Ginkgo Biloba

Introduction

Ginkgo is derived from the leaves of the ginkgo tree, one of the oldest species of trees, and has been used for thousands of years by the Chinese as an herbal remedy for a variety of ailments. The typical daily dose of ginkgo biloba is 120 milligrams of dried extract in two or three oral doses. The extract contains several flavonoids, a large group of natural plant products that are characterized by a specific chemical structure containing a series of carbon rings. Ginkgo extract also contains some biflavonoids, a related group of compounds, and two different types of terpenes, a class of naturally occurring chemicals that includes the active ingredients in catnip and marijuana.

Today ginkgo biloba is perhaps the most widely used herbal treatment aimed at augmenting cognitive functions — that is, improving memory, learning, alertness, mood and so on. In Europe, ginkgo is an important part of mainstream medicine, with sales accounting for more than 1 percent of all pharmaceutical purchases. In the U.S. alone, $310 million dollars worth was sold in 1998. But is its popularity based on folklore or on experimental findings?

While dozens of investigations have examined the cognitive effects of ginkgo in humans, many of the research reports are in non-English publications or in journals with very restricted distribution, making assessment of the findings difficult. The great majority of studies have involved subjects with mild to moderate mental impairment, usually a diagnosis of early Alzheimer's. Most of the experiments that show evidence of cognitive enhancement in Alzheimer's patients have used a standardized ginkgo extract known as EGb 761.

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