Simulating human gastrointestinal and colonic biotranformation pathways through an in vitro assay reveals insight on hydroxytyrosol and oleuropein metabolism

Hydroxytyrosol (HT) and oleuropein (OL) are significant components of olive oil and olive fruits (Olea europaea L.), inextricably linked to the Mediterranean diet. Both of them are considered as some of the chemical constituents relevant to the biological activity of olive oil, leading to a global upsurge in the investigation of their diverse health promoting and disease preventing abilities, including several chronic diseases, mainly cardiovascular and neurodegenerative disorders, and cancer. Moreover, a large body of evidence suggests that the potential biological effects of edible phenolic compounds in the human body are partly consequence of their biotransformation by the colon microbiota.

Aiming towards a detailed investigation into the absorption, metabolism and microflora-dependent transformation of HT, and its conjugated form, OL, and within the framework of the international MediHealth project, the GIDM-Colon Model was applied. The aforementioned model is an optimized, validated in vitro continuous flow dialysis system, simulating the absorption from lumen to mucosa; followed by the colon phase using pooled human faecal suspensions, which mimics the physiological conditions during human gastrointestinal digestion [1]. Throughout GIDM-Colon digestion, different samples were collected of both dialysate and retentate solutions, after gastric and small intestinal digestion, and at five different time points of colonic digestion. Data analysis and metabolite profiling were conducted using a UPLC-Orbitrap HRMS along with chemometric approaches. Results of this study provide significant insight into the bioavailability and biotransformation of HT and OL in the human gut using a validated in vitro Gastrointestinal Dialysis Model with Colon phase.

• References

• 1 Breynaert A, Bosscher D, Kahnt A, Claeys M, Cos P, Pieters L, Hermans N. Development and Validation of an in vitro Experimental GastroIntestinal Dialysis Model with Colon Phase to Study the Availability and Colonic Metabolisation of Polyphenolic Compounds. Planta Med 2015; 81: 1075-1083