Gum Tragacanth

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Economic Plant Photographs #34

Locoweeds For A Natural Gum & Medicinal Herbs

Gum Tragacanth and Astragalus Root

Legume Family (Fabaceae)

Gum Tragacanth

Astragalus (locoweed) is one of the largest genera of flowering plants with approximately 2,000 different species in the northern hemisphere. According to Rupert Barneby (1964), there are 552 species and varieties in North America, with 92 species in California. In fact, there are at 18 species in San Diego County alone. Many species of locoweeds native to the western United States are known to be poisonous to livestock. The actual mechanism of poisoning may involve: (1) Toxic levels of selenium absorbed from the soil, (2) nitrogen-containing sugar compounds called nitrogylcosides, and (3) potent swainsonine alkaloids resulting in a condition known as "locoism." The toxic alkaloids of locoweeds are discussed in the Wayne's Word article "Plants That Make You Loco" (see the following link):

Plants That Make You Loco

Several shrubby locoweeds native to arid regions of the eastern Mediterranean and southwestern Asia, including Astragalus gummifer, A. adscendens and A. microcephalus, contain a gummy, mucilaginous sap that is the source of gum tragacanth. The name "tragacanth" comes from the appearance of the exuded gum, which tends to form ribbons similar in appearance to a goat horn (from the Greek "tragos" meaning goat and "akantha" meaning horn). Unlike the perennial locoweeds of North America, the Old World tragacanth species are very spiny with persistent, stiff, sharp-pointed leafless rachises (leaf midribs). The gummy sap is not a polyterpene like the chicle used in chewing gums. It is a water-soluble carbohydrate gum containing the polysaccharides tragacanthin and bassorin. The primary source of gum tragacanth is the desert highlands of northern and western Iran, particularly the Zagros Mountains region. In Iran, the gum is harvested seasonally by making an incision on the upper part of the taproot and collecting the exuding gum. The ribbons of gum are brought to trade centers for processing and exportation.

Two examples of true spines (modified leaves). Left: Barberry (Berberis vulgaris) showing lateral buds arising in the axils of 3-pronged, modified leaves called spines. Right: Gum tragacanth, an Iranian locoweed (Astragalus), showing the rigid, sharp-pointed leaf rachises after the leaflets have dropped off. The natural polysaccharide thickening agent called gum tragacanth is obtained from the sap of this plant.

An Iranian locoweed shrub (Astragalus sp.) with buds and opened flowers of the parasite Pilostyles haussknechtii (red arrow) on its main stem. This low-growing shrub is one of the Mideastern locoweeds containing a valuable sap called gum tragacanth, a water-soluble polysaccharide used as a thickening agent and emulsifier. Note the spines formed from leaf rachises. [Scanned 35mm slide from Nikon FM2.]

Gum tragacanth has many industrial uses, including cloth finishing, calico printing and waterproofing of fabrics. It has been used medicinally for thousands of years, dating back several centuries before the Christian era. In folk medicine it has been used for a laxative, persistent cough, diarrhea, and as an aphrodesiac. Modern pharmaceutical uses include an adhesive agent for pills and tablets, and for emulsifying oil droplets in lotions, creams and pastes. Its superior water absorbing qualities make it an excellent thickening agent. Gum tragacanth is used in many everyday commercial products, from cosmetics and toothpaste to jellies and salad dressings. At one time it was the primary thickening agent in Corn Huskers Lotion®. It is also used in syrups, mayonnaise, sauces, liqueurs, candy, ice cream and popsicles. Unfortunately, due to the troubled diplomatic relationship between the United States and Iran, other natural gums (such as guar gum and locust bean gum) have largely replaced the use of gum tragacanth in the United States.

An Iranian gum tragacanth showing the spiny shrub (left), a ribbon of gum exuding from the exposed upper taproot (center), and powdered gum tragacanth (right). The flower arises directly from the main stem, and the persistent leaf rachises become sharp-pointed spines. This species may be A. microcephalus or A. gummifer)

Astragalus Root

An Asian species of locoweed (Astragalus membranaceus) has been used for centuries in traditional Chinese herbal medicine. Known as Huang Ch'i, radix astragali and astragalus root, the boiled root strips are taken in a tea to increase one's ch'i or "wind energy." The ground root is also available in capsules and as a liquid extract. According to the Committee On Scholarly Communication With The People's Republic of China (1975), this remedy is used to overcome fatigue, lower blood pressure, and to treat colds, nephritis and hypoglycemia. There are a number of published medicinal uses for this species, either by itself or decocted with other herbs, for the treatment of diabetes mellitus, cancers and malaria. Because of its antibacterial properties, it has been used in traditional Chinese medicinal tonics for upper respiratory infections. Other remedies include the treatment of coronary heart disease and anemia. It has also been effective in the treatment of chronic hepatitis by increasing cellular immunity. Complex glucoarabinan polysaccharides isolated from a related Asian species A. mongholicus have been shown to stimulate the production of T-cells and antibody-producing plasma cells (Wagner and Proksch, 1985).

Chinese astragalus root or Huang Ch'i (Astragalus membranaceus) root strips, capsules and liquid extract. This ancient herbal remedy is used for boosting the immune system by increasing the production T-cells.

Medical studies by Dr. D-T. Chu and his colleagues at the M.D. Anderson Hospital and Tumor Institute in Houston, Texas (1988) indicate that this remarkable tonic strenghthens the immune system by enhanced production of T-lymphocytes and inteferon, perhaps through some unknown synergistic reaction. More research is needed, but tentative results indicate that this ancient herb may be useful in the treatment of certain cancers and virally-induced diseases, such as AIDS and chronic cervicitis. Refer to the following references for more information.


  1. Barneby, R.C. 1964. "Atlas of North American Astragalus." Volumes I & II. Memoirs of the New York Botanical Garden 13: 1-1188.

  2. Committee On The Scholarly Communication With The People's Republic of China. 1975. Herbal Pharmacology in the People's Republic of China. National Academy of Sciences, Washington, D.C.

  3. Chu, D-T. et al. 1988. "Immunotherapy With Chinese Medical Herbs I. & II." Journal of Clinical and Laboratory Immunology 25: 119-129.

  4. Duke, J.A. 1997. The Green Phamacy. Rodale Press, Emmaus, Pennsylvania.

  5. Duke, J.A. and E.S. Ayensu. 1995. Medicinal Plants of China Vol. 1. Reference Publications, Inc.

  6. Duke, J.A. 1981. Handbook of Legumes of World Economic Importance. Plenum Press, New York.

  7. Gentry, H.S. 1957. "Gum Tragacanth in Iran." Economic Botany 11: 40-63.

  8. Hikino, H. 1985. "Chinese Medicinal Plants Used Against Hepatitis." In: Advances in Chinese Medicinal Materials Research, H.M. Chang, et al., Editors. World Scientific, Singapore.

  9. Wagner, H. and A. Proksch. 1985. "Immunostimulatory Drugs of Fungi and Higher Plants." Chap. 4 in: Economic and Medicinal Plant Research, H. Wagner, H. Hikino, and N.R. Farnsworth, Editors. Academic Press, London and New York.

  10. Weiner, M.A. and J.A. Weiner. 1994. Herbs That Heal. Quantum Books, Mill Valley, California.

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