Ginkgo Biloba

Ginkgo biloba L   Ginkgoaceae.  It is commonly called ginko or maidenhair tree, the Chinese name is yin-hsing, pai-kuo (fruit).

“Throughout history ginkgo has been used as an antimicrobal, anti-inflammatory and vasodilatory remedy.  The oldest Chinese Materia Medica (2800 BC), the Pen Tsau Ching, recommended the use of ginkgo leave to ‘benefit the brain,’ and for asthma, ‘chilblains’, coughs, elimination of filaris and vascular disorders of aging.”¹

The nuts of the ginkgo have been used more by the Chinese than the leaves.  They are cooked and used in porridge and other dishes and are considered a delicacy.  They are also used for their strengthening and tonic properties and are considered as a kidney yang tonic.²

Ginkgo is one of the oldest species on this planet, growing almost unchanged since 150 million years ago.  There are virtually no wild trees left in the world.  These trees are grown as ornamentals, street trees and on plantations for commercial use.  They are slow growing , large trees that are dioecious (having male flowers and female fruits on different trees).

The leaf is the part used in modern Western usage.  The Chinese traditionally used the leaf and the nut, both as food and medicine. Tea, capsules and unstandardized hydroalcoholic extracts are available, but are considered a minimal dosage and are used for a slower, longer-term effect.  The products standardized to 24% flavone glycosides are what most of the clinical trials have been based on and gives quicker, stronger effect.  Ginkgo is frequently mixed with Hydrocotyle asiatica (gota kola) for memory and brain function.  It is also being included in some antidepressant compounds.

The effects of ginkgo have been quite well studied and it is one of the most popular herbs in current European usage, especially in Germany.  Ginkgo increases blood flow to the brain and to the peripheral extremities.  This action is related to bilobalide, ginkgolides, and the rutin type flavones.  The action decreases blood viscosity and erythrocyte aggregation, reduces capillary fragility, and improves the tolerance of brain tissue to hypoxia by increasing cerebral blood flow.  Studies show ginkgolides improve cerebral metabolism, inhibit cerebral edema and protects the brain against ischemia.

Ginkgo has a number of free radical scavenging activities that are attributed to several substances, primarily flavonoids, flavones, ginkgolide B,  bilobalide, and ascorbic acid.  These help to protect cells, membranes, vascular walls, liver, pancreas, and eyes.  It is also active against hydroxyl, nitric oxide, peroxyl and superoxide radicals.

Ginkgo has some fairly far-reaching effects with its ability to inhibit the potent inflammatory autocoid, platelet-activating factor (PAF).  The chemicals responsible for this action appear to be the ginkgolides A,B,C, and M.  PAF mimics the allergic response in the body, is involved in the pathology of asthma, CNS disorders, ischemia and renal disease.

Gingko is shown to have a positive effect on neurotransmitter disturbances and cerebral receptor density, primarily in the aged.  It increases and stimulates serotonin receptors, increases uptake of acetylcholine by reducing loss of muscarinic choline receptors, stimulates choline uptake in hippocampus, and reduces uptake of dopamine.

Ginkgo has promise as an anti-infective agent.  It has been shown to be effective against

pneumocystis carinii, and as effective as trimetholprim/sulfamethoxazole. ³

Ginkgo is being used for peripheral vascular and cerebrovascular disease,

including vertigo, tinnitus, weakened memory, dementia and mood swings accompanied by anxiety.

It has been found effective for intermittent claudication.⁴

It is used for vericose veins and hemorrhoids.⁵  It is used for eye disorders in which the retina may be damaged by free radicals, such as senile macular degeneration.  It can reduce symptoms of asthma as well as a wide range of other allergic and immune based disorders.  It is also used for stress protection and peripheral edema.⁶

A recently published study in the Journal of the American Medical Association suggests that ginkgo can be effective in stabilizing or slightly improving Alzheimer’s patients.  They reported that overall it was only slightly less effective than Cognex (tacrine) or Aricept (donepezil), with fewer side effects.  In Germany it is approved for treating dementia.⁷

There have been at least 165 constituents isolated from ginkgo that are a complex mixture of polar and apolar compounds. There are several groups of flavonoids, the most important being quercetin, kaempferol and isorhamnetin which are standardized to 24%.  There are several unique diterpenes, the ginkgolides A, B, C, J, M, and a sesquiterpene, bilobalide.  These are considered the most active constituents.

The leaves are not strong and clinical studies have shown that it may take one to nine months to be effective if used as a tea, capsule or hydroalcoholic extract.  Standardized extracts are effective within a few days.⁸  Extracts are standardized to 24% flavone glycosides and 6% terpene lactones.  There is a debate about how much of this to take.  The trials reported in JAMA, as well as other trials overseas, used 40 mg orally three times a day before meals.

People taking ginkgo should report any dizziness, persistent headaches, double vision, blurred vision, nausea, vomiting or any signs of bleeding to their physician immediately.  They should also inform their doctor or pharmacist before using OTC analgesics, especially if they contain aspirin.⁹  Beware of possible interactions between blood coagulating drugs such as warfarin, coumarin and heparin. There have been three cases where Ginkgo has been implicated in bleeding complications, one of these was with aspirin.¹⁰ Side effects are rare, but may include gastrointestinal disturbances, headache and allergic skin reactions.