Milk vetch (Astragalus mongholicus)

This review is limited to different preparations of Astragalus mongholicus root, the most commonly used Astragalus species in Chinese medicine. Other Astragalus species which are being investigated for their anti-cancer properties are the Turkish species, and include Astragalus brachypterus, Astragalus cephalotes, Astragalus microcephalus and Astragalus trojanus.

Scientific name/Common name/Brand name

The correct scientific definition for radix Astragali is the whole dried root of Astragalus mongholicus var. mongolicus (Syn. Astragalus membranaceus BUNGE var. mongholicus (BUNGE) P.K. HSIAU and Astragalus mongolicus var. dahuricus (DC) PODLECH (Syn. Astragalus membranaceus BUNGE), common name: milk vetch. In the literature it is often named Astragalus membranaceus. The German common name is Tragant. In Traditional Chinese Medicine (TCM), Astragalus is believed to have a “Qi tonifying” effect (Qi is thought to be a vital energy, or the instigator of body functions, a concept closely linked to immunity) and is also considered an adaptogenic herb. It belongs to the family Leguminosae. According to the European Pharmacopoeia, the root should be freed from rootlets and root stock and should be collected from spring to autumn. The dried root of Astragalus mongholicus is called ‘Huangqi’ 1-2,4.

The collection of Chinese herbs used to enhance host defense against infectious and neoplastic diseases is referred to as Fuzheng therapy 4. Astragalus is often used in this context.

Other preparations of Astragalus used in cancer therapy are tragacanth, the gummy sap of Astragalus root, and swainsonine, a water-soluble indole alkaloid produced by several plants known as locoweeds, including Astragalus 30. Swainsonine is found in different aerial parts of locoweeds.

Ingredients

Polysaccharides, saponins, isoflavonoids, and flavonoids are the main constituents of Astragalus mongholicus 5. The polysaccharides originating from Astragalus are called astragalans. The saponins (or triterpene glycosides, here called astragalosides), isoflavonoids, and flavonoids consist of aglycons or glycosides.

The amounts of astragalosides, trigonosides, and flavonoid constituents of dried root depend on age, size and growing conditions of the root. Standardization is possible to 70% polysaccharides, 0.3% astragaloside content, 0.4% 4’-hydroxy-3’-methoxy-isoflavone-7-glycoside, or 0.5% triterpenoids glycoside content 6. According to the European Pharmacopoeia, the content should be minimum 0.04% of astragalosides IV.

Although several parts of the plant seem to contain active constituents, the root is especially used in herbal formulas. Saponins are the most active components. An aqueous extract of Astragalus, which mainly contains polysaccharides was found to show only immunostimulant properties and did not induce apoptosis or any effect on growth of colon cancer cells 9.

Application and dosage

Astragalus is generally administered in combination with other Chinese herbs. The combination depends on the diagnosis 1. A common herbal formula containing Astragalus root is called “Juzentaihoto”, which means Ten Significant Tonic Decoctions.

The recommended oral dose for decoction is 3-6g of Huangqi (dried root) per 350ml water 1.

Astragalus can be bought in dried slices (sliced diagonally and horizontally), shavings, powdered, shredded root, whole root, capsules and liquid extracts. TCM practitioners often administer it as a tea or shredded in soup.

History/Providers

Astragalus has been used for many centuries in TCM to correct ‘spleen deficiency’, which has been associated with cellular immune dysfunction 4.

Astragalus originates from Shanxi Province, China, but now grows in several provinces in northern China 7. Some Astragalus-species also grow in the East Mediterrean area.

In the 1980’s, Astragalus was popularized as an immunostimulant in the United States by the media 6.

Claims of efficacy

Internet sources claim that Astragalus can be used for the prevention and treatment of viral infections, ranging from colds to Swine flu, and human immunodeficiency virus (HIV). Astragalus is particularly promoted for its immunostimulating properties. It is also claimed to be a natural remedy in the treatment of cancer.

Mechanism of action

The anticancer and immunostimulating properties of Astragalus are reduced by multiple modes of action.

Apoptosis

Astragalus saponins, extracted from the root, have been shown to induce apoptosis in human hepatocellular carcinoma cells through modulation of an ERK-independent NF-κB signaling pathway 8.

NAG-1 (nonsteroidal anti-inflammatory drug (NSAID)-activated gene) is proposed as a molecular target of Astragalus saponins in its antitumorigenic and proapoptotic actions. NAG-1 is considered a biomarker for p53 activation 10. The induction of apoptosis by Astragalus saponins was confirmed in colon cancer cells and in human erythroleukemia cells 9,11.

Growth inhibition

Astragalus saponins have been shown to inhibit cell proliferation through accumulation in S phase and G2/M arrest in HT-29 human colon cancer cells. Astragalus saponins also caused suppression of p21 expression and inhibition of cyclin-dependant kinase activity. These findings were confirmed in vivo in HT-29 nude mice xenografts. The results were comparable with those produced by the chemotherapeutic drug 5-fluorouracil, but without its side effects 12.

Effect on inflammation and immune response

It has also been demonstrated that the anti-tumor activity of Astragalus is caused by abolition of tumor-induced macrophage suppression 3. Macrophages can infiltrate the tumor site to participate in inflammatory reactions leading to destruction of neoplasms. Phagocytic functions are often depressed in cancer patients. Macrophages, when activated, undergo an oxidative burst (generation of reactive oxygen intermediates). The depression of this oxidative burst in urological tumors was partially or completely reversed by an aqueous extract of the dried root of Astragalus 13-14.

Astragali polysaccharides (APS) stimulate all types of immunocytes, including T cells, B cells, and NK cells 29.

Alleged indications

In Traditional Chinese Medicine (TCM), Astragalus is used to treat symptoms allegedly caused by affections of the spleen, which are claimed to be diarrhea, fatigue, spontaneous sweating, and lack of appetite. According to TCM beliefs, it could also be used to treat colds and shortness of breath because it tonifies the lungs. Besides from cancer, other possible indications are wasting disorders, night sweats, chronic ulcerations and sores, numbness and paralyses of the limbs, and edema 1.

Legal issues

Jinfukang, a liquid formulation extracted from 12 botanicals is approved by the State Drug Administration (SDA), the Chinese equivalent of the US FDA, for use in the treatment of non-small-cell lung cancer.

Outside Asia, Astragalus is sold as a dietary supplement. It does therefore not need to be approved by the FDA or EMA (European Medicines Agency), but no medicinal claims associated with Astragalus can be made.

Costs and expenditures

On the Internet, prices for Astragalus capsules or extracts vary from $2.79 for 60 capsules to $23 for 30ml of extract.