# A Narrative Review of Metabolomic Insights into Olive Oil's Nutritional Value
## 4 Case Studies and Applications  
Examples of analytical breakthroughs have provided new insights into the health benefits of olive oil. Over the years, advanced analytical techniques have uncovered new aspects of the health-promoting properties of olive oil, possibly leading to its novel applications and therapeutic uses. According to the aim of this review, a variety of analytical techniques applied in the study of olive oil focused on how these methods assess the bioavailability and effects of specific olive oil components, particularly phenolic compounds. These findings are summarized in Table 2. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Technique for the** & **Strengths** & **Drawbacks** \\ \hline \multirow{6}{*}{NMR spectroscopy} & This allows easy quantification of metabolites. & \\  & No sample pretreatment is required. & \\  & There is no need to pre-select the conditions to & \\  & perform the analysis, guaranteeing the generation & \\  & of spectra with a high information content. & \\  & The chemical shifts are relatively stable, which & \\  & allows the results to be reproducible under & \\  & consistent experimental conditions. & \\ \hline \multicolumn{4}{l}{MALDI = matrix-assisted laser desorption/ionization; ESI = electrospray ionization; TOF = time of flight. Adapted from [83].} \\ \end{tabular}
\end{table} 
Table 1: _Cont._ \begin{table}
\begin{tabular}{c c c c} \hline \hline
\begin{tabular}{c} \hline \hline \end{tabular} \\  & Evaluate whether different \\  & food matrices influenced \\  & the pharmacokinetics and \\  & bioavailability of HT and \\  & its metabolites & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Metabolomics studies on olive oil. A randomized, double-blind, controlled crossover trial aimed to identify the biomarkers of exposure to phenolic compounds that may provide insights into the potential health effects of phenol intake. The volunteers were subjected to consistent consumption of two olive oils enriched in polyphenols over a three-week period. While the HPLC/MS/MS analytical technique allowed researchers to analyze the phenolic profile of the olive oils that were used, ultra-performance liquid chromatography coupled with tandem MS (UPLC-MS/MS) allowed thorough determination of the metabolites present in biological fluids upon treatment. In general, HT metabolites are less specific. Nevertheless, HT sulphate (sulHT) and HT acetate sulphate (sulHTAc) showed remarkable potential as biomarkers for the intake of these bioactive compounds, considering that their concentrations were significantly higher after treatment. Hence, the analytical technique used for the examination of biological samples not only allowed the identification of possible biomarkers but also proved to be reliable for phenolic biomarker profiling in nutrition studies [84]. The bioavailability of phenolic compounds is associated with their activity in the human body and, consequently, their effects on health [87]. Therefore, several studies have attempted to evaluate their bioavailability using the previously mentioned analytical techniques. For instance, a study using Sprague-Dawley rats assessed the bioavailability and metabolism after oral intake of HT, HT acetate (HTA), and 2,3-dihydroxyproxyphenylacetic acid (DOPAC) using ultra-HPLC coupled to a mass spectrometer with an ESI chamber and a triple quadrupole mass analyzer for tandem analysis (UHPLC-ESI-QqQ-MS/MS). The results demonstrated that all the compounds were absorbed in the gastrointestinal tract, and their metabolism appeared to have several resemblances. However, bioavailability depends on numerous factors such as sex, the derivative itself, and dosage. The authors found that the concentrations of HT, HTA, and DOPAC in the plasma and urine did not increase proportionally with the dosage, potentially owing to saturation of the first-phase metabolic processes and intestinal transporters [85].