Page 108 - PG 504-theoretical notes-phyto-1-2024-2025..

Clinical pharmacy PharmD program Third level Phytochemistry-1 (PG-504)

Composition:

It consists mainly of arabin. Arabin is calcium (magnesium and potassium

in small percentage) salt of arabic acid. And oxidase enzyme

Arabic acid, upon hydrolysis, yields D- galactose, L-arabinose, L-rhamnose and

D-glucuronic acid.

Partial structure of arabic acid:

The main chain consists of -galactose and glucuronic acid in ratio of 3:1

with (1➔3)-and (1➔6)-linkages. Each galactose unit is a center of branching at

1, 3 and 6 positions. The basic unit consists of 4 D-Galactose units, 2 L-Arabinose

units, 1 L-Rhamnose unit and 1 D-Glucuronic acid unit.

Properties:

▪ Gum arabic occurs in spheroidal tears, angular fragment of variable size;

externally whitish or yellowish white with numerous fissures. Gum arabic is

odorless with mucilaginous taste.

▪ Its fracture is glass-like.

▪ It contains oxidize enzyme.

Identity tests:

▪ Solution in water is levorotatory and slightly acidic.

▪ Gum arabic is precipitated form its solution (10%) with lead subacetate giving

flocculent white precipitate (Dextrin +ve, Tragacanth -ve).

▪ It is not precipitated with lead acetate (Tragacanth gives white ppt.).

▪ No blue color with iodine. "Gum tragacanth gives blue spots"

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