In vitro studies have demonstrated that G. biloba extracts scavenge free
radicals (33–37). Ginkgo biloba extracts have been reported to reduce free radicallipid
peroxidation induced by NADPH-Fe3 systems in rat microsomes (33), and
to protect human liver microsomes from lipid peroxidation caused by
ciclosporin A (34). The extract also inhibits the generation of reactive oxygen
radicals in human leukocytes treated with phorbol myristate acetate (35). The
antioxidant action of G. biloba extract may prolong the half-life of endotheliumderived
relaxing factor by scavenging superoxide anions (36, 37). Both the
flavonoid and terpenoid constituents of G. biloba appear to aid the free-radical
scavenging activity of the drug (37).
Ginkgo biloba extract protected against brain tissue hypoxic damage in vitro.
The ginkgolides and bilobalide were responsible for the antihypoxic activity of
the extract (38, 39). Ginkgolides A and B have been shown to protect rat
hippocampal neurons against ischaemic damage, which may be due to their
ability to act as antagonists to receptors for platelet-activating factor (PAF) (40–
42).