Antioxidant activity of phenolics extracted from Olea europaea L-leaves

The purpose of this study was to identify the main phenolic compounds present in an olive leaf extract (OL) in order to delineate the differential antioxidant activities of these compounds through the extent of their abilities to scavenge the ABTS(.+) radical cation and to clarify the structural elements conferring antioxidant capacity in aqueous systems. The results show that the relative abilities of the flavonoids from olive leaf to scavenge the ABTS(.+) radical cation are influenced by the presence of functional groups in their structure, mainly the B-ring catechol, the 3-hydroxyl group and the 2,3-double bond conjugated with the 4-oxo function. For the other phenolic compounds present in OL, their relative abilities to scavenge the ABTS(.+) radical cation are mainly influenced by the number and position of free hydroxyl groups in their structure. Also, both groups of compounds show synergic behaviour when mixed, as occurs in the OL. (C) 2000 Elsevier Science Ltd. All rights reserved.