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"Lost wealth may be replaced by industry, lost knowledge by study, lost health by temperance or medicine, but lost time is gone forever."
- Samuel Smiles
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Ginkgo Biloba
Ginkgo
Latin binomial: Ginkgo biloba
Synonyms: Maidenhair-Tree, Ginkgo 1
Parts Used: While both the leaves and fruit possess medicinal properties,1,2 most interest has been shown recently in preparations made from the leaves. Accordingly, this article will concentrate solely on the medicinal use of Ginkgo leaves.
Constituents: Diterpenes (ginkgolides A, B and C.), Sesquiterpenes (bilobalides), Flavonoids (flavonol glycosides), essential oils and tannins.1,3
Medicinal Action: Antiasthmatic, Bronchodilator, Vasodilator
Pharmacology
Few medicinal plants have been investigated as extensively as Ginkgo. While the physiological action of Ginkgo biloba extract (GBE) appears to be dependent on the flavonoid and terpenoid components, bioavailability is decreased when given in their isolated forms.4 GBE exerts a protective action on cell membranes, maintaining their integrity by several means. The flavonoids possess profound antioxidant properties, decreasing lipid peroxidation by free radicals.3,5 In addition, by activating the cell membrane 'sodium pump', stable intracellular polarity is ensured.6,7
The ginkgolides, notably ginkgolide B, competitively inhibit the action of platelet activating factor.8-11 Consequently, this decreases platelet aggregation and degranulation as well as conversion of membrane phospholipid into arachidonic acid. Due to this, and the fact that flavonoids inhibit cyclooxygenase and lipoxygenase, production of leukotrienes and Prostaglandins decreases.3 This may, in part, explain GBE anti-inflammatory action as well as its use in the treatment of bronchoconstriction seen in asthma.
The effect of GBE on the vascular system is quite unique. By stimulating the action of the endothelium derived relaxing factor and synthesis of prostacyclin by platelets, it exerts a vasodilatory effect. In addition, it affects the tone of the smooth muscles around the vessels in a way dependent on their original state. In cases of paralysis, GBE increases tone and in cases of spasm it exerts a relaxant effect. This action seems more pronounced in cases of ischaemia.3,12
GBE appears to have an affinity for neuronal tissue and cerebral function. It exerts a protective action especially in cases of low oxygen levels. In addition to inhibiting the lipid peroxidation of the high proportion of unsaturated fatty acids present, it maintains aerobic glycolysis in cases of hypoxia. It also appears to increase certain neurotransmitter production, notably dopamine and noradrenaline, as well as increase acetylcholine and serotonin receptor numbers in animal models.13-15 It has been suggested that the bilobalides may aid the regrowth of damaged neurons in the central nervous system.3 The results of GBE in reversing the consequences of decreased cerebral function due to vascular insufficiency have been well documented in numerous clinical trials.16
Indications  | Asthma, allergies 3,8-11 | | Cerebrovascular disease, memory loss, depression, dementia and symptoms of early-stage Alzheimer's diseases 3,18-22 | | Peripheral vascular disease, intermittent claudication and Raynaud's syndrome 4,23-25 | | Diabetic retinopathy, macular degeneration 26-28 | | Edema and vascular fragility 29 | | Impotence 30 | | Premenstrual syndrome 31 | | Ischaemic heart disease and arrhythmias 33,34 | | Inner ear dysfunction 3, 34-37 |
Toxicology and Contraindications
While adverse effects are rare, incidents of mild gastrointestinal upset, headache and allergic skin reactions have been observed. Since the fruit contains phenols, contact with the skin often results in localized irritation and welts.3
Drug Interactions
Ginkgo has no reported drug interactions.3
Administration
Even though Ginkgo is available in many forms, it is most often used as a solid standardized extract usually to 24% flavoglycoside content. The usual dosage is 120 mg to 150 mg daily taken in divided doses. If taken as the raw herb, the daily dose should be equivalent to 300 mg daily in divided doses.3
A standardized Ginkgo product is one of the most commonly prescribed medicines in Germany and is increasing in popularity in North America.
Ginkgo can be taken alone or with other botanical medicines or nutritional supplements notably Panax ginseng, Crataegus spp., choline or phosphatidylcholine.
References
1. Wren, R.C. (1988). Potter's New Cyclopaedia of Botanical Drugs and Preparations. Page 128. C.W. Daniel Company, Saffron Walden, UK
2. Hsou-Mou, Chang. Pui-Hai, P. (1986). Chinese Herbal Medicine Materia Medica. Page 1096. Eastland Press, Seattle, WA
3. Houghton, P. (1994). Ginkgo. Pharmaceutical Journal Vol. 253. Page 121-122
4. Kleijnen, J., Knipschild, P. (1992). Ginkgo biloba. Lancet 340:1136-9
5. Pincemail, J.. Deby, C. (1986). The antiradical properties of Ginkgo biloba extract. Presse Med 15(31). 1476-9
6. Murray, M. (1992). The Healing Power of Herbs. Page 123. Prima Publishing, Rocklin, CA
7. Mowrey, D. (1990). Next Generation Herbal Medicine. Second Edition. Page 65. Keats Publishing, CT
8. Chung, K.F. et a]. (1997). Effect of a ginkgolide mixture (BN 52063) in antagonizing skin and platelet responses to platelet activating factor in man. Lancet 1 :48-51.
9. Markey, A.C. et al. (1990). Platelet activating factor-induced clinical and histopathologic responses in atopic skin and their modification by the platelet activating factor-antagonist BN 52063. J Am Acad Dermatol 23(2): 263-8
10. Wilken, J.H. et al. (1990). Effects of a PAF antagonist (BN52063) on bronchoconstriction and platelet activation during exercise induced asthma. Br J Clin Pharmacol 29(l): 85-91
11. Guinot, P. et al. (1986). Effect of BN52063, a specific PAF-acether antagonist, on bronchial provocation test in asthmatic patients. A preliminary study. Prostaglandins 34(5): 723-31
12. Delafotte, S., Hellegouarch, A. and Clostre, F. (1986).The pharmacological basis for the vascular impact of ginkgo extract. Presse Med 15(31): 1524-8
13. Huguet, F., Drieu, K. and Piriou, A. (1994). Decreased cerebral 5-HT1A receptors during aging: reversal by Ginkgo biloba extract (Egb 761). J Pharm Pharmacol 46: 316-8
14. Murray, M. Page 121. Ibid.
15. Mowrey. D. Page 67. Ibid.
16. Murray, M. Page 125. Ibid.
17. Kleijnen, J., Knipschild, P. (1992). Ginkgo biloba for cerebral insufficiency. Br J Clinical Pharmacol 34:352-8
18. Vorberg, G. (1985). Ginkgo biloba extract: a long-term Study of chronic cerebral insufficiency in geriatric patients. Clin Trials J 22(2): 149-57
19. Anadere et al. (1985). Hemorheological findings in patients with complete stroke and the influence of Ginkgo biloba extract. Clin Hemorrheo 5: 411-420
20. Brown, D. (1994). Ginkgo biloba extract update. Townsend Newsletter for Doctor Vol. 133/134. Page 980
21. Hofferberth, B.(1994).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 (215-222)
22. Schubert, H. and Halama, P. (1993). Depressive episode primarily unresponsive to therapy in elderly patients: Efficacy of Gingko biloba extract (Egb 761) in combination with antidepressant. Geriat Forsch 3: 45-53. reviewed in Quarterly Review of Natural Medicine. (Winter 1993).Page 9. Seattle, WA
23. Thomson, G.J. et al. (1990). Clinical trial of Ginkgo biloba extract in patients with intermittent claudication. Int. Angiol. 9(2): 75-8. reviewed by Werbach, J., Murray, M. (1994). Botanical Influences on Illness. A Sourcebook of Clinical Research. Page 276. Third Line Press, Tarzana, CA
24. Bauer, U. (1986). Ginkgo biloba extract in the treatment of arteripathy of the lower Iimbs. Presse Medicale 1 5(3 1): 1 546-9
25. Bauer, U. (1996). Long-term treatment of peripheral occlusive arterial disease with GBE. Three year study. Vasa Suppl 15:26, reviewed by Werbach. J., Murray, M. Page 277. Ibid.
26. Doly, M. et al. (1986). Effect of GBE on the electrophysiology of the isolated retina from a diabetic rat. Presse MedOslo hôtels 15(3 1): 1480 83
27. Lebuisson, D.A. et al. (1986). Treatment of senile macular- degeneration with GBE. A preliminary double blind drug vs. placebo study. Presse Med. 15(31 ): 1556-8
28. Merte, H.J., Merkle, W. (1980). Long-term treatment with GBE of the circulatory disturbances of the retina and optic nerve. Klin Monatsbl Augenheilkd 177(5): 577-83 reviewed by Werbach, J., Murray, M. Page 292. ]bid.
29. Lagrue, G. et al. (1986). Idiopathic cyclic edema. The role of capillary hyperpermeability and its correction by GBE. Presse Med 1 5(3 1): 1 550-3
30. Sikora, R. et al. (1989). Ginkgo biloba extract in the therapy of erectile dysfunction. J. Urol 141:1 88a
31. Brown, D. (1994). Potential for GBE in Management of PMS. Townsend Newsletter for Doctors. Vol. 133/134. Page 981
32. Koltai, M. et al. (1989). Ginkgolide B protects isolated hearts against arrhythmias induced by ischaemia but not reperfusion. Europ J Pharmacol 164:293-302
33. Guillon, J.M. et al. Effects of Ginkgo biloba extract on two models of experimental myocardial ischaemia. Presse Med 15(31): 15 16- 1 5 1 9
34. Hauenauer, J. P. et al. (1986). Treatment of equilibrium disorders with Ginkgo biloba extract. A multi-center-double blind drug vs. placebo study. Presse Med. 15(31): 1569-72
35. Claussen, C.F. (1986). Diagnostic and practical value of craniocarpography in vertiginous syndromes. Presse Med 5(31): 1565 68
36. Meyer, B. (1986). A multi-centre randomised double blind drug vs. placebo study of Ginkgo biloba extract in the treatment of tinnitus. Presse Med 15(31): 1562 4
37. Dubreuil, C. (1986). Therapeutic trail in acute cochlear deafness. A comparative study of ginkgo) biloba extract and nicergoline. Presse Med 15(31): 1559-61
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