Extraction of oleuropein from olive leaves using a hydroalcoholic solvent

Abstract Olive leaves contain oleuropein, a substance known for its antioxidant, antimicrobial and antiinflammatory potentials, amongst others. The objective of this work was to study the extraction of oleuropein using a hydroalcoholic solvent. Olive leaves (OL) were macerated at 25 °C with a solvent (S) consisting of a mixture of ethanol and water (70:30 v/v), with OL:S mass ratios equal to 1:8, 1:6 and 1:3, with or without the presence of acetic acid. The highest oleuropein content found in the freeze dried extract (approximately 18 g/100 g) was obtained from the procedure using an OL:S ratio = 1: 3, in the presence of acetic acid. Finally, a test was carried out to verify the effect of the freeze dried extract on the induction time in samples of extra-virgin and refined olive oil, and increases of 3 and 2 hours, respectively, were observed. It was concluded that it is possible to obtain olive leaf extracts using renewable solvents, and that oleuropein can act as a natural antioxidant in olive oil, improving its oxidative stability.