Agriculture Reference
In-Depth Information
Description —
Vernonia amygdalina
is a shrub or small tree up to 5 m high. The leaves (15
× 5 cm) are simple and entire (or minutely toothed), obovate-oblanceolate, finely glandular below,
and displaying few lateral nerves. The flowers occur in copious corymbose panicles and are white,
fragrant, and ususlly bee infested. The species can be easily differentiated from the wild-growing
V. colorata
by the hairy leaves of the latter.
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Habitat and Distribution —
The plant grows in coastal savanna, but it is often cultivated
in many parts of the continent as an edible vegetable. It is distributed from Sudan in the north to
southern Africa.
Ethnomedicinal Uses —
The leaves are reputed to be effective remedies for gastrointesti-
nal disorders and as a general tonic. An aqueous decoction of the leaves has been used for the
treatment of fevers and diabetes. The dried leaves are chewed for the same purpose and used by
pregnant women to check nausea. The fresh leaves are, however, believed to be abortifacient.
The bitterness of the leaves is usually reduced by boiling and soaking in water followed by sev-
eral washings with fresh water. The peeled stem is used for cleaning the teeth, and the bark is
administered for venereal diseases and for diarrhea. The plant is added in very minute quantities
in several remedies, but it is not clear whether it is used to impart a bitter taste to the medication
or is included for therapeutic purposes. The leaves are ingredients in purgative enemas, diuretic
mixtures, anthelmintic preparations, and topical lotions for parasitic skin diseases. The bitterness
of the leaves is often exploited by nursing mothers to assist in weaning babies by rubbing the juice
on their breasts. Soup prepared with washed leaves is believed to improve lactation. It is used dur-
ing labor to facilitate childbirth. It is used with the leaves of
Psidium guajava
for the treatment
of hypertension and kidney problems. In Rwanda, it is added to local sorghum beer,
ikigage,
to
increase the potency and for medicinal purposes.
Constituents —
Vernonia
contains saponins, cardiac glycosides, flavonoids, and sesquiterpene
lactones.
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The major constituents include the saponin vernonin, the sesquiterpenes vernoleptin
and vernodalin, and the ubiquitous flavonoid kaempferol.
Pharmacological Studies —
Vernonin
has been shown to exert hypotensive activity and mild
cardiotonic effects when injected in dogs. A leaf extract of the plant reduced the rate and force of
contraction of the isolated frog heart and in cats caused a marked fall in blood pressure, as well
as reduction in heart rate; it also caused a strong stimulation of the isolated rabbit intestine.
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The sesquiterpene lactones have
in vitro
cytotoxic activity against KB tumor cells and Wilme's
myeloma.
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The extract of the leaves has broad-spectrum antimicrobial activity and has been
shown to induce abortion in goats. The methyl alcohol extract of the leaves, when administered to
12-13 pregnant mice, caused abortion within 24 h of the last dose in a 3-day regimen.
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Toya ng
and Verpoorte have published a good review that summarized the various uses, phytochemistry,
and pharmacological activities of
Vernonia
species.
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The major activities found in many laboratory and clinical studies of
Vernonia amygda-
lina
include antimalarial, antidiabetic, antioxidant, antihypercholestrolemic, and anthelmintic
activities and uterine contractility, immune boosting in HIV infections, and anti-inflammatory
properties. In a clinical outcome study at InterCEDD (Nsukka, Nigeria, 1992-1993) of 12 ambu-
latory volunteers with severe hemorrhoids, a weak infusion of dried
V. amygdalina
roots and
Garcinia kola
seeds completely shrunk the acute inflammation, and a maintenance taken for 8
weeks prevented the reoccurence of piles for several months. A controlled clinical study on the
use of
V. amygdalina
roots will be necessary to evaluate its efficacy in the management of acute
severe hemorrhoids.
Toxicity —
Vernonia amygdalina
is consumed throughout West and Central Africa as a veg-
etable and is generally considered nontoxic, but excessive consumption of the leaves is purgative.
In a chronic toxicity study, rats were fed with up to 75% (w/w) powdered leaves mixed with grower
mash for 65 days, and at the end of the study the only gross change observed was the lightening of
