Strategies for the purification of hydroxytyrosol-rich extracts obtained from exhausted olive pomace
Irene Gómez‐Cruz, María del Mar Contreras, Inmaculada Romero, Belina Ribeiro, Luísa B. Roseiro, Luís C. Duarte, Florbela Carvalheiro, Eulógio Castro
Abstract
Exhausted olive pomace (EOP) is a residual biomass from which hydroxytyrosol can be recovered. This compound has applications in the food/pharma sectors, but its extraction yields complex extracts that require further purification for some applications. This work explores purification strategies based on membrane technology, liquid-liquid extraction (LLE), and solid-phase extraction with adsorbents and resins. The hydroxytyrosol content, phenolic profile, antioxidant activity, and inhibition of α-glucosidase and α-amylase were monitored. Hydroxytyrosol stood out in all purified extracts. The best hydroxytyrosol recovery (88.8%) was achieved using LLE with ethyl acetate as the extractant, while the purest extracts in phenolic compounds, including hydroxytyrosol, were obtained using the latter solvent and C18, DSC-8, and Purosorb PAD910, being 529, 873 and 523 mg/g, respectively. Conversely, mannitol and glucose, at high concentrations in the extract, were selectively retained in the aqueous phases. The developed strategies are discussed regarding their suitability to provide hydroxytyrosol-concentrated extracts, up to 291 mg/g, with antioxidant and antidiabetic functionalities.