Tragacanth Gum, Tragacantha, Persian Tragacanth
Tragacanth is the dried gummy exudate obtained by incision from the stems of Astragalus gummifer Labill. and some other species of Astragalus of the family Papilionaceae.
Astragalus species, which are thorny and branching shrubs, grow naturally in Turkey, Iran and Eastern European countries. The commercial supply of the drug also comes from these countries.
Macroscopical and microscopical characters:
Tragacanth occurs as thin, flattened, curved and horny flakes, about 3 cm long, I cm wide and 3 mm thick. The flakes are translucent, white or faintly yellow in colour and marked with numerous concentric ridges. They have a short fracture. Powdered tragacanth occurs as small angular fragments. Tragacanth is odourless and almost tasteless. It is sparingly soluble in water But swells to give a homogenous gelatinous mass. It is insoluble m alcohol.
Tragacanth contains a water-soluble constituent, tragacanthin, and a water-insoluble compound, basorin. It also contains traces of starch, cellulose and nitrogenous substances.
Tragacanth is principally used as a binder in tablets and a suspending agent in mixtures. It is also used as a thickening agent m calico printing.