ASTRAGALUS
Practical Aspects of Administering the Herb
Astragalus root (huangqi) is a commonly used Chinese herb from the Fabaceae family (legumes). It belongs to the subfamily Papilionoideae, which is the source of several popular Chinese herbs, including licorice (gancao), millettia (jixueteng), sophora (kushen), and pueraria (gegen).
The applications of astragalus underwent dramatic changes during the past 50 years because of two medical concerns: the increasing use of chemotherapy for cancer, in which case herbs to counter the immune-debilitating effects were sought, and the rise of cardiovascular diseases (e.g., heart attack and stroke). For the former, the combination astragalus with ligustrum (nüzhenzi) was most publicized due to involvement of Western investigators; for the latter, the combination of astragalus with salvia (danshen) became well known.
A look at the use of astragalus before the influences of these modern trends is offered by Smith and Stuart (1), who reported at the end of the 19th century that astragalus was "in great repute as a tonic, pectoral [alleviates disorders of the lungs and chest], and diuretic medicine every sort of wasting or exhausting disease is thought to be benefited by it." At that time, a frequently occurring wasting disease involving the lungs was tuberculosis, and the herbal therapies usually included astragalus. The original description of astragalus in the Shennong Bencao Jing (ca. 220 A.D.) would be hardly recognizable for someone who learns of this herb from modern literature:
It mainly treats welling and flat abscesses and enduring festering sores by expelling pus and relieving pain, great wind lai disease [leprosy], the five kinds of hemorrhoids, and "mouse fistulas." It supplements deficiency and is good for hundreds of diseases in children.
The herb was used to treat skin disorders, superficial swellings, and children's ailments. The editors of the modern translation quoted here (2) no doubt felt compelled to offer some information that is more in keeping with the current applications of astragalus and added a footnote quoting from Wang Haogu, an herbalist of the Jin-Yuan reform period (3), more than 700 years ago: "Astragalus replenishes the defensive and, therefore, is a medicinal for the exterior. It boosts the spleen and stomach and, therefore, is a medicinal for the center. Since it is able to treat cold damage with the cubit pulse not arriving, it supplements the kidney origin and, hence, is a medicinal for the internal." Through this explanation, astragalus is seen as a broadly useful tonic ingredient to include in prescriptions.
Astragalus has been a popular herb since the publication of Taiping Huimin Hejiju Fang (ca. 1110 A.D., at the beginning of the Jin-Yuan reform period). The five traditional formulas listed in the table below (4) are perhaps the best known (last column: grams in decoction, percent by weight of astragalus in the formula):
| Formula name | Uses | Astragalus |
| Buzhong Yiqi Tang | deficiency of spleen/stomach, with symptoms of fever, spontaneous sweating, shortness of breath, fatigue, organ prolapse, etc. | 20 g 30% |
| Yiqi Congming Tang | deficiency of qi and failing of yang to rise, with impairment of vision or hearing. | 15 g 12% |
| Guipi Tang | deficiency of qi and blood, with symptoms of anxiety, palpitation, insomnia, night sweating, fatigue, bleeding, etc. | 30 g 15% |
| Shiquan Dabu Tang | deficiency of qi, blood, and yang, with fatigue, asthmatic breathing, bleeding, etc. | 15 g 16% |
| Yupingfeng San | deficiency of qi, with spontaneous sweating and susceptibility to wind affecting . | 30 g 25% |
The astragalus dosages reported here reflects modern practice in China. There is also one traditional prescription where astragalus is dominant: Danggui Buxue Tang; astragalus (30 grams) is to be cooked with a small amount of tang-kuei (6 grams), and the pair of herbs is used to help generate blood in a person who has severe deficiency, usually from excessive uterine bleeding.
A substantial number of traditional formulas indicated primarily for tonification that come to us today contain astragalus, though it may be included as a small proportion of the prescription. As an example, in the tonic section of Thousand Formulas and Thousand Herbs of Traditional Chinese Medicine (4), over 80 prescriptions are listed, including four of the ones in the above table (Yupingfeng San is placed with astringent formulas instead); about one in four of all the tonic formulas contain astragalus as an ingredient.
Two of the traditional formulas with astragalus have been adopted for modern use as "immune enhancing" prescriptions, sometimes given to patients undergoing cancer therapies: Buzhong Yiqi Tang and Shiquan Dabu Tang.
Some practitioners may think of astragalus as a "strong" qi invigorating herb because of its frequent use in tonic formulas; however, most traditional sources place it in a mild to intermediate category. Yang Yifan, in her book on Chinese Herbal Medicines: Comparisons and Characteristics (5), displays a scale of strength of qi tonics and places astragalus well below ginseng, but slightly above codonopsis (dangshen). In the Advanced Textbook on Traditional Chinese Medicine and Pharmacology (6), astragalus is listed with two other herbs, ginseng and codonopsis, as tonics that have the similarities of replenishing qi of the spleen and stomach. As to differences, ginseng is described as being able to "replenish primordial qi potently," codonopsis is described as have properties similar to ginseng but with much weaker effect, and astragalus is described as "consolidating superficial defensive qi." So, in terms of qi tonics, ginseng is considered potent, codonopsis is relatively weak, and astragalus is somewhat stronger than codonopsis, but aimed at the surface defense while codonopsis and ginseng, act on the primordial (original) qi.
There are some characteristics that may be associated with mild versus strong herbs. Mild acting herbs have these qualities: low toxicity; low incidence of adverse reactions at normal dosage; and the normal dosage is relatively high. As a contrast to mild acting herbs, there are those that have notable toxicity (such as raw aconite), those that easily cause adverse reactions (such as rhubarb causing intestinal cramping or loose stool), and those that have significant effects at low dosage (e.g., the potent heating effect of zanthoxylum at just a gram per day). Astragalus clearly fits the category of mild-acting herbs. It has a gentle warming nature, a mild, sweet taste, and can be used in doses of 30 grams or more without adverse effects. Laboratory animal studies show virtually no toxicity with administration of very high oral dosage or even with injections (7).
After several decades of study, three groups of active constituents have become known for astragalus: flavonoids (which give the yellow color to the root slice), saponins (a common ingredient of plants in this family), and polysaccharides (long-chain polysaccharides with potential medicinal benefit mediated by white blood cells). The quantities of these components will vary depending upon the species of Astragalus used, as well as the growing conditions and other factors. No other potential active constituents have been found in significant quantities. Of course, there are many other components of astragalus root, but they are either ordinary components found in foods (such as carbohydrates and proteins) or ingredients that are present in such small amounts as to not contribute significantly to the effect of the whole herb preparations even when the herb is used at high dosage (e.g., sterols). Those who have used astragalus root in decoction recognize that it is a very fibrous root, for which most of the material remains behind in the dregs after prolonged boiling.
Astragalus contains small amounts of several flavonoids, primarily isoflavones, such as formononetin (see image, below) and its glucoside, ononin, which are metabolized in the body to yield the common legume flavonoid daidzein, an ingredient in pueraria and soy beans. Flavonoids are found in all higher plants, but some plants are rich sources of them. In fact, pueraria root has flavonoids as the primary active ingredient (aside from its starches that are soothing to the gastro-intestinal system). There are numerous potential beneficial effects of flavonoids (8), but when present in modest amounts, as is the case with astragalus, the primary effect is to benefit circulation. Other actions, that are noted for high doses of flavonoids, such as anti-allergy and anti-viral activity, would not be expected from astragalus extracts.
In one recent study (9) it was noted that "In the roots, isoflavonoid content was extremely variable, but reached 3.04 mg/gram, whereas flavonol content was 0.49 mg/gram." Modern supplements that provide flavonoids such as quercetin for therapeutic benefit have several hundred milligrams making up a one day dose, while isoflavones in soy and clover (which are essentially the same as found in astragalus), are reputed to help with menopausal symptoms and have other benefits at doses of 60-180 mg or more per day. The combined isoflavonoid and flavonol content mentioned here (using the figure given for the maximum) is 3.5 mg/gram (0.35%), so that a 15 gram daily dose of astragalus in decoction would yield only about 50 mg of these flavonoids if all were extracted. This is a small amount, and most roots have lower levels of the flavonoids, typically less than 0.1%. In commercial extracts, standardization of astragalus root concentrate is for the product at just 0.4-0.5% of the main isoflavone, a tiny amount. The astragalus flavonoids contribute the yellow color seen in the central part of the roots, which is frequently used as a monitor of root quality (those with stronger yellow coloration are considered better quality).
In sum, though the flavonoids may contribute to a general beneficial effect of astragalus, their effects are probably minor until the astragalus dosage exceeds 15 grams, as is common in modern clinical practice in China, but not as herbs are usually prescribed in the West. In the book Chinese Drugs of Plant Origin (10), flavonoids are not included in the list of astragalus active constituents; only the saponins and polysaccharides are included.
The saponins of astragalus include several called astragalosides (-oside indicates that it is a glycoside, that is, has a sugar attached to an active molecule, such as a pentacyclic compound usually found in saponins). In a study of astragalus roots from China, the saponin content was found to be from 0.019 to 0.184%, with astragaloside I as the main component (10); others consider that astragaloside IV is the main component (see image, below). When astragalus extracts are made and standardized for saponin content, a 0.5% saponin level is the most that is usually attained (one Chinese source indicates a range of 0.2 to 20% saponin content available). In a previous analysis of saponin-containing herbs, it was shown that to get substantial activity for these compounds one would need to administer doses of 60-900 mg (11). Based on a maximum root content of about 0.184% saponins, a 15 gram daily dose of astragalus might yield about 28 mg total saponins, a small amount. These saponins of astragalus, if they were given in sufficient quantity, may have properties of reducing inflammation, resolving phlegm, reducing platelet sticking, and promoting cardiac function.
Ginseng (renshen) is an herb that has saponins as its primary constituent, and good quality red ginseng roots can have about 4-5% saponins in the dried material; extracts may have up to 85% saponins. Thus, the ginseng saponins are easier to get in reasonable quantities. An herb that is used like astragalus for treating abscesses and certain other skin diseases is platycodon (jiegeng); it also relies on saponins as a key active component, but it contains even more saponin than ginseng, usually over 6% in the dried roots. A traditional formula for treating abscesses that relies on both astragalus and platycodon is Qianjin Neitou San; the formula also has saponins from ginseng and licorice.
In sum, the saponins in astragalus may be present in small enough quantities that they don't provide much therapeutic effect on their own. However, when astragalus saponins are combined with saponins from other herbs in a formula, they may contribute to getting the necessary amount for the desired therapeutic effect.
The polysaccharides of astragalus, called astragalans, may be present in relatively large quantity. It is important to recognize that polysaccharides (long chains of sugars; see image of a repeating structure, below) are not soluble in alcohol, so are not present in tinctures or other alcoholic preparations; they are soluble in hot water, but the desired high molecular weight ingredients (20,000-25,000 daltons) may be only partially extracted from the herb under normal conditions. It is relatively easy to isolate polysaccharides by first using hot water extraction and then condensing these large molecules out of solution with alcohol. Commercial astragalus extracts have been standardized to 40-50% polysaccharides; some sources claim ability to provide 70-90% polysaccharides. These levels are as high as attained with mushrooms that are used specifically for their polysaccharides (typically 40% polysaccharides in the standardized extracts, but sometimes higher percentages). A reasonable estimate for the content of the dried roots is about 10% extractable medicinally active polysaccharides (in one of the most commonly used commercial astragalus extracts made by hot water extraction, the concentrated material has just 16% polysaccharide and 0.2% flavones). The crude powdered herb may be a better source of polysaccharides than a boiled preparation, but a polysaccharide rich extract is the most convenient means of getting high doses of this component.
In a previous analysis of medicinally active polysaccharides and their applications, it was shown that a daily dosage of 3.0-3.5 grams of these components would be reasonable to attain some level of immunological activity (12). A 30 gram dose of astragalus would have about this amount of polysaccharides. The polysaccharides have the reputation of enhancing immune functions and specifically in improving white blood cell responses; the large molecules probably stimulate the white blood cells to respond just as they might to saccharide chains on the surface of bacteria; there may also be a stimulation of white blood cell production by the bone marrow. Polysaccharides have been used, especially, in attempts to overcome the immune debilitating effect of radiation and chemotherapy as used in cancer treatments. In China, astragalus is most often used in doses of 15-30 grams per day in decoction for this application.
It appears that the polysaccharides are present in sufficient quantity that the high dosage astragalus preparations could affect the white blood cell activity.
The analysis of active constituents present above reveals that a dose of about 15 grams of astragalus, as frequently used in decoctions, may be sufficient to attain only some of the desired effects of the known active components, but that a 20-30 gram dose would be more suitable.
The Chinese Materia Medica recommendations for astragalus dosing are 9-15 grams/day (with the understanding that astragalus is to be used in formulas with other herbs); high doses of 30-60 grams are also suggested, at least for some applications (usually not specified). When dosing at or below 15 grams, an herbalist is counting on other herbs in a formula to contribute some similar active components in order to get the desired therapeutic action. Thus, for example, a decoction made with astragalus, ganoderma (lingzhi), and red ginseng would provide polysaccharides and saponins from all three herbs, and so long as the total dosing of these three ingredients was sufficient, then astragalus at 9-15 grams/day would be acceptable.
The formula Yiqi Congming Tang has three botanically-related herbs-astragalus, licorice, and pueraria-all contributing flavonoids and saponins, as well as having ginseng with additional saponins. Thus, astragalus is not the sole herb relied on for these active components. This formula is not used for immune enhancing purposes, so the limited amount of polysaccharides from other ingredients is not a concern.
Lower doses of astragalus would not be entirely ineffective, but the action would be limited. As an example, the polysaccharides can have benefits for the stomach (e.g., alleviating ulcers) at doses below that necessary to yield the general immunological effects, because of the direct action of the full amount of the herb ingredients on the stomach before being distributed throughout the body. Thus, pills with a relatively small amount of astragalus included will have this type of action from astragalus. Following absorption from the small intestine, the astragalus ingredients are diluted into a large volume of blood and some begin to be metabolized and eliminated after just a few minutes.
The recommended high doses of astragalus, at 30-60 grams per day (sometimes as high as 120 grams/day), are used in short-term therapies to get a stronger action of the herbs, and this dosage should yield a substantial effect from both the saponins and polysaccharides, with some effect also from flavonoids. It is not known if prolonged use of these higher dosages could be detrimental, but a reasonable caution would be to limit the duration to a few days at a time when needed, rather than a continuous therapy.
In the book Chinese-English Manual of Commonly Used Herbs in Traditional Chinese Medicine (13), five major actions and associated uses are given, as well as some miscellaneous new uses (item 6):
It is important for practitioners to distinguish between traditional indications (some of which are based solely on dogma and not on careful observation) and known effective actions (which might be confirmed through clinical trials). For example, it would be a mistake to think that a prolapsed organ would go back into place merely by taking some astragalus or by using this herb in a qi tonic formula. This indication for astragalus comes from three considerations:
These theoretical reasons for using astragalus are consistent with Chinese medical theory, but there is no evidence to show that the appropriateness of astragalus in this instance corresponds to its effectiveness in alleviating prolapse. Indeed, in order to reverse prolapse non-surgically, one usually needs to strengthen the muscles surrounding the organ, which requires doing physical exercise. If taking herbs will, by whatever mechanism, improve one's sense of energy and capability, then the person might undertake more exercise. That added activity would, in turn, control or reverse the prolapse through strengthening the muscles. If the herbs do not aid one in pursuing the physical activity, they would be unlikely to have any substantial impact on the prolapse, other than alleviating discomfort.
While an analysis of each of the claimed activities for astragalus is beyond the scope of this article, it can be said that those which directly affect digestion, such as treating low appetite, loose stool, stomach ulcer, and atrophic gastritis, may be partly explained by direct action of the ingredients on the lining of the stomach and intestine. Saponins and polysaccharides are likely to be the main active components, potentially of benefit in small doses in contact with the stomach lining. Resolving skin infections and erosion, aiding treatment of common cold, and promoting while blood cell function are actions that would require the higher dosages discussed above. Claimed diuretic effect of herbs is an area of some difficulty to interpret, as the drinking of decoctions is, in itself, a potential means of diuresis because of the fluid consumed. Further, the body's elimination of the chemical constituents contained in the herbs and their metabolites is primarily by diuresis. A diuretic effect may be stimulated by high levels of such chemical compounds, with relatively little specific diuretic action of the herbs included in the therapy. Low dosage pills are unlikely to have much diuretic effect, both because of the low dose and because of the lower fluid intake (unless they are swallowed down with a large amount of water or tea).
Astragalus can be an effective agent, though one must give due considerations to its preparation and dosage according to the intended application, and the practitioner must be careful about interpreting indications that appear in the traditional literature.
May 2006