Antioxidant mechanisms have been proposed to underlie the beneficial pharmacological
effects of EGb 761, an extract from Ginkgo bitoba leaves used for treating peripheral vascular diseases
and cerebrovascular insufficiency in the elderly. In uitro evidence has been reported that EGb 761
scavenges various reactive oxygen species, i.e. nitric oxide, and the superoxide, hydroxyl, and oxoferry1
radicals. However, the ability of EGb 761 to scavenge peroxyl radicals (reactive species mainly
involved in the propagation step of lipid peroxidation) has not been investigated. To characterize
further the antioxidant action of EGb 761, we measured the protective effects of EGb 761 during: (1)
the oxidation of B-phycoerythrin by peroxyl radicals generated in aqueous solution by 2,2’-azobis (2-
amidinopropane) hydrochloride (AAPH); and (2) the reaction of luminol or cis-parinaric acid with
peroxyl radicals generated from 2,2’-azobis (2,4-dimethylvaleronitrile) (AMVN) in liposomes or in
human low density lipoprotein (LDL), respectively. To evaluate the peroxyl radical scavenging activity
of EGb 761 in a more physiologically relevant model of damage to lipid-containing systems, we also
analyzed the effect of the extract on the oxidation of human LDL exposed to the azo-initiators in terms
of: (1) accumulation of cholesterol linoleate ester hydroperoxides, (2) depletion of cu-tocopherol and
@carotene, and (3) changes in intrinsic tryptophan fluorescence. EGb 761 afforded protection against
oxidative damage in all the systems we analyzed; thus, it is an efficient scavenger of peroxyl radicals.
This result extends the oxygen radical scavenging properties of the extract and supports the hypothesis
of an antioxidant therapeutic action of EGb 761.