NMR Spectroscopic Identification of Urolithin G, a Novel Trihydroxy Urolithin Produced by Human Intestinal <i>Enterocloster</i> Species
David Beltrán, María Dolores Frutos-Lisón, Rocío Garcı́a-Villalba, José Enrique Yuste, Vı́ctor Garcı́a-Aparicio, Juan Carlos Espı́n, María V. Selma, Francisco A. Tómas‐Barberán
Abstract
High Resolution Image Download MS PowerPoint Slide Urolithins are gut microbiota metabolites of ellagic acid. Here, we have identified and chemically characterized a novel urolithin produced from urolithin D (3,4,8,9-tetrahydroxy urolithin) by in vitro incubation with different human gut Enterocloster species under anaerobic conditions. Urolithin G (3,4,8-trihydroxy urolithin) was identified by 1 H NMR, 13 C NMR, UV, HRMS, and 2D NMR. For the identification, NMR spectra of other known urolithins were also recorded and compared. Urolithin G was present in the feces of 12% of volunteers in an overweight-obese group after consuming an ellagitannin-rich pomegranate extract. The production of urolithin G required a bacterial 9-dehydroxylase activity and was not specific to the known human urolithin metabotypes A and B. The ability to produce urolithin G could be considered an additional metabolic feature for volunteer stratification and bioactivity studies. This is the first urolithin with a catechol group in ring A while having only one hydroxyl in ring B, a unique feature not found in human and animal samples so far.