A ginkgo tree growing in Vancouver, British Columbia.
The first large-scale clinical study on ginkgo (Ginkgo biloba) conducted in the United States has found a leaf extract to be a safe treatment to improve short-term memory and social functioning in patients in the early stages of Alzheimer’s or vascular dementia. Both conditions are caused by the death of brain cells.
The one-year, placebo-controlled, double-blind, randomized study, published in the October 22, 1997, issue of The Journal of the American Medical Association, started with 327 participants, with 202 completing the study. Participants received either 40 mg of an extract standardized to contain 24 percent flavone glycosides and 6 percent terpenes or a placebo three times a day. Outcomes were measured at twelve, twenty-six, and fifty-two weeks.
Further studies are needed to determine the effects of long-term administration of the extract and whether the benefits of taking the extract persist after treatment ends. Several pilot studies involving humans have suggested that higher dosages may be more effective than the dosage given here.
European studies on people have demonstrated that ginkgo-leaf extract also helps regulate the metabolism of the brain and protects the blood-brain barrier (a mechanism that helps maintain a stable environment in the brain), dilates and regulates the tone of blood vessels and increases blood flow in the smallest blood vessels, and helps maintain the integrity and permeability of cell walls by inactivating free oxygen radicals.(1)
The genus Piper in the pepper family (Piperaceae) contains more than 1,000 species of tropical shrubs, small trees, and vines. Several are important economic plants: P. nigrum is the source of black pepper, and P. methysticum is the South Pacific herb kava-kava. Now another species, betel (P. betle), is catching the attention of scientists.
In an animal study, Shanghai researchers evaluated how well four neolignan compounds from betel reduce inflammation compared to ginkgolides from Ginkgo biloba, which are among the best-studied herbal anti-inflammatories.
Betel has been used in Asian, especially Chinese, medicine to treat inflammation in cases of asthma, rheumatoid arthritis, and wounds, which is marked by an increase in platelet-activating factor (PAF) in the extracellular fluid. The researchers discovered that the neolignans in betel selectively inhibited PAF by competing with chemical receptors, thereby reducing or preventing the aggregation of platelets that accompanies inflammation. However, they were less effective than ginkgolides.(3)
Researchers in Calcutta, India, have discovered that a methanol extract and a betulinic acid extract of the dried rhizome of sacred lotus (Nelumbo nucifera) reduce inflammation in rats as well as other common anti-inflammatories. The rats received a single dose of either 200 or 400 mg per kg of body weight of the methanol extract or either 50 or 100 mg per kg of body weight of betulinic acid. Other plants, such as an Asian species of persimmon, that contain betulinic acid and other triterpenoid compounds have previously been shown to reduce inflammation.
Sacred lotus is found from Iran to Japan and south to northeastern Australia. It is widely grown as an ornamental. In traditional Chinese medicine, the tuber joints, rhizome, stems, leaves, stamens, seeds, and seed heads of this beautiful water lily have all been used as drugs. The tuber joints have been used to stop bleeding and diarrhea, as has the rhizome in India. Laboratory studies in India have shown that the rhizome also lowers blood sugar and fevers and inhibits the growth of bacteria and fungi.(2)
(1) Le Bars, P. L., et al. “A Placebo-Controlled, Double-Blind, Randomized Trial of an Extract of Ginkgo biloba for Dementia”. Journal of the American Medical Association 1997, 278:1327–1332.
(2) Mukherjee, P. K., et al. “Studies on the Anti-inflammatory Activity of Rhizomes of Nelumbo nucifera”. Planta Medica 1997, 63:367–369.
(3) Zeng, H. W., et al. “Piperbetol, Methylpiperbetol, Piperol A and Piperol B: A New Series of Highly Specific PAF Receptor Antagonists”. Planta Medica 1997, 63:296–298.
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