High Resolution Mass Spectrometric Analysis of Secoiridoids and Metabolites as Biomarkers of Acute Olive Oil Intake-An Approach to Study Interindividual Variability in Humans

Abstract

Scope: Phenolic compounds are minor components of extra virgin olive oil (EVOO). Secoiridoids are the major components contributing to the phenolic content of EVOO. Information is lacking regarding their potential as biomarkers for EVOO intake.

Methods and results: Healthy volunteers (n = 9) ingested 50 mL of EVOO in a single dose containing 322 mg kg^-1 total phenolic content (caffeic acid equivalents) and 6 mg 20 g^-1 hydroxytyrosol and its derivatives. Plasma is collected before (0 h) and at 0.5, 1, 2, 4, and 6 h after ingestion. Urine samples are collected prior to ingestion (0 h) and at 0-4, 4-8, 8-15, and 15-24 h. Samples are analyzed by UPLC coupled with an Exactive Orbitrap MS. Partial least squares discriminant analysis with orthogonal signal correction is applied to screen for metabolites that allow sample discrimination. Plasma biomarkers and urine biomarkers are selected although individual variability is observed among volunteers. Results are in accordance with in vitro experiments performed (in vitro digestion and hepatic microsomal activity assays).

Conclusions: Plasma (elenolic acid + H₂ ; p-HPEA-EA + H₂ + glucuronide) and urinary (3,4-DHPEA-EA, 3,4-DHPEA-EA + H₂ +glucuronide, methyl 3,4-DHPEA-EA + H₂ +glucuronide) secoiridoid compounds are selected as biomarkers to monitor EVOO intake showing good predictive ability according to multivariate analysis.

Keywords: bioavailability; metabolites; olive oil; phenolic compounds; secoiridoids.