Urolithins are

microflora Microbiota are the range of microorganisms that may be commensal, symbiotic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found to ...

metabolites 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 backwards because it can be ...

derivatives, such as

ellagitannins The ellagitannins are a diverse class of hydrolyzable tannins, a type of polyphenol formed primarily from the oxidative linkage of galloyl groups in 1,2,3,4,6-pentagalloyl glucose. Ellagitannins differ from gallotannins, in that their galloyl grou ...

. They are produced in the gut, and found in the

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellular ...

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 Punicoideae, that grows between tall. The pomegranate was originally described throughout the Mediterranean Basin, Mediterranean re ...

. During intestinal metabolism by bacteria, ellagitannins and

punicalagin Punicalagin 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 velvet bushwillow, a plant ...

s are converted to urolithins, which have unknown biological activity ''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%. Ho ...

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 gut ...

enterotype An enterotype is a classification of living organisms based on the bacteriological composition of their gut microbiota. The discovery of three human enterotypes was announced in the April 2011 issue of ''Nature'' by Peer Bork and his associates. Th ...

. Individuals producing urolithins show a much higher abundance of the ''

Clostridium leptum ''Clostridium leptum'' is a bacterium species in the genus ''Clostridium''. It forms a subgroup of human fecal microbiota. Its reduction relative to other members of the gut microbiota has been observed in patients with inflammatory bowel disea ...

'' 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. Unus ...

'' or ''

Prevotella ''Prevotella'' is a genus of Gram-negative bacteria. ''Prevotella'' spp. are members of the oral, vaginal, and gut microbiota and are often recovered from anaerobic infections of the respiratory tract. These infections include aspiration pn ...

''.

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 ...

(3,8-Dihydroxyurolithin) * Urolithin A glucuronide *

Urolithin B Urolithin B (UB) is an urolithin, a type of phenolic compounds produced in the human gut after absorption of ellagitannins-containing food such as pomegranate, strawberries, red raspberries, walnuts or oak-aged red wine. Urolithin B is found ...

(3-Hydroxyurolithin) *

urolithin B glucuronide Urolithins are microflora metabolites of dietary ellagic acid derivatives, such as ellagitannins. They are produced in the gut, and found in the urine in the form of urolithin B glucuronide after absorption of ellagitannins-containing foods, su ...

* Urolithin D (3,4,8,9-Tetrahydroxyurolithin) catabolic intermediates: * Urolithin M-5 * Urolithin M-6 * Urolithin M-7 * Urolithin C ( 3,8,9-Trihydroxy urolithin) * Urolithin E ( 2,3,8,10-Tetrahydroxy urolithin)

References

{{Ellagitannin Benzochromenes Coumarins Phenolic human metabolites

Known molecules

See also

References