Health Effects Of Polyphenols Research Articles

Diabetes-correcting and antioxidant effects of grape pomace extract rich in natural complex of polyphenols

Background. The positive health effects of polyphenols have led to an increased scientific interest in these natural compounds over the past decade. Many studies confirm the effectiveness of polyphenols as additional therapy in diabetes, especially due to the sugar-lowering effect of polyphenols. The aim of the research was to investigate the morphological and functional state of peripheral blood erythrocytes and the indices of oxidative stress in the liver of rats with experimental diabetes and after the administration of grape pomace extract rich in natural complex of polyphenols. Materials and Methods. We obtained grape pomace extract, which contains a variety of polyphenolic compounds. Rats of the following groups were used in the experiments: control animals, animals treated with grape pomace extract rich in natural complex of polyphenols for 14 days, animals with streptozotocin-induced diabetes mellitus, and animals with streptozotocin-induced diabetes mellitus treated with grape pomace extract rich in natural complex of polyphenols for 14 days. The number of erythrocytes and reticulocytes, the concentration of hemoglobin and glycated hemoglobin were determined in the peripheral blood of rats. The activities of catalase, superoxide dismutase and the content of thiobarbituric acid-reactive substance and carbonyl groups of proteins were determined in the liver tissues of rats. Results. The study has shown an increase in the number of erythrocytes and the level of hemoglobin, a decrease in the level of glycated hemoglobin and the number of reticulocytes in the peripheral blood of rats after administration of grape pomace extract rich in natural complex of polyphenols to rats with experimental diabetes. A decrease in the content of thiobarbituric acid-reactive substance and the content of carbonyl groups of proteins of neutral and basic character and an increase in the activity of catalase and superoxide dismutase in liver tissues were found under the same conditions. Conclusions. The results indicate that the extract of the natural complex of polyphenols is capable of correcting the morphological and functional state of erythrocytes, as well as improving the activity of antioxidant enzymes and the content of marker molecules of oxidative stress in hepatocytes of rats under experimental diabetes mellitus.

Beneficial health effects of polyphenols metabolized by fermentation.

Beneficial health effects of polyphenols metabolized by fermentation.

Systematic Bioinformatic Analyses of Nutrigenomic Modifications by Polyphenols Associated with Cardiometabolic Health in Humans-Evidence from Targeted Nutrigenomic Studies.

Cardiometabolic disorders are among the leading causes of mortality in the human population. Dietary polyphenols exert beneficial effects on cardiometabolic health in humans. Molecular mechanisms, however, are not completely understood. Aiming to conduct in-depth integrative bioinformatic analyses to elucidate molecular mechanisms underlying the protective effects of polyphenols on cardiometabolic health, we first conducted a systematic literature search to identify human intervention studies with polyphenols that demonstrate improvement of cardiometabolic risk factors in parallel with significant nutrigenomic effects. Applying the predefined inclusion criteria, we identified 58 differentially expressed genes at mRNA level and 5 miRNAs, analyzed in peripheral blood cells with RT-PCR methods. Subsequent integrative bioinformatic analyses demonstrated that polyphenols modulate genes that are mainly involved in the processes such as inflammation, lipid metabolism, and endothelial function. We also identified 37 transcription factors that are involved in the regulation of polyphenol modulated genes, including RELA/NFKB1, STAT1, JUN, or SIRT1. Integrative bioinformatic analysis of mRNA and miRNA-target pathways demonstrated several common enriched pathways that include MAPK signaling pathway, TNF signaling pathway, PI3K-Akt signaling pathway, focal adhesion, or PPAR signaling pathway. These bioinformatic analyses represent a valuable source of information for the identification of molecular mechanisms underlying the beneficial health effects of polyphenols and potential target genes for future nutrigenetic studies.

Anti-Obesity Effects of Polyphenol Intake: Current Status and Future Possibilities.

The prevalence of obesity has steadily increased worldwide over the past three decades. The conventional approaches to prevent or treat this syndrome and its associated complications include a balanced diet, an increase energy expenditure, and lifestyle modification. Multiple pharmacological and non-pharmacological interventions have been developed with the aim of improving obesity complications. Recently, the use of functional foods and their bioactive components is considered a new approach in the prevention and management of this disease. Due to their biological properties, polyphenols may be considered as nutraceuticals and food supplement recommended for different syndromes. Polyphenols are a class of naturally-occurring phytochemicals, some of which have been shown to modulate physiological and molecular pathways involved in energy metabolism. Polyphenols could act in the stimulation of β-oxidation, adipocyte differentiation inhibition, counteract oxidative stress, etc. In this narrative review, we considered the association between polyphenols (resveratrol, quercetin, curcumin, and some polyphenolic extracts) and obesity, focusing on human trials. The health effects of polyphenols depend on the amount consumed and their bioavailability. Some results are contrasting, probably due to the various study designs and lengths, variation among subjects (age, gender, ethnicity), and chemical forms of the dietary polyphenols used. But, in conclusion, the data so far obtained encourage the setting of new trials, necessary to validate benefic role of polyphenols in obese individuals.

Poyphenols – between neuroprotection and neurotoxicity

Polyphenols are a group of secondary metabolites found in a wide variety of foods, such as fruits, vegetables, wine, tea, olive oil and chocolate. These compounds, in addition to their antioxidant activity, also possess strong anti-inflammatory properties. Numerous studies have therefore confirmed their potential role in preventing and treating various pathological conditions associated with oxidative stress and inflammation. Among these, the most prevalent ones include cancer, cardiovascular and neurodegenerative diseases, which globally represent one of the main causes of death and are therefore a major social and financial burden, Numerous studies have clarified some of the mechanisms of action of polyphenols as antioxidant and anti-inflammatory compounds and have clarified their role in treatment/prevention of certain conditions. It was shown that polyphenols could be used both as protective/prophylactic compounds and as therapeutic compounds. A sufficient amount can be achieved either by consuming a diet, rich in polyphenols, or in the form of dietary supplements and nevertheless with formulations such as nutraceuticals. The health effects of polyphenols depend not only on the amount consumed but also on their bioavailability. However, their overconsumption can cause safety concerns due to the accumulation of these molecules in the body, especially considering that the regulatory legislation in the field of dietary supplements is rather loose. Therefore, this review focuses on the major positive effects of natural-derived polyphenols, and addresses potential safety concerns, with a focus on neuroprotection and neurotoxicity.

Polyphenols from Food and Natural Products: Neuroprotection and Safety.

Polyphenols are naturally occurring micronutrients that are present in many food sources. Besides being potent antioxidants, these molecules may also possess anti-inflammatory properties. Many studies have highlighted their potential role in the prevention and treatment of various pathological conditions connected to oxidative stress and inflammation (e.g., cancer, and cardiovascular and neurodegenerative disorders). Neurodegenerative diseases are globally one of the main causes of death and represent an enormous burden in terms of human suffering, social distress, and economic costs. Recent data expanded on the initial antioxidant-based mechanism of polyphenols’ action by showing that they are also able to modulate several cell-signaling pathways and mediators. The proposed benefits of polyphenols, either as protective/prophylactic substances or as therapeutic molecules, may be achieved by the consumption of a natural polyphenol-enriched diet, by their use as food supplements, or with formulations as pharmaceutical drugs/nutraceuticals. It has also been proved that the health effects of polyphenols depend on the consumed amount and their bioavailability. However, their overconsumption may raise safety concerns due to the accumulation of high levels of these molecules in the organism, particularly if we consider the loose regulatory legislation regarding the commercialization and use of food supplements. This review addresses the main beneficial effects of food polyphenols, and focuses on neuroprotection and the safety issues related to overconsumption.

Polyphenol Consumption on Human Bile Acids Metabolism: Preliminary Data of Bile Acid Profiles in Human Biological Samples (P06-131-19)

ObjectivesBile acids (BAs) play a critical role in regulating human health through the activation of BAs receptor farnesoid X receptor (FXR) and membrane G protein coupled bile acid receptor-1 (TGR5). We aimed to develop methods to characterize BAs and their metabolites in human biological samples and characterize changes in BAs profile after chronic polyphenol consumption to help guide investigations on the potential health effects of polyphenols via BAs metabolism. MethodsPlasma, fecal and urine samples from two human studies that included berry intake were used for developing qualitative analysis of BAs using ultra high-performance liquid chromatography (UHPLC) coupled with electrospray ionization quadrupole time of flight (QTOF). The compounds were identified based on the exact mass, fragmentation pattern, available reference standards and database search. To investigate the effect of chronic polyphenol consumption on BAs composition, pooled plasma samples (fasting and postprandial 2 h, n = 6) from a chronic (45 and 90 days) strawberry supplementation study (24 g freeze dried/day) with an older population were analyzed. ResultsAmong 106 BAs and their metabolites which were tentatively identified in the samples used for method development, 70, 55, and 47 BAs species were characterized in plasma, feces and urine samples, respectively. The qualitative analysis of BAs in plasma samples from subjects following the strawberry consumption protocol detected 8 primary and 31 secondary BAs. After 90-days strawberry supplementation, two secondary BAs–glycolithocholic acid and 9(11), (5β)-cholenic acid-3α, 12α-diol were decreased to undetectable levels in the pooled fasting sample and the FRX/TGR5 agonists, including chenodeoxycholic acid, deoxycholic acid, cholic acid, glycodeoxycholic acid and taurocholic acid, showed increasing peak areas at 2 h postprandial compared to fasting. ConclusionsThe changes in BAs profiles in fasting and postprandial plasma samples after chronic strawberry feeding suggest that strawberry polyphenols may alter BAs metabolism and the FXR/TGR5 signaling. Funding SourcesThis work was funded by the California Strawberry Commission, USDA Intramural Funds and various donor funds to the Center for Nutrition Research, IIT.

Relationship between Mediterranean Dietary Polyphenol Intake and Obesity.

Obesity is a multifactorial and complex disease defined by excess of adipose mass and constitutes a serious health problem. Adipose tissue acts as an endocrine organ secreting a wide range of inflammatory adipocytokines, which leads to systemic inflammation, insulin resistance, and metabolic disorders. The traditional Mediterranean diet is characterized by a high phenolic-rich foods intake, including extra-virgin olive oil, nuts, red wine, vegetables, fruits, legumes, and whole-grain cereals. Evidence for polyphenols’ effect on obesity and weight control in humans is inconsistent and the health effects of polyphenols depend on the amount consumed and their bioavailability. The mechanisms involved in weight loss in which polyphenols may have a role are: activating β-oxidation; a prebiotic effect for gut microbiota; inducing satiety; stimulating energy expenditure by inducing thermogenesis in brown adipose tissue; modulating adipose tissue inhibiting adipocyte differentiation; promoting adipocyte apoptosis and increasing lipolysis. Even though the intake of some specific polyphenols has been associated with body weight changes, there is still no evidence for the effects of total polyphenols or some polyphenol subclasses in humans on adiposity.

I7 Interaction of polyphenols with gut microbiota; understanding the health effects of polyphenols

(Poly) Phenols constitute a large family of phytochemicals with high chemical diversity that are known to be active principles of plant-derived nutraceuticals and herbal medicinal products. Their pharmacological activity, however, is difficult to demonstrate due to their mild physiological effects, and to the large inter-individual variability observed. Many polyphenols have little bioavailability and reach the colon almost unaltered. There they encounter the gut microbes resulting in a two-way interaction in which polyphenols modulate the gut microbiota composition, and the intestinal microbes catabolize the ingested phenolic compounds to release metabolites that are often more active and better absorbed than the native phenolic compounds. The type and quantity of the polyphenol metabolites produced in humans depend on the gut microbiota composition and function, and different metabotypes have been identified. However, not all the metabolites have the same biological activity, and therefore the final health effects of dietary polyphenols depend on the gut microbiota composition. Stratification in clinical trials according to individuals’ metabotypes is necessary to fully understand the health effects of phenolic compounds. Here we present and discuss the most significant and updated knowledge regarding the reciprocal interrelation of the gut microbiota with dietary polyphenols as a key factor that modulates the health effects of these compounds. The review will focus in those polyphenols that are known to be metabolized by gut microbiota resulting in bioactive metabolites.

Exploring Possible Health Effects of Polyphenols in Foods

This article, part 2 of the series on polyphenols, examines some of the evidence for the roles of specific foods rich in polyphenols in reducing the risk of 3 common health conditions: urinary tract infections, cardiovascular disease, and type 2 diabetes. Although the research remains emerging rather than settled science, polyphenols may have beneficial health effects. Those who follow the recommended eating patterns of the Dietary Guidelines 2015–2020 can be sure that they are receiving plenty of these plant bioactives.

Feijoada whole meal shows higher in vitro antioxidant activity than combination of individual ingredients

Beneficial health effects of polyphenols depend on their daily consumption which may reflect the dietary pattern of a population. In this way, the objective of this study was to evaluate the in vitro and cellular antioxidant activity of Feijoada whole meal compared to its individual ingredients. Kale was the ingredient with the highest total phenolic content and in vitro antioxidant activity. Black beans and rice were the main sources of bound phenolics, accounting for approximately 50% of the total phenolic content in each one. Black beans were also the main providers of phenolics in the feijoada whole meal. Dose dependent effect was observed for black beans, kale, and orange when cellular antioxidant activity (CAA) was measured, being orange the ingredient with the lowest EC50 value. Antiproliferative activity using HepG2 cells was only observed for the orange and kale extracts at 60 mg/ml. Feijoada whole meal extract and the combination of individual ingredients had no effect in this cancer cell line compared to the control. The interaction among ingredients composing a meal as for whole meals itself should be used more often as an approach to understand the relationship between dietary pattern and health benefits.

Unravelling of the health effects of polyphenols is a complex puzzle complicated by metabolism

Plant metabolism creates complex mixtures of polyphenols in plant foods. Epidemiology and human trials reduced this complexity, by studying specific foods; subclasses of polyphenols; individual polyphenols, or total antioxidant capacity (TAC). This implies the following assumptions: (1) a limited number of potent polyphenols exists; (2) well-defined natural potent mixtures of polyphenols exist; (3) polyphenols share a common biological activity (e.g. antioxidant activity). To find potent polyphenols (1st assumption), in vitro screening has been widely applied, but most published results are of limited use because metabolism, changing biological activity profoundly, has frequently not been considered. The abundant anecdotal evidence for natural potent mixtures of polyphenols (2nd assumption) on the internet is very hard to verify. Additionally, cross-cultural studies have revealed the potency of e.g. cocoa. Polyphenols share the antioxidant phenolic group which inspired researchers to measure their antioxidant activity, thus greatly reducing complexity (3rd assumption). Unfortunately, the elegant antioxidant hypothesis has to be rejected, because poor absorption and extensive metabolism annihilate any contribution to the endogenous body antioxidants. In conclusion, the above assumptions are hard to verify, and no quick answers are to be expected. Future research should focus on structure–activity relations at nanomolar levels and explore metabolomics.

Phenol-Explorer 2.0: a major update of the Phenol-Explorer database integrating data on polyphenol metabolism and pharmacokinetics in humans and experimental animals

Phenol-Explorer, launched in 2009, is the only comprehensive web-based database on the content in foods of polyphenols, a major class of food bioactives that receive considerable attention due to their role in the prevention of diseases. Polyphenols are rarely absorbed and excreted in their ingested forms, but extensively metabolized in the body, and until now, no database has allowed the recall of identities and concentrations of polyphenol metabolites in biofluids after the consumption of polyphenol-rich sources. Knowledge of these metabolites is essential in the planning of experiments whose aim is to elucidate the effects of polyphenols on health. Release 2.0 is the first major update of the database, allowing the rapid retrieval of data on the biotransformations and pharmacokinetics of dietary polyphenols. Data on 375 polyphenol metabolites identified in urine and plasma were collected from 236 peer-reviewed publications on polyphenol metabolism in humans and experimental animals and added to the database by means of an extended relational design. Pharmacokinetic parameters have been collected and can be retrieved in both tabular and graphical form. The web interface has been enhanced and now allows the filtering of information according to various criteria. Phenol-Explorer 2.0, which will be periodically updated, should prove to be an even more useful and capable resource for polyphenol scientists because bioactivities and health effects of polyphenols are dependent on the nature and concentrations of metabolites reaching the target tissues. The Phenol-Explorer database is publicly available and can be found online at http://www.phenol-explorer.eu.Database URL: http://www.phenol-explorer.eu

Bioanalysis Young Investigator: Alexander Medina-Remón

Supervisor's supporting comments Alex Medina joined my research group, Natural Antioxidants, in January 2006 to start his PhD program. He has been working intensively and efficiently on several projects; initially for his thesis he developed a new bioanalytical methodology to quantify phenols in urine (Medina-Remón A et al. 2009) to correlate with the hypertension prevention in the PREDIMED study ( www.predimed.org ). Thanks to this new bioanalytical method, we are currently starting collaboration projects with different research centers. In addition, he has been working on other research projects on tomatoes, grapes, citric fruits and wine. Medina is helpful whenever needed and efficient. He has shown himself to be responsible, well-prepared, intelligent, organized and to have very good teaching skills. Moreover, he is patient and able to solve problems calmly, but at the same time, he is enthusiastic about what he does and can transmit this enthusiasm to his colleagues. He is really a thoughtful scientist. I have now contracted him as a Postdoctoral researcher. His responsibilities include leading several master's students and he is writing several papers on the health effects of polyphenols using his method.

Novel approaches for analysing gut microbes and dietary polyphenols: challenges and opportunities

Polyphenols, ubiquitously present in the food we consume, may modify the gut microbial composition and/or activity, and moreover, may be converted by the colonic microbiota to bioactive compounds that influence host health. The polyphenol content of fruit and vegetables and derived products is implicated in some of the health benefits bestowed on eating fruit and vegetables. Elucidating the mechanisms behind polyphenol metabolism is an important step in understanding their health effects. Yet, this is no trivial assignment due to the diversity encountered in both polyphenols and the gut microbial composition, which is further confounded by the interactions with the host. Only a limited number of studies have investigated the impact of dietary polyphenols on the complex human gut microbiota and these were mainly focused on single polyphenol molecules and selected bacterial populations. Our knowledge of gut microbial genes and pathways for polyphenol bioconversion and interactions is poor. Application of specific in vitro or in vivo models mimicking the human gut environment is required to analyse these diverse interactions. A particular benefit can now be gained from next-generation analytical tools such as metagenomics and metatranscriptomics allowing a wider, more holistic approach to the analysis of polyphenol metabolism. Understanding the polyphenol-gut microbiota interactions and gut microbial bioconversion capacity will facilitate studies on bioavailability of polyphenols in the host, provide more insight into the health effects of polyphenols and potentially open avenues for modulation of polyphenol bioactivity for host health.

Neuroprotective effects of naturally occurring polyphenols on quinolinic acid‐induced excitotoxicity in human neurons

Quinolinic acid (QUIN) excitotoxicity is mediated by elevated intracellular Ca(2+) levels, and nitric oxide-mediated oxidative stress, resulting in DNA damage, poly(ADP-ribose) polymerase (PARP) activation, NAD(+) depletion and cell death. We evaluated the effect of a series of polyphenolic compounds [i.e. epigallocatechin gallate (EPCG), catechin hydrate, curcumin, apigenin, naringenin and gallotannin] with antioxidant properties on QUIN-induced excitotoxicity on primary cultures of human neurons. We showed that the polyphenols, EPCG, catechin hydrate and curcumin can attenuate QUIN-induced excitotoxicity to a greater extent than apigenin, naringenin and gallotannin. Both EPCG and curcumin were able to attenuate QUIN-induced Ca(2+) influx and neuronal nitric oxide synthase (nNOS) activity to a greater extent compared with apigenin, naringenin and gallotannin. Although Ca(2+) influx was not attenuated by catechin hydrate, nNOS activity was reduced, probably through direct inhibition of the enzyme. All polyphenols reduced the oxidative effects of increased nitric oxide production, thereby reducing the formation of 3-nitrotyrosine and poly (ADP-ribose) polymerase activity and, hence, preventing NAD(+) depletion and cell death. In addition to the well-known antioxidant properties of these natural phytochemicals, the inhibitory effect of some of these compounds on specific excitotoxic processes, such as Ca(2+) influx, provides additional evidence for the beneficial health effects of polyphenols in excitable tissue, particularly within the central nervous system.

Molecular Targets of Dietary Polyphenols with Anti-inflammatory Properties

There is persuasive epidemiological and experimental evidence that dietary polyphenols have anti-inflammatory activity. Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) have long been used to combat inflammation. Recently, cyclooxygenase (COX) inhibitors have been developed and recommended for treatment of rheumatoid arthritis (RA) and osteoarthritis (OA). However, two COX inhibitors have been withdrawn from the market due to unexpected side effects. Because conventional therapeutic and surgical approaches have not been able to fully control the incidence and outcome of many inflammatory diseases, there is an urgent need to find safer compounds and to develop mechanism-based approaches for the management of these diseases. Polyphenols are found in many dietary plant products, including fruits, vegetables, beverages, herbs, and spices. Several of these compounds have been found to inhibit the inflammation process as well as tumorigenesis in experimental animals; they can also exhibit potent biological properties. In addition, epidemiological studies have indicated that populations who consume foods rich in specific polyphenols have lower incidences of inflammatory disease. This paper provides an overview of the research approaches that can be used to unravel the biology and health effects of polyphenols. Polyphenols have diverse biological effects, however, this review will focus on some of the pivotal molecular targets that directly affect the inflammation process.

Polyphenols and disease risk in epidemiologic studies2–3

Plant polyphenols, a large group of natural antioxidants, are serious candidates in explanations of the protective effects of vegetables and fruits against cancer and cardiovascular diseases. Epidemiologic studies are useful for evaluation of the human health effects of long-term exposure to physiologic concentrations of polyphenols, but reliable data on polyphenol contents of foods are still scarce. The aim of this review is to summarize available epidemiologic data on the health effects of polyphenols, focusing on the flavonoid subclasses of flavonols, flavones, and catechins and on lignans. Data obtained to date suggest beneficial effects of both flavonoids and lignans on cardiovascular diseases but not on cancer, with the possible exception of lung cancer. There is a need for more research on stroke and lung diseases such as asthma and chronic obstructive pulmonary disease. Most studies to date have included only flavonols and flavones. With data becoming available for other polyphenols, these compounds should be included in future studies. Careful design of prospective studies is important to offset some of the major drawbacks of epidemiologic studies, including residual confounding (by smoking and other dietary factors) and exposure assessment.

Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies

Polyphenols are abundant micronutrients in our diet, and evidence for their role in the prevention of degenerative diseases is emerging. Bioavailability differs greatly from one polyphenol to another, so that the most abundant polyphenols in our diet are not necessarily those leading to the highest concentrations of active metabolites in target tissues. Mean values for the maximal plasma concentration, the time to reach the maximal plasma concentration, the area under the plasma concentration-time curve, the elimination half-life, and the relative urinary excretion were calculated for 18 major polyphenols. We used data from 97 studies that investigated the kinetics and extent of polyphenol absorption among adults, after ingestion of a single dose of polyphenol provided as pure compound, plant extract, or whole food/beverage. The metabolites present in blood, resulting from digestive and hepatic activity, usually differ from the native compounds. The nature of the known metabolites is described when data are available. The plasma concentrations of total metabolites ranged from 0 to 4 mumol/L with an intake of 50 mg aglycone equivalents, and the relative urinary excretion ranged from 0.3% to 43% of the ingested dose, depending on the polyphenol. Gallic acid and isoflavones are the most well-absorbed polyphenols, followed by catechins, flavanones, and quercetin glucosides, but with different kinetics. The least well-absorbed polyphenols are the proanthocyanidins, the galloylated tea catechins, and the anthocyanins. Data are still too limited for assessment of hydroxycinnamic acids and other polyphenols. These data may be useful for the design and interpretation of intervention studies investigating the health effects of polyphenols.

Microbial Aromatic Acid Metabolites Formed in the Gut Account for a Major Fraction of the Polyphenols Excreted in Urine of Rats Fed Red Wine Polyphenols

The health effects of dietary polyphenols might be explained by both intact compounds and their metabolites formed either in the tissues or in the colon by the microflora. The quantitative importance and biological activities of the microbial metabolites have seldom been examined in vivo. We measured the microbial metabolites formed in four groups of rats (n = 8) fed for 8 d a diet supplemented with 0.12 g/100 g catechin, 0.25 or 0.50 g/100 g red wine powder containing proanthocyanidins, phenolic acids, flavanols, anthocyanins and flavonols or an unsupplemented diet. Fourteen aromatic acid metabolites were assayed in urine collected for 24 h by an HPLC-electrospray ionization (ESI)-mass spectrometry (MS)-MS method. The three main metabolites formed from the catechin diet were 3-hydroxyphenylpropionic acid, 3-hydroxybenzoic acid and 3-hydroxyhippuric acid. Their total urinary excretion accounted for 4.7 g/100 g of the catechin ingested and that of intact catechins for 45.3 g/100 g. For wine polyphenols, the same microbial metabolites as observed for the catechin diet were identified in urine along with hippuric, p-coumaric, vanillic, 4-hydroxybenzoic and 3-hydroxyphenylacetic acids. All together, these aromatic acids accounted for 9.2 g/100 g of the total wine polyphenols ingested and intact catechins for only 1.2 g/100 g. The higher excretion of aromatic acids by rats fed wine polyphenols is likely due to their poor absorption in the proximal part of the gut. Some of the microbial metabolites still bear a reducing phenolic group and should also prevent oxidative stress in inner tissues. More attention should be given in the future to these microbial metabolites and their biological properties to help explain the health effects of polyphenols that are not easily absorbed through the gut barrier.