Evaluating the reliability of specific and global methods to assess the phenolic content of virgin olive oil: Do they drive to equivalent results?

Despite the huge number of different published methodologies, there is an open debate regarding which one is the most convenient analytical strategy for the determination of phenolic compounds from virgin olive oils. Diverse technical issues together with the disparity of criteria regarding results expression cause a lot of confusion. Herewith, a systematic comparison between specific (a powerful and LC-MS method) and global methodologies (the Folin-Ciocalteau (FC) colorimetric assay, the International Olive Council (IOC) method and hydrolysis plus HPLC-DAD) has been carried out. Thus, these strategies have been applied to the analysis of 50 extra virgin olive oils (covering all the possible quantitative ranges of these substances). This is the first time in which the individual LC-MS quantification of so many phenolic substances is included in this kind of comprehensive comparison. The outcomes of all the strategies have been thoroughly confronted and their equivalence (or divergence) has been carefully evaluated, establishing possible correspondence factors. The LC-MS individual determination with the pure standard of every analyte represented the ideal situation; when only the commercially available standards were used, a drastic change was observed in the absolute concentrations of oleuropein derivatives (in terms of hydroxytyrosol). Total phenolic content (summing individual levels) proved to be higher (1.9-3.0 times when data was expressed in mg/kg) than the values given by the three non-specific methods (with R2 from 0.84 to 0.90). In any case, the IOC method, the FC assay and the hydrolysis approach could be considered as feasible strategies when a global value is pursued. Good correlations between their results were found (R2 > 0.89), with the following equivalence factors: FC(mg caffeic acid/kg) ≈ 0.60 IOC(mg TY/kg); IOC(mg TY/kg) ≈ 1.27 Sum acid hydrolysis(mg TY+HTY/kg); FC(mg HTY/kg) ≈ 1.04 Sum acid hydrolysis(mg TY+HTY/kg).

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.

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.

The NUTRAOLEOUM Study, a randomized controlled trial, for achieving nutritional added value for olive oils.

BACKGROUND: Virgin olive oil, a recognized healthy food, cannot be consumed in great quantities. We aim to assess in humans whether an optimized virgin olive oil with high phenolic content (OVOO, 429 mg/Kg) and a functional one (FOO), both rich in phenolic compounds (429 mg/Kg) and triterpenic acids (389 mg/kg), could provide health benefits additional to those supplied a by a standard virgin olive oil (VOO). METHODS/DESIGN: A randomized, double-blind, crossover, controlled study will be conducted. Healthy volunteers (aged 20 to 50) will be randomized into one of three groups of daily raw olive oil consumption: VOO, OVOO, and FOO (30 mL/d). Olive oils will be administered over 3-week periods preceded by 2-week washout ones. The main outcomes will be markers of lipid and DNA oxidation, inflammation, and vascular damage. A bioavailability and dose-response study will be nested within this sustained- consumption one. It will be made up of 18 volunteers and be performed at two stages after a single dose of each olive oil. Endothelial function and nitric oxide will be assessed at baseline and at 4 h and 6 h after olive oil single dose ingestion. DISCUSSION: For the first time the NUTRAOLEUM Study will provide first level evidence on the health benefits in vivo in humans of olive oil triterpenes (oleanolic and maslinic acid) in addition to their bioavailability and disposition. TRIAL REGISTRATION: The Trial has been registered in ClinicalTrials.gov ID: NCT02520739 .