Extraction, Analysis, and Antioxidant Activity Evaluation of Phenolic Compounds in Different Italian Extra-Virgin Olive Oils

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.

Application of deep eutectic solvents for the extraction of phenolic compounds from extra‐virgin olive oil

“…The most abundant compounds in all extracts were the secoiridoid derivatives, in agreement with literature data obtained with a conventional extraction [7,23,24]. Taking into consideration all the solvents, the order of efficiency for the extraction of PCs (the sum of concentration of selected compounds) was DES6 > DES9 > DES3 > DES7 > conventional solvent > DES4 > DES5 > DES2 > DES1 > DES10 > DES8.…”

“…Method optimization, using optimized sample preparation conditions, was carried out analyzing a mixture of two PCs representative of selected compounds for quantitative analysis, namely oleuropein and 2-(4-hydroxyphenyl)ethanol. A Core-Shell column was used for their separation applying conditions reported in a previously published paper [7]. Sepa-rated peaks were recorded with a DAD detector and the signal extracted at 280 nm.…”

“…Room temperature and sample to solvent ratio of 1:1 (w/v) were used as experimental conditions. Extracted PCs were separated and detected using HPLC-DAD/ESI-MS considering experimental conditions reported by our group [7]. In order to tentatively identify the analytes, the retention time and UV and MS spectra, use of standard compounds and data available in the literature were taken into account.…”

“…Different PCs have been identified in EVOO like phenolic alcohols, such as hydroxytyrosol and tyrosol, and their secoiridoid derivatives linked to the aldehydic and dialdehydic forms of elenolic acid, such as oleuropein, the dialdehydic form of decarboxymethylelenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA), an isomer of oleuropein [6][7][8].…”

Antique Traditional Practice: Phenolic Profile of Virgin Olive Oil Obtained from Fruits Stored in Seawater

“…The determined concentrations of hydroxytyrosol in VOO and VOO-Sea, that amount to 18.2 mg/kg and 12.9 mg/kg, respectively, are generally in the range similar to the values in some Spanish (6.9–72.7 mg/kg of oil) or Italian EVOOs (0.85–36.7 mg/kg of oil) [ 17 , 19 , 20 ], and are even higher than those previously published for Oblica variety (6.2–11.3 mg/kg of oil) [ 11 , 21 , 22 ]. Furthermore, the tyrosol concentration determined in VOO and VOO-Sea (8.10 mg/kg and 7.20 mg/kg respectively) is very similar to the values in the same literature.…”