Bioavailability of mango (poly)phenols: An evaluation of the impact of the colon, and phenylalanine and tyrosine on the production of phenolic catabolites

A mango pulp purée was ingested by ileostomists, whose colon had been removed surgically, and subjects with a full gastrointestinal (GI) tract, after which ileal fluid, urine and feces were collected over a 24 h period and analysed by UHPLC-HR-MS. The main (poly)phenols in the purée were gallotannins (356 μmol) and two hydroxy-methoxy-cinnamoyl glucose esters (43 μmol) together with the aromatic amino acids phenylalanine (22 μmol) and tyrosine (209 μmol). Analysis of ileal fluid revealed almost all the ingested gallotannins appeared to have broken down in the upper GI tract with the released benzoic acids being rapidly absorbed into the circulatory system prior to urinary excretion mainly as phase-2 metabolites. Likewise, the glucose moiety of the cinnamic acid conjugates was cleaved and the released cinnamic acids absorbed efficiently from the proximal GI tract and subjected to phase II metabolism prior to excretion. Among the main phenolics excreted after mango intake were phenylacetic and benzoic acids and hydroxybenzene catabolites which were present in lower, but none-the-less, substantial amounts, in the urine of ileostomists. This indicates that a portion of these phenolics, including the hydroxybenzene derivatives, originate from substrates absorbed in the upper GI tract and are principally products of endogenous metabolism rather than being derived from colonic microbiota-mediated catabolism. 1,2,3-Trihydroxybenzene (aka pyrogallol) was the dominant urinary catabolite in both groups. Hippuric acid excretion exceeded (poly)phenol intake indicating a significant contribution from phenylalanine and tyrosine. The aromatic amino acids, while present in the ingested pulp, can also originate from several sources including breakdown of dietary proteins in the GI tract, and endogenous breakdown of surplus mammalian proteins independent of the GI tract. The trial was registered at clinical trials.gov as NCT06182540.