Prooxidant activity-based guideline for a beneficial combination of (-)-epigallocatechin-3-gallate and chlorogenic acid

Chemical components, health-promoting effects and industrial application of a Chinese bitter tea (Kuding tea): A comprehensive review

Kuding tea (KT), a traditional Chinese bitter tea, has long been recognized as Food & Medicine Homology product, known for its various active components and health benefits. However, research on KT is fragmented, lacking a comprehensive review of its key chemical constituents, health-promoting effects, and potential future applications. This review outlines the development history and nutritional components of KT while examining its functional benefits and industrial applications. KT is a promising and cost-effective product, containing numerous bioactive constituents, including polyphenols, triterpenoids, phenylethanoids, and polysaccharides, which exhibit strong antioxidant, anti-obesity, anti-diabetic, anti-inflammatory, neuroprotective, and anti-cancer activities. We summarized the researches on the health-promoting effects of KT and emphasized its practical applications in the food, agricultural, and pharmaceutical industries. Overall, this review presents a forward-looking viewpoint on creative KT applications and offers insights into KT's potential for future sustainable growth.

Epigallocatechin Gallate Promotes Cuproptosis via the MTF1/ATP7B Axis in Hepatocellular Carcinoma

BACKGROUND

Cuproptosis is a form of copper-dependent non-apoptotic cell death. Cancer cells that prefer to use aerobic glycolysis for energy generation are commonly insensitive to cuproptosis, which hinders its application for cancer treatment. Epigallocatechin gallate (EGCG) possesses diverse pharmacological activities. However, the association between EGCG and cuproptosis has not been studied.

METHODS

The cell viability, proliferation, and cuproptosis-related protein levels were detected to investigate whether EGCG enhances the sensitivity of HCC cells to cuproptosis. The intracellular copper level, related copper metabolism proteins, and gene expression were detected to explore the mechanisms. In addition, a nude mouse xenograft model was established to determine the effects of EGCG on cuproptosis in tumor tissues.

RESULTS

The combination of EGCG and copper ionophores significantly enhanced the mortality of HCC cells and heightened the sensitivity of HCC cells to cuproptosis. There was a notable reduction in the expression of copper export protein copper-transporting P-type ATPase (ATP7B). EGCG effectively suppressed metal regulatory transcription factor (MTF1) expression and subsequently hindered the transcriptional regulation of ATP7B. EGCG also facilitated the intratumoral accumulation of copper and augmented susceptibility to cuproptosis in vivo.

CONCLUSIONS

EGCG can increase the sensitivity of hepatocellular carcinoma cells to cuproptosis by promoting intracellular copper accumulation through the MTF1/ATP7B axis.

(-)-Epigallocatechin-3-Gallate and Quercetin Inhibit Quiescin Sulfhydryl Oxidase 1 Secretion from Hepatocellular Carcinoma Cells

Liver cancer is one of the most prevalent cancers worldwide. The first-line therapeutic drug sorafenib offers only a moderate improvement in patients' conditions. Therefore, an approach to enhancing its therapeutic efficacy is urgently needed. It has been revealed that hepatocellular carcinoma (HCC) cells with heightened intracellular quiescin sulfhydryl oxidase 1 (QSOX1) exhibit increased sensitivity to sorafenib. QSOX1 is a secreted disulfide catalyst, and it is widely recognized that extracellular QSOX1 promotes the growth, invasion, and metastasis of cancer cells through its participation in the establishment of extracellular matrix. Inhibiting QSOX1 secretion can increase intracellular QSOX1 and decrease extracellular QSOX1. Such an approach would sensitize HCC cells to sorafenib but remains to be established. Since (-)-epigallocatechin-3-gallate (EGCG) has been demonstrated to be an effective inhibitor of α-fetal protein secretion from HCC cells, we screened QSOX1 secretion inhibition using polyphenolic compounds. We examined eight dietary polyphenols (EGCG, quercetin, fisetin, myricetin, caffeic acid, chlorogenic acid, resveratrol, and theaflavin) and found that EGCG and quercetin effectively inhibited QSOX1 secretion from human HCC cells (HepG2 or Huh7), resulting in high intracellular QSOX1 and low extracellular QSOX1. The combination of EGCG or quercetin, both of which change the cellular distribution of QSOX1, with sorafenib, which has no influence on the cellular distribution of QSOX1, exhibited multiple synergistic effects against the HCC cells, including the induction of apoptosis and inhibition of invasion and metastasis. In conclusion, our current results suggest that dietary EGCG and quercetin have the potential to be developed as adjuvants to sorafenib in the treatment of HCC by modulating the cellular distribution of QSOX1.

Acrolein scavengers and detoxification: From high-throughput screening of flavonoids to mechanistic study of epigallocatechin gallate

Acrolein (ACR) is a widespread, highly toxic substance that poses significant health risks. Flavonoids have been recognized as effective ACR scavengers, offering a possible way to reduce these risks. However, the lack of specific high-throughput screening methods has limited the identification of ACR scavengers, and their actual detoxifying capacity on ACR remains unknown. To address this, we developed a high-throughput screening platform to assess the ACR scavenging capacity of 322 flavonoids. Our results showed that 80.7 % of the flavonoids could scavenge ACR, but only 34.4 % exhibited detoxifying effects in an ACR-injured QSG7701 cell model. Some flavonoids even increased toxicity. Structure-activity relationship (SAR) analysis indicated that galloyl and pyrogallol units enhance scavenging but worsen ACR-induced cytotoxicity. Further investigation revealed that epigallocatechin gallate (EGCG) could exacerbate ACR-induced redox disorder, leading to cell apoptosis. Our findings provide crucial data on the scavenging and detoxifying capacities of 322 flavonoids, highlighting that ACR scavengers might not mitigate ACR-induced toxicity and could pose additional safety risks.

Phytochemical Profiles and Biological Activities of Five Wild Camellia Species from Ta Dung, Vietnam

The C. luuana Orel & Curry (TD3), C. furfuracea (Merr.) Cohen-Stuard (TD4), C. bidoupensis Truong, Luong & Tran (TD6), C. sinensis (L.) Kuntze (TD7), and C. kissii var. spp (TD8), have been traditionally used as a health-promoting beverage by local people in Ta Dung, Dak Nong. Despite their potential health benefits, further scientific data on biological and phytochemical properties of these plants is needed. To address this issue, this study was conducted to investigate phytochemical and biological properties of five Camellia species extracts, using DPPH, ABTS radical scavenging, copper chelating (Cu-chelator), and tyrosinase inhibition (TI), α-amylase (Al-AI), and α-glucosidase (Al-GI) analyses. As results, ten compounds were identified using UPLC method, in which catechins (mainly EGCG and catechin (Cat)), were the most prevalent, and followed by chlorogenic acid (ChlA), quercitrin (Querci), rutin, and quercetin (Querce). Additionally, multiple factor analysis (MFA) also revealed that TD7, TD3, and TD4 containing high TPC, TFC, high concentrations of EGCG, ChlA, and caffeine were responsible for their high DPPH, ABTS radical scavenging activities, as well asTI, Al-AI and Al-GI. Furthemore, TD6 and TD8, possessing elevated levels of Apig, Querci, Rutin, Querce, Cat, and EA, exhibited a high Cu-chelator property, but a weak enzyme inhibition. From all above-mentioned results, the antioxidative and enzyme inhibitory potentials of Camellia species extracts collected in Dak Nong province in Vietnam were scientifically demonstrated paving a pathway to develop health supplement in further studies.

A surface multiple imprinting layers membrane with well-oriented recognition sites for selective separation of chlorogenic acid from Ficus carica L

Chlorogenic acid (CGA), known as an important natural antioxidative compound in Ficus carica L, has valuable application prospects on health food, functional food, nutrition and dietary formulations. In this study, a surface multiple imprinting layers membrane (SMILM) was developed and applied to separate CGA from F. carica. Two different imprinting layers were integrated onto the membrane surface in sequence. The first imprinting layer was formed by dopamine polymerization and the second imprinting layer was fabricated by atom transfer radical polymerization (ATRP) and boronate affinity. The prepared SMILM with well-oriented multiple recognition sites exhibited high adsorption capacity (52.08 mg·g-1 in 60 min) for CGA and specific selectivity with imprinting factor (IF) of 3.06. Furthermore, the recognition mechanism of SMILM was clarified by molecular simulation and NMR. The SMILM was successfully applied to separate CGA from the fruits, peels and leaves of F. carica with recoveries of 90.22, 83.31 and 84.95 %, respectively.

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.

DNA Mutagenicity of Hydroxyhydroquinone in Roasted Coffee Products and Its Suppression by Chlorogenic Acid, a Coffee Polyphenol, in Oxidative-Damage-Sensitive SAMP8 Mice

Hydroxyhydroquinone (HHQ) is an oxidative component produced by roasting coffee beans and has been reported to generate relatively large amounts of reactive oxygen species (ROS). In this study, we used senescence-accelerated mouse prone 8 (SAMP8) mice to determine whether HHQ consumption increases oxidative-stress-induced injury, because in SAMP8 mice, the activity of 8-oxoguanine DNA glycosylase 1, which repairs oxidative modifications in DNA, is decreased. The results showed that two out of twelve (16.7%) HHQ-treated mice presented polyuria and glucosuria around 2 months after the start of treatment, indicating that HHQ may act as a mutagen against SAMP8 mice, which is sensitive to oxidative damage. No abnormalities were observed in the chlorogenic acid (coffee polyphenol, CPP)-treated group. The concentration of hydrogen peroxide in the serum of SAMP8 mice was significantly higher than that in SAMR1 (senescence-resistant) control mice, and the concentration was further increased in the HHQ-treated group. CPP, when coexisting with HHQ at the rate contained in roasted coffee, decreased the amount of hydrogen peroxide in the serum of SAMP8 mice. Although CPP can act both oxidatively and antioxidatively as a polyphenol, CPP acts more antioxidatively when coexisting with HHQ. Thus, the oxidative effect of HHQ was shown to be counteracted by CPP.

Elucidating the potential of chlorogenic acid for controlling Morganella psychrotolerans growth and histamine formation

AIM

To investigate the inhibitory impact of chlorogenic acid (CGA) on the growth of Morganella psychrotolerans and its ability to form histamine.

METHODS AND RESULTS

The antimicrobial effect of CGA on M. psychrotolerans was evaluated using the minimum inhibitory concentration (MIC) method, revealing an MIC value of 10 mg ml-1. The alkaline phosphatase (AKP) activity, cell membrane potential, and scanning electron microscopy images revealed that CGA treatment disrupted cell structure and cell membrane. Moreover, CGA treatment led to a dose-dependent decrease in crude histidine decarboxylase (HDC) activity and gene expression of histidine decarboxylase (hdc). Molecular docking analysis demonstrated that CGA interacted with HDC through hydrogen bonds. Furthermore, in situ investigation confirmed the efficacy of CGA in controlling the growth of M. psychrotolerans and significantly reducing histamine formation in raw tuna.

CONCLUSION

CGA had good activity in controlling the growth of M. psychrotolerans and histamine formation.

Bioactive Dairy-Fermented Products and Phenolic Compounds: Together or Apart

Fermented dairy products (e.g., yogurt, kefir, and buttermilk) are significant in the dairy industry. They are less immunoreactive than the raw materials from which they are derived. The attractiveness of these products is based on their bioactivity and properties that induce immune or anti-inflammatory processes. In the search for new solutions, plant raw materials with beneficial effects have been combined to multiply their effects or obtain new properties. Polyphenols (e.g., flavonoids, phenolic acids, lignans, and stilbenes) are present in fruit and vegetables, but also in coffee, tea, or wine. They reduce the risk of chronic diseases, such as cancer, diabetes, or inflammation. Hence, it is becoming valuable to combine dairy proteins with polyphenols, of which epigallocatechin-3-gallate (EGCG) and chlorogenic acid (CGA) show a particular predisposition to bind to milk proteins (e.g., α-lactalbumin β-lactoglobulin, αs1-casein, and κ-casein). Reducing the allergenicity of milk proteins by combining them with polyphenols is an essential issue. As potential 'metabolic prebiotics', they also contribute to stimulating the growth of beneficial bacteria and inhibiting pathogenic bacteria in the human gastrointestinal tract. In silico methods, mainly docking, assess the new structures of conjugates and the consequences of the interactions that are formed between proteins and polyphenols, as well as to predict their action in the body.

Intestinal polyphenol antioxidant activity involves redox signaling mechanisms facilitated by aquaporin activity

Ascertaining whether dietary polyphenols evoke an antioxidant or prooxidant activity, which translates to a functional role required to maintain intestinal cell homeostasis continues to be an active and controversial area of research for food chemists and biochemists alike. We have proposed that the paradoxical function of polyphenols to autoxidize to generate H2O2 is a required first step in the capacity of some plant phenolics to function as intracellular antioxidants. This is based on the fact that cell redox homeostasis is achieved by a balance between H2O2 formation and subsequent outcomes of antioxidant systems function. Maintaining optimal extracellular and intracellular H2O2 concentrations is required for cell survival, since low levels are important to upregulate endogenous antioxidant capacity; whereas, concentrations that go beyond homeostatic control typically result in an inflammatory response, growth arrest, or eventual cell death. Aquaporins (AQPs) are a family of water channel membrane proteins that facilitate cellular transportation of water and other small molecule-derived solutes, such as H2O2, in all organisms. In the intestine, AQPs act as gatekeepers to regulate intracellular uptake of H2O2, generated from extracellular polyphenol autoxidation, thus enabling an intracellular cell signaling responses to mitigate onset of oxidative stress and intestinal inflammation. In this review, we highlight the potential role of AQPs to control important underlying mechanisms that define downstream regulation of intestinal redox homeostasis, specifically. It has been established that polyphenols that undergo oxidation to the quinone form, resulting in subsequent adduction to a thiol group on Keap1-Nrf2 complex, trigger Nrf2 activation and a cascade of indirect intracellular antioxidant effects. Here, we propose a similar mechanism that involves H2O2 generated from specific dietary polyphenols with a predisposition to undergo autoxidation. The ultimate bioactivity is regulated and expressed by AQP membrane function and thus, by extension, represents expression of an intracellular antioxidant chemoprotection mechanism.

Chlorogenic acid as an indispensible partner of caffeic acid in coffee via selective regulation of prooxidative actions of caffeic acid

Chlorogenic acid (CGA) and caffeic acid (CA) are two major phenolic acids in coffee. Though the International Agency for Research on Cancer has classified CA as a Group2B carcinogen, coffee consumption seems generally safe within the usual levels of intake and is more likely to benefit health than to harm it. We thus speculated that CGA may effectively suppress the carcinogenic potential of CA. In a molar ratio achievable in vivo, this study shows that CGA can inhibit (i) copper reduction caused by CA, (ii) CA oxidation caused by copper, (iii) the formation of hydroxyl radicals by CA and copper, and (iv) DNA damage induced by CA, quercetin or (-)-epigallocatechin-3-gallate in the presence of copper. CA tends to undergo autoxidation to produce hydrogen peroxide and quinone, which further reacts with proteins to form quinoproteins. This autoxidation at a tolerable level normally induces beneficial adaptive responses. This study shows that CGA is less efficient than CA in producing hydrogen peroxide and quinoprotein; however, together they synergistically produce hydrogen peroxide and quinoprotein in vitro at a molar ratio achievable in vivo. In conclusion, CGA can selectively regulate the prooxidant activities of CA depending on whether copper is involved or not. CGA could be viewed as an indispensable partner of CA in coffee, given its dual role in suppressing the carcinogenic potential of CA and boosting CA autoxidation which is beneficial for disease prevention.

A chlorogenic acid-chitosan complex bifunctional coating for improving osteogenesis differentiation and bactericidal properties of zirconia implants

Poor osteogenesis caused by limited bioactivity and peri-implantitis caused by bacterial colonization are the main challenges affecting the use of zirconia-based materials in dental implants. Accordingly, the development of a surface treatment method with an antibacterial effect and that promotes osteogenesis without damage to cells is crucial for yttrium-stabilized tetragonal zirconia (Y-TZP) implants. Herein, we have developed a functional surface modification strategy whereby a poly (ethylene imine)/hyaluronic acid /chitosan-chlorogenic acid (PEI/HA/CGA-CS) conjugate is deposited on a zirconia surface by the layer-by-layer (LBL) technique, enhancing its osteogenic differentiation and antibacterial activities. The results showed that the PEI/HA/CGA-CS coating improved the wettability of the zirconia surface and maintained stable release of CGA. The PEI/HA/CGA-CS functional coating was found to promote early cell adhesion, proliferation, differentiation, and calcification. The results of bacterial adhesion and activity tests showed that the coating effectively inhibits the proliferation and activity of Porphyromonas gingivalis (P. gingivalis) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) without impairing the biological activity of osteoblasts. In addition, we found that the PEI/HA/CGA-CS coating enhances the osteogenesis of MC3T3-E1 cells by promoting the protein expression of Nephronectin (NPNT) and activating the Wnt/β-catenin signaling pathway. The above results are of profound significance for the practical application of zirconia-based implants. DATA AVAILABILITY: Data will be made available on request.

The potential of epigallocatechin gallate in the chemoprevention and therapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC), one of the most notorious malignancies globally, has a high fatality and poor prognosis. Though remarkable breakthroughs have been made in the therapeutic strategies recently, the overall survival of HCC remains unsatisfactory. Consequently, the therapy of HCC remains a great challenge. Epigallocatechin gallate (EGCG), a natural polyphenol extracted from the leaves of the tea bush, has been extensively investigated for its antitumor effects. In this review, we summarize the previous literature to elucidate the roles of EGCG in the chemoprophylaxis and therapy of HCC. Accumulating evidence has confirmed EGCG prevents and inhibits the hepatic tumorigenesis and progression through multiple biological mechanisms, mainly involving hepatitis virus infection, oxidative stress, proliferation, invasion, migration, angiogenesis, apoptosis, autophagy, and tumor metabolism. Furthermore, EGCG enhances the efficacy and sensitivity of chemotherapy, radiotherapy, and targeted therapy in HCC. In conclusion, preclinical studies have confirmed the potential of EGCG for chemoprevention and therapy of HCC under multifarious experimental models and conditions. Nevertheless, there is an urgent need to explore the safety and efficacy of EGCG in the clinical practice of HCC.

Chlorogenic acid combined with epigallocatechin-3-gallate mitigates D-galactose-induced gut aging in mice

Chlorogenic acid (CGA) and epigallocatechin-3-gallate (EGCG) are major polyphenolic constituents of coffee and green tea with beneficial health properties. In this study, we evaluated the gut protecting effect of CGA and EGCG, alone or in combination, on D-galactose-induced aging mice. CGA plus EGCG more effectively improved the cognition deficits and protected the gut barrier function, compared with the agents alone. Specifically, CGA plus EGCG prevented the D-galactose mediated reactive oxygen species accumulation by increasing the total antioxidant capacity, reducing the levels of malondialdehyde, and suppressing the activity of the antioxidant enzymes superoxide dismutase and catalase. In addition, supplementation of CGA and EGCG suppressed gut inflammation by reducing the levels of the proinflammatory cytokines TNFα, IFNγ, IL-1β and IL-6. Moreover, CGA and EGCG modulated the gut microbiome altered by D-galactose. For instance, CGA plus EGCG restored the Firmicutes/Bacteroidetes ratio of the aging mice to control levels. Furthermore, CGA plus EGCG decreased the abundance of Lactobacillaceae, Erysipelotrichaceae, and Deferribacteraceae, while increased the abundance of Lachnospiraceae, Muribaculaceae, and Rikenellaceae, at the family level. In conclusion, CGA in combination with EGCG ameliorated the gut alterations induced by aging, in part, through antioxidant and anti-inflammatory effects, along with its gut microbiota modulatory capacity.

Potential of green tea EGCG in neutralizing SARS-CoV-2 Omicron variant with greater tropism toward the upper respiratory tract

Background

COVID-19 due to SARS-CoV-2 infection has had an enormous adverse impact on global public health. As the COVID-19 pandemic evolves, the WHO declared several variants of concern (VOCs), including Alpha, Beta, Gamma, Delta, and Omicron. Compared with earlier variants, Omicron, now a dominant lineage, exhibits characteristics of enhanced transmissibility, tropism shift toward the upper respiratory tract, and attenuated disease severity. The robust transmission of Omicron despite attenuated disease severity still poses a great challenge for pandemic control. Under this circumstance, its tropism shift may be utilized for discovering effective preventive approaches.

Scope and approach

This review aims to estimate the potential of green tea epigallocatechin gallate (EGCG), the most potent antiviral catechin, in neutralizing SARS-CoV-2 Omicron variant, based on current knowledge concerning EGCG distribution in tissues and Omicron tropism.

Key findings and conclusions

EGCG has a low bioavailability. Plasma EGCG levels are in the range of submicromolar concentrations following green tea drinking, or reach at most low μM concentrations after pharmacological intervention. Nonetheless, its levels in the upper respiratory tract could reach concentrations as high as tens or even hundreds of μM following green tea consumption or pharmacological intervention. An approach for delivering sufficiently high concentrations of EGCG in the pharynx has been developed. Convincing data have demonstrated that EGCG at tens to hundreds of μM can dramatically neutralize SARS-CoV-2 and effectively eliminate SARS-CoV-2-induced cytopathic effects and plaque formation. Thus, EGCG, which exhibits hyperaccumulation in the upper respiratory tract, deserves closer investigation as an antiviral in the current global battle against COVID-19, given Omicron's greater tropism toward the upper respiratory tract.

Anti- and Pro-Oxidant Activity of Polyphenols Extracts of Syrah and Chardonnay Grapevine Pomaces on Melanoma Cancer Cells

The phenolic composition of Syrah and Chardonnay grape pomaces was studied to assess their antioxidant and prooxidant properties. Polyphenols were extracted by a "green" hydroalcoholic solvent (ethanol/water 1:1 v/v), and a detailed chemical and electrochemical characterization of the phenolic compounds was performed. The antioxidant and prooxidant capacity of the pomace was first studied by cyclic voltammetry (CV) and other reference analytical assays, then with biological tests on B16F10 metastatic melanoma cancer cells. Electrochemical data showed that, when a +0.5 V potential was applied, a low to moderate antioxidant capacity was observed. MTT test showed an increasing viability of melanoma cells, after treatments at low concentration (up to 100 μg/mL) and for a short time (6 h), but when cells were treated with higher doses of extract (≥250 μg/mL for 12/24 h), their viability decreased from 25 to 50% vs. control, depending on treatment time, dose, and extract origin. A stronger prooxidant activity resulted when 250 μg/mL of extract was combined with non-toxic doses of H₂O₂; this activity was correlated with the presence of copper in the extracts. This study shows the potential of winemaking by-products and suggests the opportunity to exploit them for the production of cosmeceuticals, or for combined therapies with approved anticancer drugs.