Previous animal studies have indicated that an extract from leaves of the Ginkgo biloba tree may protect against stroke-related brain injury. However, the mechanism involved has not been fully understood. In a recent NCCAM-funded study, researchers at Johns Hopkins University investigated whether and how the ginkgo extract Egb761 alters outcomes in mice with brain injury from stroke.
The researchers gave the mice oral doses of Egb761 for 7 days before and at 5 minutes and 4.5 hours after inducing strokes in the animals. Compared with controls, the pretreated mice had less neurological dysfunction and smaller areas of brain damage. The mice treated after the stroke also had less brain damage. The protective effects of Egb761 weren't seen in a separate group of mice lacking the gene that produces the enzyme heme oxygenase-1 (HO-1)—an indication that HO-1 is part of the protective mechanism.
These findings suggest that ginkgo extracts might be useful as a preventive therapy or as a post-stroke treatment to reduce the damaging effects of stroke. The researchers at Johns Hopkins are currently conducting additional studies to further explain the “signaling cascade” involved in ginkgo's protective effects. Although results from this study of ginkgo in mice are promising, at this time the scientific evidence for use of ginkgo to prevent or treat strokes in humans is not sufficient to make a treatment recommendation.
Saleem S, Zhuang H, Biswal S, et al.. Ginkgo biloba extract neuroprotective action is dependent on heme oxygenase 1 in ischemic reperfusion brain injury.. Stroke...2008