GINKGO BILOBA 

Common Name
Maidenhair tree

Botany
Ginkgo biloba is the world’s longest living species of tree; individual trees live as long as 1,000 years. Ginkgo grows most prominently in the southern and eastern US and in China. The leaves of the tree are used.

Historical or Traditional Use
Medicinal use of ginkgo can be traced back almost 5,000 years in Chinese herbal medicine. The nuts of the tree were most commonly recommended and used to treat respiratory tract ailments. A tea of the leaves was occasionally used for elderly persons experiencing memory loss.

Active Constituents and Proposed Mechanism of Action
The medical benefits of Ginkgo biloba extract (GBE) rely primarily on two groups of active components: the ginkgo flavone glycosides and the terpene lactones. The 24% ginkgo flavone glycoside designation on GBE labels indicates the carefully measured balance of bioflavonoids. These bioflavonoids are primarily responsible for GBE’s antioxidant activity and ability to inhibit platelet aggregation (stickiness). These two actions may help GBE prevent circulatory diseases such as atherosclerosis and support the brain and central nervous system.¹

The unique terpene lactone components found in GBE, known as ginkgolides and bilobalide typically make up 6% of the extract. They are associated with increased circulation to the brain and other parts of the body as well as exert a protective action on nerve cells.^{2 3} Ginkgolides may improve circulation and inhibit platelet-activating factor (PAF). Bilobalide protects the cells of the nervous system. Recent animal studies indicate that bilobalide may help regenerate damaged nerve cells.

Circulatory Actions
GBE increases circulation to both the brain and extremities of the body. In addition to inhibiting platelet stickiness, GBE regulates the tone and elasticity of blood vessels.⁴ In other words, it makes circulation more efficient. This improvement in circulation efficiency extends to both large vessels (arteries) and smaller vessels (capillaries) in the circulatory system.⁵

Cognitive Function
Recently, the ginkgo extract EGb 761 was found to increase alpha wave and decrease theta wave activity following oral intakes of 120 or 240 mg in healthy volunteers.⁶ These brain wave changes indicate that EGb 761 is capable of improving cognitive function as demonstrated in increased mental sharpness, concentration, and memory. Three double-blind studies have now shown that GBE is helpful for persons in early stages of Alzheimer’s disease, as well as the closely related multi-infarct dementia.^{7 8 9} Patients with other types of dementia also respond to GBE, including, as mentioned above, problems due to poor blood flow to the brain.

Antioxidant Properties
GBE has antioxidant actions in the brain, retina of the eye, and the cardiovascular system.¹⁰ One double-blind study found that GBE could help people with macular degeneration, an oxidation-related disorder causing decreased or lost vision.¹¹ Diabetic retinopathy is also improved by GBE, according to a double-blind study.¹² Its antioxidant activity in the brain and central nervous system may help prevent age-related declines in brain function. GBE’s antioxidant activity in the brain is of particular interest. The brain and central nervous system are particularly susceptible to free radical attack. Free radical damage in the brain is widely accepted as being a contributing factor in many disorders associated with aging, including Alzheimer’s disease.¹³

Antidepressant Action
One double-blind study in Germany found that elderly depressed people with mild dementia (who were not responding to antidepressant medications) responded well to GBE supplementation.¹⁴

Nerve Protection and PAF Inhibition
One of the primary protective actions of the ginkgolides is their ability to inhibit a substance known as platelet-activating factor (PAF).¹⁵ PAF is a mediator released from cells that causes platelets to aggregate (clump together). High amounts of PAF are associated with damage to nerve cells, poor blood flow to the central nervous system, inflammatory conditions, and bronchial constriction.¹⁶ Much like free radicals, higher PAF levels are also associated with aging.¹⁷ Ginkgolides and bilobalide protect nerve cells in the central nervous system from damage during periods of ischemia (lack of oxygen to tissues in the body).¹⁸ This action may be supportive for persons who have suffered a stroke.

Tinnitus and Balance
Ginkgo may improve tinnitus (ringing in the ears) and balance problems related to the inner ear, an important part of maintaining balance. Double-blind studies have confirmed the benefit of GBE for people with tinnitus or vertigo.^{19 20}

Recommended Dosage
GBE, standardized to contain 6% terpene lactones and 24% flavone glycosides, can be taken in the amount of 120–160 mg per day.²¹ Relatively high (240 mg per day) amounts have been used in reports studying people with age-associated memory loss, mild cognitive impairment, mild to moderate Alzheimer’s disease, and resistant depression. GBE may need to be taken for six to eight weeks before desired actions are noticed. Although non-standardized leaf and tinctures are available, there is no well-established dosage for these forms.

Contraindications
Ginkgo biloba extract is essentially devoid of any serious side effects.²² Mild headaches lasting for a day or two and mild upset stomach have been reported in a very small percentage of people using GBE. GBE is not contraindicated for pregnant and lactating women.

Circulatory conditions in the elderly can involve serious disease. Individuals should seek proper medical care and accurate medical diagnosis prior to self-prescribing GBE.

References:

1. Drieu K. Preparation and definition of Ginkgo biloba extract. In: Rokan (Ginkgo biloba): Recent Results in Pharmacology and Clinic, ed. EW Fünfgeld. Berlin: Springer-Verlag, 32–6.
2. Krieglstein J. Neuroprotective properties of Ginkgo biloba—constituents. Zeitschrift Phytother 1994;15:92–6.
3. Bruno C, Cuppini R, et al. Regeneration of motor nerves in bilobalide-treated rats. Planta Medica 1993;59:302–7.
4. Clostre F. From the body to the cellular membranes: the different levels of pharmacological action of Ginkgo biloba extract. In Rokan (Ginkgo biloba): Recent Results in Pharmacology and Clinic, ed. EW Fünfgeld. Berlin: Springer-Verlag, 1988, 180–98.
5. Jung F, Mrowietz C, et al. Effect of Ginkgo biloba on fluidity of blood and peripheral microcirculation in volunteers. Arzneim-Forsch Drug Res 1990;40:589–93.
6. Itil TM, Eralp E, Tsambis E, et al. Central nervous system effects of Ginkgo biloba, a plant extract. Am J Therapeutics 1996;3:63–73.
7. Le Bars PL, Katz MM, Berman N, et al. A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia. North American EGb Study Group. JAMA 1997;278:1327–32.
8. Hofferberth B. The efficacy of EGb 761 in patients with senile dementia of the Alzheimer type, a double-blind, placebo-controlled study on different levels of investigation. Human Psychopharmacol 1994;9:215–22.
9. Kanowski S, Herrmann W, Stephan K, et al. Proof of efficacy of the Ginkgo biloba special extract EGb 761 in outpatients suffering from mild to moderate primary degenerative dementia of the Alzheimer type or multi-infarct dementia. Pharmacopsychiatry 1996;29:47–56.
10. Ferrandini C, Droy-Lefaix MT, Christen Y, eds. Ginkgo biloba Extract (EGb 761) as a Free Radical Scavenger. Paris: Elsevier, 1993.
11. Lebuisson DA, Leroy L, Rigal G. Treatment of senile macular degeneration with Ginkgo biloba extract. A preliminary double-blind, drug versus placebo study. Presse Med 1986;15:1556–8 [in French].
12. Lanthony P, Cosson JP. Evolution of color vision in diabetic retinopathy treated by extract of Ginkgo biloba. J Fr Ophthalmol 1988;11:671–4 [in French].
13. Harman D. Free radical theory of aging: a hypothesis on pathogenesis of senile dementia of the Alzheimer’s type. Age 1993;16:23-30.
14. Schubert H, Halama P. Depressive episode primarily unresponsive to therapy in elderly patients: Efficacy of Ginkgo biloba extract (EGb 761) in combination with antidepressants. Geriatr Forsch 1993;3:45–53.
15. Lamant V, Mauco G, et al. Inhibition of the metabolism of platelet activating factor (PAF-acether) by three specific antagonists from Ginkgo biloba. Biochem Pharmacol 1987;36:2749–52.
16. Kroegel C. The potential pathophysiological role of platelet-activating factor in human disease. Klin Wochenschr 1988;66:373–8.
17. Kroegel C, Kortsik C, et al. The pathophysiological role and therapeutic implications of platelet activating factor in diseases of aging. Drugs Aging 1992;2:345–55.
18. Krieglstein J. Neuroprotective properties of Ginkgo biloba—constituents. Zeitschrift Phytother 1994;15:92–6.
19. Haguenauer JP, Cantenot F, Koskas H, Pierart H. Treatment of equilibrium problems with extract of Ginkgo biloba. Multicenter, double-blind, placebo-controlled study. Presse Med 1986;15:1569–72 [in French].
20. Meyer B. A multicenter, double-blind, drug versus placebo study of Ginkgo biloba extract in the treatment of tinnitus. Press Med 1986;15:1562–4 [in French].
21. Blumenthal M, Busse WR, Goldberg A, et al, eds. The Complete Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications, 1998, 136–8.
22. Blumenthal M, Busse WR, Goldberg A, et al, eds. The Complete Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications, 1998, 136–8. 

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