2.1.1. Standards and Reagents

Most of the standards used for the Ultra Pressure Liquid Chromatography (UPLC) analysis (caffeic, ferulic, *p*-coumaric, gallic, and chlorogenic acids; catechin; quercetin; 3-hydroxytyrosol, spiraeoside, oleureopin, dadzein, luteolin, naringenin, formononentin), as well as high pressure liquid chromatography (HPLC)-grade ethanol and acetonitrile were purchased from Sigma-Aldrich (Milano, Italy). Apigenin and hyperoside were purchased from Extrasynthese (Genay, France).

## 2.1.2. Extraction and Determination of Total 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]. 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.
