SILVERWEED
Potentilla Species Used in Herbal Medicine
Silverweed is the common name for several species of Potentilla (of the Rose family). Its name is based on the silvery-white color of the leaves, particularly notable on the bottom side of the leaves of some species. This coloration is due to the presence of fine white downy hairs. The plant is also called cinquefoil (meaning five-leaves), indicating the five-part leaf groups that may be found (see photo). The genus name Potentilla was given to these plants in 1753 by Linnaeus based on the powerful ("potent") healing effects attributed to the herbal medicines derived from it. The genus is a group of about 500 hardy perennials and shrubs most of them found in the cooler regions of the Northern Hemisphere: North America, Europe, and Northern Asia, though they are now planted over a wider range as an attractive garden plant with bright yellow flowers. The plants vary in height from a few inches to about 3 feet.
As a medicinal herb and food, the most widely used species is Potentilla anserina, sometimes called goosewort, goose grass, or goose tansy because it is a favored food of geese (anserine = goose). The leaves are also consumed by livestock generally, such as cattle, horses, and goats; sheep do not seem to like it, however. The starchy root-which is said to taste like parsnips, sweet potatoes, or chestnuts-has served as a human food, while its leaves are valued as a healthful tea.
Roasted, boiled, or raw, silverweed's rootstock has been consumed as food by the Native Americans, Chinese, and Europeans for centuries. Silverweed rootstock has kept people alive when nothing else was available to eat. For the past few decades, malnutrition has been a significant problem in Tibet, especially among children, and a possible contribution to resolving the problem may be the root Potentilla anserina, known there as droma. It grows on grasslands throughout Tibet. In the past, Tibetans harvested droma, ground it, and fed it to their children. Bundles of the root appear in the marketplace in Tibet and Nepal (where it is also harvested from the high plateaus). A nutrient analysis of droma revealed that its amino acid profile is complementary to that of barley, a Tibetan staple. Since barley flour is mixed with tea and fed to children from a very young age, droma can easily be added to the mixture to make a complete protein food. The Tibet Child Nutrition Project, a program of the Terma Foundation, has been introducing droma for the Tibetan diet.
In Europe, silverweed is known for its antispasmodic activity and it has been used frequently to treat menstrual cramps. Also, its high tannin content makes it a useful treatment for sore throat, oral and skin ulcerations, bleeding, and diarrhea. The famous Swiss herbalist Johann Künzle wrote in his 1911 booklet Herbs and Weeds that: "Every woman should know this herb because there hardly exists a better remedy against menstrual cramps and hemorrhages. Numerous women have found relief by drinking two cups of potentilla decoction on the ten days preceding their menstruation." He went on to point out that "the whole plant has therapeutic effects: it cools, fortifies, and acts as an astringent."
The combination of astringent tannins and antispasmodic action (which is possibly due to glycosides) makes silverweed especially useful for treating diarrhea and ulcerative colitis, since the tannins have antibacterial action and help to heal the intestines, while the antispasmodic effect reduces intestinal contractions. Künzle told of one case: "A peasant from Sion had consulted every physician all the way down to Geneva without finding relief. He weakened continuously because of the daily loss of blood in his stool. Finally, he asked a cattle dealer to drive him up to the herbalist Anna Katharine Willi [she was sometimes called "Tormentilla" named after the herb she frequently used: Potentilla tormentilla]. She gave him half a pound of potentilla powder and she recommended he take half a tablespoonful in a glass of water three times daily. This he did, and a week later he was cured and regained his strength."
Maude Grieve, in her 1931 Modern Herbal, provided a list of applications:
In Chinese medicine, Potentilla chinensis or Potentilla discolor is called fanbaicao; it is a commonly used remedy for diarrhea, especially if accompanied by blood discharge; it is also given for other hemorrhages, including menstrual bleeding and blood in the urine due to infection or gravel. In India and also in Siberia, the leaves of a related plant, Potentilla fruticosa, are used as a substitute for tea. The combination of ordinary tea with potentilla emphasizes its astringent quality.
The major components of interest in potentilla species are tannins of the ellagic-acid type, with monomeric and dimeric ellagitannins, similar to those found in green tea. The herb also contains antioxidant flavonoids (quercetin and myricetin glycosides) and proanthocyanidins. Another group of components of silverweed that are being investigated is the long and medium-chain polyprenols; they accumulate in the leaves of Potentilla anserina at a concentration of up to 0.3% fresh weight. They appear to have antiviral activity.
September 2004