Anhydrous sodium sulfate

Standards of volatile and phenolic compounds were commercially obtained as follows: (Z)-3-hexen-1-ol (Toronto research chemicals Inc., Toronto, CA, USA); linalool, nonanal, phenylethyl alcohol, decanal, eugenol, 1,3,5-trimethoxybenzene, 3-hydroxytyrosol, caffeic acid, vanillin, trans-p-coumaric acid, trans-o-coumaric acid, apigenin-7-glucoside, oleuropein, pinoresinol, quercetin, luteolin, apigenin, diosmetin tyrosol, rutin, luteolin-7-glucoside, oleacein, and ligstroside from Sigma-Aldrich (St. Louis, MO, USA); verbascoside (HWI group, Rülzheim, Germany); and oleuroside (Phytolab, Vestenbergsgreuth, Germany). Alkane standard solutions C₈-C₂₀ and C₁₀, C₂₀-C_40, and derivatization reagent N,O-Bis(trimethylsilyl)trifluoroacet-amide (BSTFA) were purchased from Sigma-Aldrich (St. Louis, MO, USA); pentane, diethyl-ether, acetonitrile, and methanol were from VWR (Radnor, PA, USA); and anhydrous sodium sulfate was from Kemika (Zagreb, Croatia).

Approximately 250 g of fresh leaves per sample were placed to air dry at room temperature (22 °C) for 15 days. A hundred grams of dried leaves per sample were chopped and then hydro-distilled in a Clevenger apparatus for two hours and 30 min. Three replicate samples were distilled simultaneously. Pentane and diethyl-ether (VWR, Radnor, PA, USA) were used as solvents. The oil samples were dried over anhydrous sodium sulfate (Kemika, Zagreb, Croatia) and then stored in glass vials at 4 °C until further analysis.