Page 308 - Pharmacognosy 2 PG303

Pharmacognosy-2 (PG303) Level 2 Clinical Pharmacy-Pharm D

shaped pieces and punctures give vermiform tears. It is produced by the
transformation of the cell walls of the pith and medullary rays into gum, which
easily absorbs water, and swells, exerting a considerable pressure on the surrounding
tissue. Therefore, when the stem is wounded the gum is forcibly pressed out. A
piece of about 2 cm long is being exuded in half an hour.

Description
Gum Tragacanth occurs in thin, curved, ribbon-shaped flakes; about 2.5 cm

long, 1 cm wide and 0.5-3 mm thick, or occasionally in straight or spirally twisted
linear pieces; white to pale yellowish white with numerous concentric ridges or
lamellae, translucent; tough and horny; fracture, short; odourless; taste,
mucilaginous. Gum Tragacanth is rendered easily powdered when heated to 50ºC.

Powdered Gum Tragacanth is white to light yellowish white; showing under
the microscope angular particles of striated mucilaginous cell walls, few simple
rounded to elliptical starch granules, 3-25 μ in diameter, and occasional compound
granules of 2-4 components; and very few or no fragments of lignified vegetable
tissue (c.f. Indian Gum).

Solubility
Gum Tragacanth is sparingly soluble in water, but swells into a homogeneous

adhesive opalescent gelatinous mass. It is insoluble in alcohol.

Tests for Identity
1- Effect of ruthenium red: Mix a small quantity of powdered gum Tragacanth

with few drops of ruthenium red T.S.; the particles do not acquire a pink colour
(c.f. Sterculia gum and Agar).
2- Test for reducing sugars and sulphate: To 4 ml of an aqueous solution of gum
Tragacanth (1/200), add 0.5 ml of HCl and heat in a water-bath for 30 mins.,
divide the liquid into 2 portions: To one portion, add 1.5 ml of NaOH T.S. and 3
ml of Fehling’s solution and warm in a water-bath; a red precipitate is formed.
To the other portion, add BaCl2 T.S., no precipitate is formed (c.f. Agar).
3- Test for oxidase enzyme: To 20 ml of an aqueous solution of Gum Tragacanth
(1/100), add 5 drops of H2O2 and 5 drops of benzidine T.S., shake and allow to
stand, neither blue coloured particles (Indian Tragacanth) nor a blue coloured
solution is obtained (Gum Arabic).

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