Scientific Name(s): Astragalus membranaceus (Moench), Astragalus mongholicus Bunge.
Common Name(s): Astragalus, Huáng chí, Huáng qí, Hwanggi, Jin Fu Kang, Membranous milk-vetch, Meng gu huang qi, Ogi, Ougi, Radix Astragali
The genus Astragalus, commonly known as milk vetches, comprises more than 2,000 species distributed worldwide. The perennial herbs grow to approximately 1 m high, are native to the northern provinces of China, and are cultivated in China, Korea, and Japan. The plants bear tubular yellowish flowers and small (3 to 6 cm) leaves. The dried root harvested from mature plants 4 to 7 years old is used medicinally and sold as 15 to 20 cm pieces with a tough, fibrous skin and a light interior.1, 2, 3, 4
Astragalus root is well known in traditional Chinese medicine and is listed in the Pharmacopoeia of the People's Republic of China. It is an important component of Chinese Fu Zheng herbal therapy, in which the goal is to restore immune system function by reinforcing the body’s Qi, and is principally used as a tonic and for treatment of diabetes and nephritis. There is extensive Chinese-language literature on the herb/plant. It is sold as shredded roots and in powder, tincture, and encapsulated form. Some products are produced by frying the roots with honey and the untreated root has a sweet, licorice-like taste of its own. Astragalus root is used in the United States as an immunostimulant to counteract the immune suppression associated with cancer chemotherapy.1, 2, 3, 4
Compounds identified in astragalus include polysaccharides, saponins, flavonoids, isoflavonoids, sterols, amino acids (including gamma-aminobutyric acid), volatile oils, and other mineral elements (eg, zinc, iron, copper, manganese, vanadium, tin).
The polysaccharides include the astragalans and astraglucans and are of primary interest along with the triterpene saponin astragalosides. The flavones kaempferol and quercetin and isoflavones, isoflavonones, and pterocarpans are also of interest. The saponin astragaloside intravenous (IV) has been used as a marker for quality assurance of astragalus products.3, 5, 6, 7
Uses and Pharmacology
Astragalus root as adjunctive therapy in cancer has been studied in limited Chinese trials, including a combination preparation (Jin Fu Kang) used in China for the treatment of non–small cell lung cancer, and IV astragalus in malignant tumor.8, 9, 10 An IV extract (PG2) from A. membranaceus has been studied for cancer-related fatigue in an open-label study, which found improvements in subjective outcomes.11
A systematic review of herbal medicines as adjuvants to the leucovorin calcium (folinic acid), fluorouracil, and oxaliplatin (FOLFOX-4) regimen used for treating colorectal cancer was conducted to identify evidence of safety and efficacy of treatment, as well as management of chemotherapy adverse reactions. A total of 13 randomized Chinese clinical trials involving 940 patients compared herbal medicines plus the FOLFOX-4 combination with the FOLFOX-4 regimen alone in patients with advanced (stage IV) colorectal cancer. Although 58 different herbs and/or extracts were used in 7 studies, A. membranaceus was the most common herb found in treatment preparations. Tumor response rate, overall survival at 1 year, time to progression, quality of life, body weight, nausea/vomiting symptoms, and neutropenia improved significantly (P values from P < 0.00001 to P = 0.01) with herbal adjuvants. Astragalus was included in each of the studies contributing to these results.12
Contractility improved in isolated frog and toad hearts, and extracts produced hypotension in cats, dogs, and rabbits. Saponins from astragalus exerted positive inotropic activity in isolated rat heart tissue.3 Astragalosides also increased fibrinolytic potential in human umbilical vein tissue with effects on plasminogen expression.13
No clinical reports of interference with hemostasis have been published.13 Astragalus has been studied in Chinese clinical trials using patients with cardiopulmonary bypass, ischemic heart disease, angina pectoris, and chronic heart failure with positive effect.14, 15, 16, 17 No effect of astragalus has been found in improving clinical outcomes in viral myocarditis, and the quality of those studies included in the Cochrane review was reported to be poor.18
In vitro and animal data
A number of clinical trials have been conducted in Chinese populations with immune-related conditions including systemic lupus erythematosus, myasthenia gravis, and herpes simplex keratitis. Although the studies were small and published in Chinese, findings were generally supportive of enhanced immune function as demonstrated by indices of cytokines or other relevant measures.27, 28, 29, 30, 31 Other clinical studies have been published reporting effects of the extract on long-term fatigue (astragalus in combination), and cancer-related fatigue with improvements in subjective outcomes, but not cytokine expression.11, 32 T cell activation by A. membranaceus has been reported in healthy volunteers given the extract orally.33
Astragalus has been studied in viral diseases including HIV, herpes simplex, and coxsackie-B infections as adjunctive therapy, most likely due to immune effects rather than direct action on a virus itself. T cell responses to A. membranaceus in patients with viral myocarditis reflected an enhanced immune response; however, no reduction in deaths due to cardiac failure was shown.18 Initial interest in the extract for a therapeutic role in HIV treatment34, 35, 36 has not persisted, with no further clinical trials reported.
Studies in rodents suggest potential applications of A. membranaceus in diabetes. A small clinical study in type 2 diabetes showed improvements in glucose metabolism, but not other glycemic indices.6, 37
Natriuretic activity of oral Radix Astragali has been demonstrated in healthy adult men.38 Chinese studies have demonstrated effects on kidney function, including reducing proteinuria in chronic kidney disease; however, methodologies have varied, and solid evidence for efficacy has not been determined.7, 39
Astragaloside IV has been shown to promote the repair of sciatic nerve injury in a rodent study.40 Although astragalus is often recommended for prevention of the common cold, there are no published English-language clinical trials that support this use. Antioxidant properties and a wide range of other effects have been demonstrated in limited studies.
The saponin astragaloside IV has been used as a marker for quality assurance of astragalus products, but is not considered a major bioactive constituent.7
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Although clinically important case reports are lacking, potentiation of acyclovir and related compounds of interleukin and interferon and suppression of immunosuppressant medicines could occur. Potentiation of thrombolytics may also be possible.13
An astragalus hot water extract was mutagenic in the Ames test in Salmonella typhimurium TA98 when activated by S9 rat liver fractions. The same preparations given by intraperitoneal injection at 1 to 10 g/kg produced chromosomal aberrations in the bone marrow of mice and increased the incidence of micronucleated cells in bone marrow. No attempt was made to isolate the mutagenic compounds responsible for these effects.43 Other tests suggest astragalus to be antimutagenic.3 At doses 100 times higher than effective oral doses in humans, no adverse effects were observed in mice, while a median lethal dose for intraperitoneal administration of 40 g/kg in mice has been reported.3
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