Liquid chromatography tandem mass spectrometric determination of triterpenes in human fluids: Evaluation of markers of dietary intake of olive oil and metabolic disposition of oleanolic acid and maslinic acid in humans

Abstract

Olive oil is rich in several minor components like maslinic (MA) and oleanolic (OA) acids which have cardioprotective, antitumor, and anti-inflammatory properties. In order to assess the health benefits in humans provided by the olive oil triterpenes (MA and OA), suitable analytical methods able to quantify the low concentrations expected in human fluids are required. In this study, the LC-MS/MS quantification of both OA and MA in plasma and urine has been evaluated. The plasmatic method is based on the direct determination of the analytes. The urinary detection requires more sensitivity which was reached by derivatization with 2-picolylamine. Additionally, the urinary species present after MA and OA ingestion were evaluated by the direct detection of several phase II metabolites previously synthesized. Our results showed that OA is metabolized as both sulfate and glucuronide conjugates whereas MA is mainly excreted as glucuronide. Based on this information, the method for the urinary detection of MA and OA involved an enzymatic hydrolysis. Both plasmatic and urinary methods were validated with suitable precision and accuracy at all tested levels. Required sensitivity was achieved in both matrices. Up to our knowledge, this is the first method able to quantify the low concentration levels of triterpenes present in urine. Samples from two healthy volunteers who received virgin olive oils with different triterpenes content were analyzed. Some preliminary clues on the metabolic disposition of OA and MA after olive oil intake are provided.