Ginkgo Biloba Monograph

This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to:    Frankp@chiro.org

FROM:   Alternative Medicine Review 1998 (Feb);   3 (1):   54–57 ~ FULL TEXT

Mechanisms of Action

Ginkgo biloba is an antioxidant [1–4] with the ability to reduce clastogenic activity of the plasma. [5] Ginkgo extracts are capable, in vitro, of scavenging various reactive oxygen species, [6] and inhibiting or reducing the functional and morphological impairments observed after lipoperoxide release. [7–8] It is possible that a large part of its anti-ischemic effect involves an inhibition of free radical formation. [9] One of the components of Ginkgo biloba, ginkgolide B, is a potent platelet-activating factor antagonist. It is also likely that the flavonoid fraction, containing free radical scavengers, is important in this respect. [10] Extracts from the leaves of Ginkgo biloba are reported to be effective at increasing vascular relaxation via a nitrous oxide pathway. [11] Ginkgo extracts (specifically the bilobalide component) can suppress hypoxia-induced membrane breakdown (release of choline from phospholipids) in the brain. [12] Oral administration can prevent the decline in muscarinic (cholinergic) receptor density in the hippocampus of rats, [13] and might have ability to inhibit the degradation of acetylcholine by acetylcholinesterase. [14] Experimental evidence indicates Ginkgo’s effect on the central adrenergic system might also be involved in its therapeutic actions, [15] since the extract appears to reactivate noradrenergic activity, [16] particularly in aged animals. [17] Extracts of Ginkgo biloba leaves produce reversible inhibition of rat brain monoamine (MAO). Both MAO-A and -B types were inhibited to a similar extent. [18] The antistress and neuroprotective effects of Ginkgo biloba extract might also be related to its effect on glucocorticoid biosynthesis. Ginkgo extract, and specifically its components ginkgolide A and B, decrease corticosteroid synthesis. [19] Ex vivo treatment with Ginkgo extract has resulted in 50% reduction of ACTH-stimulated corticosterone production by adrenocortical cells. [20]

Clinical Uses

Research indicates ginkgo extract may be efficacious in the treatment of a wide array of conditions associated with age-related physical and mental deterioration. These include:

1) Alzheimer’s Disease/senile dementia: Ginkgo extracts appear to be capable of stabilizing and, in some cases, improving the cognitive performance and the social functioning of patients with dementia. [21–22]

2) Cardiovascular Disease: Treatment with Ginkgo biloba extract lowers fibrinogen levels and decreases plasma viscosity. [23] Ginkgo administration might improve the clinical outcome following cardiopulmonary bypass by limiting oxidative stress. [24]

3) Cerebral vascular insufficiency and impaired cerebral performance: [25–26] Administration of Ginkgo biloba extracts has been shown to improve a variety of conditions associated with cerebral insufficiency, including visual field disturbances associated with chronic lack of bloodflow, [27] oculomotor and complex choice reaction, [28] vigilance and reaction times, [29] depressive mood, [30] memory and mental performance, [31–32] dizziness, [32] and decreased blood flow. [33]

Other therapeutic applications include:

1) Congestive symptoms of premenstrual syndrome: Ginkgo extract was effective for the treatment of the congestive (particularly breast symptoms) and neuropsychological symptoms of PMS,34 and in the alleviation of idiopathic cyclic oedema. [35]

2) Diabetes: Although human clinical trials have not been conducted, in experimental models, Ginkgo biloba extract appears to positively modify some complications associated with diabetes. [36–37]

3) Impotence [38]

4) Intermittent Claudication [39–40]

5) Liver Fibrosis: Ginkgo biloba was shown to be effective in arresting the development of liver fibrosis associated with chronic hepatitis B. [41]

6) Macular degeneration: In spite of the small population sample, a statistically significant improvement in long distance visual acuity was observed in patients with macular degeneration after treatment with Ginkgo biloba extract. [42]

7) Tinnitus: Studies have shown contradictory results in the treatment of tinnitus, which might be due to the diverse etiology of this condition. [43–46]

8) Vertigo/Equilibrium Disorders [47–48]

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