Agriculture Reference
In-Depth Information
VOACANGA AFRICANA
Botanical Name —
Voacanga africana
Stapf. et Eliot
Synonyms —
Voacanga africana
Stapf. ex Eliot,
Voacanga glbra
K. Schum.,
Voacanga mag-
nifolia
Wernham,
Voacanga eketensis
Wernham,
V. talbotti
Wernham,
V. glaberrina
Wernham.
Family —
Apocynaceae
African Names —
Hausa: kokiyar (
V. thouarsii
); Igbo: pete-pete; Swahili: kirongasi (
V. obtusa
);
Yoruba: ako-dodo
Description —
Voacanga africana
is a small tree or shrub, reaching 6 m in height with a low,
widely spreading crown. The leaves are opposite obovate and acuminate. They are dark green and
glossy above, greenish-green below, and usually stalkless. The flowers are white and borne in axil-
lary or terminal loosely branched glabrous inflorescence. The fruits occur mainly in pairs and
are spherical, mottled green with seeds wrapped in yellow pulp. The plant can be distinguished
from the closely related species
V. thouarsii
Roem. & Schult. (syn.
Annularia natalensis
Hochst.,
Tabernaemontana thouarsii
Pal.,
Voacana obtuse
Schum.) by the smaller size and larger flowers of
V. thouarsii,
as well as the oblanceolate leaves with distinct stalks and rounded apex in the latter.
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Habitat and Distribution —
The plant is found in the understory of forests. It is distributed
from Senegal to Sudan and south to Angola and Zaire.
V. thourasii
grows in swampy forests and
well-watered stream sides of savanna regions.
Ethnomedicinal Uses —
A decoction of the stem and root is used in the treatment of mental
disorders. The latex is applied to carious teeth. The decoction of the bark is considered an anal-
gesic and is added to embrocation mixtures used as a paste during fracture repair. In southeastern
Nigeria, the plant is featured in many healing rituals.
Constituents —
The roots and stem of the stem bark contain several closely related indole alka-
loids, of which voacamine, voacangine, and vobasine are the principal alkaloids. Other compounds
found in the plant include voacristine, voamidine, and voacarine. Voaphiline and vobtusine occur
in the leaves, and tabersonine is a constituent of the seeds. The seeds and root bark have yielded
the aspidosperma-aspidosperma-type bisindole alkaloids and the iboga-vobasine-type bisindoles.
1070
Pharmacological Studies —
Voacanga
alkaloids have been shown to possess cardiotonic, sym-
patholytic, and hypotensive properties.
78
A dose of 100 µg of voacamine sulfate has an estimated
equivalence of 0.25 units of standardized digitalis in isolated rabbit auricles.
78
The compound does
not belong to the same class as the cardiac glycosides cardiotonic proteins and has no cumulative
action but does exert a direct myotonic effect on the cardiac fiber.1071
1071
It is well tolerated as a cardio-
tonic in clinical application because it is devoid of the toxicity associated with digitalis compounds.
Its duration of action is also longer; it does not appear to affect the heart rate much. Voacangine has
an analgesic and local anesthetic action.
78
