Abstract
The analysis of phenolic compounds in extra virgin olive oils was carried out by high-performance liquid chromatography utilizing photodiode array and mass spectrometry detectors. The chromatographic profile of thirty samples from four Italian Regions highlighted the presence of secoiridoids, phenolic alcohols, flavonoids, and phenolic acid classes. A similar qualitative profile was observed with some differences in peak area and fifteen compounds were tentatively identified. Quantitative analysis was performed by UV detection considering eight standard phenolic compounds. The chromatographic method, after optimization, was validated studying some parameters, e.g., intra-day and inter-day retention time precision, limit of detection, limit of quantification, and linearity. Recovery of the method was performed achieving good results (10 and 50 g·g−1 with recovery of 72.9–92.1% (w/w) and 79.1–102.8% (w/w), respectively). In all samples secoiridoids were the main compounds ranging from 85 to more than 99% (w/w) of the total concentration of detected phenolic compounds while phenolic acids accounted for the lowest percentage (0.1–0.6%, w/w). Finally, total concentration of phenolic compounds and antioxidant activity were determined with different chemical assays. A good and significant correlation among total phenolic compound concentration and antioxidant activity was observed. A significant different phenolic compound concentration and antioxidant activity was determined between samples from Puglia and Sicily. This was studied performing statistical analysis by one-way analysis of variance (ANOVA) followed by Bonferroni post-hoc test.
Highlights
Virgin olive oil (VOO) is the product obtained from the fruit of the olive tree (Olea europea L.)solely by mechanical or other physical means such as washing, decantation, centrifugation, or filtration.Extra virgin olive oils (EVOOs) are classified as VOOs having a free acidity, in terms of oleic acid, lower than 0.8 g per 100 g [1]
Pearson R2 values ranged between 0.607 and 0.893. These results indicated that as the total phenolic compounds concentration increases the antioxidant capacity, measured by tests based on different reaction mechanisms, increases independently from the sample origin
analysis of variance (ANOVA) test showed a significant difference between antioxidant activities measured by Trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays between samples from Puglia and Sicily as observed for total phenolic compounds concentration measured by high-performance liquid chromatography (HPLC)
Summary
Chiara Fanali 1, *, Susanna Della Posta 1 , Alessandra Vilmercati 1 , Laura Dugo 1 , Marina Russo 1 , Tommasangelo Petitti 1 , Luigi Mondello 1,2,3 and Laura de Gara 1. Dipartimento di “Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali”, University of Messina-Polo. Chromaleont S.r.L., c/o Dipartimento di “Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali”, University of Messina-Polo Annunziata, Viale Annunziata, 98168 Messina, Italy. Received: 28 October 2018; Accepted: 6 December 2018; Published: 8 December 2018
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