Tragacanth

Scientific Name(S): A wide variety of Astragalus species, but most commonly A. gummifera, are used in commerce. Family: Leguminosae or Fabaceae.

Common Name(S): Goat's thorn, green dragon, gum dragon, gum tragacanth, gummi tragacanthae, hog gum, Syrian tragacanth, tragacanth.

Botany

The tragacanth species are generally characterized as low-growing, thorny shrubs that are native to the mountainous regions of the Middle East. Gum tragacanth is obtained by tapping the branches and tap roots. The gum dries as it exudes and is collected rapidly. The word tragacanth is said to derive from the Greek meaning "goat's horn," which may describe the appearance and texture of the crude gum.

Uses

Tragacanth has been used as a demulcent in cough and cold preparations and to manage diarrhea. It also has been shown to moderate the blood sugar level, but this has not been demonstrated consistently.

Side Effects

Presently, tragacanth is not recognized as having any adverse effects.

History

Tragacanth has been used since ancient times as an emulsifier, thickening agent, and suspending agent. Today it is used extensively in foods and dressings and to thicken ice cream.

Chemistry

Tragacanth contains from 20% to 30% of a water-soluble fraction called tragacanthin (composed of tragacanthic acid and arabinogalactan). It also contains from 60% to 70% of a water-insoluble fraction called bassorin. Tragacanthic acid is composed of D-galacturonic acid, D-xylose, L-fructose, D-galactose, and other sugars. Tragacanthin is composed of uronic acid and arabinose and dissolves in water to form a viscous colloidal solution (sol), while bassorin swells to form a thick gel.

Tragacanthin partially dissolves and partially swells in water yielding a viscous colloid. The maximal viscosity is attained only after 24 hours at room temperature or after heating for 8 hours at high temperatures. The viscosity of these solutions is generally considered to be the highest among the plant gums. The solutions are heat stable and stable under a wide range of pH levels.

Summary

Gum tragacanth is widely used throughout the world as a thickener and suspending agent in foods and pharmaceuticals. It is characterized by a very safe use profile. It does not appear to nave any beneficial influence on serum lipid or glucose levels as do other soluble gums.