Ginkgo Extract Protects Brain from Stroke Damage

An extract prepared from leaves of the Ginkgo biloba tree, long favored in Chinese and alternative medicine to improve brain function, has been found to protect the brain from some of the damage caused by ischemic stroke.

Investigators at Johns Hopkins University (Baltimore, MD, USA) induced stroke-like damage in a population of laboratory mice by briefly blocking an artery to one side of the brain. Some of the animals in the study were treated with the Ginkgo extract, EGb761, prior to the stroke, while some of the animals received the treatment after the stroke. A control group was not treated with the extract.

Results published in the October 9, 2008, online edition of the journal Stroke revealed that the pretreated animals had 50.9% less neurological dysfunction and 48.2% smaller areas of brain damage than untreated mice. Treatment five minutes or four and a half hours after the stroke also led to significant reduction in damage.

The experiment was carried out a second time on a population of mice that had been genetically engineered to lack the gene for the enzyme heme oxygenase-1 (HO-1). HO-1 breaks down heme into carbon monoxide, iron, and biliverdin. It has been shown to act as an antioxidant and have a protective effect against inflammation in animal models. The HO-1 deficient animals did not show any benefit from EGb761 treatment, either before or after the stroke.

"Our results suggest that some element or elements in ginkgo actually protect brain cells during stroke,” explained senior author Dr. Sylvain Doré, associate professor of anesthesiology and critical care medicine at Johns Hopkins University. "Ginkgo increases HO-1 levels, and the antioxidant properties of this enzyme eliminate free radicals at the surrounding regions of the stroke site. Ginkgo has long been touted for its positive effects on the brain and is even prescribed in Europe and Asia for memory loss. Now we have a possible understanding for how Ginkgo actually works to protect neurons from damage.”

"It is still a large leap from rodent brains to human brains but these results strongly suggest that further research into the protective effects of Ginkgo is warranted,” said Dr. Doré. "If further work confirms what we have seen, we could theoretically recommend a daily regimen of ginkgo to people at high risk of stroke as a preventive measure against brain damage.”

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