2.2.1.2 Tragacanth
Synonym Gum Tragacanth
Biological Source The dried gummy exudation from Astragalus gummifer Labill. (white gavan)
or other Asiatic species of Astragalus belonging to the family of Leguminoseae.
Geographical Source It is naturally found in various countries, viz., Iran, Iraq, Armenia, Syria,
Greece and Turkey. A few species of Astragalous are located in India, viz., Kumaon, Garhwal and Punjab.Persian tragacanth are exported from Iran and North Syria, whereas the Smyrna tragacanth from the Smyrna port in Asiatic Turkey.
Collection The thorny shrubs of tragacanth normally grow at an altitude of 1000-3000 meters.
As an usual practice transverse incisions are inflicted just at the base of the stem, whereby the gum is given out both in the pith and medullary rays. Thus, the absorption of water helps the gum to swell-up and subsequently exude through the incisions. The gummy exudates are duly collected and dried rapidly to yield the best quality white product. It usually takes about a week to collect the gum exudates right from the day the incisions are made; and this process continues thereafter periodically.
Description
Colour: White or pale
Odour: Odourless
Taste: Tasteless
Shape: Curved or twisted ribbon –like flakes marked with concentric ridges that is indicative of successive exudation and solidification. Fracture is normally short and horny.
Size: Flakes are usually 25 × 12 × 12 mm.
Appearance: Translucent
Chemical Constituents Interestingly, tragacanth comprises of two vital fractions: first, being watersoluble and is termed as ‘tragacanthin’ and the second, being water-insoluble and is known as ‘bassorin’. Both are not soluble in alcohol. The said two components may be separated by carrying out the simple filtration of a very dilute mucilage of tragacanth and are found to be present in concentrations ranging from 60-70% for bassorin and 30-40% for tragacanthin. Bassorin actually
gets swelled up in water to form a gel, whereas tragacanthin forms an instant colloidal solution. It has been established that no methoxyl groups are present in the tragacanthin fraction, whereas the bassorin fraction comprised of approximately 5.38% methoxyl moieties. Rowson (1937) suggested that the gums having higher methoxyl content i.e., possessing higher bassorin contents, yielded the most viscous mucilages.
Chemical Test
1. An aqueous solution of tragacanth on boiling with conc. HCl does not develop a red colour.
2. Ruthenim Red* solution (0.1% in H2O) on being added to powdered gum tragacanth whereby the particles will not either acquire a pink colour or are merely stained lightly.
3. When a solution of tragacanth is boiled with few drops of FeCl3 [aqueous 10% (w/v)] it produces a deep-yellow precipitate.
4. It gives a heavy precipitate with lead acetate.
5. When tragacanth and precipitated copper oxide are made to dissolve in conc. NH4OH it yields a meagre precipitate.
Substituents/Adulterants Karaya gum which is sometimes known as sterculia gum or Indian tragacanth and is invariably used as a substitute for gum tragacanth.
Uses
1. It is used as a demulcent in throat preparations.
2. It is employed as an emolient in cosmetics (e.g., hand lotions).
3. It is used as a pharmaceutical aid as a suspending agent for insoluble and heavy powders in mixtures.
4. It is effectively employed as a binding agent for the preparation of tablets and pills.
5. It is also used as an emulsifying agent for oils and waxes.
6. A substantial amount find its application in calico printing and in confectionary.
7. It is used in making medicinal jellies e.g., spermicidal jelly.
8. A 0.2-0.3% concentration is frequently used as a stabilizer for making ice-creams and various types of sauces e.g., tomato sauce, mustard sauce.
9. It is used to impart consistence to troches.
10. The mucilages and pastes find their usage as adhesives.
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* Ruthenium oxychloride ammoniated, Cl6H42N14O2Ru3, soluble in water and used in microscopy as reagent for pectin and gum.
