Acacia

• BPAcacia
• JPAcacia
• Ph. Eur.Acacia
• USP–NFAcacia

Acacia gum; arabic gum; gum acacia; gum arabic; gummi arabicum; Senegal gum; E414

Acacia (dried gummy exudate of Acacia senegal and related species) · [9000-01-5]

Polymer, mixture or material of variable composition — no single molecular formula applies.

Gelling agent, viscosity modifier, Surfactant, emulsifier, Binder

Typical concentrations: 1–5% binder · 5–10% suspending · Dosage forms: Solid, Liquid

Used mainly as a suspending and emulsifying agent in oral and topical preparations, often together with tragacanth, and as a tablet binder in wet granulation. It is also the classic base for pastilles and lozenges and is widely used in foods and confectionery. Typical concentrations: emulsifying agent 10–20%; suspending agent 5–10%; pastille base 10–30%; tablet binder 1–5%.

Available as pale white to yellowish tears, flakes, granules or powder. It is practically odourless with a bland, mucilaginous taste. Chemically it is a complex branched polysaccharide (arabic acid, built from galactose, arabinose, rhamnose and glucuronic acid) present as its calcium, magnesium and potassium salts, with a small protein fraction that contributes to its emulsifying power.

Acidity/alkalinity

pH 4.5–5.0 (5% w/v aqueous solution)

Loss on drying

not more than 15% w/w (pharmacopoeial limit)

Solubility

soluble in about 2.7 parts of water and about 20 parts of glycerol or propylene glycol; practically insoluble in ethanol (95%)

Viscosity

low for a gum: solutions remain pourable up to about 30–40% w/v, so it is a weak thickener compared with tragacanth or cellulose ethers

The dry gum is stable but should be kept in an airtight container in a cool, dry place. Aqueous solutions are prone to bacterial and enzymatic degradation and need a preservative (for example 0.1% benzoic acid or sodium benzoate, or a methyl/propyl paraben mixture). Briefly boiling the solution inactivates the oxidase enzymes naturally present in the gum.

The native oxidase/peroxidase enzymes can oxidise easily oxidised drugs and phenolics such as phenol, cresol, thymol, vanillin, tannins, morphine and apomorphine unless the gum has been heat-treated. It is precipitated by ethanol at high concentration, and many electrolytes, ferric salts and borax can lower viscosity or cause gelation or precipitation.

Collected as the dried exudate that forms on the stems and branches of Acacia senegal and related African Acacia species after the bark is cut. The tears are sorted, cleaned and may be kibbled, milled or spray-dried; heat treatment is used to deactivate enzymes and lower the microbial count.

Widely used in oral and topical medicines and in food, and generally regarded as non-toxic and non-irritant. Hypersensitivity reactions occur occasionally, including asthma after inhalation of the dust and skin reactions. JECFA has allocated an ADI 'not specified'.

Observe normal precautions for the quantity handled. Avoid creating dust, as inhaled acacia can sensitise; eye protection and a dust mask are recommended.

GRAS listed. Accepted as a food additive in Europe (E414). Included in the FDA Inactive Ingredient Database (oral and buccal/sublingual preparations) and in non-parenteral medicines licensed in Europe.

Ceratonia; guar gum; tragacanth; xanthan gum.

Acacia is a poor thickener on its own, so it is commonly combined with tragacanth or another viscosity builder in suspensions. Spray-dried and heat-treated grades dissolve faster and have lower microbial and enzyme activity than raw tears, which makes them preferable for pharmaceutical use.