Ginkgo biloba is a tree once widely distributed but now isolated to China and cultivated elsewhere. Also known as maidenhair tree, ginkgo is a living fossil, meaning there is fossilized evidence of it, but it continues to exist today. The leaf has been used for centuries in Chinese medicine and more recently as a "smart drug" to enhance cognitive function and memory. This association may originally be based on the fact that the leaf is a favorite food of the elephant, which is reputed to never forget. Science, on the other hand, shows that ginkgo stimulates blood flow and electrical activity in the brain. Check with your doctor before using this herb, however, especially if you take medication.
CHEMICAL COMPOSITION
According to the "Physicians' Desk Reference for Herbal Medicines," the leaf and inner portion of the seed contain various flavonoid glycosides, including derivatives of quercetin, kaempferol and p-coumaric acid. The herb also contains a number of terpenoid compounds collectively referred to as ginkgolides and bilobalides.
PHARMACOLOGICAL EFFECTS
Ginkgo has demonstrated antioxidant, anti-inflammatory, cardiovascular and neurological effects. A review published in the January issue of the "Journal of Food Science" states that the flavonoid and terpenoid constituents in ginkgo may work synergistically to produce these effects. Phyllis A. Balch, CNC, author of "Prescription for Herbal Healing," writes that electroencephalograph, or EEG measurements, of people with Parkinson's disease suggest that ginkgo may improve oxygen and glucose utilization in the brain. In addition, studies in healthy volunteers show that ginkgo extracts increase alpha brain wave activity, leading to enhanced mental clarity and recall.
APPLICATIONS
The World Health Organization states that clinical evidence supports the use of ginkgo to address symptoms of mild-to-moderate cerebrovascular insufficiency, which include poor concentration, impaired memory and depression. The herb also reduces walking pain and other symptoms associated with peripheral arterial occlusive disorders, such as intermittent claudication, numbing or tingling of the extremities, vertigo and tinnitus, or ringing in the ears. However, the mechanism of action behind these effects is more likely due to improving blood flow and oxygen delivery and protecting neurons from ischaemic damage from anemia than increasing brain wave activity.
SAFETY CONSIDERATIONS
Toxicity studies indicate that ginkgo leaf extract is generally safe with few side effects reported aside from stomach upset, headache, dizziness and allergic skin reactions. The University of Maryland Medical Center warns that ginkgo should not be taken during pregnancy or while nursing. Gingko may increase the risk of bleeding if taken in conjunction with anticoagulants, or blood-thinning drugs. This herb may also affect the metabolism of other medications, including diabetes drugs, antidepressants, diuretics and medications to reduce blood pressure.