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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, such as pomegranate. During intestinal metabolism by bacteria, ellagitannins and punicalagins are converted to urolithins, which have unknown biological activity in vivo.[medical citation needed]
Ellagitannins exhibit low bioavailability and are transformed in the gut to ellagic acid and its microbiota metabolites.[medical citation needed] Urolithins are found in plasma mostly as glucuronides at low concentrations. Urolithins production is dependent on the gut microbiome enterotype. Individuals producing urolithins show a much higher abundance of the Clostridium leptum group of Firmicutes phylum than Bacteroides or Prevotella.[medical citation needed]
catabolic intermediates: