Agriculture Reference
In-Depth Information
Description —
The genus
Aloe
includes herbs, shrubs, and trees, bearing spikes of white, yel-
low, or red flowers. The leaves are fleshy, strongly cuticularized, and prickly at the margins.
A
.
ferox
is a shrub, 3-4 m in height and about 12 cm in diameter, with a large rosette of leaves. The leaves
are oval-lanceolate, 40-60 cm long and 10-12 cm wide, with a thorny ridge and edges. Flowers have
a perianth 2.5 cm in diameter, tinged with yellow and purplish-blue, striped with red and green.
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Habitat and Distribution —
It is a subtropical plant but widely cultivated in dry forest areas
of the continent.
Constituents —
Aloe contains anthraquinone glycosides, the principal one being a yellow,
crystalline substance called barboloin. It also contains resin and aloe-emodin. The pharmaceutical
“aloe” is the solid residue obtained by evaporating the liquid that drains from the parenchyma tissue
in the center of the leaves of various species of
Aloe.
The aloe mostly used in cosmetics formulations
is the Curacao aloe from
A. barbadensis
Miller (see
Aloe vera
Linne). The major aglycone found
in
A
.
ferox
is aloe-emodin and is associated with decomposition product aloe-emodin-9-anthrone.
Production of Aloes —
Aloes for pharmaceutical uses are prepared from the wild species of
A.
ferox
or are cultivated species of
A. barbadensis
by making transverse cuts near the base of the leaves
and collecting the ensuing juice for about 6 h. It is concentrated by boiling for about 4 h in an open
flame.
Aloe ferox
gel can be differentiated from AVG by the analysis of their monosaccharide con-
tent;
A. ferox
yields a mixture of glucose and galactose, whereas
A. vera
contains mainly mannose.
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Pharmacological Studies —
The main pharmaceutical use of the aloes is as a laxative, the
activity being due to anthraquinone glycosides. An anaerobic bacterium,
Eubacterium
sp., has been
isolated from human feces, which is capable of transforming barboloin to aloin-emodin anthrone,
and the bacterium is believed to be one of the bacteria responsible for metabolizing barboloin in
the intestine.
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The mechanism of cathartic action of aloe-emodin-9-anthrone causes a significant
increase in water content of the rat large intestine, which has been attributed to its inhibition of
rat colonic Na
+
, K
+
-adenosine triphosphatase (ATPase)
in vitro
and an increase in the pericellular
permeability across the rat colonic mucosa
in vivo
.
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Aloes have also been found effective as anti-
hyperglycemics and hypoglycemics in experimental animals.
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Aloe has been identified as one of
the most commonly used herbal proprietary products.
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In a comparative analysis of the gels from various
Aloe
species for wound healing and antifun-
gal properties,
A. ferox
was found to have the highest antifungal activity, measured as absence of
or low percentage of infected wounds.
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The antifungal activity was positively correlated with gel
aloin content. The use of Cape aloe in traditional medicine in Africa as a general tonic and restor-
ative medicine seems to be validated by the scientific evidence of its anti-inflammatory, anticholin-
esterase, and antioxidant activities,
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as well as its antimicrobial and wound-healing properties.
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ALSTONIA BOONEI
Botanical Name —
Alstonia boonei
de Wild.
Family —
Apocynaceae
Common Names —
Boone's, Alstonia, stool wood, pattern wood
African Names —
Igbo: egbu; Bini: ukhu; Efik: ukpo; Yoruba: awun
Description —
The plant is a large tree commonly found in the drier areas of the lowland and
rain forest. It often grows to significant heights (33 m high and 3 m in girth) with a straight and
fluted stem and without buttress roots. The bark occurs in commerce as brownish-gray, deeply fis-
sured pieces, with irregular fragments, up to about 1 cm thick. The dark brown bark is fairly rough
and flakes off in small patches. A cut through the bark exudes copious white latex, a characteristic
of most members of the family Apocynaceae. The latex can be used as a rubber adulterant. The
plant is often confused with
A. congensis
, even in the scientific literature; both plants differ substan-
tially in their appearance and habitat.
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