Affiliation:
1. Laboratory of Food Chemistry and Biochemistry, School of Agriculture, Aristotle University of Thessaloniki (AUTH), 54124 Thessaloniki, Greece
2. Łukasiewicz Research Network-New Chemical Syntheses Institute, Al. Tysiąclecia Państwa Polskiego 13a, 24-110 Puławy, Poland
3. University of Belgrade, Faculty of Technology and Metallurgy, Karnegijeva 4, 11120 Belgrade, Serbia
Abstract
An eco-friendly approach towards the recovery of value-added extracts from olive tree leaves with the aid of supercritical CO2 at 30 MPa was carried out. The impact of extraction temperature (35–90 °C) and presence of co-solvents (ethanol, water, and aqueous ethanol) on the total phenolic, flavonoid, and pigment content, as well as oleuropein, hydroxytyrosol, tyrosol, and α-tocopherol content was determined. In addition, the antioxidant activity of extracts from tree leaves using DPPH, ABTS, and CUPRAC assays was investigated. The results of the study showed that the most effective supercritical CO2 extraction was at 90 °C with an addition of ethanol, which enabled the separation of extract with the highest content of tested compounds. Some of the highest recorded values were for oleuropein 1.9 mg/g, for carotenoids 5.3 mg/g, and for α-tocopherol 2.0 mg/g. Our results are expected to contribute to the efforts towards the valorization of olive leaves as a sustainable source of valuable compounds, and boost local economies as well as the interest of pharmaceutical, food, and cosmetic industries for novel food by-product applications.