Forget about it

Ginkgo biloba when used as a herbal remedy/supplement is derived from the plant leaves which contain flavonoid glycosides and terpenoids.

The large 2002 National Institute on Aging trial is available here.

"When taken following the manufacturer's instructions, ginkgo provides no measurable benefit in memory or related cognitive function to adults with healthy cognitive function."

The online magazine Slate had an interesting article in 2007 on the issue that takes a critical look at the evidence: Ginkgo Biloba? Forget About It. A history of the top-selling brain enhancer.

"Regardless, herbal companies will continue to advertise their ginkgo supplements with such watery, asterisked statements as, "May help to support mental sharpness." Starbucks, of course, could reasonably make the same claim."