The ginkgo tree is a living fossil, the last species in its division (a taxonomic rank equivalent to all of the flowering plants). It is a gymnosperm, but only distantly related to other gymnosperms such as pines. Native to China, the ginkgo is believed to be extinct in the wild; it was nearly wiped out by climate change during and following the most recent Ice Age, and was preserved for centuries by cultivation at monasteries. It has unique fan-shaped leaves with a notch at the center, and its seeds are berrylike with a fleshy outer layer. The inner kernel of the seed is edible, although the outer layer contains foul-smelling butyric acid. The sexes are separate in this plant, and male trees are preferred for their lack of smelly fruits.

Ginkgo leaves are used to produce phytomedicinals that are used to treat dementia and memory loss in the elderly, as well as a variety of conditions caused by insufficient blood flow. These uses have been supported by numerous clinical trials; controlled trials have demonstrated, for example, that ginkgo slows the progress of dementia about as well as single-compound pharmaceuticals, but with much fewer side effects and at lower expense. Ginkgo is also used for tinnitus, but the balance of evidence suggests that it is of limited value for most people. It may have the potential to increase bleeding problems when combined with drugs such as blood thinners. Extracts from ginkgo leaves must be highly concentrated to be active, so people cannot effectively make their own products at home. A well-characterized commercial extract called EGb 761 has been the subject of many dozens of clinical trials and other studies.

Selected References

DeFeudis, F. V., and K. Drieu. 2000. Ginkgo biloba extract (EGb 761) and CNS functions: basic studies and clinical applications. Curr. Drug Targets 1: 25-58.

Fu L., Li N., and R. R. Mill. 1999. Ginkgoaceae. P. 8 in: Wu Z.-Y. and P. H. Raven, eds. Flora of China, vol. 4. Science Press: Beijing and Missouri Botanical Garden Press: St. Louis, MO.

Horsch, S., and C. Walther. 2004. Ginkgo biloba special extract EGb 761 in the treatment of peripheral arterial occlusive disease ? a review based on randomized, controlled studies.

Jacoby, D., and E. R. Muller III. 2004. Drug treatment of intermittent claudication. Drugs 64: 1657-1670.

Schulz, V. 2003. Ginkgo extract or cholinesterase inhibitors in patients with dementia: what clinical trials and guidelines fail to consider. Phytomedicine 10 Suppl. 4: 74-79.

Wettstein, A. 2000. Cholinesterase inhibitors and Ginkgo extracts ? are they comparable in the treatment of dementia? Comparison of published placebo-controlled efficacy studies of at least six months? duration. Phytomedicine 6: 393-401.