Concentrated oleuropein powder from olive leaves using alcoholic extraction and supercritical CO2assisted extraction

In this work, a simple approach at oleuropein (OLE) extraction/concentration from olive leaves was proposed. OLE extraction yield was 5.4% w/w of dry leaves and a concentration of OLE of 20% w/w in the ethanol extract was obtained. Then, supercritical antisolvent extraction (SAE) was performed on the ethanol OLE solution, operating at different pressures between 100 and 200 bar and temperatures between 35 and 60 °C. SAE produced a powder rich in OLE up to 36% w/w at 35 °C, 150 bar. Precipitated powder showed different mean diameters dependent on SAE operating conditions: at 60 °C, 130 bar it consisted of micrometric and coalescing particles; at 35 °C, 150 bar it consisted of nanometric non coalescing particles. Therefore, OLE concentration was successful and its bioavailability should be improved by nanometric size of precipitates.