Inter-individual variability in the production of flavan-3-ol colonic metabolites: preliminary elucidation of urinary metabotypes

The bioavailability of polyphenols following acute consumption of pigmented barley and wheat

Polyphenols from pigmented cereal grains exert health-promoting effects but data on their bioavailability are limited. This study investigated the acute bioavailability of polyphenols from the consumption of pigmented whole grain cereal porridges, including purple barley (PB), purple wheat (PW), and blue wheat (BW), compared to a non-pigmented regular wheat (RW). A secondary objective was to assess their effects on plasma antioxidant and inflammatory status postprandially. Phenolic characterisation and antioxidant profiling were performed on extracts from the cooked cereals. Three healthy individuals consumed 200 g of a cereal in a 4-way crossover trial with a one-week washout in between meals. Blood samples were collected at fasting baseline, 30 minutes, 1 hour, 2 hours and 4 hours postprandially. Urine samples were collected at fasting baseline and the 4-hour time point. Pigmented grains exhibited significantly higher phenolic content and antioxidant capacity (p < 0.001) compared to RW. This suggests that pigmented grains may be a better source of polyphenols and potentially offer greater health benefits. However, polyphenol bioavailability following pigmented grain consumption was reduced (less than 6%), suggesting that a substantial fraction remained unabsorbed. The bioavailable phenolic compounds detected included phenolic acids (protocatechuic and caffeic acid), hippuric acid and other phenolic metabolites. Interpersonal variability and the type of grain consumed had an impact on the absorption and excretion of phenolic acids. Only PW consumption resulted in significant (p < 0.01) increases in plasma antioxidant status but no short-term impact on the inflammatory status. This study provides valuable insights into the complex dynamics of polyphenol bioavailability from pigmented cereal consumption and warrants further investigation.

Metabolic profiling of (poly)phenolic compounds in mouse urine following consumption of hull-less and purple-grain barley

The present study attempted for the first time to investigate the metabolic fate of (poly)phenolic compounds provided by a hull-less and purple grain barley genotype biofortified in anthocyanins. Balb/c mice were supplemented either with standard purified diet (SD) or whole-grain barley supplemented diet (WGB) for six weeks. Subsequently, (poly)phenolic metabolites were determined in urine samples by UPLC-MS/MS, and the principal metabolic pathways were elucidated. Thirty-nine (poly)phenolics compounds were identified in WGB which were distributed between the free (58%) and bound (42%) fractions, encompassing anthocyanins, phenolic acids, flavan-3-ols and flavones. Upon WGB intake, forty-two (poly)phenolic metabolites were identified, predominantly comprising phase-II sulphate, glucuronide, and/or methylated conjugates, along with colonic catabolites. Noteworthy metabolites included peonidin-3-O-glucuronide, peonidin-3-O-6''-O-malonylglucoside, and peonidin-3-O-glucoside among anthocyanins; hydroxyphenylpropanoic acid-O-sulphate among phenolic acids; and 5-(3',4'-dihydroxyphenyl)-γ-valerolactone-O-sulphate among flavan-3-ols. Metabolites like phenylpropionic, phenylacetic, hydroxybenzoic, and hippuric acids were found in both WGB and SD groups, with higher levels after barley consumption, indicating both endogenous and polyphenolic metabolism origins. Overall, this study offers valuable insights into the metabolism of (poly)phenols in purple barley, setting the stage for future investigations into the health benefits linked to the consumption of purple grain barley.

Evaluating birch leaf tea as a functional herbal beverage: Beneficial impact on the urinary tract, and metabolism in human organism

Herbal teas are considered as a potential constituent of novel functional beverages consumed daily. One of the commonly used herbal teas is silver birch (Betula pendula Roth) leaf infusion, traditionally used in urinary tract diseases. In this study, the potential of birch leaf infusion as a functional beverage, emphasizing its active ingredients' bioavailability, anti-inflammatory, and antiadhesive properties concerning urinary tract health, was investigated. A complex approach was proposed, which included phytochemical screening, bioavailability, gut microbiota biotransformation, and an in vivo test for urine metabolomics assessment. The bioassays confirmed significant anti-inflammatory (interleukins IL-6 and IL-8 secretion) and anti-adhesive (Uropathogenic Escherichia coli and T24 bladder cells) activities. The high-resolution mass spectrometry metabolomics studies linked gut microbiota metabolites and the metabolites present in the urine. Several metabolites connected with phenolics' consumption were detected in the urine, e.g., glucuronides and sulfates of caffeic acid and dihydroxyphenyl-γ-valerolactones. Based on the presented results, the birch leaf should be considered useful in designing functional beverages, especially targeted to the groups at high risk of urinary diseases.

Factors driving the inter-individual variability in the metabolism and bioavailability of (poly)phenolic metabolites: A systematic review of human studies

This systematic review provides an overview of the available evidence on the inter-individual variability (IIV) in the absorption, distribution, metabolism, and excretion (ADME) of phenolic metabolites and its determinants. Human studies were included investigating the metabolism and bioavailability of (poly)phenols and reporting IIV. One hundred fifty-three studies met the inclusion criteria. Inter-individual differences were mainly related to gut microbiota composition and activity but also to genetic polymorphisms, age, sex, ethnicity, BMI, (patho)physiological status, and physical activity, depending on the (poly)phenol sub-class considered. Most of the IIV has been poorly characterised. Two major types of IIV were observed. One resulted in metabolite gradients that can be further classified into high and low excretors, as seen for all flavonoids, phenolic acids, prenylflavonoids, alkylresorcinols, and hydroxytyrosol. The other type of IIV is based on clusters of individuals defined by qualitative differences (producers vs. non-producers), as for ellagitannins (urolithins), isoflavones (equol and O-DMA), resveratrol (lunularin), and preliminarily for avenanthramides (dihydro-avenanthramides), or by quali-quantitative metabotypes characterized by different proportions of specific metabolites, as for flavan-3-ols, flavanones, and even isoflavones. Future works are needed to shed light on current open issues limiting our understanding of this phenomenon that likely conditions the health effects of dietary (poly)phenols.

Using Targeted Metabolomics to Unravel Phenolic Metabolites of Plant Origin in Animal Milk

Milk holds a high nutritional value and is associated with diverse health benefits. The understanding of its composition of (poly)phenolic metabolites is limited, which necessitates a comprehensive evaluation of the subject. This study aimed at analyzing the (poly)phenolic profile of commercial milk samples from cows and goats and investigating their sterilization treatments, fat content, and lactose content. Fingerprinting of phenolic metabolites was achieved by using ultra-high-performance liquid chromatography coupled with triple-quadrupole mass spectrometry (UHPLC-QqQ-MS/MS). Two hundred and three potential microbial and phase II metabolites of the main dietary (poly)phenols were targeted. Twenty-five metabolites were identified, revealing a diverse array of phenolic metabolites in milk, including isoflavones and their microbial catabolites equol and O-desmethylangolensin, phenyl-γ-valerolactones (flavan-3-ol microbial catabolites), enterolignans, urolithins (ellagitannin microbial catabolites), benzene diols, and hippuric acid derivates. Goat's milk contained higher concentrations of these metabolites than cow's milk, while the sterilization process and milk composition (fat and lactose content) had minimal impact on the metabolite profiles. Thus, the consumption of goat's milk might serve as a potential means to supplement bioactive phenolic metabolites, especially in individuals with limited production capacity. However, further research is needed to elucidate the potential health effects of milk-derived phenolics.

(Poly)phenol-related gut metabotypes and human health: an update

Dietary (poly)phenols have received great interest due to their potential role in the prevention and management of non-communicable diseases. In recent years, a high inter-individual variability in the biological response to (poly)phenols has been demonstrated, which could be related to the high variability in (poly)phenol gut microbial metabolism existing within individuals. An interplay between (poly)phenols and the gut microbiota exists, with (poly)phenols being metabolised by the gut microbiota and their metabolites modulating gut microbiota diversity and composition. A number of (poly)phenol metabolising phenotypes or metabotypes have been proposed, however, potential metabotypes for most (poly)phenols have not been investigated, and the relationship between metabotypes and human health remains ambiguous. This review presents updated knowledge on the reciprocal interaction between (poly)phenols and the gut microbiome, associated gut metabotypes, and subsequent impact on human health.

Assessing the Gut Microbiota's Ability to Metabolize Oligomeric and Polymeric Flavan-3-ols from Aronia and Cranberry

Clinical trials investigating the health effects of flavan-3-ols yield heterogeneous results due to interindividual variability in the gut microbiota metabolism. In fact, different groups in the population have similar metabolic profiles following (-)-epicatechin and (+)-catechin gut microbial metabolism and can be regrouped into so-called metabotypes. In this study, the capacity of 34 donors to metabolize polymeric B-type flavan-3-ols from aronia and oligomeric A-type flavan-3-ols from cranberry is investigated by in vitro fecal batch fermentations. Less than 1% of the flavan-3-ols from both sources are converted into microbial metabolites, such as phenyl-γ-valerolactones (PVLs). To further confirm this result, gut microbial metabolites from flavan-3-ols are quantified in urine samples collected from participants, before and after a 4-day supplementation of cranberry extract providing 82.3 mg of flavan-3-ols per day. No significant difference is observed in the urinary excretion of flavan-3-ols microbial metabolites. Hence, it demonstrates by both in vitro and in vivo approaches that flavan-3-ols from aronia and cranberry are poorly degraded by the gut microbiota. The beneficial health impacts of these molecules likely stem from their capacity to affect gut microbiota and their interactions with the gut epithelium, rather than from their breakdown into smaller metabolites.

Characterization of the Interindividual Variability Associated with the Microbial Metabolism of (-)-Epicatechin

Although the relationship between gut microbiota and flavan-3-ol metabolism differs greatly between individuals, the specific metabolic profiles, known as metabotypes, have not yet been clearly defined. In this study, fecal batch fermentations of 34 healthy donors inoculated with (-)-epicatechin were stratified into groups based on their conversion rate of (-)-epicatechin and their quali-quantitative metabolic profile. Fast and slow converters of (-)-epicatechin, high producers of 1-(3'-hydroxyphenyl)-3-(2″,4″,6″-trihydroxyphenyl)-propan-2-ol (3-HPP-2-ol) and 5-(3',4'-dihydroxyphenyl)-γ-valerolactone (3,4-DHPVL) were identified. Fecal microbiota analysis revealed that fast conversion of (-)-epicatechin was associated with short-chain fatty acid (SCFA)-producing bacteria, such as Faecalibacterium spp. and Bacteroides spp., and higher levels of acetate, propionate, butyrate, and valerate were observed for fast converters. Other bacteria were associated with the conversion of 1-(3',4'-dihydroxyphenyl)-3-(2″,4″,6″-trihydroxyphenyl)-propan-2-ol into 3-HPP-2-ol (Lachnospiraceae UCG-010 spp.) and 3,4-DHPVL (Adlercreutzia equolifaciens). Such stratification sheds light on the mechanisms of action underlying the high interindividual variability associated with the health benefits of flavan-3-ols.

Performance of Urinary Phenyl-γ-Valerolactones as Biomarkers of Dietary Flavan-3-ol Exposure

BACKGROUND

Phenyl-γ-valerolactones (PVLs) have been identified as biomarkers of dietary flavan-3-ol exposure, although their utility requires further characterization.

OBJECTIVES

We investigated the performance of a range of PVLs as biomarkers indicative of flavan-3-ol intake.

METHODS

We report the results of 2 companion studies: a 5-way randomized crossover trial (RCT) and an observational cross-sectional study. In the RCT (World Health Organization, Universal Trial Number: U1111-1236-7988), 16 healthy participants consumed flavan-3-ol-rich interventions (of apple, cocoa, black tea, green tea, or water [control]) for 1 d each. First morning void samples and 24-h urine samples were collected with diet standardized throughout. For each participant, 1 intervention period was extended (to 2 d) to monitor PVL kinetics after repeat exposure. In the cross-sectional study, 86 healthy participants collected 24-h urine samples, and concurrent weighed food diaries from which flavan-3-ol consumption was estimated using Phenol-Explorer. A panel of 10 urinary PVLs was quantified using liquid chromatography tandem mass spectrometry.

RESULTS

In both studies, 2 urinary PVLs [5-(3'-hydroxyphenyl)-γ-valerolactone-4'-sulfate and putatively identified 5-(4'-hydroxyphenyl)-γ-valerolactone-3'-glucuronide] were the principal compounds excreted (>75%). In the RCT, the sum of these PVLs was significantly higher than the water (control) after each intervention; individually, there was a shift from sulfation toward glucuronidation as the total excretion of PVLs increased across the different interventions. In the extended RCT intervention period, no accumulation of these PVLs was observed after consecutive days of treatment, and after withdrawal of treatment on the third day, there was a return toward negligible PVL excretion. All results were consistent, whether compounds were measured in 24-h urine or first morning void samples. In the observational study, the sum of the principal PVLs correlated dose dependently (Rs = 0.37; P = 0.0004) with dietary flavan-3-ol intake, with similar associations for each individually.

CONCLUSIONS

Urinary 5-(3'-hydroxyphenyl)-γ-valerolactone-4'-sulfate and putatively identified 5-(4'-hydroxyphenyl)-γ-valerolactone-3'-glucuronide are recommended biomarkers for dietary flavan-3-ol exposure.

The gut-derived metabolites as mediators of the effect of healthy nutrition on the brain

Nutrition is now well recognized to be an environmental factor which positively or negatively influences the risk to develop neurological and psychiatric disorders. The gut microbiota has recently been shown to be an important actor mediating the relationship between environmental factors, including nutrition, and brain function. While its composition has been widely studied and associated with the risk of brain diseases, the mechanisms underlying the relationship between the gut and brain diseases remain to be explored. The wide range of bioactive molecules produced by the gut microbiota, called gut-derived metabolites (GDM), represent new players in the gut to brain interactions and become interesting target to promote brain health. The aim of this narrative review is to highlight some GDMs of interest that are produced in response to healthy food consumption and to summarize what is known about their potential effects on brain function. Overall, GDMs represent future useful biomarkers for the development of personalized nutrition. Indeed, their quantification after nutritional interventions is a useful tool to determine individuals' ability to produce microbiota-derived bioactive compounds upon consumption of specific food or nutrients. Moreover, GDMs represent also a new therapeutic approach to counteract the lack of response to conventional nutritional interventions.

Human gut microbiota stratified by (+)-catechin metabolism dynamics reveals colon region-dependent metabolic profile

Catechins have proven to have several health benefits, yet a huge interindividual variability occurs. The metabolic potency of the colonic microbiota towards catechin is a key determinant of this variability. Microbiota from two donors - previously characterized as a fast and a slow converter- were incubated with (+)-catechin in vitro. The robustness of in vitro metabolic profiles was verified by well-fitted human trials. The colon region-dependent and donor-dependent patterns were reflected in both metabolic features and colonic microbiota composition. Upstream and downstream metabolites were mainly detected in the proximal and distal colons, respectively, and were considered important explanatory variables for microbiota clustering in the corresponding colon regions. Higher abundances of two catechin-metabolizing bacteria, Eggerthella and Flavonifractor were found in the distal colon compared to the proximal colon and in slow converter than fast converter. Additionally, these two bacteria were enriched in treatment samples compared to sham treatment samples.

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.

Revisiting the bioavailability of flavan-3-ols in humans: A systematic review and comprehensive data analysis

This systematic review summarizes findings from human studies investigating the different routes of absorption, metabolism, distribution and excretion (ADME) of dietary flavan-3-ols and their circulating metabolites in healthy subjects. Literature searches were performed in PubMed, Scopus and the Web of Science. Human intervention studies using single and/or multiple intake of flavan-3-ols from food, extracts, and pure compounds were included. Forty-nine human intervention studies met inclusion criteria. Up to 180 metabolites were quantified from blood and urine samples following intake of flavan-3-ols, mainly as phase 2 conjugates of microbial catabolites (n = 97), with phenyl-γ-valerolactones being the most representative ones (n = 34). Phase 2 conjugates of monomers and phenyl-γ-valerolactones, the main compounds in both plasma and urine, reached two peak plasma concentrations (C_max) of 260 and 88 nmol/L at 1.8 and 5.3 h (T_max) after flavan-3-ol intake. They contributed to the bioavailability of flavan-3-ols for over 20%. Mean bioavailability for flavan-3-ols was moderate (31 ± 23%, n bioavailability values = 20), and it seems to be scarcely affected by the amount of ingested compounds. While intra- and inter-source differences in flavan-3-ol bioavailability emerged, mean flavan-3-ol bioavailability was 82% (n = 1) and 63% (n = 2) after (-)-epicatechin and nut (hazelnuts, almonds) intake, respectively, followed by 25% after consumption of tea (n = 7), cocoa (n = 5), apples (n = 3) and grape (n = 2). This highlights the need to better clarify the metabolic yield with which monomer flavan-3-ols and proanthocyanidins are metabolized in humans. This work clarified in a comprehensive way for the first time the ADME of a (poly)phenol family, highlighting the pool of circulating compounds that might be determinants of the putative beneficial effects linked to flavan-3-ol intake. Lastly, methodological inputs for implementing well-designed human and experimental model studies were provided.

Effects of green tea catechins and exercise training on body composition parameters

The impact of phytochemicals, as green tea catechins, on body composition measures has become a relevant topic as ongoing epidemiological evidence suggests their potential role in weight loss. Although catechins have been shown to modulate fat and energy metabolism, clinical effects of green tea consumption still remain controversial. Given the role played by physical exercise in weight management, it is important to determine whether the association of catechins and exercise is able to improve outcomes over and above the beneficial effects of exercise alone. Considering that scientific findings on this topic are not entirely consistent, aim of the present review was to assess the current scientific literature regarding the interplay between green tea catechins and exercise in overweight and obese populations. In particular, it was evaluated whether the addition of green tea supplementation to exercise training was able to further improve the exercise-induced changes in body composition parameters.

Catechin Bioavailability Following Consumption of a Green Tea Extract Confection Is Reduced in Obese Persons without Affecting Gut Microbial-Derived Valerolactones

Obesity-related cardiometabolic disorders are driven by inflammation, oxidative stress, and gut dysbiosis. Green tea catechins protect against cardiometabolic disorders by anti-inflammatory, antioxidant, and prebiotic activities. However, whether obesity alters catechin bioavailability remains unknown. We hypothesized that obesity would decrease catechin bioavailability due to altered gut microbiota composition. Obese and healthy persons completed a pharmacokinetics trial in which a confection formulated with green tea extract (GTE; 58% epigallocatechin gallate, 17% epigallocatechin, 8% epicatechin, 6% epicatechin gallate) was ingested before collecting plasma and urine at timed intervals for up to 24 h. Stool samples were collected prior to confection ingestion. Catechins and γ-valerolactones were assessed by LC-MS. Obesity reduced plasma area under the curve (AUC_0-12h) by 24-27% and maximum plasma concentrations by 18-36% for all catechins. Plasma AUC_0-12h for 5'-(3',4'-dihydroxyphenyl)-γ-valerolactone and 5'-(3',4',5'-trihydroxyphenyl)-γ-valerolactone, as well as total urinary elimination of all catechins and valerolactones, were unaffected. ⍺-Diversity in obese persons was lower, while Slackia was the only catechin-metabolizing bacteria that was altered by obesity. Ascorbic acid and diversity metrics were correlated with catechin/valerolactone bioavailability. These findings indicate that obesity reduces catechin bioavailability without affecting valerolactone generation, urinary catechin elimination, or substantially altered gut microbiota populations, suggesting a gut-level mechanism that limits catechin absorption.

Exposure to (Poly)phenol Metabolites after a Fruit and Vegetable Supplement Intake: A Double-Blind, Cross-Over, Randomized Trial

Dietary (poly)phenol intake derived from the daily consumption of five portions of fruits and vegetables could protect against the development of non-communicable diseases. However, the general population does not meet the recommended intake. Supplementation with (poly)phenol-rich ingredients, within a varied and balanced diet, could help in filling this nutritional gap. This study aimed to validate the proof-of-concept of a (poly)phenolic supplementation developed to enhance the daily consumption of potentially bioactive compounds. Oxxynea^® is a (poly)phenol-rich ingredient developed to provide the quantity and the variety corresponding to five-a-day fruit and vegetable consumption. In this double-blind, randomized cross-over study, 10 participants were supplemented with 450 mg of a (poly)phenol-based supplement or a placebo. Pharmacokinetics and urinary excretion profiles were measured for 24 and 48 h, respectively, using UPHLC-MS/MS analysis. The pharmacokinetic profile displayed a triphasic absorption, indicating peaks of circulating metabolites at 1.75 ± 0.25 h, 4.50 ± 0.34 h, 9.50 ± 0.33 h and an average T_max (time of maximal plasma concentration) of 6.90 ± 0.96 h. Similarly, the urinary profile showed maximum metabolite excretion at 3-6 h, 6-10 h and 14-24 h after supplement consumption. Compared to individual metabolites belonging to different (poly)phenolic subfamilies, the total circulating and excreted metabolites showed a reduced coefficient of variation (CV 38%). The overall bioavailability estimated was 27.4 ± 3.4%. Oxxynea^® supplementation may provide a sustained exposure to several (poly)phenolic metabolites and catabolites and reduces the inter-individual variation that could arise from supplementing only one class of (poly)phenol.

A Screening of Native (Poly)phenols and Gut-Related Metabolites on 3D HCT116 Spheroids Reveals Gut Health Benefits of a Flavan-3-ol Metabolite

SCOPE

Epidemiological evidence suggests that a reduced risk of colorectal cancer (CRC) is correlated with high consumption of fruits and vegetables, which are major sources of fiber and phytochemicals, such as flavan-3-ols. However, it remains unknown how these phytochemicals and their specific gut-related metabolites may alter cancer cell behavior.

METHODS AND RESULTS

A focused screening using native (poly)phenols and gut microbial metabolites (GMMs) on 3D HCT116 spheroids is carried out using a high-throughput imaging approach. Dose-responses, IC50 , and long-term exposure are calculated for the most promising native (poly)phenols and GMMs. As a result, this research shows that (poly)phenol catabolites may play a key role in preventing cancer propagation. Indeed, µM concentration levels of (4R)-5-(3',4'-dihydroxyphenyl)-γ-valerolactone significantly decrease spheroid size at early stages of spheroid aggregation and gene expression of matrix metalloproteinases.

CONCLUSION

A chronic exposure to (4R)-5-(3',4'-dihydroxyphenyl)-γ-valerolactone may lead to a reduced CRC risk. Daily intake of monomeric, oligomeric, and polymeric flavan-3-ols may increase the colonic concentrations of this metabolite, and, in turn, this compound may act locally interacting with intestinal epithelial cells, precancerous and cancer cells.

UPEC Colonic-Virulence and Urovirulence Are Blunted by Proanthocyanidins-Rich Cranberry Extract Microbial Metabolites in a Gut Model and a 3D Tissue-Engineered Urothelium

Uropathogenic Escherichia coli (UPEC) ecology-pathophysiology from the gut reservoir to its urothelium infection site is poorly understood, resulting in equivocal benefits in the use of cranberry as prophylaxis against urinary tract infections. To add further understanding from the previous findings on PAC antiadhesive properties against UPEC, we assessed in this study the effects of proanthocyanidins (PAC) rich cranberry extract microbial metabolites on UTI89 virulence and fitness in contrasting ecological UPEC's environments. For this purpose, we developed an original model combining a colonic fermentation system (SHIME) with a dialysis cassette device enclosing UPEC and a 3D tissue-engineered urothelium. Two healthy fecal donors inoculated the colons. Dialysis cassettes containing 7log10 CFU/mL UTI89 were immersed for 2h in the SHIME colons to assess the effect of untreated (7-day control diet)/treated (14-day PAC-rich extract) metabolomes on UPEC behavior. Engineered urothelium were then infected with dialysates containing UPEC for 6 h. This work demonstrated for the first time that in the control fecal microbiota condition without added PAC, the UPEC virulence genes were activated upstream the infection site, in the gut. However, PAC microbial-derived cranberry metabolites displayed a remarkable propensity to blunt activation of genes encoding toxin, adhesin/invasins in the gut and on the urothelium, in a donor-dependent manner. Variability in subjects' gut microbiota and ensuing contrasting cranberry PAC metabolism affects UPEC virulence and should be taken into consideration when designing cranberry efficacy clinical trials. IMPORTANCE Uropathogenic Escherichia coli (UPEC) are the primary cause of recurrent urinary tract infections (UTI). The poor understanding of UPEC ecology-pathophysiology from its reservoir-the gut, to its infection site-the urothelium, partly explains the inadequate and abusive use of antibiotics to treat UTI, which leads to a dramatic upsurge in antibiotic-resistance cases. In this context, we evaluated the effect of a cranberry proanthocyanidins (PAC)-rich extract on the UPEC survival and virulence in a bipartite model of a gut microbial environment and a 3D urothelium model. We demonstrated that PAC-rich cranberry extract microbial metabolites significantly blunt activation of UPEC virulence genes at an early stage in the gut reservoir. We also showed that altered virulence in the gut affects infectivity on the urothelium in a microbiota-dependent manner. Among the possible mechanisms, we surmise that specific microbial PAC metabolites may attenuate UPEC virulence, thereby explaining the preventative, yet contentious properties of cranberry against UTI.

Metabolism of phenolics in coffee and plant-based foods by canonical pathways: an assessment of the role of fatty acid β-oxidation to generate biologically-active and -inactive intermediates

ω-Phenyl-alkenoic acids are abundant in coffee, fruits, and vegetables. Along with ω-phenyl-alkanoic acids, they are produced from numerous dietary (poly)phenols and aromatic amino acids in vivo. This review addresses how phenyl-ring substitution and flux modulates their gut microbiota and endogenous β-oxidation. 3',5'-Dihydroxy-derivatives (from alkyl-resorcinols, flavanols, proanthocyanidins), and 4'-hydroxy-phenolic acids (from tyrosine, p-coumaric acid, naringenin) are β-oxidation substrates yielding benzoic acids. In contrast, 3',4',5'-tri-substituted-derivatives, 3',4'-dihydroxy-derivatives and 3'-methoxy-4'-hydroxy-derivatives (from coffee, tea, cereals, many fruits and vegetables) are poor β-oxidation substrates with metabolism diverted via gut microbiota dehydroxylation, phenylvalerolactone formation and phase-2 conjugation, possibly a strategy to conserve limited pools of coenzyme A. 4'-Methoxy-derivatives (citrus fruits) or 3',4'-dimethoxy-derivatives (coffee) are susceptible to hepatic "reverse" hydrogenation suggesting incompatibility with enoyl-CoA-hydratase. Gut microbiota-produced 3'-hydroxy-4'-methoxy-derivatives (citrus fruits) and 3'-hydroxy-derivatives (numerous (poly)phenols) are excreted as the phenyl-hydracrylic acid β-oxidation intermediate suggesting incompatibility with hydroxy-acyl-CoA dehydrogenase, albeit with considerable inter-individual variation. Further investigation is required to explain inter-individual variation, factors determining the amino acid to which C6-C3 and C6-C1 metabolites are conjugated, the precise role(s) of l-carnitine, whether glycine might be limiting, and whether phenolic acid-modulation of β-oxidation explains how phenolic acids affect key metabolic conditions, such as fatty liver, carbohydrate metabolism and insulin resistance.

In Vitro Microbial Metabolism of (+)-Catechin Reveals Fast and Slow Converters with Individual-Specific Microbial and Metabolite Markers

The bioavailability of catechin highly relies on gut microbiota which may determine its metabolic profile, resulting in different health outcomes. Here, we investigated in vitro (+)-catechin metabolism by human microbial communities. There were substantial interindividual differences in the metabolic profiles of (+)-catechin, with 5-(3',4'-dihydroxyphenyl)-γ-valerolactone being the major contributor. Furthermore, the microbial metabolic rate of catechin enabled stratification of 12 participants (fast, medium, and slow converters), despite the interference from the strong intrinsic interindividual variability in fecal microbiota. Correlations were established between this stratified population and microbiota features, such as ecosystem diversity. Additionally, fast converters had significantly higher prevalences of amplicon sequence variants (ASVs) with potential capacity of C-ring cleavage (ASV233_Eggerthella and ASV402_Eubacterium), B-ring dihydroxylation (ASV402_Eubacterium), and short-chain fatty acid (SCFA)-producing ASVs. In conclusion, metabolic-capability-based stratification allows us to uncover differences in microbial composition between fast and slow converters, which could help to elucidate interindividual variabilities in the health benefits of catechins.

Sustained Consumption of a Decaffeinated Green Coffee Nutraceutical Has Limited Effects on Phenolic Metabolism and Bioavailability in Overweight/Obese Subjects

Knowledge on the bioavailability of coffee (poly)phenols mostly come from single dose postprandial studies. This study aimed at investigating the effects of regularly consuming a green coffee phenolic extract (GCPE) on the bioavailability and metabolism of (poly)phenols. Volunteers with overweight/obesity consumed a decaffeinated GCPE nutraceutical containing 300 mg hydroxycinnamates twice daily for two months. Plasma and urinary pharmacokinetics, and fecal excretion of phenolic metabolites were characterized by LC-MS-QToF at weeks 0 and 8. Fifty-four metabolites were identified in biological fluids. Regular consumption of the nutraceutical produced certain changes: reduced forms of caffeic, ferulic and coumaric acids in urine or 3-(3′-hydroxypenyl)propanoic, and 3,4-dihydroxybenzoic acids in feces significantly increased (p < 0.05) after 8 weeks; in contrast, coumaroylquinic and dihydrocoumaroylquinic acids in urine decreased (p < 0.05) compared to baseline excretion. The sum of intestinal and colonic metabolites increased after sustained consumption of GCPE, without reaching statistical significance, suggesting a small overall effect on (poly)phenols’ bioavailability.

(Poly)phenolic compounds and gut microbiome: new opportunities for personalized nutrition

For decades, (poly)phenols have been linked to cardiometabolic health, but population heterogeneity limits their apparent efficacy and the development of tailored, practical protocols in dietary interventions. This heterogeneity is likely determined by the existence of different metabotypes, sub-populations of individuals metabolizing some classes of (poly)phenols differently. The gut microbiota plays a major role in this process. The impact of microbiota-related phenolic metabotypes on cardiometabolic health is becoming evident, although the picture is still incomplete, and data are absent for some classes of (poly)phenols. The lack of a complete understanding of the main microbial actors involved in the process complicates the picture. Elucidation of the mechanisms behind phenolic metabotypes requires novel experimental designs that can dissect the inter-individual variability. This paper, in addition to providing an overview on the current state-of-the-art, proposes wider metabotyping approaches as a means of paving the way towards effective personalized nutrition with dietary (poly)phenols.

Metabolites profiling reveals gut microbiome-mediated biotransformation of green tea polyphenols in the presence of N-nitrosamine as pro-oxidant

The gut microbiome contributes to host physiology and nutrition metabolism. The interaction between nutrition components and the gut microbiota results in thousands of metabolites that can contribute to various health and disease outcomes. In parallel, the interactions between foods and their toxicants have captured increasing interest due to their impact on human health.  Taken together, investigating dietary interactions with endogenous and exogenous factors and detecting interaction biomarkers in a specific and sensitive manner is an important task. The present study sought  to identify for the first time the metabolites produced during the interaction of diet-derived toxicants e.g., N-nitrosamines with green tea polyphenols, using liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). In addition, the metabolic products resulting from the incubation of green tea with a complex gut microbiome in the presence of N-nitrosamine were assessed in the same manner. The quinone products of (epi)catechin, quercetin, and kaempferol were identified when green tea was incubated with N-nitrosamine only; whereas, incubation of green tea with N-nitrosamine and a complex gut microbiome prevented the formation of these metabolites. This study provides a new perspective on the role of gut microbiome in protecting against potential negative interactions between food-derived toxicants and dietary polyphenols.

Interaction Between Diet and Microbiota in the Pathophysiology of Alzheimer's Disease: Focus on Polyphenols and Dietary Fibers

Animal studies increasingly indicate that the gut microbiota composition and function can be involved in the pathophysiology and progression of Alzheimer's disease (AD) at multiple levels. However, few studies have investigated this putative gut-brain axis in human beings, and none of them considered diet as a determinant of intestinal microbiota composition. Epidemiological studies highlight that a high intake of fruit and vegetables, such as that typical of the Mediterranean diet, can modulate AD progression. Thus, nutritional interventions are being increasingly studied as a possible non-pharmacological strategy to slow down the progression of AD. In particular, polyphenols and fibers represent the nutritional compounds with the higher potential of counterbalancing the pathophysiological mechanisms of dementia due to their antioxidant, anti-inflammatory, and anti-apoptotic properties. These actions are mediated by the gut microbiota, that can transform polyphenols and fibers into biologically active compounds including, among others, phenyl-γ-valerolactones, urolithins, butyrate, and other short-chain fatty acids. In this review, the complex mechanisms linking nutrition, gut microbiota composition, and pathophysiology of cognitive decline in AD are discussed, with a particular focus on the role of polyphenols and fibers. The gaps between pre-clinical and clinical studies are particularly emphasized, as well as the urgent need for studies comprehensively evaluating the link between nutrition, microbiome, and clinical aspects of AD.

Purified recombinant enzymes efficiently hydrolyze conjugated urinary (poly)phenol metabolites

Purified recombinant enzymes are efficient at hydrolyzing microbial (poly)phenol metabolite phase II conjugates, and hence, can be used to accurately quantify them using unconjugated analytical standards.

The Donor-Dependent and Colon-Region-Dependent Metabolism of (+)-Catechin by Colonic Microbiota in the Simulator of the Human Intestinal Microbial Ecosystem

The intestinal absorption of dietary catechins is quite low, resulting in most of them being metabolized by gut microbiota in the colon. It has been hypothesized that microbiota-derived metabolites may be partly responsible for the association between catechin consumption and beneficial cardiometabolic effects. Given the profound differences in gut microbiota composition and microbial load between individuals and across different colon regions, this study examined how microbial (+)-catechin metabolite profiles differ between colon regions and individuals. Batch exploration of the interindividual variability in (+)-catechin microbial metabolism resulted in a stratification based on metabolic efficiency: from the 12 tested donor microbiota, we identified a fast- and a slow-converting microbiota that was subsequently inoculated to SHIME, a dynamic model of the human gut. Monitoring of microbial (+)-catechin metabolites from proximal and distal colon compartments with UHPLC-MS and UPLC-IMS-Q-TOF-MS revealed profound donor-dependent and colon-region-dependent metabolite profiles with 5-(3',4'-dihydroxyphenyl)-γ-valerolactone being the largest contributor to differences between the fast- and slow-converting microbiota and the distal colon being a more important region for (+)-catechin metabolism than the proximal colon. Our findings may contribute to further understanding the role of the gut microbiota as a determinant of interindividual variation in pharmacokinetics upon (+)-catechin ingestion.

Metabotypes of flavan-3-ol colonic metabolites after cranberry intake: elucidation and statistical approaches

Purpose

Extensive inter-individual variability exists in the production of flavan-3-ol metabolites. Preliminary metabolic phenotypes (metabotypes) have been defined, but there is no consensus on the existence of metabotypes associated with the catabolism of catechins and proanthocyanidins. This study aims at elucidating the presence of different metabotypes in the urinary excretion of main flavan-3-ol colonic metabolites after consumption of cranberry products and at assessing the impact of the statistical technique used for metabotyping.

Methods

Data on urinary concentrations of phenyl-γ-valerolactones and 3-(hydroxyphenyl)propanoic acid derivatives from two human interventions has been used. Different multivariate statistics, principal component analysis (PCA), cluster analysis, and partial least square-discriminant analysis (PLS-DA), have been considered.

Results

Data pre-treatment plays a major role on resulting PCA models. Cluster analysis based on k-means and a final consensus algorithm lead to quantitative-based models, while the expectation–maximization algorithm and clustering according to principal component scores yield metabotypes characterized by quali-quantitative differences in the excretion of colonic metabolites. PLS-DA, together with univariate analyses, has served to validate the urinary metabotypes in the production of flavan-3-ol metabolites and to confirm the robustness of the methodological approach.

Conclusions

This work proposes a methodological workflow for metabotype definition and highlights the importance of data pre-treatment and clustering methods on the final outcomes for a given dataset. It represents an additional step toward the understanding of the inter-individual variability in flavan-3-ol metabolism.

Trial registration

The acute study was registered at clinicaltrials.gov as NCT02517775, August 7, 2015; the chronic study was registered at clinicaltrials.gov as NCT02764749, May 6, 2016.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02692-z.

Main drivers of (poly)phenol effects on human health: metabolite production and/or gut microbiota-associated metabotypes?

Despite the high human interindividual variability in response to (poly)phenol consumption, the cause-and-effect relationship between some dietary (poly)phenols (flavanols and olive oil phenolics) and health effects (endothelial function and prevention of LDL oxidation, respectively) has been well established. Most of the variables affecting this interindividual variability have been identified (food matrix, gut microbiota, single-nucleotide-polymorphisms, etc.). However, the final drivers for the health effects of (poly)phenol consumption have not been fully identified. At least partially, these drivers could be (i) the (poly)phenols ingested that exert their effect in the gastrointestinal tract, (ii) the bioavailable metabolites that exert their effects systemically and/or (iii) the gut microbial ecology associated with (poly)phenol metabolism (i.e., gut microbiota-associated metabotypes). However, statistical associations between health effects and the occurrence of circulating and/or excreted metabolites, as well as cross-sectional studies that correlate gut microbial ecologies and health, do not prove a causal role unequivocally. We provide a critical overview and perspective on the possible main drivers of the effects of (poly)phenols on human health and suggest possible actions to identify the putative actors responsible for the effects.

Dietary polyphenol and microbiota interactions in the context of prostate health

Recent data strongly indicate a relationship between prostate health and gut microbiota, in which composition and physiological function strictly depend on dietary patterns. The bidirectional interplay of foods containing polyphenols, such as ellagitannins, condensed tannins, lignans, isoflavones, and prenylated flavonoids with human gut microbiota, has been proven to contribute to their impact on prostate health. Considering the attributed role of dietary polyphenols in the prevention of prostate diseases, this paper aims to critically review the studies concerning the influence of polyphenols' postbiotic metabolites on processes associated with the pathophysiology of prostate diseases. Clinical, in vivo, and in vitro studies on polyphenols have been juxtaposed with the current knowledge regarding their pharmacokinetics, microbial metabolism, and potential interactions with microbiota harboring different niches of the human organism. Directions of future research on dietary polyphenols regarding their interaction with microbiota and prostate health have been indicated.

Gut microbiota as a driver of the interindividual variability of cardiometabolic effects from tea polyphenols

Tea polyphenols have been extensively studied for their preventive properties against cardiometabolic diseases. Nevertheless, the evidence of these effects from human intervention studies is not always consistent, mainly because of a large interindividual variability. The bioavailability of tea polyphenols is low, and metabolism of tea polyphenols highly depends on individual gut microbiota. The accompanying reciprocal relationship between tea polyphenols and gut microbiota may result in alterations in the cardiometabolic effects, however, the underlying mechanism of which is little explored. This review summarizes tea polyphenols-microbiota interaction and its contribution to interindividual variability in cardiometabolic effects. Currently, only a few bacteria that can biodegrade tea polyphenols have been identified and generated metabolites and their bioactivities in metabolic pathways are not fully elucidated. A deeper understanding of the role of complex interaction necessitates fully individualized data, the ntegration of multiple-omics platforms and development of polyphenol-centered databases. Knowledge of this microbial contribution will enable the functional stratification of individuals in the gut microbiota profile (metabotypes) to clarify interindividual variability in the health effects of tea polyphenols. This could be used to predict individual responses to tea polyphenols consumption, hence bringing us closer to personalized nutrition with optimal dose and additional supplementation of specific microorganisms.

LC-MS based metabolomic approach for the efficient identification and relative quantification of bioavailable cocoa phenolics in human urine

This study was designed to investigate the rate and extent of urinary excretion of cocoa phenolic metabolites after human intake using metabolomics approach. In this context, a feeding trial was conducted where urine samples were collected at different time points over 48-h period. Several biomarkers were highlighted in LC-MS based chemometrics using principal component (PCA) and partial least squares discriminant analysis (PLS-DA), which revealed the presence of both epicatechin and gut microbial phenyl-γ-valerolactones (PVLs) conjugated analogues. The presences of these metabolites segregated and grouped the samples based on cocoa and non-cocoa ingestion. Furthermore, semi quantification of major bioavailable metabolites was performed to determine the interindividual differences and assess the relative bioavailability of cocoa compounds in the human body. Our approach presented here is unique in displaying a combination of LC-MS based chemometrics visualization strategies, which revealed and identified significant biomarkers that could reduce the problems associated with data screening complexity.

(Poly)phenol-Rich Diets in the Management of Endothelial Dysfunction in Diabetes Mellitus: Biological Properties in Cultured Endothelial Cells

Processed and ready-to-eat foods become routinely consumed resulting in a sharp rise of sugar intake in people's daily diets. The inclusion of fresh fruits and vegetables rich in (poly)phenols has been encouraged by the World Health Organization (WHO) as part of the daily choices to ameliorate endothelial dysfunction and ease the socio-economic burden of diabetes. Research in Food, Nutrition, and Cell Metabolism areas is revealing that the health benefits of (poly)phenol-rich foods go beyond their antioxidant properties and are in fact key modulators of redox and glycaemia status, and inflammatory response contributing to improved endothelial function and vascular health in diabetes. Other beneficial aspects include appetite modulation, regulation of hydrolytic enzymes involved in sugar and lipid metabolism, and mediation of cell-cell aggregation events. This work overviews the current knowledge on the biological properties of ingested (poly)phenols in cultured endothelial cells with emphasis on the circulating (poly)phenols, providing support to (poly)phenol-rich diets as alternatives to drug-based therapies in the prevention, treatment, and management of diabetes. A critical evaluation on the caveats and challenges involve in current experimental cell-based designs and approaches adopted is also discussed.

A multi-omics approach for understanding the effects of moderate wine consumption on human intestinal health

The human gut is a highly diverse microbial ecosystem. Although showing a well-defined core of dominant taxa, an interindividual variability exists in microbiome arrangement patterns, and the presence and proportion of specific species, determining individual metabolic features-metabotypes-which govern the health effects of dietary interventions (i.e. polyphenol consumption). Starting with a 19-volunteer human intervention study, divided into low, medium, and high wine-polyphenol-metabolizers, we detected interindividual discrepancies on the effect of wine consumption in gut bacterial alpha-diversity, but a significant homogenization of beta-diversity among moderate wine consumers, independently of their metabotype. In addition, the abundance of key health-related taxa such as Akkermansia sp. increased after moderate wine intake in the group of high polyphenol-metabolizers. Regarding the metabolic activity, significant (p < 0.05) positive correlations in the production of SCFAs were observed after wine intake. Finally, we were able to correlate the microbiome and the metabolome of the three metabotypes, and to identify some metabolites-biomarker species, highlighting the genera Phascolarctobacterium, Pelotomaculum and Prevotella, as positively correlated with polyphenol concentration, and Prevotella, Zymophilus and Eubacterium as positively correlated with SCFAs concentration in faeces. Our results contribute to the evidence of the need of including the microbiome variable in personalized nutrition programs, as different metabotyes respond differently to dietary interventions.

Evaluation of the potential of total proanthocyanidin content in feces as an intake biomarker

Due to the health benefits associated with proanthocyanidins (PAs), it is useful to identify dietary PA biomarkers that can be determined by simple methods. Since increased levels of circulating PA metabolites are associated with increased fecal PA content, this study explores the spectrophotometric measurement of fecal PA content and its use as a biomarker of PA intake. To this end, fecal PA content was measured using an adaptation of Porter's spectrophotometric method in samples from a preclinical study and an observational study. In the former, excretion of 250-400 mg PA polymer equivalents/100 g feces was observed during supplementation and the day after, together with a significant association (p < 0.05) between PA intake and the excretion of both intact PAs and some PA metabolites, i.e., (+)-catechin, (-)-epicatechin and syringic acid. No relationship between intake and excretion was found in the observational study, either for the entire group (mean excretion of 240 ± 226 mg PA polymer equivalents/100 g feces) or after stratification into tertiles of consumption. In conclusion, the spectrophotometric determination of total PA content in feces proved to be a valid compliance marker in a preclinical study, but it was not associated with PA intake in free-living subjects. The potential of total PA excretion in observational studies, determined in fecal samples collected the day before dietary recall or in several fecal samples from the same subject, remains to be elucidated, as does a complete validation of the method proposed here.

Effect of Gut Microbiota Biotransformation on Dietary Tannins and Human Health Implications

Tannins represent a heterogeneous group of high-molecular-weight polyphenols that are ubiquitous among plant families, especially in cereals, as well as in many fruits and vegetables. Hydrolysable and condensed tannins, in addition to phlorotannins from marine algae, are the main classes of these bioactive compounds. Despite their low bioavailability, tannins have many beneficial pharmacological effects, such as anti-inflammatory, antioxidant, antidiabetic, anticancer, and cardioprotective effects. Microbiota-mediated hydrolysis of tannins produces highly bioaccessible metabolites, which have been extensively studied and account for most of the health effects attributed to tannins. This review article summarises the effect of the human microbiota on the metabolism of different tannin groups and the expected health benefits that may be induced by such mutual interactions. Microbial metabolism of tannins yields highly bioaccessible microbial metabolites that account for most of the systemic effects of tannins. This article also uses explainable artificial intelligence to define the molecular signatures of gut-biotransformed tannin metabolites that are correlated with chemical and biological activity. An understanding of microbiota-tannin interactions, tannin metabolism-related phenotypes (metabotypes) and chemical tannin-metabolites motifs is of great importance for harnessing the biological effects of tannins for drug discovery and other health benefits.

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.

Evaluation of the Diuretic Activity of the Aqueous and 80% Methanol Extracts of Ficus sur Forssk (Moraceae) Leaves in Saline-loaded Rats

Background

Although investigations on different pharmacological activities of the experimental plant, Ficus sur have been conducted, its folklore use for diuresis has not yet been validated. The current study, therefore, focused on the diuretic activity of aqueous and 80% methanol extracts of F. sur Forssk. leaves in rats.

Methods

Rats were randomly assigned into eight groups each consisting of six rats. Test groups received either 100 mg/kg, 200 mg/kg, or 400 mg/kg of aqueous or 80% methanol leaves extract. The negative control group and positive control were treated with 2 mL/100 g of distilled water and furosemide (10 mg/kg), respectively. Thereafter urine volume was recorded every hour until the end of the fifth hour, and cumulative urine volume of each rat was measured. Then, diuretic activity, diuretic index, saliuretic index, natriuretic index and carbonic anhydrase inhibition index in each group were calculated, and results were compared among the groups.

Results

The middle (200 mg/kg) and the highest (400 mg/kg) doses of both extracts significantly increased diuresis at the fifth hour (p<0.001) compared to the negative control, although the diuretic activity was less than that of the positive control. Regarding electrolyte excretion, all dose levels of both extracts showed significant natriuresis (p<0.001) and chloriuresis (p<0.01) compared to the negative control. Aqueous extract displayed more significant diuretic effect than 80% methanol extract. The aqueous and 80% methanol extracts produced alkaline urine.

Conclusion

The crude leaves extracts of F. sur increased urinary excretion and concentration of urinary electrolytes in a dose-dependent manner. These findings are in agreement with the traditional claim for use of F. sur as diuretic agent.

Functional Deficits in Gut Microbiome of Young and Middle-Aged Adults with Prediabetes Apparent in Metabolizing Bioactive (Poly)phenols

Background: Gut microbiota metabolize select dietary (poly)phenols to absorbable metabolites that exert biological effects important in metabolic health. Microbiota composition associated with health/disease status may affect its functional capacity to yield bioactive metabolites from dietary sources. Therefore, this study assessed gut microbiome composition and its related functional capacity to metabolize fruit (poly)phenols in individuals with prediabetes and insulin resistance (PreDM-IR, n = 26) compared to a metabolically healthy Reference group (n = 10). Methods: Shotgun sequencing was used to characterize gut microbiome composition. Targeted quantitative metabolomic analyses of plasma and urine collected over 24 h were used to assess microbial-derived metabolites in response to a (poly)phenol-rich raspberry test drink. Results: PreDM-IR compared to the Reference group: (1) enriched Blautia obeum and Blautia wexlerae and depleted Bacteroides dorei and Coprococcus eutactus. Akkermansia muciniphila and Bacteroides spp. were depleted in the lean PreDM-IR subset; and (2) impaired microbial catabolism of select (poly)phenols resulting in lower 3,8-dihydroxy-urolithin (urolithin A), phenyl-γ-valerolactones and various phenolic acids concentrations (p < 0.05). Controlling for obesity revealed relationships with microbial species that may serve as metagenomic markers of diabetes development and therapeutic targets. Conclusions: Data provide insight from multi-omics approaches to advance knowledge at the diet–gut–disease nexus serving as a platform for devising dietary strategies to improve metabolic health.

Interindividual Differences in Human Intestinal Microbial Conversion of (-)-Epicatechin to Bioactive Phenolic Compounds

To quantify interindividual differences in the human intestinal microbial metabolism of (-)-epicatechin (EC), in vitro anaerobic incubations with fecal inocula from 24 healthy donors were conducted. EC-derived colonic microbial metabolites were qualitatively and quantitively analyzed by liquid chromatography triple quadrupole mass spectrometry (LC-TQ-MS) and liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS). Quantitative microbiota characterization was achieved by 16S rRNA analysis. The results obtained show 1-(3',4'-dihydroxyphenyl)-3-(2″,4″,6″-dihydroxyphenyl)-2-propanol (3,4-diHPP-2-ol) and 5-(3',4'-dihydroxyphenyl)-γ-valerolactone (3,4-diHPV) to be key intermediate microbial metabolites of EC and also revealed the substantial interindividual differences in both the rate of EC conversion and the time-dependent EC metabolite pattern. Furthermore, substantial differences in microbiota composition among different individuals were detected. Correlations between specific microbial phylotypes and formation of certain metabolites were established. It is concluded that interindividual differences in the intestinal microbial metabolism of EC may contribute to interindividual differences in potential health effects of EC-abundant dietary foods or drinks.

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.

Dietary Phenolics against Breast Cancer. A Critical Evidence-Based Review and Future Perspectives

Breast cancer (BC) is the most common malignancy and the leading cause of cancer-related death in adult women worldwide. Over 85% of BC cases are non-hereditary, caused by modifiable extrinsic factors related to lifestyle, including dietary habits, which play a crucial role in cancer prevention. Although many epidemiological and observational studies have inversely correlated the fruit and vegetable consumption with the BC incidence, the involvement of their phenolic content in this correlation remains contradictory. During decades, wrong approaches that did not consider the bioavailability, metabolism, and breast tissue distribution of dietary phenolics persist behind the large currently existing gap between preclinical and clinical research. In the present review, we provide comprehensive preclinical and clinical evidence according to physiologically relevant in vitro and in vivo studies. Some dietary phenolics such as resveratrol (RSV), quercetin, isoflavones, epigallocatechin gallate (EGCG), lignans, and curcumin are gaining attention for their chemopreventive properties in preclinical research. However, the clinical evidence of dietary phenolics as BC chemopreventive compounds is still inconclusive. Therefore, the only way to validate promising preclinical results is to conduct clinical trials in BC patients. In this regard, future perspectives on dietary phenolics and BC research are also critically discussed.

Kinetic profile and urinary excretion of phenyl-γ-valerolactones upon consumption of cranberry: a dose-response relationship

Cranberries are a rich source of poly(phenols), mainly monomeric and oligomeric flavan-3-ols. However, information on the appearance of their main circulating microbial metabolites, namely phenyl-γ-valerolactones and phenylvaleric acid, is lacking despite its relevance to understanding the health effects attributed to cranberries. The aim of this study was to evaluate the absorption, metabolism and urinary excretion of cranberry flavan-3-ols through the targeted analysis of phenyl-γ-valerolactones and their related phenylvaleric acids, considering also their potential as biomarkers of flavan-3-ol intake and inter-individual variability in their appearance in plasma and urine. A six-arm acute crossover, randomized, double-blinded, controlled intervention trial was performed in ten healthy males who consumed a cranberry juice drink (375, 716, 1131, 1396, 1741 mg of total flavan-3-ols) or an isocaloric control drink with one-week washout. Plasma and urine were analyzed by UHPLC-ESI-QqQ-MS/MS and 22 compounds were identified. Glucuronide and sulfate conjugates of 5-(3',4'-dihydroxyphenyl)-γ-valerolactone were the main circulating and excreted metabolites after cranberry juice intake, with glucuronidation appearing to be the most favorable conjugation route. These compounds reached maximum plasma concentration at about 4-6 h. Plasma and urinary concentrations of the sum of the metabolites increased in relation to the amounts of cranberry flavan-3-ols provided by the drink, showing a clear and linear dose-dependent relationship and underscoring their potential as biomarkers of flavan-3-ol intake. A high inter-individual variability in circulating and urinary metabolite levels was observed and, interestingly, some subjects seemed to display a greater efficiency in metabolizing flavan-3-ols and producing phenyl-γ-valerolactones.

Impact of lignans in oilseed mix on gut microbiome composition and enterolignan production in younger healthy and premenopausal women: an in vitro pilot study

BACKGROUND

Dietary lignans belong to the group of phytoestrogens together with coumestans, stilbenes and isoflavones, and themselves do not exhibit oestrogen-like properties. Nonetheless, the gut microbiota converts them into enterolignans, which show chemical similarity to the human oestrogen molecule. One of the richest dietary sources of lignans are oilseeds, including flaxseed. The aim of this pilot study was to determine the concentration of the main dietary lignans in an oilseed mix, and explore the gut microbiota-dependent production of enterolignans for oestrogen substitution in young and premenopausal women. The oilseed mix was fermented in a pH-controlled batch culture system inoculated with women's faecal samples. The lignan content and enterolignan production were measured by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), and the faecal-derived microbial communities were profiled by 16S rRNA gene-based next-generation sequencing.

RESULTS

In vitro batch culture fermentation of faecal samples inoculated with oilseed mix for 24 h resulted in a substantial increase in enterolactone production in younger women and an increase in enterodiol in the premenopausal group. As for the gut microbiota, different baseline profiles were observed as well as different temporal dynamics, mainly related to Clostridiaceae, and Klebsiella and Collinsella spp.

CONCLUSIONS

Despite the small sample size, our pilot study revealed that lignan-rich oilseeds could strongly influence the faecal microbiota of both younger and premenopausal females, leading to a different enterolignan profile being produced. Further studies in larger cohorts are needed to evaluate the long-term effects of lignan-rich diets on the gut microbiota and find out how enterolactone-producing bacterial species could be increased. Diets rich in lignans could potentially serve as a safe supplement of oestrogen analogues to meet the cellular needs of endogenous oestrogen and deliver numerous health benefits, provided that the premenopausal woman microbiota is capable of converting dietary precursors into enterolignans.

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.

Quantification of Urinary Phenyl-γ-Valerolactones and Related Valeric Acids in Human Urine on Consumption of Apples

Flavan-3-ols are dietary bioactive molecules that have beneficial effects on human health and reduce the risk of various diseases. Monomeric flavan-3-ols are rapidly absorbed in the small intestine and released in the blood stream as phase II conjugates. Polymeric flavan-3-ols are extensively metabolized by colonic gut microbiota into phenyl-γ-valerolactones and their related phenylvaleric acids. These molecules are the main circulating metabolites in humans after the ingestion of flavan-3-ol rich-products; nevertheless, they have received less attention and their role is not understood yet. Here, we describe the quantification of 8 phenyl-γ-valerolactones and 3 phenylvaleric acids in the urine of 11 subjects on consumption of apples by using UHPLC-ESI-Triple Quad-MS with pure reference compounds. Phenyl-γ-valerolactones, mainly as sulfate and glucuronic acid conjugates, reached maximum excretion between 6 and 12 after apple consumption, with a decline thereafter. Significant differences were detected in the cumulative excretion rates within subjects and in the ratio of dihydroxyphenyl-γ-valerolactone sulfate to glucuronide conjugates. This work observed for the first time the presence of two distinct metabotypes with regards to the excretion of phenyl-γ-valerolactone phase II conjugates.

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.