Acacia; a pharmaceutical excipient

Acacia; a pharmaceutical excipient

Acacia, commonly known as the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia, but it has now been limited to contain only the Australasian species. The genus name is New Latin, borrowed from the Greek ἀκακία (akakia), a term used by Dioscorides for a preparation extracted from the leaves and fruit pods of Vachellia nilotica, the original type of the genus. In his Pinax (1623), Gaspard Bauhin mentioned the Greek ἀκακία from Dioscorides as the origin of the Latin name

Acacia excipient is available as white or yellowish-white thin flakes, spheroidal tears, granules, powder, or spray-dried powder. It is odorless and has a bland taste.

Nonproprietary Names

  • BP: Acacia
  • JP: Acacia
  • PhEur: Acacia
  • USP-NF: Acacia
Acacia; a pharmaceutical excipient


Acaciae gummi; acacia gum; arabic gum; E414; gum acacia; gummi africanum; gum arabic; gummi arabicum; gummi mimosae; talha gum.


Related Substances

Ceratonia; guar gum; tragacanth

Empirical Formula and Molecular Weight

Acacia is a complex, loose aggregate of sugars and hemicelluloses with a molecular weight of approximately 240 000–580 000. The aggregate consists essentially of an arabic acid nucleus to which are connected calcium, magnesium, and potassium along with the sugars arabinose, galactose, and rhamnose.

Functional Category

Emulsifying agent; stabilizing agent; suspending agent; tablet binder; viscosity-increasing agent.

Applications in Pharmaceutical Formulation or Technology

Acacia is mainly used in oral and topical pharmaceutical formulations as a suspending and emulsifying agent, often in combination with tragacanth. It is also used in the preparation of pastilles and lozenges, and as a tablet binder, although if used incautiously it can produce tablets with a prolonged disintegration time. Acacia has also been evaluated as a bioadhesive; and has been used in novel tablet formulations, and modified release tablets. Acacia is also used in cosmetics, confectionery, food products, and spray-dried flavors.

Typical Properties

  • Acidity/alkalinity pH = 4.5–5.0 (5% w/v aqueous solution). Acid value 2.5 
  • Hygroscopicity At relative humidities of 25–65%, the equilibrium moisture content of powdered acacia at 258C is 8–13% w/w, but at relative humidities above about 70% it absorbs substantial amounts of water.
  • Solubility Soluble 1 in 20 of glycerin, 1 in 20 of propylene glycol, 1 in 2.7 of water; practically insoluble in ethanol (95%). In water, acacia dissolves very slowly, although almost completely after two hours, in twice the mass of water leaving only a very small residue of powder. The solution is colorless or yellowish, viscous, adhesive, and translucent. Spray-dried acacia dissolves more rapidly, in about 20 minutes.
  • Specific gravity 1.35–1.49 
  • Viscosity (dynamic) 100 mPa s (100 cP) for a 30% w/v aqueous solution at 208C. The viscosity of aqueous acacia solutions varies depending upon the source of the material, processing, storage conditions, pH, and the presence of salts. Viscosity increases slowly up to about 25% w/v concentration and exhibits Newtonian behavior. Above this concentration, viscosity increases rapidly (non-Newtonian rheology). Increasing temperature or prolonged heating of solutions results in a decrease of viscosity owing to depolymerization or particle agglomeration



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