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Urolithins are
microflora Microbiota are the range of microorganisms that may be commensal, mutualistic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found ...
metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...
s of dietary
ellagic acid Ellagic acid is a polyphenol found in numerous fruits and vegetables. It is the dilactone of hexahydroxydiphenic acid. Name The name comes from the French term ''acide ellagique'', from the word ''galle'' spelled backward because it can be o ...
derivatives, such as
ellagitannins image:Castalagin.svg, 130px, Castalagin is a representative ellagitannin, characterized by coupled gallic acid substituents The ellagitannins are a diverse class of hydrolyzable tannins, a type of polyphenol formed primarily from the oxidative link ...
. They are produced in the gut, and found in the
urine Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...
in the form of urolithin B glucuronide after absorption of ellagitannins-containing foods, such as
pomegranate The pomegranate (''Punica granatum'') is a fruit-bearing deciduous shrub in the family Lythraceae, subfamily Punica, Punicoideae, that grows between tall. Rich in symbolic and mythological associations in many cultures, it is thought to have o ...
. During intestinal metabolism by bacteria, ellagitannins and
punicalagin Punicalagin (''Pyuni-cala-jen'') is an ellagitannin, a type of phenolic compound. It is found as alpha and beta isomers in pomegranates (''Punica granatum''), '' Terminalia catappa'', '' Terminalia myriocarpa'', and in '' Combretum molle'', the ...
s are converted to urolithins, which have unknown
biological activity In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or ...
''in vivo''. Ellagitannins exhibit low
bioavailability In pharmacology, bioavailability is a subcategory of absorption and is the fraction (%) of an administered drug that reaches the systemic circulation. By definition, when a medication is administered intravenously, its bioavailability is 100%. H ...
and are transformed in the gut to ellagic acid and its microbiota metabolites. Urolithins are found in plasma mostly as
glucuronide A glucuronide, also known as glucuronoside, is any substance produced by linking glucuronic acid to another substance via a glycosidic bond. The glucuronides belong to the glycosides. Glucuronidation, the conversion of chemical compounds to glucu ...
s at low concentrations. Urolithins production is dependent on the
gut microbiome Gut microbiota, gut microbiome, or gut flora are the microorganisms, including bacteria, archaea, fungi, and viruses, that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the g ...
enterotype. Individuals producing urolithins show a much higher abundance of the '' Clostridium leptum'' group of Firmicutes phylum than ''
Bacteroides ''Bacteroides'' is a genus of Gram-negative, obligate anaerobic bacteria. ''Bacteroides'' species are non endospore–forming bacilli, and may be either motile or nonmotile, depending on the species. The DNA base composition is 40–48% GC. Un ...
'' or ''
Prevotella ''Prevotella'' is a genus of Gram-negative bacteria. ''Prevotella'' species are widely distributed across varied ecological habitats, with 57 characterized species spanning both human and other mammalian hosts. In mammals, this genus is notabl ...
''.


Known molecules

*
Urolithin A Urolithin A is a metabolite compound resulting from the transformation of ellagitannins by the gut bacteria. It belongs to the class of organic compounds known as benzo-coumarins or dibenzo-α-pyrones. Its precursors – ellagic acids and ellagit ...
(3,8-Dihydroxyurolithin) * Urolithin A glucuronide * Urolithin B (3-Hydroxyurolithin) * urolithin B glucuronide * Urolithin D (3,4,8,9-Tetrahydroxyurolithin) catabolic intermediates: * Urolithin M-5 * Urolithin M-6 *
Urolithin M-7 Urolithins are Microbiota, microflora metabolites of dietary ellagic acid derivatives, such as ellagitannins. They are produced in the Gastrointestinal tract, gut, and found in the urine in the form of urolithin B glucuronide after absorption of ...
* Urolithin C ( 3,8,9-Trihydroxy urolithin) * Urolithin E ( 2,3,8,10-Tetrahydroxy urolithin)


See also

*
Pomegranate ellagitannin The pomegranate ellagitannins, which include punicalagin isomers, are ellagitannins found in the sarcotestas, rind (peel), bark or heartwood of the pomegranate fruit (''Punica granatum''). Chemistry As the chemistry of punicalagins became kno ...
s


References

{{Ellagitannin Benzochromenes Coumarins Phenolic human metabolites