Ginkgo biloba: a living fossil for today's health needs - includes related information

Ginkgo leaf extracts have been shown to have a wide range of biological activities. The most well-known use among Americans is the documented ability of the extracts to improve short-term memory.

The best-selling phytomedicine (medicinal plant) on the European market is derived from the leaves of an ancient tree, known at one time to survive only in China. Sales of this botanical's extracts are in excess of $280 million per year. The tree is ginkgo -- Ginkgo biloba -- a living fossil.

Ginkgo is considered the oldest tree species to survive on earth, with a history dating back over 200 million years.

Ginkgo's survival record is excellent

Ginkgo biloba is the only surviving member of the ginkgo family. Ginkgo species were once common in North America and Europe. While its relatives became extinct in other parts of the world, ginkgo biloba survived in China, where it became known to Europeans in the 18th century, and subsequently was introduced as an ornamental tree throughout the Western world. Now ginkgo trees are found in virtually every city in the United States; it was first introduced here in 1784. The common name "Ginkgo" is a phonetic pronunciation of a Japanese name for the tree. The species name "biloba" refers to the-two distinct lobes, characteristic of the tree's leaves.

Ginkgos have survived over millions of years because of their genetic tenacity. They are remarkably resistant to disease, pests, and

fires. They also are extremely tolerant of air pollution, and are often planted in urban environments with harsh air pollution and heavy populations where most trees will not survive. The most common tree along Manhattan sidewalks, for example, is ginkgo. The trees will get to be over 100 feet tall. In Japan and China, trees over a thousand years old are found still growing at ancient temples. Its unique fan-shaped leaves with two lobes make it one of the easiest trees to identify once you become familiar with the unusual features.

Ginkgo's roots are in ancient Chinese medicine

Despite the fact that the tree grows in China, the leaves are not one of the famous classical herbal drugs in ancient Chinese medicine. The first mention in Chinese herbals of use of the leaves comes relatively late. Ginkgo leaf was first mentioned in Lan Mao's Dian Nan Ben Cao (Pharmaceutical Natural History of Southern Yunnan), published in 1436 during the Ming dynasty. Lan Mao notes external use to treat skin and head sores as well as freckles. Internal use of the leaves was first noted in Liu Wen-Tai's Ben Cao Pin Hui Jing Yao (Essentials of the Pharmacopoeia

Ranked According to Nature and Efficacy), an imperial-commissioned work recorded in 1505. Liu Wen Tai notes use of the leaves in the treatment of diarrhea.

The leaves of ginkgo are known in Chinese medicine as bai-guo-ye. Recent clinical reports in modern China suggest that the leaves lower serum cholesterol levels and have some clinical value in easing angina pectoris (brief attacks of chest pain precipitated by deficient oxygenation of the heart muscle).

In Traditional Chinese Medicine the seeds, with fleshy rind removed, are considered more beneficial than are the leaves. The seeds are used as an astringent for the lungs, to stop asthma, enuresis (urinary incontinence), and excessive leucorrhea (a type of vaginal discharge). It is thought to benefit qi (ch'i, vital energy), cough, and regulate urinary frequency. Studies have shown that the known constituents ginkgoic acid and ginnol inhibit certain bacteria and fungal infections. In large doses, the seeds are thought to have some toxic effect, perhaps leading to skin disorders or mucous membrane irritation.

Ginkgo leaves, although a Chinese herb, have been used much more in the West than in their homeland. Over 300 scientific studies on the chemistry, pharmacology and clinical effects of ginkgo leaf have been conducted by European researchers over the last 20 to 30 years.

Unlike most herbs, ginkgo leaf extracts, rather than crude leaf material, are used for clinical purposes.

The majority of studies on ginkgo leaf extract have involved a product produced by a German/French consortium, referred to in the scientific literature as EGb761.

Ginkgo products are standardized to include 24 percent bioflavonoids from the leaf

Ginkgo products are standardized to contain 24 percent of the bioflavonoids (see sidebar on p. 57) which occur in the leaf, as well as ginkgolides and bilobilides, a complex group of compounds found only in the ginkgo tree. Since virtually all research on ginkgo has involved high standardized extracts calibrated to specific quantities of chemical components, it is not possible to apply information from studies on the standardized extracts to the ginkgo leaf itself.

This complex extract, rather than a single isolated component, is believed to be responsible for ginkgo's biological activity. However, various research groups have recently focused on the effects of the ginkgolides themselves. They have been found to be very selective antagonists of platelet aggregation (clumping) induced by platelet-activating factor (PAF), an inflammatory autocid. Autocids, synthesized in local tissue sites, mediate tissue response, such as pain perception, blood coagulation, and smooth muscle contraction.

PAF is involved in various inflammatory, cardiovascular, and respiratory disorders. The ginkgolides have an anti-PAF action, helping to modulate various enzyme systems and ion pumps. The PAF antagonist effect of ginkgolides helps to explain ginkgo's broad-spectrum biological activity.

Most of the extracts available on the American market are made in Europe. Supplies are also coming from Japan, China, and elsewhere.

Interestingly, most of the ginkgo leaf used to manufacture European products is produced on a farm owned by a German company in South Carolina.

Ginkgo's wide range of biological activities

Ginkgo leaf extracts have been shown to have a wide range of biological activities. The most well-known use among Americans is the perceived ability of the products to improve short-term memory. Other important effects include a protective effect on the blood-brain barrier and an anti-radical (antioxidant) effect. The leaf extracts have also been shown to increase vasodilation and peripheral blood flow rate in capillary vessels and end-arteries in various circulatory disorders. Other studies have shown vascular-tone regulating effects, and help in modulating cerebral energy metabolism.

Ginkgo extracts have been widely used in Europe for a wide variety of clinical conditions, including: vertigo (dizziness), tinnitus (ringing in the ear), treatment of poor circulation, heart disease, eye diseases, chronic cerebral insufficiency, accidents involving brain trauma, dementia, and various conditions associated with senility. The standardized extract of the leaves has been shown to be beneficial in a broad range of health problems, including those involved with: circulation, blood conditions, metabolism, immune function, varicose conditions, and post-thrombotic (blood clot) syndrome. It has been shown to improve short-term memory (especially in older populations), and cognitive disorders secondary to depression, among other conditions.

Ginkgo leaf extract studied in treating erectile dysfunction

New uses for ginkgo leaf extracts are emerging as more is learned about the extracts' usefulness in various clinical situations, especially those involving circulatory, problems. For example, a 1991 study published in the Journal of Sex Education and Therapy evaluated the effect of ginkgo leaf extract in the treatment of erectile dysfunction in 50 patients. The men, diagnosed with arterial erectile impotence, received 240 mg of ginkgo leaf extract daily for a period of nine months.

The patients were divided into two groups based on their response to conventional therapies. Twenty of the patients had previously experienced some success with conventional drug therapy, and were placed in the first group. The second group of 30 patients had not experienced proper function following conventional therapies.

Following six months of treatment with the ginkgo leaf extract, all patients in the first group (20 men) regained proper function. The improvement continued through the nine-month treatment period. Nineteen of the 30 patients in the second group responded positively to the treatment, while 11 remained impotent. No side effects were reported by any of the participants in the study. This is only the second study published on the use of ginkgo leaf extracts in the treatment of impotence. A Dutch research group has produced a retrospective analysis of ginkgo clinical studies, assessing their quality and reliability based on a number of objective parameters. They look at 40 clinical trials published since 1975 on the use of ginkgo extracts in treating cerebral insufficiency. Clinical trials reporting results in healthy volunteers were excluded. The dosage was 120 mg/day of the ginkgo extract (given for at least 4-6 weeks). Of the 40 studies, eight were considered to be well-performed using. rigorous scientific standards. The authors of the retrospective stressed the need for additional trials, in which double-blindedness is checked, a larger number of patients are involved, with better descriptions of randomization procedures, patient characteristics, and more effective measurement of data.

RELATED ARTICLE: Ginkgo's broad spectrum of benefits

THE ACTIVE CONSTITUENTS in ginkgo leaves are flavoglycosides (heterodisides), and quercetin, as found in the leaf. These constituents should not be isolated, but should be present in a concentrated extract. Such an extract would be expected to contain about 24 percent flavoglycosides and 10 percent quercetin (which is itself a flavonoid).

In addition to the guaranteed potency constituents, a substantial amount of pharmacologically active terpene derivatives (ginkgolides and bilobalides) should also be present.

Here is a brief overview of ginkgo biloba's known and proven clinical benefits, according to Daniel B. Mowrey, Ph.D., in his book, Herbal Tonic Therapies:

* Cerebral vascular effects: In a typical preclinical study using standard pharmacological procedures, microscopic particles are injected

into the carotid artery of rats to mimic aterial blockage which normally leads to a decrease in the blood and oxygen supply to the brain. The administration of ginkgo biloba successfully protects the animals against

the destructive effects of this procedure. Under the influence of ginkgo, increased levels of glucose and ATP occur, which help to maintain energy levels within individual cells of the brain.

* Inhibits platelet aggregation: Ginkgo has an inhibitory effect on blood platelet aggregation, meaning that it effectively reduces the tendency of blood components to stick together; therefore, it reduces the tendency for dangerous clots, or thrombi, to form in veins and arteries.

* A free-radical inhibitor. Ginkgo demonstrates an ability to neutralize free radicals. Since oxygen is the major source of free radicals, oxygen scavengers are among the best substances used to prevent the formation of free radicals. The flavonoids of ginkgo, including quercetin,

are extremely potent oxygen scavengers.

* Affects important brain neurotransmitters: Treatment with ginkgo significantly increases blood flow to the brain, and, perhaps more critically, it also produces a significant rise in dopamine synthesis, a neurotransmitter that is critical to the transfer of information and electrochemical impulses between nerves and other nerves, and between nerves and muscles, glands, organs, blood vessels, and other structures of the body.

* Used to treat vascular disturbances of the inner ear. Both structural and functional disturbances of the inner ear have been successfully treated with ginkgo. These problems all stem from some underlying vascular defect. In one study, ginkgo was given to patients suffering from hearing loss due to old age (presbyacusia), patients with persistent ringing in the ears, and patients with vertigo (dizziness). Improved hearing was experienced by 40 percent of the presbyacusia patients; those who didn't respond were assumed to have irreversible lesions of the sensory structures of the inner ear. Most of those patients with ringing in the ear experienced significant improvement within 10 to 20 days. The action of ginkgo on cerebral circulation resulted in swift and complete disappearance of vertigo.

* Has mental and behavioral effects: In one study using 166 patients, researchers tracked the effects of ginkgo on a battery of behavioral, clinical and physiological measures of cerebral disorders due to aging. Differences between control and treatment groups became clearly apparent after just three months. Over the ensuing months, the differences increased -- a dramatic demonstration of benefits available from the use of ginkgo extract.

* May affect the course of Alzheimer's disease: Of special concern are people who are just beginning to experience deterioration in their cognitive function. Ginkgo biloba extract might delay deterioration and enable these subjects to maintain a normal life and escape institutionalization.

SOURCE: Mowrey, Daniel B., Ph.D. Herbal Tonic Therapies. New Canaan, Conn.: Keats Publishing, Inc., 1993, pp. 166-174.

RELATED ARTICLE: What are bioflavonoids?

ACCORDING TO SHARI LIEBERMAN in her book, The Real Vitamin Mineral Book:

* Bioflavonoids are now believed to be antioxidants.

* They are not quite vitamins, but they are present along with vitamin C in citrus fruit, in the white portion of the peel.

* Increase vitamin C absorption. Studies have shown

that bioflavonoids ingested with vitamin C increase vitamin C absorption to a great extent.

* Strengthen capillary veins. In addition, bioflavonoids strengthen capillary walls, preventing capillary damage which

leads to bleeding disorders including spider veins, varicose

veins, hemorrhages, and black and blue marks.

* Antibiotic-like activity. Bioflavonoids have been shown to have antibiotic-like activity.

Other benefits:

* They may lower cholesterol.

* They were shown to be potent anti-inflammatory agents.

* They may prove useful in the treatment of arthritis.

* Anti-cataract. In both human and animal research, bioflavonoids were shown to have anticataract activity.

For optimum general health, the Optimum Daily Allowance for bioflavonoids is:

500-5,000 mg for men and women (recommended to be taken along with an equivalent amount of vitamin C).

SOURCE: Lieberman, Sliari, and Bruning, Nancy. The Real Vitamin & Mineral Book. Garden City Park, N.Y.: Avery Publishing Group, Inc., 1990, p. 122.

REFERENCES

Sohn, M. and R. Sikora. 1991. Ginkgo biloba extract in the therapy of erectile dysfunction. J Se Educ. 7her. 17-53-61.

Kleijnen, J. and P. Knipschild. 1992. Ginkgo biloba for cerebral insufficiency. Br. J Clin. Pharmac. 34:352-358.

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