Astragalus is a large genus of about 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to temperate regions of the Northern Hemisphere. Common names include milkvetch (most species), locoweed (in North America, some species) and goat's-thorn (A. gummifer, A. tragacanthus). Some pale-flowered vetches are similar in appearance, but vetches are more vine-like.
Astragalus species are used as food plants by the larvae of some Lepidoptera species including many case-bearing moths of the genus Coleophora: C. cartilaginella, C. colutella, C. euryaula, and C. onobrychiella feed exclusively on Astragalus, C. astragalella and C. gallipennella feed exclusively on the species Astragalus glycyphyllos, and C. hippodromica is limited to Astragalus gombo.
The natural gum tragacanth is made from several species of Astragalus occurring in the Middle East, including A. adscendens, A. gummifer, A. brachycalyx, and A. tragacanthus. Also Astragalus propinquus (syn. A. membranaceus) has a history of use as a herbal medicine used in systems of traditional Chinese medicine and Persian medicine. In traditional Chinese medicine A. membranaceus has been used to reinforce qi and strengthen the superficial resistance, and promote the discharge of pus and the growth of new tissue.
Biotechnology firms are working on deriving a telomerase activator from Astragalus. The chemical constituent cycloastragenol (also called TAT2) is being studied to help combat HIV, as well as infections associated with chronic diseases or aging. However, the National Institutes of Health states: "The evidence for using astragalus for any health condition is limited. High-quality clinical trials (studies in people) are generally lacking. There is some preliminary evidence to suggest that astragalus, either alone or in combination with other herbs, may have potential benefits for the immune system, heart, and liver, and as an adjunctive therapy for cancer".
Research at the UCLA AIDS Institute focused on the function of cycloastragenol in the aging process of immune cells, and its effects on the cells' response to viral infections. It appears to increase the production of telomerase, an enzyme that mediates the replacement of short bits of DNA known as telomeres, which play a key role in cell replication, including in cancer processes.
Extracts of Astragalus propinquus ( syn. A. membranaceus) are marketed as life-prolonging extracts for human use. A proprietary extract of the dried root of A. membranaceus, called TA-65, "was associated with a significant age-reversal effect in the immune system, in that it led to declines in the percentage of senescent cytotoxic T cells and natural killer cells after six to twelve months of use". There are mixed data regarding Astragalus, its effects on telomerase, and cancer. For example, although 80% of cancer cells utilize telomerase for their proliferation—a factor that might theoretically be exacerbated by Astragalus—the shortening of telomeres (resulting from such factors as stress and aging and possible contributors to malignancy), might also be mitigated by Astragalus. Thus, short telomeres result in chromosome instability, and the potential for telomere lengthening as a protection against cancer is possible. Additionally, scientists recently reported that cancer cells may proliferate precisely because of the lack of differentiation occurring via damaged or shortened telomere length. They propose that "forced" elongation of telomeres promotes the differentiation of cancer cells, probably reducing malignancy, which is strongly associated with a loss of cell differentiation.
Side effects and toxicology
Astragalus may interact with medications that suppress the immune system, such as cyclophosphamide. It may also affect blood sugar levels and blood pressure. Some Astragalus species can be toxic. For example, several species native to North America contain the alkaloid swainsonine, which may cause "locoism" in livestock. The toxicity of Astragalus taxa varies.
Several species, including A. alpinus (bluish-purple flowers), A. hypoglottis (purple flowers), and A. lotoides, are grown as ornamental plants in gardens.
- Astragalus acutirostris—sharpkeel milkvetch
- Astragalus agnicidus—Humboldt County milkvetch
- Astragalus agrestis—field milkvetch, purple milkvetch, cock's-head
- Astragalus albens—Cushenbury milkvetch
- Astragalus alpinus—alpine milkvetch, mountain locoweed
- Astragalus amphioxys—crescent milkvetch
- Astragalus ampullarioides—Shivwits milkvetch
- Astragalus andersonii—Anderson's milkvetch
- Astragalus anisus
- Astragalus annularis
- Astragalus anserinus—Goose Creek milkvetch
- Astragalus anxius—troubled milkvetch
- Astragalus applegatei—Applegate's milkvetch
- Astragalus asymmetricus—San Joaquin milkvetch
- Astragalus atropilosulus
- Astragalus austiniae—Austin's milkvetch
- Astragalus australis—Indian milkvetch
- Astragalus barrii—Barr's milkvetch
- Astragalus bernardinus—San Bernardino milkvetch
- Astragalus bibullatus—limestone-glade milkvetch
- Astragalus bicristatus—crested milkvetch, two-crested milkvetch
- Astragalus bidentatus
- Astragalus bisulcatus—two-groove milkvetch
- Astragalus bolanderi—Bolander's milkvetch
- Astragalus brachycalyx
- Astragalus brauntonii—Braunton's milkvetch
- Astragalus breweri—Brewer's milkvetch
- Astragalus californicus—California milkvetch
- Astragalus canadensis—Canadian milkvetch
- Astragalus casei—Case's milkvetch
- Astragalus centralpinus
- Astragalus cicer—wild lentil, chickpea milkvetch
- Astragalus cimae—Cima milkvetch
- Astragalus clarianus—Clara Hunt's milkvetch, Napa milkvetch
- Astragalus clevelandii—Cleveland's milkvetch
- Astragalus coccineus—scarlet milkvetch, scarlet locoweed
- Astragalus congdonii—Congdon's milkvetch
- Astragalus cremnophylax—Sentry milkvetch
- Astragalus crotalariae—Salton milkvetch
- Astragalus curtipes—Morro milkvetch
- Astragalus deanei—Deane's milkvetch, Dean's milkvetch
- Astragalus desereticus—Deseret milkvetch
- Astragalus didymocarpus—two-seeded milkvetch, dwarf white milkvetch, white dwarf locoweed
- Astragalus douglasii—Douglas's milkvetch
- Astragalus ehrenbergii
- Astragalus ertterae—Walker Pass milkvetch
- Astragalus falcatus
- Astragalus filipes—basalt milkvetch
- Astragalus funereus—Funeral Mountain milkvetch
- Astragalus gambelianus—Gambel's dwarf milkvetch, dwarf locoweed
- Astragalus gibbsii—Gibbs' milkvetch
- Astragalus gilmanii—Gilman's milkvetch
- Astragalus glycyphyllos—wild liquorice, licorice milkvetch
- Astragalus holmgreniorum—Holmgren locoweed
- Astragalus humillimus—Mancos milkvetch
- Astragalus hypoxylus—Huachuca Mountain milkvetch
- Astragalus inversus—Susanville milkvetch
- Astragalus inyoensis—Inyo milkvetch
- Astragalus iodanthus—Humboldt River milkvetch
- Astragalus iselyi—Isely's milkvetch
- Astragalus jaegerianus—Lane Mountain milkvetch
- Astragalus johannis-howellii—Long Valley milkvetch
- Astragalus kentrophyta—spiny milkvetch
- Astragalus layneae—widow's milkvetch
- Astragalus lemmonii—Lemmon's milkvetch
- Astragalus lentiformis—lens pod milkvetch
- Astragalus lentiginosus—freckled milkvetch, mottled locoweed, speckled locoweed, spotted locoweed
- Astragalus leptaleus
- Astragalus leucolobus—Bear Valley woollypod, Bear Valley milkvetch
- Astragalus linifolius—Grand Junction milkvetch
- Astragalus loanus—Glenwood milkvetch
- Astragalus lotoides
- Astragalus malacus—shaggy milkvetch
- Astragalus membranaceus—huang qi (黄芪/黃芪 huáng qi; běi qí 北芪)
- Astragalus microcymbus—Skiff milkvetch
- Astragalus miguelensis—San Miguel milkvetch
- Astragalus missouriensis—Missouri milkvetch
- Astragalus mohavensis—Mojave milkvetch
- Astragalus molybdenus
- Astragalus monoensis—Mono milkvetch
- Astragalus monspessulanus
- Astragalus montii
- Astragalus mulfordiae—Mulford's milkvetch
- Astragalus nevinii—San Clemente Island milkvetch
- Astragalus newberryi—Newberry's milkvetch
- Astragalus nitidiflorus—Tallante's milkvetch
- Astragalus nutans—Providence Mountains milkvetch
- Astragalus nuttallianus—small-flowered milkvetch
- Astragalus nuttallii—Nuttall's milkvetch
- Astragalus obscurus—arcane milkvetch
- Astragalus onobrychis
- Astragalus oocarpus—Descanso milkvetch, San Diego milkvetch
- Astragalus oophorus—egg milkvetch
- Astragalus osterhoutii—Osterhout milkvetch
- Astragalus oxyphysus—Mt. Diablo milkvetch, Diablo locoweed
- Astragalus pachypus—thickpod milkvetch
- Astragalus panamintensis—panamint milkvetch
- Astragalus pauperculus—depauperate milkvetch
- Astragalus phoenix—Ash Meadows milkvetch
- Astragalus platytropis—broadkeel milkvetch
- Astragalus pomonensis—Pomona milkvetch, Pomona locoweed
- Astragalus propinquus—huang qi (黄芪/黃芪 huáng qi; běi qí 北芪)
- Astragalus proximus
- Astragalus pseudiodanthus—Tonopah milkvetch
- Astragalus pulsiferae—Ames' milkvetch
- Astragalus purshii—Pursh's milkvetch, Woollypod milkvetch, woollypod locoweed
- Astragalus pycnostachyus—Marsh milkvetch
- Astragalus rattanii—Rattan's milkvetch
- Astragalus ripleyi
- Astragalus robbinsii—Robbins' milkvetch
- Astragalus sabulonum—gravel milkvetch
- Astragalus scaphoides—bitterroot milkvetch
- Astragalus schmolliae—Schmoll milkvetch
- Astragalus shevockii—Shevock's milkvetch, Little Kern milkvetch
- Astragalus sinuatus—Whited's milkvetch
- Astragalus subvestitus—Kern County milkvetch
- Astragalus tener—alkali milkvetch
- Astragalus tennesseensis—Tennessee milk vetch
- Astragalus tidestromii—Tidestrøm's milkvetch
- Astragalus tragacantha
- Astragalus traskiae—Trask's milkvetch
- Astragalus tricarinatus—triple-ribbed milkvetch
- Astragalus trichopodus—Santa Barbara milkvetch, coast locoweed, Southern California locoweed
- Astragalus tuyehensis from Iran
- Astragalus tyghensis
- Astragalus umbraticus—Bald Mountain milkvetch
- Astragalus webberi—Webber's milkvetch
- Astragalus wetherillii
- Astragalus whitneyi—balloon-pod milkvetch
- Astragalus zionis—Zion milkvetch
- List of the largest genera of flowering plants
- List of species of Astragalus in Latin with Russian translation
- This may actually be a valid genus.
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- Astragalus, NCCAM
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- Astragalus - Compounds, Mechanism of action, and Uses
- Astragalus - Clinical summary and Constituents, MSKCC Memorial Sloan Kettering Cancer Center
- Large list of species
- Astragalus at a Glance This fact sheet from the U.S. National Institutes of Health provides basic information about Astragalus – common names, uses, potential side effects, and resources for more information.
- Astragalus alpinus This Rare Species Guide profile from the Minnesota Department of Natural Resources provides information about the basis for the species' listing, habitat, biology and life history, conservation and management, and conservation efforts.
- Chinese Milkvetch, Astragalus membranaceus, Kansas State University