Agriculture Reference
In-Depth Information
The leaves of
A. boonei
are simple, about 20-20 cm long and 5-8 cm broad, appearing in whorls
of 5-8 leaves at each node. The individual leaf is glossy, dark green on the upper surface with some
bluish tint on the lower surface; it is leathery and smooth to the touch. Leaves are very shortly
pointed at the apex and gradually wedge-shaped common stalks at the base. The individual flower
is shortly stalked. Flowering occurs between October and March. The fruits (December-March)
are borne in follicles of up to 50 cm long, hanging down in pairs from the branches. They are finely
hairy and contain numerous elongated seeds about 5 cm long, which bear a tuft of long, silky hairs
at each end. When ripe, they split lengthwise.
9,28,33
Habitat and Distribution —
It is found in
forest fringes, deciduous forest, swampy land. It
occurs in Ghana, Nigeria, Angola, Kenya, and southern Sudan.
Ethnomedicinal Uses —
The plant is highly prized in African ethnomedicine for the treatment
of malaria, especially when the allopathic antimalarial drugs are found ineffective either because
of the presence of the drug-resistant malaria infection strains or because of acquired tolerance
from repeated dosing with synthetic antimalarials. For this purpose,
Alstonia
stem bark or leaves
are administered as a strong decoction or “teas” and sometimes as an ingredient in malaria “stem
therapy.”
Alsonia
was listed in the British pharmacopoeia of 1914 as an antimalarial drug. The
infusion of the bark alone is dispensed as a remedy for snakebite and sometimes for the treatment
of arrow poison.
The latex of the plant is smeared on swellings caused by filarial worms and then bandaged with
the crushed bark of the ordeal tree (
Erythrophleum guineense
) for cure.
81
The plant has also been
reported to be an astringent, an alterative tonic, and a febrifuge for relapsing fevers; it has been
claimed to be useful in muscle tone after debilitating fevers.
165
The leaves and latex are used topi-
cally to reduce swellings and for the treatment of rheumatic pains. The latex has also been used to
stimulate lactation. A decoction of the bark is taken after childbirth to facilitate the expulsion of the
placenta.
123
Extracts of
Alstonia boonei
have been employed in folk medicine for the treatment of
muscular pains, spasms, and hypertension. The plant has also been dispensed as an emmenagogue,
astringent, galactagogue, and anthelmintic.
166
Constituents —
The plants contain several indole alkaloids, including echitamine, echitami-
dine, akuammidine, picraline, quebrachidine and its esters, vincamajine, alstonine, and akuammi-
line.
167
The triterpenes β-amyrine and lupeol have been reported as occurring in the bark and ursolic
acid in the leaves.
168
Pharmacological Studies —
The extracts of
Alstonia
have been shown to have antipyretic,
analgesic, and anti-inflammatory activity. Echitamine, one of the major constituents of
A
.
boonei,
has been reported as being able to lower carotid pressure and increase renal output.
169
This find-
ing was corroborated by later using hypertensive cats; it was observed that the compound caused
a significant fall in blood pressure.
170
In a later investigation, however, it was observed that the
hypotensive effect of the compound occurred only occasionally after a first intravenous injection of
6 mg/kg, and it was suggested that the diuretic action on saline-loaded dogs and cats may explain
the hypotensive action.
171
The same investigators reported the effect of the triterpene ursolic acid,
hitherto considered an inert compound, on the electrolytic balance. They established that a dose of 3
mg produced sodium retention in suprarenalectomized rats equivalent to that of 3 g DOCA (deoxy-
cortisone acetate) and considerably higher potassium retention. They also reported that echitamine
in particular potentiated the barbiturate sleeping time of mice and rats and enhanced the lethality
of strychnine; on an isolated toad rectus abdominis preparation, increased concentrations of acetyl-
choline enhanced its action, whereas in isolated rat hemidiaphragm, its action was reversed by phy-
sostigmine. Echitamine also regressed methylcholanthrene-induced fibrosarcoma by 80% and 53%
in Wistar rats at doses of 7.5 and 5 mg/kg, respectively, when given subcutaneously. The compound
also showed activity against p-388 lymphocytic leukemia at a dose of 16 mg/kg.
172
The antipyretic and antihypertensive activity of the drug has been experimentally shown to be
due (at least partly) to echitamine.
173,174
Although
Alstonia
has enjoyed a folk reputation in three
