Strategies for the purification of hydroxytyrosol-rich extracts obtained from exhausted olive pomace

•Separation of phenolic compounds from glucose and mannitol was addressed.•Hydroxytyrosol-rich extracts with different purities were obtained.•Purified phenolic extracts showed α-glucosidase and α -amylase inhibition.•New light on the distribution performance of different olive-derived molecules. 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.