Valorization of an UnderutilizedWaste from Olive Oil Production by Recovery of Hydroxytyrosol

Hydroxytyrosol (HT) is one of the most powerful natural antioxidants, mainly containedin olive oil and its by-products. Here, a procedure for the preparation of an HT-enriched sampleis described. An acidic aqueous extract (pH 1.25) from Olive Oil Dregs (OOD), a by-product fromoil mills, was prepared by incubation at 37 °C for 1 h. The total phenolic content and HT amountwere 6.24 +/- 0.10 mg gallic acid equivalent/g OOD and 532.98 +/- 5.78 ug/g OOD, respectively.Amberlite XAD16N and XAD7HP resins were used for the recovery of HT from the raw extract.Several elution conditions were tested with both resins, and elution with 25% ethanol providedthe highest HT recovery (92.50% from XAD7HP). Antioxidant activities were assessed in the poolcontaining the highest quantity of HT. The results were compared with those of the raw extract. Ferricreducing antioxidant power values were comparable (95.71 +/- 2.50 and 96.64 +/- 13.47 ug ascorbic acidequivalent/mg for HT-enriched pool and raw extract, respectively), while the radical scavengingactivity was higher for the pool (92.83% +/- 0.44 and 44.12% +/- 1.82, respectively). The results reportedhere demonstrate that HT can be recovered with a high yield from OOD, providing a preparationwith high radical scavenging power. In addition, it is proved that this by-product, poorly consideredup to now, can be usefully exploited.