The bound phenolics were obtained by using the previous procedure described by Liyana-Pathirana and Shahidi (2005, 2006) and Zhou, Robards, Helliwell, and Blanchard (2004), with slight modifications. Briefly, a half of one gram of olive leaf (or olive fruit) was dissolved with 20 mL of 80% ethanol to remove soluble phenolic acids, and then defatted with 6 mL hexane. The extract was centrifuged at 8000 rpm for 10 min, and the bound phenolics were then released by hydrolyzing the left- over solid residue with 20 mL of 4 M NaOH (aq.) at room temperature with stirring under nitrogen atmosphere for 4 h. The transparent mixture was acidified to pH 1.5–2.0 by gradual addition of 6 M HCl. After centrifugation at 8000 rpm for 30 min, the supernatant was extracted five times with 30 mL ethyl acetate. The fraction of ethyl acetate was dried through an- hydrous Na2SO4 and evaporated to dryness using a rotary
vacuum evaporator at 30 °C. The resulting residue was then dissolved in 80% ethanol to 10 mL. The extract obtained was stored at −20 °C until used within a week.