Availability and Metabolic Fate of Olive Phenolic Alcohols Hydroxytyrosol and Tyrosol in the Human GI Tract Simulated by the In Vitro GIDM-Colon Model.

Hydroxytyrosol (HTyr) and tyrosol (Tyr) are the most well studied phenolic alcohols of olive oil and olive products demonstrating numerous and significant beneficial health effects. However, their activity in the human organism as food bioactives is strongly associated with their bioavailability and metabolism, while manifested through their metabolites. Nevertheless, there are limited studies investigating their biotransformation and mainly catabolism by gut microflora under a holistic interpretation close to the human organism. Thus, in the present study, the GastroIntestinal Dialysis (GIDM)-colon model, a continuous flow in vitro dialysis system mimicking physiological conditions during human gastrointestinal digestion, was used to explore the metabolism of HTyr and Tyr as pure compounds. The GIDM-colon model simulates absorption from the lumen to the mucosa, followed by the colon phase using pooled human fecal suspensions. Samples were collected at different time points and analyzed via LC-Orbitrap MS. An integrated approach combining Multivariate Data Analysis (MVA) and thorough dereplication procedures led to the identification of HTyr and Tyr metabolites in different phases (gastric, small intestine, and colon), yielding also valuable information about metabolites kinetics. To our knowledge, this is the first study reporting full spectrometric data of HTyr and Tyr metabolites along with possible transformation mechanisms in the GI tract.