THURSDAY, Oct. 9, 2008 (HealthDay News) -- A study with genetically engineered mice found that an extract from the leaves of the ginkgo tree can prevent or reduce brain damage from a stroke.
The ginkgo extract appears to help by neutralizing the activity of free radicals, molecules known to attack and kill cells, explained study author Sylvain Dore, an associate professor of anesthesiology and critical care medicine at Johns Hopkins University.
"What is interesting here is that we are looking at a mechanism of action that has not been proposed before," Dore said.
The Hopkins group is already getting ready to design human trials of ginkgo treatment for stroke, Dore said. "We want to see what is the optimal therapeutic window, the safest dose, how long after a stroke it can be given," he said.
The findings were published in the Oct. 10 issue of Stroke.
The implications of the study for patients drew a cautious response from Dr. Larry B. Goldstein, director of the Duke University Stroke Center.
"While this study in an animal model was well done, it was primarily intended to explore the possible mechanism of ginkgo's actions as a neuroprotective drug," he said. "For a variety of possible reasons, numerous past studies suggesting benefits in animal models of stroke have not translated into effective treatments after clinical trials were done, and there is no FDA-approved neuroprotective drug."
In the study, Dore and his colleagues worked with both normal mice and mice bred to lack the enzyme heme oxygenase. Some mice were given standardized doses of the ginkgo extract for seven days while others weren't. Brain arteries in the rodents were then blocked to cause a stroke.
Tests showed that normal mice that got the ginkgo extract had 50.9 percent less neurological damage and 48.2 percent smaller areas of brain damage than mice that didn't get the extract.
"What we have shown here is that by induction of an antioxidant enzyme, ginkgo extract can be effective," Dore said.
The results of the trial were encouraging enough that "we have put a team together to actively continue looking at the efficacy/safety and mechanisms of action of the ginkgo extract in preclinical models of ischemic stroke that could ultimately help in the design an optimal clinical trial," he said.
Goldstein said: "The clinical trials that have been done on ginkgo so far have not been inadequate. In a meta-analysis, the bottom line was that there was no clear benefit, but it's impossible to draw any firm conclusions because the quality of the studies was not optimal."
Dore and Goldstein agreed on one point -- that the study results should not prompt people to start using the well-advertised ginkgo products that are widely available and touted as memory enhancers.
The Hopkins trial used a standardized extract, while the quality of the extracts sold commercially can be uncertain, Dore said.
"Ginkgo can interact with prescribed drugs and aspirin, and there is the risk of bleeding complications," Goldstein noted. One recent trial of ginkgo as a memory booster in older people even found a slightly increased risk of stroke, he said.
The U.S. Centers for Disease Control and Prevention describes proven ways to reduce the risk of stroke.