Antioxidant activity of phenolics extracted from Olea europaea L-leaves

The purpose of this study was to identify the main phenolic compounds prese nt in an olive leaf extract (OL) in order to delineate the differential ant ioxidant activities of these compounds through the extent of their abilitie s to scavenge the ABTS(.+) radical cation and to clarify the structural ele ments conferring antioxidant capacity in aqueous systems. The results show that the relative abilities of the flavonoids from olive leaf to scavenge t he ABTS(.+) radical cation are influenced by the presence of functional gro ups in their structure, mainly the B-ring catechol, the 3-hydroxyl group an d the 2,3-double bond conjugated with the 4-oxo function. For the other phe nolic compounds present in OL, their relative abilities to scavenge the ABT S(.+) radical cation are mainly influenced by the number and position of fr ee hydroxyl groups in their structure. Also, both groups of compounds show synergic behaviour when mixed, as occurs in the OL. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.