity effects, primarily due to their polyphenolic components. Additionally, PTPs show great potential as natural colorants and in applications such as dietary supplements and tea-flavored beverages. Based on these overviews, key challenges and possible future research directions are also outlined, especially in advancing production techniques, systematically evaluating health benefits, and expanding food applications.

Epigallocatechin-3-Gallate Inhibits Oxidative Stress Through the Keap1/Nrf2 Signaling Pathway to Improve Alzheimer Disease

Alzheimer disease (AD) is a common neurodegenerative disease with an intricate pathophysiological mechanism. Oxidative stress has been shown in several investigations as a significant factor in AD progression. For instance, studies have confirmed that oxidative stress inhibition may considerably improve AD symptoms, with potent antioxidants being touted as a possible interventional strategy in the search for AD treatment. Epigallocatechin-3-gallate (EGCG) acts as a natural catechin that has antioxidant effect. It activates the kelch-like epichlorohydrin-associated proteins (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway to inhibit oxidative stress. The Keap1/Nrf2 signal pathway is not only an upstream signaling target for a variety of antioxidant enzymes, but also minimizes high levels of reactive oxygen species. This report analyzes the antioxidant effect of EGCG in AD, elaborates its specific mechanism of action, and provides a theoretical basis for its clinical application in AD.

Bioavailability of Tea Polyphenols: A Key Factor in Understanding Their Mechanisms of Action In Vivo and Health Effects

Tea polyphenols (TPP) are key contributors to the beneficial health effects of green tea and black tea. However, their molecular mechanisms of action remain unclear. This article discusses the importance of the bioavailability of TPP in understanding their mechanisms of action and health effects of tea consumption. The systemic bioavailability is rather high for smaller catechins, low for galloyl catechins, and very low or null for oligomers and polymers from black tea. The bioavailability of TPP oxidation-derived polymers and self-assembled nanomaterials is not clearly known. If the large molecular weight TPP cannot get into systemic circulation, then the biological activities and mechanisms of action derived from studies in vitro are unlikely to be relevant to their actions in internal organs in vivo. In that case, their interactions with microbiota and actions on the epithelial cells of the gastrointestinal tract are important to their health effects. Therefore, the bioavailability of different types of TPP is an important factor in determining their mechanisms of action and the health effects of tea consumption.

The preparation and evaluation of granulated chitosan-catechin tablets with excellent disintegration properties

In this study, we prepared granulated chitosan (G-CS)/catechin tablets with excellent disintegration properties. We then compared their physical properties, dissolution behavior, and pharmacokinetic profile to non-granulated chitosan (N-CS)/catechin tablets. During the tableting process, the G-CS/catechin tablets demonstrated significantly higher compatibility and superior manufacturability, as evidenced by lower ejection and detachment stress than the N-CS/catechin tablets. This resulted in more robust tablets with better physical properties. The dissolution of catechin from the G-CS/catechin tablets occurred significantly faster than from the N-CS/catechin tablets, resulting in a significantly higher 2,2'-azino-bis(3 ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity. Similarly, the primary catechin components of the tablets, epigallocatechin gallate (EGCG) and caffeine, showed faster dissolution and membrane uptake from the G-CS/catechin tablets. These indicate a more efficient tablet formulation than N-CS/catechin tablets. Furthermore, the absorption and bioavailability of EGCG and caffeine in rats were significantly higher after oral administration of the G-CS/catechin tablets than the N-CS/catechin tablets. These findings suggest that G-CS/catechin tablets, having better disintegration properties than N-CS/catechin tablets, could allow for combination with other supplements, leading to the design of highly efficient supplement combination tablets.

Phloretin prolongs lifespan of Caenorhabditis elegans via inhibition of NDUFS1 and NDUFS6 at mitochondrial complex Ⅰ

Phloretin has been widely perceived as an antioxidant. However, the bioavailability of phloretin in vivo is generally far too low to elicit a direct antioxidant effect by scavenging reactive oxygen species (ROS). Here we showed that administration of phloretin of apple polyphenols extended lifespan of Caenorhabditis elegans and promoted fitness. Specially phloretin enhanced the survival rates of nematodes under oxidants in an inverted U-shaped dose-response manner. The lifespan-extending effects of phloretin were mediated by ROS via mitochondrial complex I inhibition. The increase of ROS stimulated p38 MAPK/PMK-1 as well as transcription factors of NRF2/SKN-1 and FOXO/DAF-16. Consistent with the involvement of NRF2/SKN-1 and FOXO/DAF-16 in lifespan-extending effects, activities of superoxide dismutase (SOD) and catalase (CAT) were enhanced by phloretin. The exogenous application of antioxidants butylated hydroxyanisole and N-acetylcysteine abolished the increase of ROS, the enhancement of SOD and CAT activities, and the lifespan extending effects of phloretin. Meanwhile, with the inhibition of mitochondrial complex I, ATP was instantly decreased. Both energy sensors of AMPK/AAK-2 and SIRT1/SIR-2.1 were involved in the lifespan extension by phloretin. Transcriptomic, real-time qPCR and molecular docking analyses demonstrated that the binding of phloretin at complex I located at NDUFS1/NUO-5, NDUFS2/GAS-1, and NDUFS6/NDUF-6. The molecular dynamic simulation and binding free energy calculations showed that phloretin had high binding affinities towards NDUFS1 (-7.21 kcal/mol) and NDUFS6 (-7.02 kcal/mol). Collectively, our findings suggested phloretin had effects of life expectancy enhancement and fitness promotion via redox regulations in vivo. NDUFS1/NUO-5 and NDUFS6/NDUF-6 might be new targets in the lifespan and wellness regulations.

Oligomerization mechanism of epigallocatechin-3-O-gallate during autoxidation

The autoxidation of tea catechins by dissolved oxygen proceeds in pH-neutral aqueous solutions, and the major products are oligomers. However, the reaction mechanisms have not been clarified. In this study, the autoxidation of (-)-epigallocatechin-3-O-gallate (1) was examined. The autoxidation with β-cyclodextrin, which includes the A-ring of 1, significantly suppressed oligomer production and increased the formation of products generated by the oxidative cleavage of the B-ring, indicating the participation of the A-ring in the oligomerization. Further, the autoxidation of 1 in the presence of phloroglucinol, a mimic of the catechin A-ring, yielded products via the nucleophilic addition of phloroglucinol to the B-ring quinone of 1. These results indicated that the oxidative A-B ring couplings accounted for the major oligomerization mechanism.

Influence of EGCG oxidation on inhibitory activity against the SARS-CoV-2 main protease

SARS-CoV-2 main protease (Mpro) is a well-recognized target for COVID-19 therapy. Green tea (-)-epigallocatechin-3-gallate (EGCG) possesses Mpro-inhibitory activity; however, the influence of EGCG oxidation on its inhibition activity remains obscure, given its high oxidation propensity. This study reveals that prolonged EGCG oxidation in the presence of Mpro dramatically increases its inhibitory activity with an IC50 of 0.26 μM. The inhibitory mechanism is that EGCG-quinone preferentially binds the active site Mpro-Cys145-SH, which forms a quinoprotein. Though Mpro is present in the cell lysate, EGCG preferentially depletes its thiols. Non-cytotoxic EGCG effectively generates a quinoprotein in living cells, thus EGCG might selectively inhibit Mpro in SARS-CoV-2 infected cells. Chlorogenic acid facilitates EGCG oxidation. Together, they synergistically deplete multiple Mpro thiols though this is not more beneficial than EGCG alone. By contrast, excessive EGCG oxidation prior to incubation with Mpro largely compromises its inhibitory activity. Overall, the low IC50 and the high selectivity imply that EGCG is a promising dietary Mpro inhibitor. While EGCG oxidation in the presence of Mpro has a pivotal role in inhibition, enhancing EGCG oxidation by chlorogenic acid no longer increases its inhibitory potential. EGCG oxidation in the absence of Mpro should be avoided to maximize its Mpro-inhibitory activity.

Epicatechin-Promoted Formation of Acrylamide from 3-Aminopropionamide Via Postoxidative Reaction of B-Ring

The role of thermally generated 3-aminopropionamide as an intermediate in acrylamide formation in the Maillard reaction has been well established. Herein, the effect of epicatechin on the conversion of 3-aminopropionamide into acrylamide under oxidative conditions was investigated at 160-220 °C. Epicatechin promoted acrylamide generation and 3-aminopropionamide degradation. The stable isotope-labeling technique combined with UHPLC-Orbitrap-MS/MS analysis showed adduct formation between 3-aminopropionamide and the oxidized B ring of epicatechin to form a Schiff base. This initially formed Schiff base could directly degrade to acrylamide, undergo reduction or dehydration to other intermediates, and subsequently generate acrylamide. Based on accurate mass analysis, five intermediates with intact or dehydrated C rings were tentatively identified. Furthermore, reaction pathways were proposed that were supported by the changes in the levels of adducts formed during heating. To the authors' knowledge, this study is the first to reveal pathways through which flavanols promoted the formation of acrylamide in Maillard reactions.

Reactive Carbonyl Species Scavenger: Epigallocatechin-3-Gallate

Epigallocatechin-3-gallate (EGCG), a prominent polyphenol found abundantly in tea, has garnered significant attention for its potential in preventing and ameliorating a wide range of diseases. Its remarkable antioxidant properties and ability to capture reactive carbonyl species make it a key player among tea's polyphenolic components. This paper delves into the synthesis and origins of both EGCG and reactive carbonyl species (RCS), emphasizing the toxicity of RCS in various food sources and their formation during food processing. Understanding EGCG's capability to capture and metabolize RCS is crucial for harnessing its health benefits. Thus, this paper explores the underlying mechanisms of EGCG for RCS inhibition and its role in capturing these compounds to generate EGCG-RCS adducts. And the absorption and metabolism of EGCG-RCS adducts is also discussed.

EGCG oxidation-derived polymers induce apoptosis in digestive tract cancer cells via regulating the renin-angiotensin system

Green tea polyphenol (-)-Epigallocatechin-3-gallate (EGCG) has been well studied for its biological activities in the prevention of chronic diseases. However, the biological activities of EGCG oxidation-derived polymers remain unclear. Previously, we found that these polymers accumulated in intraperitoneal tissues after intraperitoneal injection and gained an advantage over native EGCG in increasing insulin sensitivity via regulating the renin-angiotensin system (RAS) in type 2 diabetic mice. The present study determined the pro-apoptosis activities and anticancer mechanisms of the EGCG oxidation-derived polymer preparation (the >10 kDa EGCG polymers) in digestive tract cancer cells. Upon incubation of the >10 kDa EGCG polymers with CaCo2 colon cancer cells, these polymers coated the cell surface and regulated multiple components of the RAS in favor of cancer inhibition, including the downregulation of angiotensin-converting enzyme (ACE), angiotensin-II (AngII) and AngII receptor type 1 (AT1R) in the pro-tumor axis, as well as the upregulation of angiotensin-converting enzyme 2 (ACE2) and angiotensin1-7 (Ang(1-7)) in the anti-tumor axis. The treatment also markedly increased angiotensinogen (AGT), which is the precursor of the angiotensin peptides. The regulation of these RAS components occurred prior to apoptosis. Similar pro-apoptotic mechanisms of the >10 kDa EGCG polymers, were also observed in TCA8113 oral cancer cells. The >10 kDa EGCG polymers exhibited compromised activities in scavenging or initiating reactive oxygen species compared to EGCG, but gained a higher reactivity toward sulfhydryl groups, including protein cysteine thiols. We propose that the polymers bind onto the cell surface and regulate multiple RAS components by reacting with the sulfhydryl groups on the ectodomains of transmembrane proteins.

EGCG-like non-competitive inhibitor of DYRK1A rescues cognitive defect in a down syndrome model

Overexpression of the chromosome 21 DYRK1A gene induces morphological defects and cognitive impairments in individuals with Down syndrome (DS) and in DS mice models. Aging neurons of specific brain regions of patients with Alzheimer's disease, DS and Pick's disease have increased DYRK1A immunoreactivity suggesting a possible association of DYRK1A with neurofibrillary tangle pathology. Epigallocatechin-3-gallate (EGCG) displays appreciable inhibition of DYRK1A activity and, contrary to all other published inhibitors, EGCG is a non-competitive inhibitor of DYRK1A. Prenatal exposure to green tea polyphenols containing EGCG protects from brain defects induced by overexpression of DYRK1A. In order to produce more robust and possibly more active analogues of the natural compound EGCG, here we synthetized new EGCG-like molecules with several structural modifications to the EGCG skeleton. We replaced the ester boun of EGCG with a more resistant amide bond. We also replaced the oxygen ring by a methylene group. And finally, we positioned a nitrogen atom within this ring. The selected compound was shown to maintain the non-competitive property of EGCG and to correct biochemical and behavioral defects present in a DS mouse model. In addition it showed high stability and specificity.

Engineering Antimicrobial Metal-Phenolic Network Nanoparticles with High Biocompatibility for Wound Healing

Antibiotic-resistant bacteria pose a global health threat by causing persistent and recurrent microbial infections. To address this issue, antimicrobial nanoparticles (NPs) with low drug resistance but potent bactericidal effects have been developed. However, many of the developed NPs display poor biosafety and their synthesis often involves complex procedures and the antimicrobial modes of action are unclear. Herein, a simple strategy is reported for designing antimicrobial metal-phenolic network (am-MPN) NPs through the one-step assembly of a seeding agent (diethyldithiocarbamate), natural polyphenols, and metal ions (e.g., Cu2+ ) in aqueous solution. The Cu2+ -based am-MPN NPs display lower Cu2+ antimicrobial concentrations (by 10-1000 times) lower than most reported nanomaterials and negligible toxicity across various models, including, cells, blood, zebrafish, and mice. Multiple antimicrobial modes of the NPs have been identified, including bacterial wall disruption, reactive oxygen species production, and quinoprotein formation, with the latter being a distinct pathway identified for the antimicrobial activity of the polyphenol-based am-MPN NPs. The NPs exhibit excellent performance against multidrug-resistant bacteria (e.g., methicillin-resistant Staphylococcus aureus (MRSA)), efficiently inhibit and destroy bacterial biofilms, and promote the healing of MRSA-infected skin wounds. This study provides insights on the antimicrobial properties of metal-phenolic materials and the rational design of antimicrobial metal-organic materials.

Bibliometric and visual analysis in the field of tea in cancer from 2013 to 2023

Objective

Tea has been utilized in cancer research and is progressively gaining wider recognition, with its roles in cancer prevention and treatment being increasingly affirmed. The objective of this study is to investigate the current state and research hotspots in the field of tea's involvement in cancer research from 2013 to 2023, aiming to offer reference and direction for future studies.

Methods

We analyzed 4,789 articles published between 2013 and 2022 from the Web of Science database using VOSviewer, R software, and CiteSpace software.

Result

Tea-related cancer research showed an overall upward trend, with China leading in publications, followed by the United States, India, Japan, and Italy. China also had significant international collaborations, notably with Harvard University and the Egyptian Knowledge Bank. The 'Journal of Agricultural and Food Chemistry' was the most cited journal. Key topics included 'green tea,' 'cancer,' 'in vitro,' 'oxidative stress,' and 'apoptosis.' Research focused on tea's pharmacological effects, anticancer properties, mechanisms of natural compounds (e.g., polyphenols and EGCG), antioxidant and antimicrobial properties, and molecular mechanisms in cancer treatment.

Conclusion

Tea's potential as an anti-cancer medication is gaining global recognition. Our study provides a comprehensive analysis of tea-related cancer research from 2013 to 2023, guiding future investigations in this field.

Controlled oxidation and digestion of Pickering emulsions stabilized by quinoa protein and (-)-epigallocatechin-3-gallate (EGCG) hybrid particles

In this study, we prepared Pickering emulsions stabilized by quinoa protein isolate (QPI) and (-)-epigallocatechin-3-gallate (EGCG) non-covalent hybrid particles using ultrasonic emulsification technique and demonstrated lipid oxidation and in vitro digestion process of Pickering emulsions. The interaction forces between QPI and EGCG were characterized using fluorescence spectroscopy, isothermal titration calorimetry, and Fourier transform infrared spectroscopy. Results indicated that the non-covalent QPI/EGCG hybrid particles were formed mainly via hydrophobic interactions, hydrogen bonds, and electrostatic interactions at pH 5. Then, the QPI/EGCG non-covalent hybrid particles were applied to modify the Pickering emulsion with ultrasonic homogenization. The rheological experimental results showed that the energy storage modulus (G') was higher than the loss modulus (G″), indicating that the emulsion had solid-like properties. As a physical barrier, interfacial layer fabricated by antioxidant QPI/EGCG hybrid particles limited lipid oxidation at 60 °C for 15 days. At 37 °C, the QPI/EGCG hybrid particles stabilized Pickering emulsions with robust antioxidant interfacial structure limited the lipid digestion under simulated gastrointestinal tract (gastric, small intestine phases). Thus, EGCG and quinoa proteins were more resistant to free radical oxidation and gastrointestinal digestion with the assistance of ultrasound. It provides a basis for better development of food and drug delivery systems by fully utilizing the antioxidant properties of plant polyphenols.

Epigallocatechin-3-Gallate Reduces Cd-Induced Developmental Toxicity of Bodysize in Caenorhabditis elegans via the PEK-1/eIF-2α/ATF-4 Pathway

Cadmium (Cd), a harmful heavy metal that has no biological purpose, can harm healthy fetal and child development. Epigallocatechin-3-gallate (EGCG), the most abundant polyphenol in tea, has been shown to increase cell viability under Cd exposure and ameliorate Cd-induced kidney injury in adult male rats. Using the Caenorhabditis elegans (C. elegans) model, we demonstrated that EGCG mitigated Cd-induced body size developmental toxicity through a mechanism that did not involve chelation with EGCG and was not associated with Cd accumulation and efflux. Our research indicated that the beneficial effects of EGCG on Cd-induced body size developmental toxicity were associated with the mitigation of endoplasmic reticulum stress. Furthermore, our observations indicate that EGCG reduced Cd-induced developmental toxicity in C. elegans via the PEK-1/eIF-2α/ATF-4 pathway. Our results provide important evidence for the potential benefits of consuming tea as a detoxification agent.

Mechanisms Underlying the Effects of the Green Tea Polyphenol EGCG in Sarcopenia Prevention and Management

Sarcopenia is prevalent among the older population and severely affects human health. Tea catechins may benefit for skeletal muscle performance and protect against secondary sarcopenia. However, the mechanisms underlying their antisarcopenic effect are still not fully understood. Despite initial successes in animal and early clinical trials regarding the safety and efficacy of (-)-epigallocatechin-3-gallate (EGCG), a major catechin of green tea, many challenges, problems, and unanswered questions remain. In this comprehensive review, we discuss the potential role and underlying mechanisms of EGCG in sarcopenia prevention and management. We thoroughly review the general biological activities and general effects of EGCG on skeletal muscle performance, EGCG's antisarcopenic mechanisms, and recent clinical evidence of the aforesaid effects and mechanisms. We also address safety issues and provide directions for future studies. The possible concerted actions of EGCG indicate the need for further studies on sarcopenia prevention and management in humans.

Targeting the TNF-α-TNFR interaction with EGCG to block NF-κB signaling in human synovial fibroblasts

The tumor necrosis factor alpha (TNF-α)-TNF-α receptor (TNFR) interaction plays a central role in the pathogenesis of various autoimmune diseases, particularly rheumatoid arthritis, and is therefore considered a key target for drug discovery. However, natural compounds that can specifically block the TNF-α-TNFR interaction are rarely reported. (-)-Epigallocatechin-3-gallate (EGCG) is the most active, abundant, and thoroughly investigated polyphenolic compound in green tea. However, the molecular mechanism by which EGCG ameliorates autoimmune arthritis remains to be elucidated. In the present study, we found that EGCG can directly bind to TNF-α, TNFR1, and TNFR2 with similar μM affinity and disrupt the interactions between TNF-α and TNFR1 and TNFR2, which inhibits TNF-α-induced L929 cell death, blocks TNF-α-induced NF-κB activation in 293-TNF-α response cell line, and eventually leads to inhibition of TNF-α-induced NF-κB signaling pathway in HFLS and MH7A cells. Thus, regular consumption of EGCG in green tea may represent a potential therapeutic agent for the treatment of TNF-α-associated diseases.

Epigallocatechin gallate improves meiosis maturation against Diazinon exposure in porcine oocytes

Diazinon (DZN) is a refractory organophosphorus pesticide (OP) in the surrounding environment due to its overuse in agriculture. The antioxidant activity of Epigallocatechin gallate (EGCG) from green tea is at least 100 times greater than that of vitamin C. This study aimed to study the effects of DZN on the meiotic maturation of porcine oocytes, as well as the protective roles of EGCG. Firstly, the effects of DZN and EGCG on meiotic nuclear maturation of porcine oocytes were detected, and then embryonic development was investigated by chemical parthenogenetic activation. Next, the spindle assembly, mitochondrial membrane potential (MMP), reactive oxygen species (ROS), DNA damage, and finally the early apoptosis of oocytes were examined by immunofluorescence staining. The results revealed that DZN exposure significantly reduced the quality of porcine oocytes, such as failure of nuclear and cytoplasmic maturation, evidenced by abnormal spindle assembly, disordered chromosome alignment, low MMP, observably increased ROS, severe DNA damage, and early apoptosis. Appropriate EGCG could significantly reduce all these defects caused by DZN. In conclusion, EGCG can help prevent the harm that DZN exposure can do. These findings offer convincing support for enhancing the oocyte quality from EGCG through daily ordinary beverages.

Establishment of a Cell Line Stably Expressing the Growth Hormone Secretagogue Receptor to Identify Crocin as a Ghrelin Agonist

The growth hormone secretagogue receptor-1a (GHSR1a) is the endogenous receptor for ghrelin. Activation of GHSR1a participates in many physiological processes including energy homeostasis and eating behavior. Due to its transitory half-life, the efficacy of ghrelin treatment in patients is restricted; hence the development of new adjuvant therapy is an urgent need. This study aimed to establish a cell line stably expressing GHSR1a, which could be employed to screen potential ghrelin agonists from natural compounds. First, by means of lentiviral transduction, the genome of a human HEK293T cell was modified, and a cell platform stably overexpressing GHSR1a was successfully established. In this platform, GHSR1a was expressed as a fusion protein tagged with mCherry, which allowed the monitoring of the dynamic cellular distribution of GHSR1a by fluorescent microscopy. Subsequently, the authenticity of the GHSR1a mediated signaling was further characterized by using ghrelin and teaghrelin, two molecules known to stimulate GHSR1a. The results indicated that both ghrelin and teaghrelin readily activated GHSR1a mediated signaling pathways, presumably via increasing phosphorylation levels of ERK. The specific GHSR1a signaling was further validated by using SP-analog, an antagonist of GHSR1a as well as using a cell model with the knockdown expression of GHSR1a. Molecular modeling predicted that crocin might be a potential ghrelin agonist, and this prediction was further confirmed by the established platform.

Epigallocatechin Gallate Attenuates Gentamicin-Induced Nephrotoxicity by Suppressing Apoptosis and Ferroptosis

Gentamicin (GEN) is a kind of aminoglycoside antibiotic with the adverse effect of nephrotoxicity. Currently, no effective measures against the nephrotoxicity have been approved. In the present study, epigallocatechin gallate (EG), a useful ingredient in green tea, was used to attenuate its nephrotoxicity. EG was shown to largely attenuate the renal damage and the increase of malondialdehyde (MDA) and the decrease of glutathione (GSH) in GEN-injected rats. In NRK-52E cells, GEN increased the cellular ROS in the early treatment phase and ROS remained continuously high from 1.5 H to 24 H. Moreover, EG alleviated the increase of ROS and MDA and the decrease of GSH caused by GEN. Furthermore, EG activated the protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1). After the treatment of GEN, the protein level of cleaved-caspase-3, the flow cytometry analysis and the JC-1 staining, the protein levels of glutathione peroxidase 4 (GPX4) and SLC7A11, were greatly changed, indicating the occurrence of both apoptosis and ferroptosis, whereas EG can reduce these changes. However, when Nrf2 was knocked down by siRNA, the above protective effects of EG were weakened. In summary, EG attenuated GEN-induced nephrotoxicity by suppressing apoptosis and ferroptosis.

Epigallocatechin gallate is a potent inhibitor of cystathionine beta-synthase: Structure-activity relationship and mechanism of action

Epigallocatechin gallate (EGCG) is the main bioactive component of green tea. Through screening of a small library of natural compounds, we discovered that EGCG inhibits cystathionine β-synthase (CBS), a major H₂S-generating enzyme. Here we characterize EGCG's mechanism of action in the context of CBS-derived H₂S production. In the current project, biochemical, pharmacological and cell biology approaches were used to characterize the effect of EGCG on CBS in cellular models of cancer and Down syndrome (DS). The results show that EGCG binds to CBS and inhibits H₂S-producing CBS activity almost 30-times more efficiently than the canonical cystathionine formation (IC₅₀ 0.12 versus 3.3 μM). Through screening structural analogs and building blocks, we identified that gallate moiety of EGCG represents the pharmacophore responsible for CBS inhibition. EGCG is a mixed-mode, CBS-specific inhibitor with no effect on the other two major enzymatic sources of H₂S, CSE and 3-MST. Unlike the prototypical CBS inhibitor aminooxyacetate, EGCG does not bind the catalytic cofactor of CBS pyridoxal-5'-phosphate. Molecular modeling suggests that EGCG blocks a substrate access channel to pyridoxal-5'-phosphate. EGCG inhibits cellular H₂S production in HCT-116 colon cancer cells and in DS fibroblasts. It also exerts effects that are consistent with the functional role of CBS in these cells: in HCT-116 cells it decreases, while in DS cells it improves viability and proliferation. In conclusion, EGCG is a potent inhibitor of CBS-derived H₂S production. This effect may contribute to its pharmacological effects in various pathophysiological conditions.

Efficacy and Safety of Oral Green Tea Preparations in Skin Ailments: A Systematic Review of Clinical Studies

Green-tea-based products and their polyphenols, especially epigallocatechin-3-gallate, have attracted great attention over the years as possible nutraceuticals, due to their promising bioactivities, especially antioxidant and anti-inflammatory, which could be exploited in several diseases, including skin ailments. In this context, the present study aimed at reviewing clinical evidence about the benefits of the oral administration of green tea preparations and its polyphenols to relieve skin disorders, to point out the current knowledge, and to suggest possible novel strategies to effectively exploit the properties of green tea, also managing safety risks. To this end, a systematic review of the existing literature was carried out, using the PRISMA method. Few studies, including five focused on UV-induced erythema and skin alterations, three on photoaging, two on antioxidant skin defenses, and one on acne and genodermatosis, were retrieved. Despite several benefits, clinical evidence only supports the use of oral green tea preparations to protect skin from damage induced by ultraviolet radiation; in other cases, conflicting results and methodological limits of clinical trials do not allow one to clarify their efficacy. Therefore, their application as adjuvant or alternative sunscreen-protective interventions could be encouraged, in compliance with the safety recommendations.