Extraction and Quantification of EVOO Polyphenols

The extraction of polyphenols from EVOOs, necessary for the chromatographic analyses, was performed using hexane (1:1 w/v), following the method of Fratianni et al. [15 (link)]. The mixture was then charged onto cartridges SPE C₁₈, and eluted three times with methanol. The three residues were pooled, dried, re-suspended in 1 mL of methanol and filtered through a 0.20 mm filter before the analysis. Total phenolic (TP) content was determined using the Folin-Ciocalteau reagent [16 ]. The absorbance at λ = 760 nm was determined (Cary UV/Vis spectrophotometer, Varian, Palo Alto, CA, USA) at room temperature. A standard curve generated using gallic acid as standard was used to quantify total polyphenols.