Astragalus is both the common name of one of the most widely used herbs in Chinese medicine, as well as the name of the plant group from which it originates. Astragalus membranaceus is known in China as “huang-qi” which means “yellow leader”. “Huang” means “yellow,” referring to the yellow interior of the root. “ Qi” means “leader,” referring to this herb as one of the superior “tonics” in Chinese medicine. Another plant Astragalus membranaceus var. mongholicus (A. mongholicus) is also used as huang-qi. Regionally in China, several local species are considered acceptable substitutes for the officially listed source plants.

Botany

First, let’s look at the botany. The genus Astragalus is a bewilderingly large and complex plant group of the pea family (Leguminosae). Most of the nearly 2000 species of Astragalus occur in northern temperate zones. In Europe, for example, there are 133 Astragalus species. In North America there are 368 Astragalus species, mostly confined to the western United States and Canada. In the second edition (1991) of Gleason and Cronquist’s Manual of Vascular Plants of Northeastern United States and Adjacent Canada, only 16 species are listed. By comparison 112 species are described for Utah alone in S. L. Welsh et al.’s A Utah Flora (1987). This complex and large group contains a few ornamentals, medicinal plants as well as poisonous plants. One species found in Utah takes-up selenium from the soil and its presence on certain soil types is used as an indicator for the possibility of finding uranium.

Locoweeds and Other Toxic Astragalus species

In the United States, the genus Astragalus is most famous as the plant group producing the western North American “locoweeds.” Woolly Loco (Astragalus mollissimus), abundant in New Mexico and Texas, is one of the first plants to produce foliage in the spring that may be eaten by livestock. Locoweeds cause livestock deaths especially in the Rocky Mountain States westward, affecting various animals in different ways. Locoism makes animals act in an irrational manner, including seeking out locoweeds over palatable forage. The disease causes structural changes in nerve cells. Historically, it has caused many livestock deaths. If eaten by livestock, they can develop a narcotic–like craving for the plant once they graze on it, refusing to feed on other forage. Death occurs gradually after heavy feeding. Poisoning is observed in two stages, the first (lasting several months) produces depression, laziness, weight loss, general scrawniness, lack of coordination, and mania, with bizarre antics. After refusing to eat other plants, animals will become emaciated, with sunken eye–balls, dull hair, and weakness. They may die from starvation in one to two years. Bees and prairie dogs, as well as livestock, are also affected by locoism. Horses are most severely affected. Loco is a Spanish word meaning crazy or foolish, referring to the affect of the plant on livestock. A second group of toxic Astragalus species, such as Narrow–leaved Poison Vetch (Astragalus pectinatus), poison livestock because of their ability to accumulate selenium, causing chronic syndromes such as “blind staggers,” and “alkali disease.” A third group of toxic Astragalus species poison livestock because they contain nitrogen compounds, producing acute poisoning, usually occurring in less than a week, or in cattle, within 4–20 hours. Symptoms may include labored breathing, loss of motor control causing knocking together of hind feet (“cracker heel”). Still other Astragalus species are considered safe and palatable forage plants for livestock. Some are used as foods, cosmetics, and coffee or tea substitutes. Gum tragacanth, widely used for colloidal properties in lotions, pharmaceutical suspensions, resinous tinctures, creams, jelly and even ice cream, is derived from several Astragalus species, including A. gummifer. It is native to Western and Central Asia, an area that harbors hundreds of Astragalus species.

Astragalus in American Gardens

One of the interesting things about the famous Chinese herb Huang-qi from Astragalus membranaceus is that it is no longer an obscure Chinese herb available only from China. The plant was introduced to the United States through the Plant Introduction Office of USDA in 1925. It came from the Botanical Garden in St. Petersburg, and was introduced primarily for the use of forage-crop specialists. Germplasm is maintained through the National Germplasm System of USDA. In recent years other accessions of the species have come to the U.S. from Korea, Japan, as well as Chinese botanical gardens, through seed exchange programs in which botanical gardens worldwide participate. Seed is now widely available for herb gardeners through various commercial sources Astragalus membranaceus is an herbaceous perennial, growing to about 2 feet tall, with sprawling stems. The alternate leaves have 12–24 leaflets. Small, light yellow pea-like flowers arise from leaf axils. I have grown the plant over a three-year period. It is easily grown from seed, though the seed, like many legumes, has a hard coat. If the small kidney-shaped seeds are nicked with a file, or rubbed between sand paper, then soaked in water overnight, they germinate easily, usually within a week. Seeds can be planted outside after the last frost in spring, and will sprout within 2–3 weeks at most. Astragalus seems to be adaptable to growing conditions. It thrives in a deep, sandy, well-drained, somewhat alkaline soil. Good drainage is important. Once young seedlings develop 4–6 leaves, they can be thinned to a spacing of one foot. The Chinese consider the quality of the cultivated roots to be superior to wild-harvested Astragalus roots. Astragalus membranaceus is a wide-ranging species in China, occurring from the northeastern province of Heilongjiang, south to the Shandong peninsula, west to mountains of Sichuan, and north to the western-most province of Xinjiang. It is found along forest margins, in shrub thickets, thin open woods, as well as grasslands near the edge of forests. It appears to be quite hardy, having survived temperatures of –20 degrees F., here in my home in the Ozarks. In China the roots are harvested when plants are four to five years old. Before completely dry, the roots are generally sliced into thin diagonal slices, or sliced lengthwise, producing a dried product that looks much like a tongue depressor, a form commonly seen on American herb markets in which the herb is sold.

Astragalus in Traditional Chinese Medicine

Dr. Alexander von Bunge, a Russian physician who explored East Asian plants in the first half of the nineteenth century, first described the Chinese species, Astragalus membranaceus, in the 1860s in Western terms. Chinese knowledge of the plant is ancient. Under the name “Huang-qi “ it was listed in the superior class of three classes of herbs in the 2,000-year-old classic, Shen Nong Ben Cao Jing (attributed to the divine plowman emperor, Shen-Nong, who is thought to have lived about 4000 years ago). The mythical Shen-Nong is depicted in ancient drawings with horns atop his head like the pagan God Pan. The listing of 365 herbs and descriptions attributed to him survives from about 2,000 years ago. Most of the herbs listed in the work are still the most important herbs in Chinese medicine. In the “Medical Case-book of Shi-shan” (Shi Shan Yi An), published in 1531 huang-qi and its use with ginseng, still a well-known Chinese herbal prescription. With ginseng (Panax ginseng) it is used as a tonic for fatigue, general debility, lack of appetite, and spontaneous perspiration. Westerners were quick to realize the importance of this valuable Chinese herb. Writing on Astragalus his 1911 work, Chinese Materia Medica, G. A. Stuart noted, “It is in great repute as a tonic, pectoral, and diuretic medicine, the diseases for which it is prescribed, therefore, are almost numberless.” According to various books on Traditional Chinese Medicine, Astragalus is used to “invigorate vital energy (qi or ch’i) and strengthen body resistance.” It has been used in prescriptions for shortness of breath, general weakness, and lack of appetite; also as a diuretic, and for the treatment of colds, flu, stomach ulcers, and diabetes. It is widely used in modern herbal practice in China. It is an official drug in the modern Pharmacopoeia of the People’s Republic of China. In Western herbalism, Astragalus has been described as a diuretic, tonic, pectoral, and antipyretic. The sliced root, whole root, capsulated products, teas, tinctures and other product forms of huang-qi are commonly available in health and natural food stores in North America. Astragalus is becoming one of the better known Chinese herbs used as an immune system stimulant.

Astragalus Studies

Scientists, particularly in Asia, have extensively studied Astragalus since it is one of the important tonic herbs of traditional Chinese medicine. Pharmacological and clinical studies confirm its immunostimulant, antibacterial, antiviral, anti-inflammatory, adaptogenic, liver-protecting, and diuretic effects. It also improves stamina. Like ginseng, Astragalus is considered an adaptogen. Adaptogens are defined as an innocuous substance that causes minimal disorders of an organism's function. It must have a “nonspecific action” that normalizes body functions, no matter what the condition or disease. Adaptogens are essentially general tonics. No single compound is responsible for its wide-ranging effects, though polysaccharides are involved in immunostimulant activity. Astragalus is one of a number of herbs used in fu-zheng therapy. Fu-zheng refers to treating disease by enhancing or promoting the host defense mechanism, or normalizing the central energy. In the West, we would classify it as an immunostimulant. This activity is believed to come from polysaccharides, especially astragalan I, II, and III. Other components that may contribute to beneficial effects include saponins and triterpenes. Chinese research groups in the mid-1970s stimulated scientific interest in Astragalus. They were attempting to verify and pharmacological and clinical basis for the ancient practice of fu-zheng therapy. However, this time they were studying its value in modern medicine. In modern China, three systems of medicine are recognized: 1) modern western medicine; 2) the ancient system of traditional Chinese medicine; 3) a combination of western and traditional Chinese medicine. It is in the context of combined Chinese and western medicine that researchers sought to find answers. Realizing that various agents used in chemotherapy in cancer patients tended to suppress the immune system, making patients more susceptible to secondary disease conditions, the researchers looked at the potential of Astragalus to increase immune function in chemotherapy patients. The fu-zheng therapy research group began its work in 1975. In the 1970s and early 1980s, Chinese scientists published several studies on the use of Astragalus as immune system stimulants for chemotherapy and radiation-treated cancer patients. Astragalus was found to act as non-specific immune system stimulant, and helped to protect adrenal cortical function during radiation or chemotherapy treatment. The Astragalus treatment enhanced the activity of bone marrow, depressed by the chemotherapy and radiation, to produce more white blood cells, the guardians of the immune system, while increasing their ability to “ingest” invading particles (such as bacteria or viruses). The Astragalus treatment also modified gastrointestinal toxicity of patients receiving conventional cancer therapies. The end result was a significant increase in survival rates for the patients receiving fu-zheng therapy as an adjunct to Western medical cancer treatments. Researchers at several institutions in Houston, Texas performed a number of laboratory and clinical studies on Astragalus as well as Chinese privet (Ligustrum lucidum). In testing the restorative effect of water extracts of the polysaccharide fraction of Astragalus membranaceus on 19 cancer patients and 15 healthy persons they found that the extracts restored T-cell function in 9 of 10 patients. Using an assay for T-cell restoration, they confirmed that the extracts appeared to restore levels in the cancer patients to those observed in the normal healthy donors. The small clinical study coupled with laboratory tests showed that the herb extract had a strong immune stimulant effect, providing further evidence of it efficacy. Further laboratory studies revealed other mechanisms of action, as well as a polysaccharide fraction, believed to be primarily responsible for the immunostimulant effects. The research was discontinued due to lack of funding. While chemotherapy and radiation may cause a reduction in the activity of the immune system, certain types of tumors may also produce a suppression of the immune system. In addition to immunostimulatory effects on cancer patients, several laboratory studies with mice have shown anticancer activity with Astragalus, related to its ability to potential natural killer cells. A number of studies have shown strong antiviral activity for patients suffering from Coxsackie B vial myocarditis. Extracts of Astragalus have been tested for antiviral activity against the HIV virus, but with negative results. Experimentally, it has also been shown to augment interferon response to viruses. Astragalus has been the focus of other scientific research over the past forty years. Laboratory studies have shown that the root has diuretic activity. When a decoction of the root was given to mice over a three-week period, their swimming duration increased, as did their body weight, suggesting the root has an adaptogenic effect like ginseng. Other experiments have show Astragalus can have a positive result in reducing blood pressure, dilating blood vessels and improving circulation. Since the early 1990s, a number of Asian research groups have conducted research that shows Astragalus root protects the liver against liver toxic compounds. The active components were found to be saponins, though one study found that polysaccharides were also liver-protectant in a model of liver damage in mice. No toxic side effects have been reported with the use of Astragalus membranaceus. In traditional Chinese medicine, it is often used in doses of 9 of the root 15 g. simmered in a quart of water down to a pint. The dried sliced root, which looks like a tongue depressor, is the form the dried is supplied from Chinese sources. Tinctures, tablets, capsules, powdered herb, extracts, and combination products are found in the American herb market. It is often combined with ginseng. Typically, capsules deliver a dose of up to 500 mg. Two average capsules three times a day would be equivalent to a dose of 3–4 g. For commercial products, follow manufacturers label instructions. Astragalus, an important herb in Chinese traditions for over two millennia, is becoming increasingly important in the American market. Traditional use has been confirmed by numerous pharmacological studies and some clinical studies. Scientists have demonstrated immunostimulant activity, antiviral effects and an immuno-restorative function in various cancers. Its acceptance in the American market will be further solidified by well-designed, controlled clinical trials. These studies have yet to be conducted.

Selected References

Chu, D. A., et al. “Immunotherapy with Chinese Medicinal Herbs II. Reversal of Cyclphophamide-induced Immune Suppression by Administration of Fractionated Astragalus membranaceus in vivo.” Journal of Clinical and Laboratory Immunology 25 (1988): 125-129.

Foster, S. Herbs for Your Health. Loveland, Colorado: Interweave Press, 1996.

Foster, S. and Yue Chongxi. Herbal Emissaries - Bringing Chinese Herbs to the West. Rochester, Vermont: Healing Arts Press, 1992.

Ríos, L. and P. G. Waterman. “A Review of the Pharmacology and Toxicology of Astragalus.” Phytotherapy Research, 11 (1997):411-418.

Stuart, G.A. Chinese Materia Medica. Vegetable Kingdom, Extensively Revised from F. Porter Smith (1871). (reprint ed. 1973), as Chinese Medicinal Herbs, Georgetown Press, San Francisco, 1911

Sun, Y., et al. “Immune Restoration and/or Augmentation of Local Graft Versus Host Reaction by Traditional Chinese Medicine Herbs.” Cancer 52(1) (1983): 70-73.