Phenolic extract obtained from steam-treated olive oil waste: Characterization and antioxidant activity

- Hydroxytyrosol is the most abundant phenol in the steam-treated alperujo extract.
- Elenolic acid derivatives were formed in the process.
- DHPG, HT-acetate, Ty, comsegoloside, protocatechuic acid also had been found.
- The antioxidant activity was mainly due to the presence of cited phenols.
- PPF has high antioxidant activity in a lipid system and radical scavenging activity.

Alperujo or olive oil waste was hydrothermally treated at 160 °C for 60 min to increase the phenols in the liquid phase. The extract obtained from the liquid using ethyl acetate extraction was divided into 27 phenolic fractions using adsorbent and polyamide resins. Phenolic alcohols and acids, secoiridoid molecules, elenolic acid derivatives, flavonoids, verbascoside, degradation products of sugar and a polymeric phenolic fraction (PPF) were characterized using HPLC-ESI-MS. The antiradical activity, ferric reducing power and the inhibition of primary and secondary oxidation were examined for each fraction. Hydroxytyrosol was the most abundant phenol in the ethyl acetate extract and possibly the main component responsible for the in vitro antioxidant activity of the entire phenol extract. However, other phenolic and secoiridoid molecules with interesting biological properties were also identified, and the crude extract could be considered a potential source of natural antioxidants.