Agriculture Reference
In-Depth Information
Synonyms —
Rauwolfia vomitoria
Afzel.,
Rauvolfia
congolana
De Wild. & T. Durand,
Rauvolfia senegambiae
A. DC.,
Rauvolfia
pleiosiadica
K. Schum.,
Rauvolfia
stuhlmannii
K.
Schum.,
Hylacium owariense
P. B e a u v.
Family —
Apocynaceae
Common Names —
The swizzle stick, African rauwolfia
African Names —
Anyi: baka egbe, ngbe ngbe; Ashanti (Twi, Wassaw): kakapenpen, penpen;
Bini: akata; Efik: uto enyin; Igbo: akanta, ekpiri; Swahili: mesesewe; Yoruba: ira-igbo, asofeiyeje
Description —
R. vomitoria
is a small tree that sometimes grows up to 15 m in height. The
genus can be characterized by the occurrence of phloem sclereids, nonarticulated lactiferous tubes,
nonseptate fibers, and heterogeneous rays. The stem can be differentiated from the root by the pres-
ence of a well-defined central pit and unlignified fibers in the pericyclic region. The bark is gray
with a pale brown slash exuding a bitter white latex, which changes slowly to rose color on exposure
to air. It has simple, whorled leaves in groups of 4 or 5. The leaves are widely lanceolate and acu-
minate, with petioles 8-25 cm long and shadowy grooved above. The margins are entire; the base
is cuneate, with a shiny green upper surface, and dull medium green below; the midrib is impressed
above, and there are 8-16 pairs of major lateral veins. The flowers are borne in threes at the end of
the ultimate branches and puberulus; the corolla is creamy white, up to 1 cm long; there are small
lobes and 5 sepals, ovate. It bears red solitary or paired drupes, about 6 mm in diameter. It flowers
January-June and fruits April-November.
9,28
Habitat and Distribution —
It grows in moist lowland forest and well-watered tropical savan-
nas. It is widespread in sub-Saharan Africa, occurring in Sierra Leone, Senegal, Ghana, Cameroon,
Nigeria, Gabon, Zaire, Sudan, Tanzania, and Zimbabwe.
Ethnomedicinal Uses —
The plant is a common ingredient in traditional medicine, with the
dose and method of preparation critical for the various indications. It is boiled with fruits of
Xylopia
aethiopica
to treat convulsions in children. A decoction of the leaves, prepared with leaves of
Indigofera macrophylla
and
Cajanus cajan
, and whole herb of
Olyra latifolia
is used as a remedy
for smallpox. An infusion of the leaves is indicated for treatment of constipation and indigestion.
The root and stem bark infusion is mixed with
Capsicum annum
and taken for malaria fever. In
southern Nigeria, the root decoction is prepared with ash from palm husk for the treatment of
aggressive maniac behavior.
Constituents —
Rauwolfia
contains more than 40 indole alkaloids, each possessing remark-
able pharmacological activities. The alkaloids of
Rauwolfia
can be grouped into five main types:
the yohimbine and its esters, including reserpine; the ajmaline type, which includes compounds
with vasoactive properties; the ajmaline-sarpagine series with antiarrthmic dihydroindoles; the
anhydronium bases, including the quick-acting hypotensive compound alstonine; and the oxyin-
doles and pseudoindoxyls.
917,918
This species contains more reserpine and ajmaline than the Asian
species
R. serpentine
.
919-921
Pharmacological Studies —
Rauwolfia
alkaloids exert their antihypertensive effect by a com-
bination of various biochemical mechanisms. One of the primary modes of action is the deple-
tion of norepinephrine through inhibition of catecholamine storage in postganglionic adrenergic
nerve endings. The hypotensive effect is often accompanied by a reduction in heart rate, contrac-
tion of the pupils, and stimulation of intestinal peristalsis.
10
Rauwolfia
does not cause significant
alteration in cardiac output or renal blood flow. The carotid sinus reflex is inhibited, but postural
hypotension is rarely observed.
922
The cardiovascular and CNS effects may persist even after with-
drawal of the drug.
The sedative and tranquilizing properties of
Rauwolfia
are believed to be related to depletion of
amines in the CNS. It is this secondary activity that informs the use of
Rauwolfia
in the treatment of
chronic anxiety states often associated with the incidence of hypertension. Other pharmacological
properties are similar, but not identical, to those described under reserpine.
