Agriculture Reference
In-Depth Information
Description —
Aloe barbadensis
is a perennial herb with rosettes of long pointed leaves from
a shortly branched creeping rhizome. The leaves are brittle and exude a clear yellowish viscous sap
when broken. They have soft marginal prickles. The flowers are yellow and borne in an elongated
compact raceme from the center of the rosette. Propagation is by means of the rhizome branches
since it does not produce fruit.
32
Habitat and Distribution —
It grows in subtropical regions of the continent. The plant is prob-
ably a native of South and East Africa and the Mediterranean regions, although it is widespread
throughout the continent. It is not very discriminatory to soil types and climatic conditions, but as
a member of the Liliaceae family, it will prefer a well-drained clayey loam, with rainfall of at least
80 in. per annum.
Ethnomedicinal Uses —
The fresh leaf is used for wound dressing and for the treatment of
vertigo. In Nigeria, the exudate from freshly cut leaf is used in the treatment of guinea worm infes-
tation. In Trinidad and Tobago, the exudate is mixed with egg white and taken for colds and asthma
and to heal bruises; it is taken with seawater for stomach ulcers.
136
The dried exudate is used in the
treatment of severe constipation. Aloe vera possesses healing, moisturizing, and emollient proper-
ties useful in a wide range of cosmetic formulations. It is employed as a humectant in skin prepa-
rations such as moisturizers, suntan lotions, and aftershave creams. It has been found useful for
application to severely chapped skin.
Constituents —
Aloes contain C-glycosides and resins. The crystalline glycoside known as
aloin is used in pharmacy as a cathartic. It is, however, the gel, said to contain several organic acids
and the so-called biostimulators, that the plant secretes as a repair agent on physical injury that
has the topical healing properties. The plant also contains polysaccharides, glycoproteins, sterols,
organic acids, and saponins.
123,137
Preparation of
Aloe vera
—
AVG is prepared in various ways depending on the manufactur-
ing house. A common practice is to drain the free-flowing aloes first and then allow the leaves to
be soaked in 15% ethanol solution in the dark for up to 14 days; then, the finely chopped material
is subjected to a mill press. There is no scientific report on the differences (if any) between the
pharmaceutical aloes and those processed for cosmetic use. The methods of preparation are highly
customized and are the subjects of several patents, with each manufacturing house claiming the
superiority of its own method and product.
Pharmacological Studies —
Aloe vera
is one of the most effective wound- and burn-healing
agents in current use. Several publications are available in the literature substantiating the healing
properties of AVG, and only recent reports are reviewed here. Animal studies have shown that it
possesses both oral and topical wound-healing activity.
138
In the oral experiment, animals were
administered 25% aloe vera in their drinking water for 2 months. The animals in the topical experi-
ment were given 25% of the drug in a cream. The results showed that a 62.5% reduction in wound
diameter was noted in mice that received a 100 mg/kg/day oral dose of the substance; for the topi-
cally treated animals, a 50.8% reduction was recorded. In both groups, the wounds were induced on
both sides of the vertebral column of ICR mice with a biopsy punch.
138
In another study, full-face dermabrasion was used to evaluate the wound-healing activity of AVG
in comparison with the standard polyethylene oxide gel dressing.
139
It was found that by 24-48 h,
there was dramatic vasoconstriction and accompanying reduction in edema on the side treated with
aloe vera; by the third to fourth day, there was less exudate and crusting at the site treated with the
drug; the fifth to sixth day witnessed the complete reepithelialization of the aloe site. It was esti-
mated that there was a 72-h acceleration of wound healing in the aloe-vera-treated sites against the
side of the face dressed with standard polyethylene oxide gel. It was observed that the acceleration
of wound healing is significant in the reduction of bacterial contamination, possible keloid forma-
tion, and pigmentary changes.
139
A suggestion has been made that the cicatrizant activity of aloe
vera is due, at least in part, to the gibberellin content of the plant.
140
Both aloe and gibberellins
