Hydroxytyrosol-enriched preparation from olive oil dregs

Introduction: Hydroxytyrosol is a powerful natural antioxidant contained in olive oil and its by-products. Among them, olive oil dregs (OOD), an underexploited semi-solid residue that precipitates in unfiltered olive oils, contain significant amounts of hydroxytyrosol. The purpose of this work was the enrichment of the polyphenolic component, in particular hydroxytyrosol, in OOD extract through liquid chromatography on Amberlite XAD7HP and XAD16N resins. Material & Methods: An OOD aqueous extract was prepared , and Amberlite XAD16N and XAD7HP were used for the recovery of hydroxytyrosol. Different elution conditions were tested. Polyphenols were estimated by Folin-Ciocalteu. Hydroxytyrosol was quantified by RP-HPLC. Antioxidant activities were assessed in the pool containing the highest quantity of hydroxytyrosol. Results: Total Phenolic Content and hydroxytyrosol in the OOD extract were 6.24±0.10 mg Gallic Acid Equivalents/g and 532.98±5.78 ug/g, respectively. Elution with 25% ethanol provided the highest hydroxytyrosol recovery (92.50% from XAD7HP). Ferric Reducing Antioxidant Power of hydroxytyrosol-enriched preparation was comparable to the OOD extract, while Radical Scavenging Activity was higher for the preparation (92.83%±0.44 and 44.12%±1.82, respectively). Conclusion: The results demonstrate that hydroxytyrosol can be recovered with high yield from OOD, providing a preparation with high radical scavenging power. Moreover, it is proved that this by-product can be usefully exploited.