1,721,021 research outputs found
Absorption and metabolism of milk thistle flavonolignans in humans
No full textThis study evaluated the absorption and metabolism of milk thistle flavonolignans silychristin, silydianin, silybin and isosilybin isomers (all together known as silymarin) in humans. Fourteen volunteers consumed an extract of milk thistle and urine was collected up to 48 hours after consumption. Thirty-one metabolites were identified in urine by means of HPLC-MS/MS, monoglucuronides being the most common excreted form, followed by sulphate-glucuronides and diglucuronides, respectively. The excretion of monoglucuronides peaked 2 hours after consumption, whereas sulphate-glucuronide and diglucuronide excretion peaked at 8 hours. The bioavailability of milk thistle flavonolignans was 0.45 ± 0.28% (mean ± SD). In conclusion, milk thistle flavonolignans are extensively modified after ingestion and recovered in urine as sulpho- and glucuronyl-conjugates, indicating a strong affinity for hepatic phase II enzymes. All future studies (in vitro and in vivo) dealing with the effects of milk thistle should start by considering the modification of its flavonolignans after ingestion by humans
Identification of microbial metabolites derived from in vitro fecal fermentation of different polyphenolic food sources.
No full textObjective: The biological effects of dietary polyphenols are linked to their bioavailability and
catabolism in humans. The colon, with its symbiotic microbiota, is an active site where complex
polyphenolic compounds are possibly modified to smaller and more absorbable molecules. The
aim of this study was to identify the major metabolites derived from microbial colonic fermentation
of some common polyphenol-rich foods.
Methods: An in vitro fecal fermentation model was applied to 16 polyphenol-rich foods and
polyphenolic precursors. Phenolic metabolites were identified by high-performance liquid chromatography
coupled with tandem mass spectrometric detection.
Results: Twenty-four phenolic fermentation metabolites were characterized. Some metabolites
were common to several polyphenol-rich foods, whereas others were characteristic of specific
sources.
Conclusion: The metabolites identified in vitro likely are generated in the human colon after
consumption of polyphenol-rich foods. Their occurrence in plasma and/or urine should be
considered when evaluating the bioavailability of polyphenols from specific food groups in humans
and in the definition of markers of exposure to specific foods or food groups in epidemiologic
studies. However, the search for these and other microbial metabolites after a feeding study in vivo
should consider their possible further conjugation at the level of the liver
Colonic Metabolism of Polyphenols From Coffee, Green Tea, and Hazelnut Skins
Full text linkDietary polyphenolic compounds are poorly absorbed in
the small intestine. The absorbed fraction follows the common metabolic pathway of drugs, undergoing phase II enzymatic detoxification with the conjugation of glucuronic acid, sulfate, and methyl groups. However, the unabsorbed fraction can reach the colon, becoming available for the wide array of enzymes produced by the local commensal microbiota. Gut bacteria can hydrolyze glycosides, glucuronides, sulfates, amides, esters, and lactones and are able to break down the polyphenolic skeleton and perform
reactions of reduction, decarboxylation, demethylation, and
dehydroxylation. These complex modifications generate several low–molecular-weight metabolites that can be efficiently absorbed in situ, subsequently undergoing further phase II metabolism, locally and/or at the liver level, before entering the systemic blood circulation and finally being excreted in urine in substantial quantities that exceed the excretion of phenolic metabolites formed in the upper gastrointestinal tract. This brief work focuses on the phenolic composition and colonic microbial transformation of 2 of the most polyphenol-rich dietary sources, namely, green tea and
coffee, and a new interesting and innovative ingredient, hazelnut skin, recently evaluated as one of the richest edible sources of polyphenolic compounds
Gastrointestinal stability of urolithins: an in vitro approach
No full textPurpose: Urolithins are bioactive ellagitannin-derived metabolites showing a wide phenotypic variation in their production by the gut microbiota. This work represents a first in vitro step toward the development of new strategies focused on the oral supplementation of urolithins with the aim of overcoming their selective production and making their putative health benefits available for the whole population. Methods: In order to study their gastrointestinal stability, urolithin A, urolithin B, and urolithin B-glucuronide, as well as ellagic acid, were subjected to a simulated gastrointestinal digestion model consisting of oral, gastric, and pancreatic steps followed by a 24-h fecal fermentation. The effect of the entero-hepatic recirculation on urolithin B-glucuronide, a phase II metabolite, was also investigated. Results: Urolithin B was the molecule able to resist to a greater extent the conditions of the gastrointestinal tract, while urolithin A and ellagic acid were drastically unstable during the colonic step. Conjugation with glucuronic acid, ideally occurring in the liver, conferred to urolithin B an increased stability, which may be interesting in the framework of entero-hepatic recirculation. Conclusion: This set of experiments lets hypothesize that orally supplemented urolithins may come into contact with the colonic epithelium and become accessible for uptake or exert local anti-inflammatory activity, overcoming the limitations of enterotypes unable to convert ellagitannins into these putatively beneficial metabolites
Solid state lactic acid fermentation: A strategy to improve wheat bran functionality
Full text linkWheat bran, a by-product produced in huge amount during cereal milling, is today largely unexploited because of its poor suitability as food ingredient. Solid-state fermentation (SSF) using a Lactobacillus rhamnosus strain was applied to wheat bran and its influence on bioactive compounds (free and bound phenolic acids) and antioxidant activity were evaluated. Moreover, the phytic acid (PAc) degradation and arabinoxylans (WEAX) solubilization properties were studied: the SSF treatment resulted in an almost 37% decrement and a three times increment of PAc and WEAX, respectively. Finally, in order to get the bigger picture, microbial metabolites and the volatile profile of fermented wheat bran were characterized, showing amino acids and lipids metabolites and a complex aroma profile. Overall, lactic acid fermentation can be considered a valuable pre-treatment for the valorisation of cereal by-products
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