Effects of Metabolites Produced from (-)-Epigallocatechin Gallate by Rat Intestinal Bacteria on Angiotensin I-Converting Enzyme Activity and Blood Pressure in Spontaneously Hypertensive Rats

Immunomodulatory Effects of Green Tea Catechins and Their Ring Fission Metabolites in a Tumor Microenvironment Perspective

Green tea is the second most consumed beverage following water, and the health benefits provided by its consumption have been well established from research in recent decades. The main bioactive compounds found in all Camellia sinensis-based teas are catechins, which have been reported to have antioxidant, anticancer, anti-inflammatory, and immunomodulatory properties. Although most of the health benefits are well established, studies show that the intact catechins as found in tea are poorly absorbed in the digestive tract. These compounds are degraded and undergo ring fission by the gut microbiota, increasing their absorption. In this review, we gather knowledge of the health benefits of green tea catechins and their metabolites, with a particular emphasis on the immunomodulatory effects in a cancer microenvironment scenario.

Dietary (poly)phenols as modulators of the biophysical properties in endothelial cell membranes: its impact on nitric oxide bioavailability in hypertension

Hypertension is a major contributor to premature death, owing to the associated increased risk of damage to the heart, brain and kidneys. Although hypertension is manageable by medication and lifestyle changes, the risk increases with age. In an increasingly aged society, the incidence of hypertension is escalating, and is expected to increase the prevalence of (cerebro)vascular events and their associated mortality. Adherence to plant-based diets improves blood pressure and vascular markers in individuals with hypertension. Food flavonoids have an inhibitory effect towards angiotensin-converting enzyme (ACE1) and although this effect is greatly diminished upon metabolization, their microbial metabolites have been found to improve endothelial nitric oxide synthase (eNOS) activity. Considering the transmembrane location of ACE1 and eNOS, the ability of (poly)phenols to interact with membrane lipids modulate the cell membrane's biophysical properties and impact on nitric oxide (·NO) synthesis and bioavailability, remain poorly studied. Herein, we provide an overview of the current knowledge on the lipid remodeling of endothelial membranes with age, its impact on the cell membrane's biophysical properties and ·NO permeability across the endothelial barrier. We also discuss the potential of (poly)phenols and other plant-based compounds as key players in hypertension management, and address the caveats and challenges in adopted methodologies.

Flavan-3-ols and Vascular Health: Clinical Evidence and Mechanisms of Action

Cardiovascular diseases (CVDs) are one of the main causes of mortality and morbidity worldwide. A healthy diet rich in plant-derived compounds such as (poly)phenols appears to have a key role in improving cardiovascular health. Flavan-3-ols represent a subclass of (poly)phenols of great interest for their possible health benefits. In this review, we summarized the results of clinical studies on vascular outcomes of flavan-3-ol supplementation and we focused on the role of the microbiota in CVD. Clinical trials included in this review showed that supplementation with flavan-3-ols mostly derived from cocoa products significantly reduces blood pressure and improves endothelial function. Studies on catechins from green tea demonstrated better results when involving healthy individuals. From a mechanistic point of view, emerging evidence suggests that microbial metabolites may play a role in the observed effects. Their function extends beyond the previous belief of ROS scavenging activity and encompasses a direct impact on gene expression and protein function. Although flavan-3-ols appear to have effects on cardiovascular health, further studies are needed to clarify and confirm these potential benefits and the rising evidence of the potential involvement of the microbiota.

Gut microbial metabolites of dietary polyphenols and their potential role in human health and diseases

Polyphenols contribute as one of the largest groups of compounds among all the phytochemicals. Common sources of dietary polyphenols are vegetables, fruits, berries, cereals, whole grains, etc. Owing to their original form, they are difficult to get absorbed. Dietary polyphenols after undergoing gut microbial metabolism form bioaccessible and effective metabolites. Polyphenols and derived metabolites are all together a diversified group of compounds exhibiting pharmacological activities against cardiovascular, cancer, oxidative stress, inflammatory, and bacterial diseases. The formed metabolites are sometimes even more bioavailable and efficacious than the parent polyphenols. Studies on gut microbial metabolism of dietary polyphenols have introduced new approach for the use of polyphenol-rich food in the form of supplementary diet. This review provides insights on various aspects including classification of polyphenols, gut microbiota-mediated metabolism of polyphenols, chemistry of polyphenol metabolism, and pharmacological actions of gut microbial metabolites of polyphenols. It also suggests the use of polyphenols from marine source for the microbial metabolism studies. Till date, gut microbial metabolism of polyphenols from terrestrial sources is extensively studied as compared to marine polyphenols. Marine ecosystem is a profound but partially explored source of phytoconstituents. Among them, edible seaweeds contain high concentration of polyphenols, especially phlorotannins. Hence, microbial metabolism studies of seaweeds can unravel the pharmacological potential of marine polyphenol-derived metabolites.

Gut microbiota-mediated metabolism of green tea catechins and the biological consequences: An updated review

Multiple beneficial effects have been attributed to green tea catechins (GTCs). However, the bioavailability of GTCs is generally low, with only a small portion directly absorbed in the small intestine. The majority of ingested GTCs reaches the large intestinal lumen, and are extensively degraded via biotransformation by gut microbiota, forming many low-molecular-weight metabolites such as phenyl-γ-valerolactones, phenolic acids, butyrate, and acetate. This process not only improves the overall bioavailability of GTC-derived metabolites but also enriches the biological activities of GTCs. Therefore, the intra- and inter-individual differences in human gut microbiota as well as the resulting biological contribution of microbial metabolites are crucial for the ultimate health benefits. In this review, the microbial degradation of major GTCs was characterized and an overview of the in vitro models used for GTC metabolism was summarized. The intra- and inter-individual differences of human gut microbiota composition and the resulting divergence in the metabolic patterns of GTCs were highlighted. Moreover, the potential beneficial effects of GTCs and their gut microbial metabolites were also discussed. Overall, the microbial metabolites of GTCs with higher bioavailability and bioactive potency are key factors for the observed beneficial effects of GTCs and green tea consumption.

Absorption, metabolism, bioactivity, and biotransformation of epigallocatechin gallate

Epigallocatechin gallate (EGCG), a typical flavone-3-ol polyphenol containing eight free hydroxyl groups, is associated with a variety of bioactivities, such as antioxidant, anti-inflammatory, anti-cancer, and antibacterial activities. However, the poor bioavailability of EGCG restricts its use. In this review, we discuss the processes involved in the absorption and metabolism of EGCG, with a focus on its metabolic interactions with the gut microbiota. Next, we summarize the bioactivities of some key metabolites, describe the biotransformation of EGCG by different microorganisms, and discuss its catabolism by specific bacteria. A deeper understanding of the absorption, metabolism, and biotransformation of EGCG may enable its disease-preventive and therapeutic properties to be better utilized. This review provides a theoretical basis for further development and utilization of EGCG and its metabolites for improving the gut microbiota and physiological health.

Common pregnancy complications and polyphenols intake: an overview

During pregnancy, the body undergoes a great amount of changes in order to support a healthy developing fetus. In this context, maternal dietary supplementation is widely encouraged to provide adequate nutrition for the newborn. In the past few years, studies have emerged highlighting the benefits of polyphenols intake during pregnancy. Indeed, despite differences among reports, such as experimental model, polyphenol employed, dosage and regimen of administration, there is no doubt that the ingestion of these molecules has a protective effect in relation to three pregnancy-associated diseases or conditions: preeclampsia, gestational diabetes and fetal growth restriction. In this review, we describe the effects of different polyphenols and polyphenol-rich extracts or juices on the main outcomes of these common pregnancy-associated complications, obtained in human, animal and in vitro studies. Therefore, this work provides a critical analysis of the literature, and a summary of evidences, from which future research using polyphenols can be designed and evaluated.

Polyphenols as Drivers of a Homeostatic Gut Microecology and Immuno-Metabolic Traits of Akkermansia muciniphila: From Mouse to Man

Akkermansia muciniphila is a mucosal symbiont considered a gut microbial marker in healthy individuals, as its relative abundance is significantly reduced in subjects with gut inflammation and metabolic disturbances. Dietary polyphenols can distinctly stimulate the relative abundance of A. muciniphila, contributing to the attenuation of several diseases, including obesity, type 2 diabetes, inflammatory bowel diseases, and liver damage. However, mechanistic insight into how polyphenols stimulate A. muciniphila or its activity is limited. This review focuses on dietary interventions in rodents and humans and in vitro studies using different phenolic classes. We provide critical insights with respect to potential mechanisms explaining the effects of polyphenols affecting A. muciniphila. Anthocyanins, flavan-3-ols, flavonols, flavanones, stilbenes, and phenolic acids are shown to increase relative A. muciniphila levels in vivo, whereas lignans exert the opposite effect. Clinical trials show consistent findings, and high intervariability relying on the gut microbiota composition at the baseline and the presence of multiple polyphenol degraders appear to be cardinal determinants in inducing A. muciniphila and associated benefits by polyphenol intake. Polyphenols signal to the AhR receptor and impact the relative abundance of A. muciniphila in a direct and indirect fashion, resulting in the restoration of intestinal epithelial integrity and homeostatic crosstalk with the gut microbiota by affecting IL-22 production. Moreover, recent evidence suggests that A. muciniphila participates in the initial hydrolysis of some polyphenols but does not participate in their complete metabolism. In conclusion, the consumption of polyphenol-rich foods targeting A. muciniphila as a pivotal intermediary represents a promising precision nutritional therapy to prevent and attenuate metabolic and inflammatory diseases.

Green and Oolong Tea Extracts With Different Phytochemical Compositions Prevent Hypertension and Modulate the Intestinal Flora in a High-Salt Diet Fed Wistar Rats

Green tea (GT) and oolong tea (OLT) are widely consumed beverages, and their preventive and regulatory effects on hypertension have been reported. However, the interventional effects of GT and OLT on hypertension induced by a high-salt diet and its mechanism have not been fully explored. This study evaluated the anti-hypertensive effects of GT and OLT and their underlying mechanisms. The in vivo anti-hypertensive effects of GT and OLT and their capability to prevent hypertension and regulate the intestinal microbiota in Wistar rats fed with a high-salt diet were evaluated. Our results show that GT and OLT supplementations could regulate oxidative stress, inflammation, gene expression, and parameter levels related to blood pressure (BP) and prevent the increase in BP induced by a high-salt diet. Furthermore, both GT and OLT boosted the richness and diversity of intestinal microbiota, increased the abundance of beneficial bacteria and reduced the abundance of harmful bacteria and conditionally pathogenic bacteria, and regulated the intestinal microbial metabolism pathway related to BP. Among them, OLT presented better effects than GT. These findings indicate that GT and OLT can prevent hypertension caused by high-salt diets, which may be due to the regulation of intestinal flora by GT and OLT.

Chemico-biological aspects of (-)-epigallocatechin-3-gallate (EGCG) to improve its stability, bioavailability and membrane permeability: Current status and future prospects

Natural products have been a bedrock for drug discovery for decades. (-)-Epigallocatechin-3-gallate (EGCG) is one of the widely studied natural polyphenolic compounds derived from green tea. It is the key component believed to be responsible for the medicinal value of green tea. Significant studies implemented in in vitro, in cellulo, and in vivo models have suggested its anti-oxidant, anti-cancer, anti-diabetic, anti-inflammatory, anti-microbial, neuroprotective activities etc. Despite having such a wide array of therapeutic potential and promising results in preclinical studies, its applicability to humans has encountered with rather limited success largely due to the poor bioavailability, poor membrane permeability, rapid metabolic clearance and lack of stability of EGCG. Therefore, novel techniques are warranted to address those limitations so that EGCG or its modified analogs can be used in the clinical setup. This review comprehensively covers different strategies such as structural modifications, nano-carriers as efficient drug delivery systems, synergistic studies with other bioactivities to improve the chemico-biological aspects (e.g., stability, bioavailability, permeability, etc.) of EGCG for its enhanced pharmacokinetics and pharmacological properties, eventually enhancing its therapeutic potentials. We think this review article will serve as a strong platform with comprehensive literature on the development of novel techniques to improve the bioavailability of EGCG so that it can be translated to the clinical applications.

Flavonoids and intestinal microbes interact to alleviate depression

Flavonoids have a variety of biological activities that are beneficial to human health. However, owing to low bioavailability, most flavonoids exert beneficial effects in the intestine through metabolism by the flora into a variety of structurally different derivatives. Also, flavonoids can modulate the type and structure of intestinal microorganisms to improve human health. It has been reported that the development of depression is accompanied by changes in the type and number of intestinal microorganisms, and gut microbes can significantly improve depressive symptoms through the gut-brain axis. Therefore, the interaction between flavonoids and intestinal microbes to alleviate depression is discussed. © 2021 Society of Chemical Industry.

Flavanols from Nature: A Phytochemistry and Biological Activity Review

Flavanols, a common class of secondary plant metabolites, exhibit several beneficial health properties by acting as antioxidant, anticarcinogen, cardioprotective, anti-microbial, anti-viral, and neuroprotective agents. Furthermore, some flavanols are considered functional ingredients in dairy products. Based on their structural features and health-promoting functions, flavanols have gained the attention of pharmacologists and botanists worldwide. This review collects and summarizes 121 flavanols comprising four categories: flavan-3-ols, flavan-4-ols, isoflavan-4-ols, and flavan-3,4-ols. The research of the various structural features and pharmacological activities of flavanols and their derivatives aims to lay the groundwork for subsequent research and expect to provide mentality and inspiration for the research. The current study provides a starting point for further research and development.

Biochemistry of Amaranthus polyphenols and their potential benefits on gut ecosystem: A comprehensive review of the literature

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Amaranthus is phytonutrients-rich plant distributed worldwide and has been recognized as having medicinal value in traditional use against several diseases and conditions. There are a large amount of research data on the polyphenol profiles of Amaranthus plants and their links with potential benefits against gastrointestinal disorders.

AIM OF THE REVIEW

This review article aims to provide a comprehensive review of Amaranthus phenolic compounds and their microbial metabolites, as well as the biological and/or pharmacological effects of those compounds/metabolites.

METHODOLOGY

The relevant information about the genus Amaranthus was collected from various sources and databases, including Google Scholar, Google Books, PubMed, Web of Science, Scopus, Science Direct, and other internet sources. The World Flora Online (2021) database was used to verify the scientific names of the plants.

RESULTS

Comprehensive review of identified compounds in Amaranthus plants revealed the presence of phenolic acids, flavonoids, and coumarins in each part of the plants. The biotransformation by gut microbiota enzymes prominently produces diverse bioactive metabolites that are potentially active than their precursors. Lines of the evidence support the beneficial roles of Amaranthus extracts in several gastrointestinal diseases, particularly with the polar extracts of several plant parts. Dietary fibers in Amaranthus plants also coordinate the alteration of gut microbiota-related metabolisms and may be beneficial to certain gastrointestinal disorders in particular, such as constipation.

CONCLUSIONS

Amaranthus plants are rich in polyphenols and dietary fibers. Several microbial metabolites are biologically active, so alteration of gut microbiota is largely linked to the metabolic feature of the plants. Based on the evidence available to date, several Amaranthus plants containing a combination of phytonutrients, particularly polyphenols and dietary fibers, may be a promising candidate that is of interest to be further developed for use in the treatment of certain gastrointestinal conditions/disorders.

A review on the medicinal potential, toxicology, and phytochemistry of litchi fruit peel and seed

The perception that many fruit wastes, particularly the peel, contain more phytochemicals than the edible portions has been largely supported by scientific evidence, making them potential sources of bioactive and therapeutic phytochemicals. The peel and seed of Litchi (Litchi chinensis Sonn.) contain bioactive principles and have been shown to exhibit antioxidative, antidiabetic, cancer preventive, anti-obesogenic, and anti-inflammatory properties. This review presents a critical analysis of previous and current perspectives on the medicinal, toxicological, and phytochemical profiles of litchi fruit peel and seed, thus providing an evidence-based platform to explore their medicinal potential. A literature search was done on "PubMed," "Google Scholar," and "ScienceDirect." Peer-reviewed published data on the medicinal profiles of litchi fruit peel and seed were identified and critically analyzed. The fruit peel and seed improved glycemic control and insulin signaling and downregulated lipogenic and cholesterogenic processes. Their neuroprotective, hepatoprotective, and renal protective potentials were influenced by antioxidative and anti-inflammatory actions. The anticancer effect was mediated by upregulated proapoptotic, proinflammatory, antiproliferative, and anti-metastatic processes in cancer cells. Simple flavonols, sesquiterpenes, phenolic acids, jasmonates, and proathocyanidins are the possible bioactive principles influencing the medicinal effects. Appropriate toxicity studies are, however, still lacking. Litchi fruit wastes may be further studied as useful sources of therapeutic agents that may have medicinal relevance in oxidative, metabolic, vascular, and carcinogenic ailments. PRACTICAL APPLICATIONS: Underutilized fruit wastes contribute to environmental pollution. Interestingly, these wastes contain phytochemicals that could be of medicinal relevance if their medicinal potentials are maximized. Litchi fruit is a widely consumed fruit with commercial value. Its peel and seeds contribute to fruit wastes. The review exposes the medicinal potential and bioactive principles and/or nutrients of the fruit's peel and seed while elucidating the underlying therapeutic mechanisms or modes of actions through which litchi peel and seed potentiate medicinal effects. Thus, the review provides an evidence-based platform to explore the medicinal potential of underutilized wastes from litchi fruit. Additionally, the fruit peel and seed could be low-cost residues that could afford ecofriendly opportunity if their medicinal potentials are properly maximized.

Polyphenol-Mediated Gut Microbiota Modulation: Toward Prebiotics and Further

The genome of gut microbes encodes a collection of enzymes whose metabolic functions contribute to the bioavailability and bioactivity of unabsorbed (poly)phenols. Datasets from high throughput sequencing, metabolome measurements, and other omics have expanded the understanding of the different modes of actions by which (poly)phenols modulate the microbiome conferring health benefits to the host. Progress have been made to identify direct prebiotic effects of (poly)phenols; albeit up to date, these compounds are not recognized as prebiotics sensu stricto. Interestingly, certain probiotics strains have an enzymatic repertoire, such as tannase, α-L-rhamnosidase, and phenolic acid reductase, involved in the transformation of different (poly)phenols into bioactive phenolic metabolites. In vivo studies have demonstrated that these (poly)phenol-transforming bacteria thrive when provided with phenolic substrates. However, other taxonomically distinct gut symbionts of which a phenolic-metabolizing activity has not been demonstrated are still significantly promoted by (poly)phenols. This is the case of Akkermansia muciniphila, a so-called antiobesity bacterium, which responds positively to (poly)phenols and may be partially responsible for the health benefits formerly attributed to these molecules. We surmise that (poly)phenols broad antimicrobial action free ecological niches occupied by competing bacteria, thereby allowing the bloom of beneficial gut bacteria. This review explores the capacity of (poly)phenols to promote beneficial gut bacteria through their direct and collaborative bacterial utilization and their inhibitory action on potential pathogenic species. We propose the term duplibiotic, to describe an unabsorbed substrate modulating the gut microbiota by both antimicrobial and prebiotic modes of action. (Poly)phenol duplibiotic effect could participate in blunting metabolic disturbance and gut dysbiosis, positioning these compounds as dietary strategies with therapeutic potential.

Going "Green" in the Prevention and Management of Atherothrombotic Diseases: The Role of Dietary Polyphenols

During the 20th century processed and ready-to-eat foods became routinely consumed resulting in a sharp rise of fat, salt, and sugar intake in people's diets. Currently, the global incidence of obesity, raised blood lipids, hypertension, and diabetes in an increasingly aged population contributes to the rise of atherothrombotic events and cardiovascular diseases (CVD) mortality. Drug-based therapies are valuable strategies to tackle and help manage the socio-economic impact of atherothrombotic disorders though not without adverse side effects. The inclusion of fresh fruits and vegetables rich in flavonoids to human diets, as recommended by WHO offers a valuable nutritional strategy, alternative to drug-based therapies, to be explored in the prevention and management of atherothrombotic diseases at early stages. Though polyphenols are mostly associated to color and taste in foods, food flavonoids are emerging as modulators of cholesterol biosynthesis, appetite and food intake, blood pressure, platelet function, clot formation, and anti-inflammatory signaling, supporting the health-promoting effects of polyphenol-rich diets in mitigating the impact of risk factors in atherothrombotic disorders and CVD events. Here we overview the current knowledge on the effect of polyphenols particularly of flavonoid intake on the atherothrombotic risk factors and discuss the caveats and challenges involved with current experimental cell-based designs.

Plant Phenolics and Extracts in Animal Models of Preeclampsia and Clinical Trials-Review of Perspectives for Novel Therapies

The current health requirements set the direction in pharmacological research, especially as regards diseases that require improvement of existing therapeutic regimens. Such diseases include preeclampsia, which is a hypertensive disorder of pregnancy during which there occurs progressive increasing activation of the immune system through elevation of pro-inflammatory cytokines and antiangiogenic factors, which is dangerous for the mother and fetus. A promising field of research for new drugs to treat this disease is the study of natural phenolic compounds of plant origin and herbal extracts, which are complex matrices of chemical compounds with broad biological activities. Many plant substances with anti‑inflammatory and anti‑hypertensive properties are known, but studies in animal models of preeclampsia and clinical trials concerning this disease constitute a new and developing research trend of significant medical importance. The aim of our research review was to identify and analyze the results of already available studies on baicalin, curcumin, epigallocatechin gallate, punicalagin, quercetin, resveratrol, salvianolic acid A (danshensu), silibinin, and vitexin, as well as plant extracts from Brassica oleracea L., Euterpe oleracea Mart., Moringa oleifera Lam., Punica granatum L., Silybum marianum (L.) Gaertner, Thymus schimperi Ronniger, Uncaria rhynchophylla (Miq.) Miq. ex Havil., and Vitis vinifera L., which are potential and promising candidates for further research and for potential new therapies.

Genus Parkia: Phytochemical, Medicinal Uses, and Pharmacological Properties

The genus Parkia (Fabaceae, Subfamily, Mimosoideae) comprises about 34 species of mostly evergreen trees widely distributed across neotropics, Asia, and Africa. This review aims to provide an overview of the current status of the species from the genus Parkia in terms of its relationship between its phytochemistry and medical uses. Comprehensive information on Parkia species was retrieved from electronic databases, which were Web of Science, ScienceDirect, PubMed, and Google Scholar. This review identified nine species from genus Parkia with properties of medicinal use. They are used traditionally to treat several ailments, such as diabetes, diarrhea, wounds, hypertension, cough, chronic piles, conjunctivitis, and measles. The most common species studied are P. biglobosa, P. speciosa, P. javanica, P. bicolor, P. biglandulosa, P. filicoidea, and P. clappertoniana. A considerable number of secondary metabolites, such as terpenoids, phenolic acids, flavonoids (aglycone and glycosides), and numerous volatile compounds have been identified in this genus, which are responsible for their diverse pharmacological activities. Their extracts, pure compounds and seed lectins have been reported for their anticancer, antimicrobial, antihypertensive, antiulcer, antidiabetic, anti-inflammatory, antioxidant, antimalarial, hepatoprotective, and antidiarrheal activities. The information gathered in this review might be of help for future studies in terms of the current knowledge on the link between the phytochemical components and medicinal uses. This could facilitate more discoveries on its potentials particularly in the pharmacological characteristics and potential to be developed into modern medicines.

Plasma and Urinary (Poly)phenolic Profiles after 4-Week Red Raspberry (Rubus idaeus L.) Intake with or without Fructo-Oligosaccharide Supplementation

Red raspberries (RRB) are high in anthocyanin- and ellagitannin- type (poly)phenols. This study aimed to investigate the effect of 4-week RRB supplementation on (poly)phenolic metabolism in adults with prediabetes and insulin-resistance (PreDM-IR); and whether adding fructo-oligosaccharides (FOS), prebiotics, would augment the microbial metabolites of RRB (poly)phenols. In a randomized crossover clinical trial, subjects (n = 35: PreDM-IR, n = 25; healthy Reference group, n = 10) consumed 1 cup RRB (fresh weight equivalence) per day and RRB with 8 g FOS per day each for 4 weeks in random order separated by 4-week washout. Plasma and urinary (poly)phenolic metabolites were characterized after (0–24 h) consuming a RRB-based test drink (2 cups RRB) at baseline/week 0 and again after 4-week supplementations. A total of 123 (poly)phenolic metabolites were quantified. After 4-week RRB supplementation, several metabolite groups were significantly increased (p < 0.05), including urolithins, phenyl-γ-valerolactones, and phenolic acids. Supplementing FOS with RRB for 4 weeks enhanced benzoic acid derivatives compared to the baseline (p < 0.05). Specific effects of supplementation by metabolic status indicated 4-week RRB supplementation significantly increased microbial metabolites that were lower in PreDM-IR group. Our results suggest alterations in the capacity of PreDM-IR group to metabolize and render bioavailable raspberry-derived (poly)phenols when consumed regularly.

Gut/Oral Bacteria Variability May Explain the High Efficacy of Green Tea in Rodent Tumor Inhibition and Its Absence in Humans

Consumption of green tea (GT) and GT polyphenols has prevented a range of cancers in rodents but has had mixed results in humans. Human subjects who drank GT for weeks showed changes in oral microbiome. However, GT-induced changes in RNA in oral epithelium were subject-specific, suggesting GT-induced changes of the oral epithelium occurred but differed across individuals. In contrast, studies in rodents consuming GT polyphenols revealed obvious changes in epithelial gene expression. GT polyphenols are poorly absorbed by digestive tract epithelium. Their metabolism by gut/oral microbial enzymes occurs and can alter absorption and function of these molecules and thus their bioactivity. This might explain the overall lack of consistency in oral epithelium RNA expression changes seen in human subjects who consumed GT. Each human has different gut/oral microbiomes, so they may have different levels of polyphenol-metabolizing bacteria. We speculate the similar gut/oral microbiomes in, for example, mice housed together are responsible for the minimal variance observed in tissue GT responses within a study. The consistency of the tissue response to GT within a rodent study eases the selection of a dose level that affects tumor rates. This leads to the theory that determination of optimal GT doses in a human requires knowledge about the gut/oral microbiome in that human.

Insight into Polyphenol and Gut Microbiota Crosstalk: Are Their Metabolites the Key to Understand Protective Effects against Metabolic Disorders?

Lifestyle factors, especially diet and nutrition, are currently regarded as essential avenues to decrease modern-day cardiometabolic disorders (CMD), including obesity, metabolic syndrome, type 2 diabetes, and atherosclerosis. Many groups around the world attribute these trends, at least partially, to bioactive plant polyphenols given their anti-oxidant and anti-inflammatory actions. In fact, polyphenols can prevent or reverse the progression of disease processes through many distinct mechanisms. In particular, the crosstalk between polyphenols and gut microbiota, recently unveiled thanks to DNA-based tools and next generation sequencing, unravelled the central regulatory role of dietary polyphenols and their intestinal micro-ecology metabolites on the host energy metabolism and related illnesses. The objectives of this review are to: (1) provide an understanding of classification, structure, and bioavailability of dietary polyphenols; (2) underline their metabolism by gut microbiota; (3) highlight their prebiotic effects on microflora; (4) discuss the multifaceted roles of their metabolites in CMD while shedding light on the mechanisms of action; and (5) underscore their ability to initiate host epigenetic regulation. In sum, the review clearly documents whether dietary polyphenols and micro-ecology favorably interact to promote multiple physiological functions on human organism.

Anti-inflammatory activities of green tea catechins along the gut-liver axis in nonalcoholic fatty liver disease: lessons learned from preclinical and human studies

Nonalcoholic fatty liver disease (NAFLD), which is the most prevalent hepatic disorder worldwide, affecting 25% of the general population, describes a spectrum of progressive liver conditions ranging from relatively benign liver steatosis and advancing to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. Hallmark features of NASH are fatty hepatocytes and inflammatory cell infiltrates in association with increased activation of hepatic nuclear factor kappa-B (NFκB) that exacerbates liver injury. Because no pharmacological treatments exist for NAFLD, emphasis has been placed on dietary approaches to manage NASH risk. Anti-inflammatory bioactivities of catechin-rich green tea extract (GTE) have been well-studied, especially in preclinical models that have detailed its effects on inflammatory responses downstream of NFκB activation. This review will therefore discuss the experimental evidence that has advanced an understanding of the mechanisms by which GTE, either directly through its catechins or potentially indirectly through microbiota-derived metabolites, limits NFκB activation and NASH-associated liver injury. Specifically, it will describe the hepatic-level benefits of GTE that attenuate intracellular redox distress and pro-inflammatory signaling from extracellular receptors that otherwise activate NFκB. In addition, it will discuss the anti-inflammatory activities of GTE on gut barrier function as well as prebiotic and antimicrobial effects on gut microbial ecology that help to limit the translocation of gut-derived endotoxins (e.g. lipopolysaccharides) to the liver where they otherwise upregulate NFκB activation by Toll-like receptor-4 signaling. This summary is therefore expected to advance research translation of the hepatic- and intestinal-level benefits of GTE and its catechins to help manage NAFLD-associated morbidity.

Phenyl-γ-valerolactones and phenylvaleric acids, the main colonic metabolites of flavan-3-ols: synthesis, analysis, bioavailability, and bioactivity

Covering: 1958 to June 2018 Phenyl-γ-valerolactones (PVLs) and their related phenylvaleric acids (PVAs) are the main metabolites of flavan-3-ols, the major class of flavonoids in the human diet. Despite their presumed importance, these gut microbiota-derived compounds have, to date, in terms of biological activity, been considered subordinate to their parent dietary compounds, the flavan-3-ol monomers and proanthocyanidins. In this review, the role and prospects of PVLs and PVAs as key metabolites in the understanding of the health features of flavan-3-ols have been critically assessed. Among the topics covered, are proposals for a standardised nomenclature for PVLs and PVAs. The formation, bioavailability and pharmacokinetics of PVLs and PVAs from different types of flavan-3-ols are discussed, taking into account in vitro and animal studies, as well as inter-individual differences and the existence of putative flavan-3-ol metabotypes. Synthetic strategies used for the preparation of PVLs are considered and the methodologies for their identification and quantification assessed. Metabolomic approaches unravelling the role of PVLs and PVAs as biomarkers of intake are also described. Finally, the biological activity of these microbial catabolites in different experimental models is summarised. Knowledge gaps and future research are considered in this key area of dietary (poly)phenol research.

Role of Dietary Flavonoid Compounds in Driving Patterns of Microbial Community Assembly

Flavonoids are a group of polyphenolic dietary compounds found in many different plant-based foods. There is increasing evidence that higher flavonoid intake may be causally linked to a reduced risk of cardiovascular disease and other chronic diseases. The bioactivity and bioavailability of many dietary flavonoids can be influenced by gastrointestinal microbiome metabolism. However, the role that habitual flavonoid intake plays in shaping the human gut microbiome is poorly understood. We describe an application of an ecosystem-based analytic approach to nutritional, microbiome, and questionnaire data from a cohort of more than 240 generally healthy adult males to assess the role of dietary flavonoid compounds in driving patterns of microbial community assembly. We identified six subclass-specific microbial communities (SMCs) uniquely and independently associated with intakes of the six flavonoid subclasses. Eggerthela lenta was positively associated with intakes of flavonol and flavanone, and Adlercreutzia equolifaciens was positively associated with intakes of flavonols and flavanol monomers. In contrast, for nearly all flavonoid subclasses, Flavonifractor plautii was inversely associated with subclass consumption. Consuming tea at least once per week explained 10.4% of the total variance in assembly of the 20 species comprising the flavanol monomer SMC. The novel methodology employed, necessitated by multidimensional microbiome data that consist of nonindependent features that exhibit a wide range of distributions and mean values, addresses a major challenge in our ability to understand associations of the microbiome in a wide range of clinical and epidemiologic settings.IMPORTANCE Dietary flavonoids, which have been implicated in lowering chronic disease risk and improving blood pressure, represent a diverse group of polyphenolic compounds found in many commonly consumed foods such as tea, red wine, apples, and berries. The bioactivity and bioavailability of more dietary flavonoids can be influenced by gastrointestinal microbiome metabolism. With demonstrated prebiotic and antimicrobial effects in in vitro and in animal models, it is surprising that there are not many human studies investigating the role dietary flavonoids play in shaping the gastrointestinal microbiome. Our analysis revealed patterns of community assembly that uniquely and independently characterize an individual's exposure to various flavonoid compounds. Furthermore, this study confirmed, independent from effects of other dietary and lifestyle factors included in the multivariate-adjusted model, that flavonoid intake is associated with microbial community assembly.

Microbial Metabolites of Flavan-3-Ols and Their Biological Activity

Flavan-3-ols are the main contributors to polyphenol intake. Many varying beneficial health effects in humans have been attributed to them, including the prevention of cardiovascular disease and cancer. Nevertheless, the mechanisms by which these flavonoids could exert beneficial functions are not entirely known. Several in vitro studies and in vivo animal models have tried to elucidate the role of the specific colonic metabolites on the health properties that are attributed to the parent compounds since a larger number of ingested flavan-3-ols reach the colon and undergo there microbial metabolism. Many new studies about this topic have been performed over the last few years and, to the best of our knowledge, no scientific literature review regarding the bioactivity of all identified microbial metabolites of flavan-3-ols has been recently published. Therefore, the aim of this review is to present the current status of knowledge on the potential health benefits of flavan-3-ol microbial metabolites in humans while using the latest evidence on their biological activity.

Function of Green Tea Catechins in the Brain: Epigallocatechin Gallate and its Metabolites

Over the last three decades, green tea has been studied for its beneficial effects, including anti-cancer, anti-obesity, anti-diabetes, anti-inflammatory, and neuroprotective effects. At present, a number of studies that have employed animal, human and cell cultures support the potential neuroprotective effects of green tea catechins against neurological disorders. However, the concentration of (−)-epigallocatechin gallate (EGCG) in systemic circulation is very low and EGCG disappears within several hours. EGCG undergoes microbial degradation in the small intestine and later in the large intestine, resulting in the formation of various microbial ring-fission metabolites which are detectable in the plasma and urine as free and conjugated forms. Recently, in vitro experiments suggested that EGCG and its metabolites could reach the brain parenchyma through the blood–brain barrier and induce neuritogenesis. These results suggest that metabolites of EGCG may play an important role, alongside the beneficial activities of EGCG, in reducing neurodegenerative diseases. In this review, we discuss the function of EGCG and its microbial ring-fission metabolites in the brain in suppressing brain dysfunction. Other possible actions of EGCG metabolites will also be discussed.

Effects of Microbial Metabolites of (-)-Epigallocatechin Gallate on Glucose Uptake in L6 Skeletal Muscle Cell and Glucose Tolerance in ICR Mice

Glucose uptake ability into L6 skeletal muscle cell was examined with eleven kinds of ring fission metabolites of (-)-epigallocatechin gallate (EGCG) produced by intestinal bacteria. The metabolites 5-(3,5-dihydroxyphenyl)-γ-valerolactone (EGC-M5), 4-hydroxy-5-(3,4,5-trihydroxyphenyl)valeric acid (EGC-M6), 5-(3,4,5-trihydroxyphenyl)-γ-valerolactone (EGC-M7) and 5-(3-hydroxyphenyl)valeric acid (EGC-M11) have been found to promote uptake of glucose into L6 myotubes significantly. EGC-M5, which is one of the major ring fission metabolites of EGCG, was also found to have a promotive effect on glucose transporter 4 (GLUT4) translocation accompanied by phosphorylation of AMP-activated protein kinase (AMPK) signaling pathway in skeletal muscle both in vivo and in vitro. Furthermore, the effect of oral single dosage of EGC-M5 on glucose tolerance test with ICR mice was examined and significant suppression of hyperglycemia was observed. These data suggested that EGC-M5 has an antidiabetic effect in vivo.

Inhibitory Effects of Green Tea Polyphenols on Microbial Metabolism of Aromatic Amino Acids in Humans Revealed by Metabolomic Analysis

The bioactivities and potential health benefits of green tea polyphenols (GTP) have been extensively investigated, but the metabolic impact of chronic GTP intake on humans is not well defined. In this study, fecal and urine samples from postmenopausal female subjects taking a GTP supplement or placebo for 12 months were compared by liquid chromatography-mass spectrometry-based metabolomic analysis. The GTP-derived and GTP-responsive metabolites were identified and characterized by structural elucidation and quantitative analysis of the metabolites contributing to the separation of control and treatment samples in the multivariate models. Major GTP and their direct sulfate and glucuronide metabolites were absent in feces and urine. In contrast, GTP-derived phenyl-γ-valerlactone and phenylvaleric acid metabolites were identified as the most abundant GTP-derived metabolites in feces and urine, suggesting extensive microbial biotransformation of GTP in humans. Interestingly, GTP decreased the levels of microbial metabolites of aromatic amino acids (AAA), including indoxyl sulfate, phenylacetylglutamine, and hippuric acid, in urine. However, it did not affect the levels of AAA, as well as other microbial metabolites, including short-chain fatty acids and secondary bile acids, in feces. 16S rRNA gene sequencing indicated that the fecal microbiome was not significantly affected by chronic consumption of GTP. Overall, microbial metabolism is responsible for the formation of GTP metabolites while GTP metabolism may inhibit the formation of AAA metabolites from microbial metabolism. Because these GTP-derived and GTP-responsive metabolites have diverse bioactivities, microbial metabolism of GTP and AAA may play important roles in the beneficial health effects of green tea consumption in humans.

Dynamic Profiling of Phenolic Acids during Pu-erh Tea Fermentation Using Derivatization Liquid Chromatography-Mass Spectrometry Approach

Pu-erh tea, a famous traditional Chinese tea with multiple health benefits, is produced by microbial fermentation. It has been reported that major known bioactive compounds in green tea, e.g. epicatechin, epigallocatechin gallate, and theanine, decreased during fermentation. Then which components account for the benefits of Pu-erh tea? Phenolic acids are aromatic secondary metabolites and possess various biological properties. In this research, phenolic acids in Pu-erh tea were investigated qualitatively and quantitatively to reveal the influence of fermentation and their potential effects using 5-(diisopropylamino)amylamine (DIAAA) derivatization-ultrahigh performance liquid chromatography-quadrupole-time-of-flight/mass spectrometry (UHPLC-Q-TOF/MS) approach. A total of 33 phenolic acids were determined, and most of them were detected in Pu-erh tea for the first time. Moreover, gallic acid and theogallin were the major components in ripened and raw Pu-erh tea, respectively. Dynamic profiling revealed the increase of simple phenolic acids and the decrease of most of phenolic acid esters during Pu-erh tea fermentation. These results provided firm basis for practical fermentation and quality control of Pu-erh tea.

Bioactivity of dietary polyphenols: The role of metabolites

A polyphenol-rich diet protects against chronic pathologies by modulating numerous physiological processes, such as cellular redox potential, enzymatic activity, cell proliferation and signaling transduction pathways. However, polyphenols have a low oral bioavailability mainly due to an extensive biotransformation mediated by phase I and phase II reactions in enterocytes and liver but also by gut microbiota. Despite low oral bioavailability, most polyphenols proved significant biological effects which brought into attention the low bioavailability/high bioactivity paradox. In recent years, polyphenol metabolites have attracted great interest as many of them showed similar or higher intrinsic biological effects in comparison to the parent compounds. There is a huge body of literature reporting on the biological functions of polyphenol metabolites generated by phase I and phase II metabolic reactions and gut microbiota-mediated biotransformation. In this respect, the review highlights the pharmacokinetic fate of the major dietary polyphenols (resveratrol, curcumin, quercetin, rutin, genistein, daidzein, ellagitannins, proanthocyanidins) in order to further address the efficacy of biometabolites as compared to parent molecules. The present work strongly supports the contribution of metabolites to the health benefits of polyphenols, thus offering a better perspective in understanding the role played by dietary polyphenols in human health.

Ginsenosides, catechins, quercetin and gut microbiota: Current evidence of challenging interactions

Recent studies have shown the role of gut microbiota in favoring the absorption of herbal products and the transformation of their active principles into metabolites endowed with biological activity. This review focuses on the evidence supporting the changes occurring, after metabolic reactions by specific bacteria that colonize the human gut, to ginseng-derived ginsenosides, green tea-derived catechins, and quercetin, this latter being a flavonoid aglycon bound to sugars and abundant in some vegetables and roots. Furthermore, the results of several studies demonstrating the potential beneficial effects of the active metabolites generated by these biotransformations on ginsenosides, catechins and quercetin will be reported.

Amalgamation of polyphenols and probiotics induce health promotion

The residing microbiome with its vast repertoire of genes provide distinctive properties to the host by which they can degrade and utilise nutrients that otherwise pass the gastro-intestinal tract unchanged. The polyphenols in our diet have selective growth promoting effects which is of utmost importance as the state of good health has been linked to dominance of particular microbial genera. The polyphenols in native form might more skilfully exert anti-oxidative and anti-inflammatory properties but in a living system it is the microbial derivatives of polyphenol that play a key role in determining health outcome. This two way interaction has invoked great interest among researchers who have commenced several clinical surveys and numerous studies in in-vitro, simulated environment and living systems to find out in detail about the biomolecules involved in such interaction along with their subsequent physiological benefits. In this review, we have thoroughly discussed these studies to develop a fair idea on how the amalgamation of probiotics and polyphenol has an immense potential as an adjuvant therapeutic for disease prevention as well as treatment.

Inhibitory Activity of Catechin Metabolites Produced by Intestinal Microbiota on Proliferation of HeLa Cells

Eleven kinds of catechin metabolites produced from (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCg) by intestinal microbiota were evaluated for inhibitory activity on the proliferation of HeLa cells, which are human cervical cancer cells. Among the catechin metabolites, 1-(3,4,5-trihydroxyphenyl)-3-(2,4,6-trihydroxyphenyl)propan-2-ol (EGC-M2), 4-hydroxy-5-(3,4,5-trihydroxyphenyl)valeric acid (EGC-M7), and 5-(3,4,5-trihydroxyphenyl)valeric acid (EGC-M9) were found to show inhibitory activity on HeLa cell proliferation as compared with control. The results suggested that three adjacent hydroxyl groups in the phenyl moiety may play an important role in the inhibitory activity. In addition, the inhibitory activity was also examined with four (-)-epicatechin (EC) metabolites possessing two adjacent hydroxyl groups in the phenyl moiety. Only 5-(3,4-dihydroxyphenyl)valeric acid (EC-M9) showed inhibitory activity and therefore valeric acid moiety likely contributes to the inhibitory activity. EGC-M9 showed the strongest inhibitory activity with IC₅₀ of 5.58 µM. Thus, in this study it was found for the first time that several catechin metabolites derived from EGC, EGCg, and EC inhibit the proliferation of cervical cancer cells.

Challenges and complexity of functionality evaluation of flavan-3-ol derivatives

Flavan-3-ol derivatives are common plant-derived bioactive compounds. In particular, (-)-epigallocatechin-3-O-gallate shows various moderate biological activities without severe toxicity, and its health-promoting effects have been widely studied because it is a main ingredient in green tea and is commercially available at low cost. Although various biologically active flavan-3-ol derivatives are present as minor constituents in plants as well as in green tea, their biological activities have yet to be revealed, mainly due to their relative unavailability. Here, I outline the major factors contributing to the complexity of functionality studies of flavan-3-ol derivatives, including proanthocyanidins and oligomeric flavan-3-ols. I emphasize the importance of conducting structure-activity relationship studies using synthesized flavan-3-ol derivatives that are difficult to obtain from plant extracts in pure form to overcome this challenge. Further discovery of these minor constituents showing strong biological activities is expected to produce useful information for the development of functional health foods.

Alterations in the gut microbiota can elicit hypertension in rats

Gut dysbiosis has been linked to cardiovascular diseases including hypertension. We tested the hypothesis that hypertension could be induced in a normotensive strain of rats or attenuated in a hypertensive strain of rats by exchanging the gut microbiota between the two strains. Cecal contents from spontaneously hypertensive stroke prone rats (SHRSP) were pooled. Similarly, cecal contents from normotensive WKY rats were pooled. Four-week-old recipient WKY and SHR rats, previously treated with antibiotics to reduce the native microbiota, were gavaged with WKY or SHRSP microbiota, resulting in four groups; WKY with WKY microbiota (WKY g-WKY), WKY with SHRSP microbiota (WKY g-SHRSP), SHR with SHRSP microbiota (SHR g-SHRSP), and SHR with WKY microbiota (SHR g-WKY). Systolic blood pressure (SBP) was measured weekly using tail-cuff plethysmography. At 11.5 wk of age systolic blood pressure increased 26 mmHg in WKY g-SHRSP compared with that in WKY g-WKY (182 ± 8 vs. 156 ± 8 mmHg, P = 0.02). Although the SBP in SHR g-WKY tended to decrease compared with SHR g-SHRSP, the differences were not statistically significant. Fecal pellets were collected at 11.5 wk of age for identification of the microbiota by sequencing the 16S ribosomal RNA gene. We observed a significant increase in the Firmicutes:Bacteroidetes ratio in the hypertensive WKY g-SHRSP, as compared with the normotensive WKY g-WKY (P = 0.042). Relative abundance of multiple taxa correlated with SBP. We conclude that gut dysbiosis can directly affect SBP. Manipulation of the gut microbiota may represent an innovative treatment for hypertension.

Epigallocatechin Gallate Reduces Slow-Twitch Muscle Fiber Formation and Mitochondrial Biosynthesis in C2C12 Cells by Repressing AMPK Activity and PGC-1α Expression

Epigallocatechin gallate (EGCG) is a major active compound in green tea polyphenols. EGCG acts as an antioxidant to prevent the cell damage caused by free radicals and their derivatives. In skeletal muscle, exercise causes the accumulation of intracellular reactive oxygen species (ROS) and promotes the formation of slow-type muscle fiber. To determine whether EGCG, as a ROS scavenger, has any effect on skeletal muscle fiber type, we applied different concentrations (0, 5, 25, and 50 μM) of EGCG in the culture medium of differentiated C2C12 cells for 2 days. The fiber-type composition, mitochondrial biogenesis-related gene expression, antioxidant and glucose metabolism enzyme activity, and ROS levels in C2C12 cells were then detected. According to our results, 5 μM EGCG significantly decreased the cellular activity of SDH, 25 μM EGCG significantly downregulated the MyHC I, PGC-1α, NRF-1, and p-AMPK levels and SDH activity while enhancing the CAT and GSH-Px activity and decreasing the intracellular ROS levels, and 50 μM EGCG significantly downregulated MyHC I, PGC-1α, and NRF-1 expression and HK and SDH activity while increasing LDH activity. Furthermore, 300 μM H2O2 and 0.5 mM AMPK agonist (AICAR) improved the expression of MyHC I, PGC-1α, and p-AMPK, which were all reversed by 25 μM EGCG. In conclusion, the effect of EGCG on C2C12 cells may occur through the reduction of the ROS level, thereby decreasing both AMPK activity and PGC-1α expression and eventually reducing slow-twitch muscle fiber formation and mitochondrial biosynthesis.

EGCG Suppresses ERK5 Activation to Reverse Tobacco Smoke-Triggered Gastric Epithelial-Mesenchymal Transition in BALB/c Mice

Tobacco smoke is an important risk factor of gastric cancer. Epithelial-mesenchymal transition is a crucial pathophysiological process in cancer development. ERK5 regulation of epithelial-mesenchymal transition may be sensitive to cell types and/or the cellular microenvironment and its role in the epithelial-mesenchymal transition process remain elusive. Epigallocatechin-3-gallate (EGCG) is a promising chemopreventive agent for several types of cancers. In the present study we investigated the regulatory role of ERK5 in tobacco smoke-induced epithelial-mesenchymal transition in the stomach of mice and the preventive effect of EGCG. Exposure of mice to tobacco smoke for 12 weeks reduced expression of epithelial markers E-cadherin, ZO-1, and CK5, while the expression of mesenchymal markers Snail-1, Vimentin, and N-cadherin were increased. Importantly, we demonstrated that ERK5 modulated tobacco smoke-mediated epithelial-mesenchymal transition in mice stomach, as evidenced by the findings that tobacco smoke elevated ERK5 activation, and that tobacco smoke-triggered epithelial-mesenchymal transition was reversed by ERK5 inhibition. Treatment of EGCG (100 mg/kg BW) effectively attenuated tobacco smoke-triggered activation of ERK5 and epithelial-mesenchymal transition alterations in mice stomach. Collectively, these data suggested that ERK5 was required for tobacco smoke-triggered gastric epithelial-mesenchymal transition and that EGCG suppressed ERK5 activation to reverse tobacco smoke-triggered gastric epithelial-mesenchymal transition in BALB/c mice. These findings provide new insights into the mechanism of tobacco smoke-associated gastric tumorigenesis and the chemoprevention of tobacco smoke-associated gastric cancer.

Green Tea Catechin Metabolites Exert Immunoregulatory Effects on CD4(+) T Cell and Natural Killer Cell Activities

Tea catechins, such as (-)-epigallocatechin-3-O-gallate (EGCG), have been shown to effectively enhance immune activity and prevent cancer, although the underlying mechanism is unclear. Green tea catechins are instead converted to catechin metabolites in the intestine. Here, we show that these green tea catechin metabolites enhance CD4(+) T cell activity as well as natural killer (NK) cell activity. Our data suggest that the absence of a 4'-hydroxyl on this phenyl group (B ring) is important for the effect on immune activity. In particular, 5-(3',5'-dihydroxyphenyl)-γ-valerolactone (EGC-M5), a major metabolite of EGCG, not only increased the activity of CD4(+) T cells but also enhanced the cytotoxic activity of NK cells in vivo. These data suggest that EGC-M5 might show immunostimulatory activity.

Polyphenols: Potential source of drugs for the treatment of ischaemic heart disease

Polyphenols, which are naturally present in plants, have been studied for their chemical and pharmacological properties. Polyphenols have been found to exhibit various bioactivities such as antioxidant, free radical scavenging and anti-inflammatory effects, in addition to regulating the intracellular free calcium levels. These bioactivities are related to the underlying mechanisms of ischaemic heart diseases. Pharmacological studies have proven polyphenols to be effective in treating cardiovascular diseases in various ways, particularly ischaemic heart diseases. Based on their mode of action, we propose that some polyphenols can be developed as drugs to treat ischaemic heart diseases. For this purpose, a strategy to evaluate the therapeutic value of drugs for ischaemic heart diseases is needed. Despite several advances in percutaneous coronary intervention (PCI), the incidence of myocardial infarction and deaths due to cardiovascular diseases has not decreased markedly in China. Due to their pleiotropic properties and structural diversity, polyphenols have been of great interest in pharmacology. In the present review, we summarize the pharmacological effects and mechanisms of polyphenols reported after 2000, and we analyse the benefits or druggability of these compounds for ischaemic heart diseases.