Isolation and identification of radical scavengers in olive tree (Olea europaea) wood

Several extracts of Olea europaea wood (Picual olive cultivar) were obtained with solvents of different polarity and their antioxidant activities determined. The active compounds were detected in fractions of an ethyl acetate extract using HPLC with on-line radical scavenging detection. After applying different separation techniques, hydroxytyrosol, tyrosol, cycloolivil, 7-deoxyloganic acid, oleuropein and ligustroside were isolated and characterized. Hydroxytyrosol showed a higher activity than the natural antioxidant rosmarinic acid in scavenging the DPPH model radical. Cycloolivil and oleuropein showed stronger activities than the synthetic antioxidant BHT against the same radical. Ligustroside, tyrosol and 7-deoxyloganic acid showed little activity. The latter compound has not been previously identified in the genus Olea.