Ginkgo leaf extract
by Paul Berger
Medical Herbalism 2(1):1,5-6
Ginkgo leaf extracts are now the leading prescription medicines in both Germany and France. The extracts account for 1.2% and 1.5% of total prescription sales in Germany and France respectively. Sales levels are 20% ahead of the next highest selling medicines, and are growing at about 15% annually.
Ginkgo extract is most often prescribed as a cerebral vasodilator and brain tonic for the symptoms of senility, including memory loss, confusion, and depression. It is also frequently prescribed for dizziness, tinnitus (ringing and other sounds in the ear), Raynaud’s Syndrome (poor circulation in the hands), and intermittent claudication (pain in the lower limbs from arteriosclerotic blockages). The products have been thoroughly studied for safety and efficacy. (La Presse Medicale 1986) The European products are such complex concentrated extracts of Ginkgo leaf that they are properly classified as drugs rather than herbs.
Clinical problems with U.S. products
Clinical problems not reported in the European literature have been observed with Ginkgo products in the U.S. Some physicians have reported frequent side effects of nausea and headache, and others have questioned whether Ginkgo is effective at all. These problems may have arisen because of the variety of Ginkgo forms available in the U.S.
European extraction process
The European product is a
sophisticated patented extract. (Drieu 1986) Because the active
constituents (flavonoids and other compounds) are present in only small
amounts in the leaves (from unmeasurable amounts to about 0.5% during
peak season), the leaves are harvested from plantations only when
chemical tests show the flavonoid content at a peak, in late summer and
early fall. They are then carefully dried until they lose 75% of their
weight in water. Next they are subjected to an acetone solvent.
Successive treatments then remove “useless” and “undesirable”
substances. They are eventually concentrated by 50:1 (50 pounds of leaf
to make one pound of extract), and standardized to 24% flavonoid
content. The final product is checked for the levels and/or presence of
at least 5 and possibly more constituents. They are also checked to
make sure that undesirable constituents have been removed. These
“undesirable constituents” may be the cause of side effects in other
products in the U.S.
Side effects observed with 8:1 extracts
The first products available in the U.S. were not the original European products, but much simpler 8:1 extracts. Although dosages are adjusted to give adequate flavonoid levels, and appear clinically effective, they may also contain levels of the “undesirable” constituents, normally removed from the European products. The side effects reported with these products, nausea and headache, may result from unremoved tannins. Studies of the European product show a 3-4% incidence of gastrointestinal complaints, the only significant side effect (Choussat). In one study (Coles 1988) 2 of 23 patients reported digestive problems and 2 reported headache. Physicians using the 8:1 extract in the U.S. report a higher level of side effects. Some have stated that having the patient take the medicine with meals eliminates the problem.
Is the tincture effective?
Anecdotal reports about the effectiveness of Ginkgo tincture have varied. Some case reports are highly favorable. A man had lower leg pain which would return whenever he did not take his tincture for a few days. An elderly man’s wife jokingly complained that he was remembering too much. Patients with favorable results have usually used other treatments concurrently, or used tinctures that contain other circulatory or cerebral tonics. Such reports are also common with placebos. Some physicians have found the tincture to be completely ineffective. The flavonoid level present in tinctures is unlikely to give the same pharmacological effect as the concentrates. A standard 20% tincture would contain at most, under optimal conditions, about 6 grams of crude Ginkgo material per ounce, and a 90 drop daily dose would contain about 2.7 mg of flavonoids. Since the daily dose of the European product is about 30 mg, the daily dose of the tincture to get an equivalent level would be an ounce a day.
Ginkgo and tinnitus
Several studies have reported contradictory results for the use of Ginkgo for tinnitus. In the best quality study (Meyer 1986), Ginkgo extracts improved the hearing of all participants, regardless of the cause of the loss. The study reported better results with certain classes of patients. Sprenger (1986) reported the complete abolition of tinnitus in 12 of 33 patients, with a reduction in another five. An uncontrolled study (Coles 1988) found Ginkgo to have almost no effect. Coles could find no explanation for his failure to replicate the results of others, but he may have had a negative prejudicial effect on his small, uncontrolled group, by “taking care to discourage unrealistic expectations of benefit.”
Ginkgo and stroke
Ginkgo extracts have been found to
reduce platelet aggregation and inhibit the formation of blood clots in
various in vitro, animal and human studies. Anadere, et al. gave Ginkgo
extracts to 60 patients with completed stroke, and found that
hematocrit and blood and plasma viscosity improved relative to a 90
patient control group.
Anadere, et al. “Hemorheological findings in patients with completed stroke and the influence of Ginkgo biloba extract. Clin Hemorheo 5, 411-420 (1985) (as reported in Trunzler)
Choussat. Unpublished report of the Ipsen Institute, France
Coles, R. “Trial of an extractof Ginkgo biloba (EGB) for tinnitus and hearing loss.” Clin Otolaryngol (1988) 13: 501-502
Drieu, K. “Preparation and Definition of Ginkgo biloba extract.” La Presse Medicale, (1986) 15(31).
La Presse Medicale, (1986) 15(31) (September 25) The entire issue is devoted to the history, pharmacology, and clinical studies of Ginkgo. Articles in French with English abstracts.
Meyer, B. “A multicentre, randomized, double-blind drug versus placebo study of Ginkgo biloba extract in the treatment of tinnitus” La Presse Medicale, (1986) 15(31) p. 1562.
Sprenger F.H. “Gute Therapieergebnisse mit Ginkgo biloba” Arztliche Praxis. (1986) 12, 938-940
Trunzler, G. “Phytotherapeutische
M<148>glichkeiten bei Herz- und arteriellen
Gef<132>sserkrankungen” Zeitschrift fur Phytotherapy (1989) 10:
Copyright 2001 Paul Bergner