Acacia senegal (L.) Willd.
Syn.: Acacia verek Guill. et Perr.
Gum Arabic, Senegal Gum, Sudan Gum Arabic, Kher, Kumta
Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.
- Folk Medicine
- Yields and Economics
- Biotic Factors
Tree yields commercial gum arabic, used extensively in pharmaceutical
preparations, inks, pottery pigments, water-colors, wax polishes, and liquid
gum; for dressing fabrics, giving lustre to silk and crepe; for thickening
colors and mordants in calico-printing; in confections and sweetmeats. Causing
partial destruction of many alkaloids including atropine, hyoscyamine,
scopolamine, homatropine, morphine, apomorphine, cocaine, and physostigmine,
gum arabic might be viewed as a possible antidote. Pharmaceutically used
mainly in the manufacture of emulsions and in making pills and troches (as an
excipient); as demulcent for inflammations of the throat or stomach and as
masking agent for acrid tasting substances such as capsicum; also as a
film-forming agent in peel-off masks. Its major use is in foods, for example,
as suspending or emulsifying agent, stabilizer, adhesive, flavor fixative, and
to prevent crystallization of sugar, etc. Used in practically all categories
of processed foods (candy, snack foods, alcoholic and nonalcoholic beverages,
baked goods, frozen dairy desserts, gelatins, and puddings, imitation dairy
products, breakfast cereals, and fats and oils). Use levels range from less
than 0.004% (40 ppm) in soups and milk products, 0.7 to 2.9% in nonalcoholic
beverages, imitation dairy, and snack foods, to as high as 45% in candy
products (Leung, 1980). Strong rope made from bark fibers. White wood used
for tool handles, black heartwood for weaver's shuttles. The long flexible
strands of surface roots provide one of the strongest of local fibers, used for
cordage, well-ropes, fishing nets, horsegirdles, footropes, etc. Seeds are
dried and preserved for human consumption (NAS, 1980). Young foliage makes
good forage. Plants useful for afforestation of arid tracts, soil reclamation,
and windbreaks (Duke, 1981a). In modern pharmacy, it is commonly employed as a
demulcent in preparations designed to treat diarrhea, dysentery, coughs, throat
irritation, and fevers. It serves as an emulsifying agent and gives viscosity
to powdered drug materials; is used as a binding agent in making pills and
tablets and particularly cough drops and lozenges. Because of its enzyme, the
gum is not suitable for use in products having readily oxidizable ingredients.
For example, it reduces the vitamin A content of cod liver oil by 54% within
three weeks. It is incompatible with aminopyrine, morphine, vanillin, phenol,
thymol, a- and b-naphthol, guiacol, cresols, creosol, eugenol,
apomorphine, eserine, epinephrine, isobarbaloin, gallic acid, and tannin; also
with strongly alcoholic liquids, solutions of ferric chloride and lead
subacetate and strong solutions of sodium borate. It was formerly given
intravenously to counteract low blood pressure after hemorrhages and surgery
and to treat edema associated with nephrosis, but such practices caused kidney
and liver damage and allergic reactions and have been abandoned (Morton, 1977).
The demulcent, emollient gum is used internally in inflammation of intestinal
mucosa, and externally to cover inflamed surfaces, as burns, sore nipples and
nodular leprosy. Also said to be used for antitussive, astringent, catarrh,
colds, coughs, diarrhea, dysentery, expectorant, gonorrhea, hemorrhage, sore
throat, typhoid, urinary tract (Duke and Wain, 1981).
Gum acacia contains neutral sugars (rhamnose, arabinose, and galactose), acids
(glucuronic acid and 4-methoxyglucuronic acid), calcium, magnesium, potassium,
and sodium. Its complex structure is still not completely known. Its backbone
chain consists of D-galactose units, and its side chains are composed of
D-glucuronic acid units with l-rhamnose or l-arabinose as end units. The
molecular weight has been reported to be between 200,000 to 300,000 and as
high as 600,000 (Leung, 1980).
Ingested orally, acacia is nontoxic. However, some people are allergic to its
dust and develop skin lesions and severe asthmatic attacks when in contact with
it. Acacia can be digested by rats to an extent of 71%; guinea pigs and
rabbits also seem to utilize it for energy, as does man to a certain extent.
Gum arabic may actually elevate serum or tissue cholesterol levels in rats
Savanna shrub or tree, up to 20 m tall, over 1.3 m in girth, spiny; bark gray
to brown or blackish, scaly, rough; young branchlets densely to sparsely
pubescent, soon glabrescent, crown dense; stipules not spinescent; prickles
just below the nodes, either in threes up to 7 mm long, with the middle one
hooked downwards and the lateral ones curved upwards, or solitary with the
laterals absent; leaves bioinnate, up to 2.5 cm long; leaf-axis finely downy
with 2 glands; pinnae 620 pairs; leaflets small, 725 pairs, rigid, leathery,
glabrous, linear to elliptic-oblong, ciliate on margins, pale glaucous-green,
apex obtuse to subacute; flowers in spikes 510 cm long, not very dense, on
peduncles 0.72 cm long, normally produced with the leaves; calyx
bell-shaped, glabrous, deeply toothed; corolla white to yellowish, fragrant,
sessile; pod straight or slightly curved, retrap-shaped, 7.518 cm long, 2.5 cm
wide, thin, light brown or gray, papery or woody, firm, indehiscent, glabrous,
56-(-15) seeded; seeds greenish-brown. Fl. Jan.Mar.; fr. Jan.Apr., July,
Aug. or Oct. (Duke, 1981a).
Tree with a single central stem and a dense flat-topped crown, bark without any
papery peel, rough, gray or brown, with pubescent, rarely glabrous
inflorescence, and pods variable in size, rounded to somewhat pointed but not
rostrate or acuminate at apex. Variety rostrata Brenan is a shrub,
branching at or close to base, or a small tree, with a single stem, 16 m tall,
with dense flattened crown, bark normally with a flaking papery peel,
creamy-yellow to yellow-green or gray-brown, inflorescence axis always
pubescent and pods 23.5 times as long as wide, rostrate or acuminate at apex.
Variety leiorhachis Brenan, is always a tree with central stem, and
rounded or irregular with straggling branches; bark with conspicuous yellow
papery peel, and inflorescence axis always glabrous. Variety
pseudoglaucophylla occurs on fixed sand duned in Africa. Assigned to
the African Center of Diversity, gum arabic is reported to exhibit tolerance to
alkali, drought, fire, high pH, poor soil, sand, slope, and wind. (2n=26)
Widespread in tropical Africa from Mozambique, Zambia to Somalia, Sudan,
Ethiopia, Kenya, and Tanzania. Cultivated in India, Nigeria, and Pakistan.
Thrives on dry rocky hills, in low-lying dry savannas, and areas where annual
rainfall is 2536 cm. This hardy species survives many adverse conditions, and
seems to be favored by low rainfall and absence of frost. Ranging from Warm
Temperate Thorn through Tropical Thorn to Tropical Dry Forest Life Zones, gum
arabic is reported to tolerate annual precipitation of 3.822.8 dm (mean of 9
cases = 12.4 dm), annual mean temperature of 16.227.8°C (mean of 9 cases
23.8°C), and pH of 5.07.7 (mean of 7 cases = 6.4), but Cheema and Qadir
(1973) report 7.48.2.
In Sudan, trees are cultivated over a very large area. Best propagated from
seeds which are produced once every few years, grown in Sudan, in special "gum
gardens." Elsewhere, it is collected from wild trees. In Pakistan, the best
period for afforestation is the early monsoon season (Apr.Jun.). Surface
sowing is recommended in mildly alkaline sandy soils. Plants can also be
reproduced by shoot cuttings. Trees coppice well (NAS, 1980).
Gum exudes froin cracks in bark of wild trees, mostly in the dry season, with
little or none in the rainy season when flowers are out. In some areas, a long
strip of bark is torn off and the gum allowed to exude. In Africa, it is
regularly tapped from trees which are about 6 years old by making narrow
transverse incisions in bark in February and March. In about a month, tears of
gum form on surface and are gathered. Trees begin to bear between 418 years
of age and are said to yield only when they are in unhealthy state due to poor
soil, lack of moisture or damaged. Attempts to improve conditions tend to
reduce yield. Gum from wild trees is variable and somewhat darker colored than
that from cultivated plants. Collected gum is carefully freed of extraneous
matter, sorted and sometimes ripened in sun before export. Gum arabic is
oderless with a bland taste, yellowish and some tears are vermiform in shape.
Ripened or bleached gum occurs in rounded or ovoid tears over 2.5 cm in
diameter, and in broken fragments. Tears are nearly white or pale yellow and
break readily with a glassy fracture. Gum is almost completely soluble in an
equal volume of water and gives a translucent, viscous, slightly acid solution,
but is insoluble in 90% alcohol. Kordofan (Sudan) Gum is yellow or pinkish,
has fewer cracks and is more transparent (Duke, 1981a).
Annual yields from young trees may range from 188 to 2856 g (avg. 900 g), from
older trees, 379 to 6754 g (avg. 2,000 g). Gum arabic is important export
product for some areas in tropical Africa and Mauritania. From Africa some
genuine gum is shipped to India then to Europe and America. Between 1940 and
1950, United States imports range from 3,1798,989 MT (Duke, 1981a) Morton
(1977) reports >11,000 MT more recently.
Considered the best firewood in Mauritius and Senegal, this is not a big
yielder, annual running 0.55 m3/ha wood, with an energy value of ca 3,500
kcal/kg. A nitrogen,fixing species, it can be used to reestablish vegetation
cover in degraded areas, as well as for sand-dune fixation and wind erosion
control (NAS, 1980a).
Fungi reported on this crop are Cladosporium herbarum, Fusarum sp.,
Ravenelia acaciae-senegalae and R. acaciocola. Many insect visitors
mimic the plant, the buffalo treehopper, Stictocephala bisonia, being a
good example. Spiders (Cyclops sp.) may completely cover the young growing
apex. Seedlings are often grazed by gazelles, goats, and pigs (Morton, 1977).
Complete list of references for Duke, Handbook of Energy Crops
Cheema, M.S.Z.A. and Qadir, S.A. 1973. Autecology of Acacia senegal (L.)
Willd. Vegetatio Vol. 27(13):131162.
- Duke, J.A. 1981a. Handbook of legumes of world economic importance. Plenum
- Duke, J.A. and Wain, K.K. 1981. Medicinal plants of the world. Computer index
with more than 85,000 entries. 3 vols.
- Leung, A.Y. 1980. Encyclopedia of common natural ingredients used in food,
drugs, and cosmetics. John Wiley & Sons. New York.
- Morton, J.F. 1977. Major medicinal plants. C.C. Thomas, Springfield, IL.
- N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production.
National Academy of Sciences, Washington, DC.
Last update December 19, 1997