2. Materials and methods
2.1. Solvents and reagents
The 2,2-diphenyl-1-picryl-hydrazyl (DPPH) reagent was
obtained from Sigma–Aldrich (USA). Carbon dioxide (for the
extraction procedure) was supplied by Air-Liquid Hellas in cylinders
and the absolute ethanol (for DPPH tests and supercritical
CO2 extraction apparatus) was obtained by Carlo Erba Reagents.
Methanol (HPLC grade) was obtained from Merck KGaA, Darmstadt
and acetic acid 100% glacial from Riedel-de Haën. HPLC-grade
water was obtained by double-distillation and purification with a
Labconco Water Pro PS polishing station (Labconco Corporation,
Kansas City, MSU).
2.2. Plant material
Olea europaea (variety Koroneiki) leaves were collected in 2009
in the region of Attica, dried in a well ventilated shady place and
subsequently stored. Before the extraction the leaves were grinded
using an AllenWest type SCIS grinder with a sieve of 3 mm.