Acacia

Acacia

1 Nonproprietary Names

BP: Acacia

JP: Acacia

PhEur: Acaciae gummi

USPNF: Acacia

2 Synonyms

Acacia gum; arabic gum; E414; gum acacia; gummi africanum;

gum arabic; gummi arabicum; gummi mimosae; talha gum.

3 Chemical Name and CAS Registry Number

Acacia [9000-01-5]

4 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.

5 Structural Formula

See

Section 4.

6 Functional Category

Emulsifying agent; stabilizing agent; suspending agent; tablet

binder; viscosity-increasing agent.

7 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;

1)

modified release tablets.

Acacia is also used in cosmetics, confectionery, food

products, and spray-dried flavors.

(and has been used in novel tablet formulations,(2) and(3) See Table I.(4)

See also

Section 18.

Table I:

Uses of acacia.

Use Concentration (%)

Emulsifying agent 10–20

Pastille base 10–30

Suspending agent 5–10

Tablet binder 1–5

8 Description

Acacia 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.

9 Pharmacopeial Specifications

The PhEur 2005 provides monographs on acacia and spraydried

acacia, while the USPNF 23 describes acacia in a single

monograph that encompasses tears, flakes, granules, powder,

and spray-dried powder. The JP 2001 also has monographs on

acacia and powdered acacia.

See Table II.

Table II:

Pharmacopeial specifications for acacia.

Test JP 2001 PhEur 2005 USPNF 23

Identification

‏ ‏ ‏

Characters

‏ ‏ ‏

Microbial limit —

4104/g ‏

Water

417.0% 415.0% 415.0%

4

Total ash

Acid-insoluble ash

Insoluble residue

Arsenic — —

Lead — —

Heavy metals — —

Starch, dextrin, and agar

15.0%(a) 410.0%(b) —44.0% 44.0% 44.0%40.5% — 40.5%40.2% 40.5% 450mg43 ppm40.001%40.004%‏ ‏ ‏

Tannin-bearing gums

‏ ‏ ‏

Tragacanth —

Sterculia gum —

Glucose and fructose —

Solubility and reaction — —

‏ —‏ —‏ —‏

Organic volatile impurities — —

‏

(a)

Powdered acacia.

(b)

Spray-dried acacia.

10 Typical Properties

Acidity/alkalinity:

pH = 4.5–5.0 (5% w/v aqueous solution)

Acid value:

2.5

Hygroscopicity:

moisture content of powdered acacia at 25

8–13% w/w, but at relative humidities above about 70% it

absorbs substantial amounts of water.

at relative humidities of 25–65%, the equilibrium8C is

Solubility:

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.

soluble 1 in 20 of glycerin, 1 in 20 of propylene

Specific gravity:

1.35–1.49

Viscosity (dynamic):

solution at 20

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.

100 mPa s (100 cP) for a 30% w/v aqueous8C. The viscosity of aqueous acacia solutionsSee also Section 12.

11 Stability and Storage Conditions

Aqueous solutions are subject to bacterial or enzymatic

degradation but may be preserved by initially boiling the

solution for a short time to inactivate any enzymes present;

microwave irradiation can also be used.

may also be preserved by the addition of an antimicrobial

preservative such as 0.1% w/v benzoic acid, 0.1% w/v sodium

benzoate, or a mixture of 0.17% w/v methylparaben and

0.03% propylparaben. Powdered acacia should be stored in an

airtight container in a cool, dry place.

(5) Aqueous solutions

12 Incompatibilities

Acacia is incompatible with a number of substances including

amidopyrine, apomorphine, cresol, ethanol (95%), ferric salts,

morphine, phenol, physostigmine, tannins, thymol, and vanillin.

An oxidizing enzyme present in acacia may affect preparations

containing easily oxidizable substances. However, the

enzyme may be inactivated by heating at 100

time;

Many salts reduce the viscosity of aqueous acacia solutions,

while trivalent salts may initiate coagulation. Aqueous solutions

carry a negative charge and will form coacervates with

gelatin and other substances. In the preparation of emulsions,

solutions of acacia are incompatible with soaps.

8C for a shortsee Section 11.

13 Method of Manufacture

Acacia is the dried gummy exudate obtained from the stems

and branches of

related species of

in the Sudan and Senegal regions of Africa.

The bark of the tree is incised and the exudate allowed to dry

on the bark. The dried exudate is then collected, processed to

remove bark, sand, and other particulate matter, and graded.

Various acacia grades differing in particle size and other

physical properties are thus obtained. A spray-dried powder is

also commercially available.

Acacia senegal (Linne) Willdenow or otherAcacia (Fam. Leguminosae) that grow mainly

14 Safety

Acacia is used in cosmetics, foods, and oral and topical

pharmaceutical formulations. Although it is generally regarded

as an essentially nontoxic material, there have been a limited

number of reports of hypersensitivity to acacia after inhalation

or ingestion.

following the parenteral administration of acacia and it is now

no longer used for this purpose.

(6,7) Severe anaphylactic reactions have occurred(6)

The WHO has not set an acceptable daily intake for acacia

as a food additive because the levels necessary to achieve a

desired effect were not considered to represent a hazard to

health.

(8)

LD

50 (hamster, oral): >18 g/kg(9)

LD

LD

LD

50 (mouse, oral): >16 g/kg50 (rabbit, oral): 8.0 g/kg50 (rat, oral): >16 g/kg

15 Handling Precautions

Observe normal precautions appropriate to the circumstances

and quantity of material handled. Acacia can be irritant to the

eyes and skin and upon inhalation. Gloves, eye protection, and

a dust respirator are recommended.

16 Regulatory Status

GRAS listed. Accepted for use in Europe as a food additive.

Included in the FDA Inactive Ingredients Guide (oral preparations

and buccal or sublingual tablets). Included in the

Canadian List of Acceptable Non-medicinal Ingredients.

Included in nonparenteral medicines licensed in the UK.

17 Related Substances

Ceratonia; guar gum; tragacanth.

18 Comments

Concentrated aqueous solutions are used to prepare pastilles

since on drying they form solid rubbery or glasslike masses

depending upon the concentration used. Foreign policy changes

and politically unstable conditions in Sudan, which is the

principal supplier of acacia, has created a need to find a suitable

replacement.

make an oil/water emulsion with similar rheological characteristics

to acacia. Other natural by-products of foods can also be

used.

emulsifier, stabilizer, and thickener. A specification for acacia

is contained in the Food Chemicals Codex (FCC).

The EINECS number for acacia is 232-519-5.

(10) Poloxamer 188 (12–15% w/w) can be used to(11) Acacia is also used in the food industry as an

19 Specific References

1 Attama AA, Adiknu MV, Okoli ND. Studies on bioadhesive

granules.

2 Streubel A, Siepmann J, Bodmeier R. Floating matrix tablets based

on low density foam powder.

3 Bahardwaj TR, Kanwar M, Lai R, Gupta A. Natural gums and

modified natural gums as sustained-release carriers.

Pharm

4 Buffo R, Reineccius G. Optimization of gum acacia/modified

starch/maltodextrin blends for spray drying of flavors.

Flavorist

5 Richards RME, Al Shawa R. Investigation of the effect of

microwave irradiation on acacia powder.

STP Pharma Sci 2003; 13(3): 177–181.Eur J Pharm Sci 2003; 18: 37–45.Drug Dev Ind2000; 26(10): 1025–1038.Perfumer&2000; 25: 45–54.J Pharm Pharmacol

1980;

6 Maytum CK, Magath TB. Sensitivity to acacia.

32: 45P.J Am Med Assoc

1932;

7 Smolinske SC.

Boca Raton, FL: CRC Press, 1992: 7–11.

8 FAO/WHO. Evaluation of certain food additives and contaminants.

Thirty-fifth report of the joint FAO/WHO expert committee

on food additives.

789.

9 Lewis RJ, ed.

99: 2251.Handbook of Food, Drug, and Cosmetic Excipients.World Health Organ Tech Rep Ser 1990; No.Sax’s Dangerous Properties of Industrial Materials,

11th edn. New York: Wiley, 2004: 289.

10 Scheindlin S. Acacia – a remarkable excipient: the past, present,

and future of gum arabic.

11 I-Achi A, Greenwood R, Akin-Isijola A. Experimenting with a new

emulsifying agent (tahini) in mineral oil.

JAMA 2001; 41(5): 669–671.Int J Pharm Compound

2000;

4(4): 315–317.2 Acacia