To identify the chemical characters of a given sample.
Gum Arabic consists almost entirely of glycosidic acid named Arabic acid, combined with potassium, magnesium and calcium. By hydrolysis Arabic acid yields 1 molecule of l-rhamnose, 2 molecules of D – galactose and 3 molecules of l– arabinose and an aldobionic acid. It also
contains diastase and an oxidase enzyme.
- Dissolve about 0.25 gm of the coarsely powdered drug in 5 ml of distilled water by shaking in the cold. Add 0.5 ml of hydrogen peroxide and 0.5 ml of benzidine solution, shake and allow to stand for few minutes; a deep blue colour or greenish-blue colour is formed due to the presence of the oxidase enzyme.
- A 10% aqueous solution of acacia fails to produce any precipitate with a dilute solution of lead acetate (a clear distinction from Agar and Tragacanth); it does not give any colour change with Iodine solution (a marked distinction from starch and dextrin), and it never produces a bluish-black colour with FeCl3 solution (an apparent distinction from tannins).
- Hydrolysis of an aqueous solution of acacia with dilute HCl yields reducing sugars whose presence is ascertained by boiling with Fehling’s solution to give a brick-red precipitate of cuprous oxide
From the above morphological characters and chemical tests, the given crude drug is identified as Acacia.
1.Kokate CK. Practical Pharmacognosy, 4 edition, VallabhPrakashan. Delhi; 1994: 98