Astragalus Root
scientific name : Astragalus Membranaceus
common name : Huang Chi, Huang qi, Astragalus
Tomoda reported a complex 60 kD acidic polysaccharide, AMem-P with a high hexuroic acid content from A. membranaceus and a similar but distinct 76 kD acidic polysaccharide, AMon-S from A. mongholicu5.16 Bornbardelli and Pozzi patented polysaccharides known as astroglucans A-C from A. membranaceu.?
Botany
The genus Astragalus is an enormous group of more than 2000 species distributed worldwide, commonly known as milk vetches. The Chinese species A. membranaceus and the related A. mongholicus are now thought to be varieties of the same species.1 Both are perennial herbs native to the northern proVinces of China and are cultivated in China, Korea, and Japan. The dried root is used medicinally. Astragalus roots are sold as 15to 20-cm long pieces, which have a tough, fibrous skin with a lighter interior. Some products are produced by frying the roots with honey, although the untreated root itself also has a sweetish, licorice-like taste.
History
Astragalus root is a very old and well-known drug in traditional Chinese medicine, and is currently official in the Chinese Pharmacopeia. It is used in China principally as a tonic and for treatment of diabetes and nephritis. It is an important component of Fu-Zheng therapy in China, where the goal is to restore immune system function. There is extensive Chinese language literature on the drug.
Chemistry
A PCR method for measuring astragalus content in a polyherbal preparation has been published. Markers for each component were developed using decamer oligonucleotide primers.2 Hairy root culture of Astragalus have been established and found to produce cycloartane saponins.
Astragalus root contains a series of cycloartane triterpene glycosides denoted astragalosides I to VII, that are based on the genin cycloastragenol and contain from 1 to 3 sugars attached at the 3-, 6-, and 25-positions.6-9 In the predominant astraglosides I to III the 3-glucose is acetylated. Several saponins based on the oleanene skeleton have also been reported. 1 0 The aboveground parts of astragalus contain similar but distinct saponins in the cycloartane series.11,12 and many other species of astragalus contain cycloartane saponins.
A variety of polysaccharides have been reported from astragalus root. Astragalan I is a neutral 36 kD heterosaccharide containing glucose, galactose, and arabinose, while astragalans II and III are 12 kD and 34 kD glucans, respectively.1,14 Huang, et aI., isolated 3 similar polysaccharides and an acidic polysaccharide, AG-2, as well.
Isoflavan glycosides based on mucronulatol and isomu. cronulatol have been found in the roots of A. membrana. ceus.9,18 Several products appear to use these com. pounds for standardization despite the lack of reported biological activity. In addition, the free isoflavones afror. mosin, calycosin, formononetin, and odoratin have been isolated from the roots.
A unique biphenyl was isolated from A. membranaceus var. mongholicus as an anti hepatotoxic agent.
Pharmacology
The most common use of astraga. Ius root in herbal medicine in the US is as an immunestimulant to counteract the immune suppression associ. ated with cancer chemotherapy. This use is based on several observations. The cycloartane saponins are ca. pable of stimulating the growth of isolated human Iymphecytes.13 The polysaccharides astragalans I and II were found to potentiate immunological responses in mice following IP administration, though not after oral adminis. tration.14 The glycans AMem-P and AMon-S increased phagocytic indices on IP injection into mice.
Aqueous extract of astragalus root stimulated phago. cytosis of murine macrophages, and augmented prom. eration of human monocytes in response to phytohemagglutinin, concanavalin A, and pokeweed mitogen.21,22In cells from cancer patients, which were comparatively resistant to such stimulation, astragalus extract stimulated mononuclear cells. Using a graft-vs-host model, astragalus extract restored the GVH reaction in vivo for healthy and immune-suppressed patients.
These in vitro and in vivo effects justify further human trials of the immunostimulant activity of astragalus root extracts in patients whose immune system has been suppressed by cancer chemotherapeutic drug regimens, A second use of astragalus root in the US is for HIV infection. Such use must depend on a host-mediated.