Acokanthera oppositifolia

Acokanthera oppositifolia, the poison arrow tree, is a shrub used as the source of an arrow poison and to coat caltrops made from the sharp fruits of the puncture vine (Tribulus terrestris). All plants of the genus Acokanthera contain toxic cardiac glycosides strong enough to cause death. Acokanthera oppositifolia is widespread in southern and central Africa from Cape Province north to The Democratic Republic of the Congo + Tanzania. Acokanthera schimperi is employed for the same purpose. Unlike all other parts of the plant, the ripe fruit is sweet and edible. Unripe fruit are still poisonous, so only really ripe fruit are eaten.

Description

A shrub or small tree. It grows 5 m tall. There are prickles along the stem. The leaves are twice divided and there are 8-18 pairs of pinnae. There are up to 50 pairs of pinnules on each pinnae. The flowers are yellow. They are in large clusters at the ends of branches. The pods are flattened.

Edible Uses

The fruit can be eaten when fully ripe and has been used for making jams, though this use is cautioned against. The latex from the fruit is chewed as gum by children.

Traditional Uses

CAUTION: This fruit is poisonous when unripe. It contains alkaloids that can affect the heart. Although used for jams it is probably not wise. The fruit should only be used when very ripe. The latex from the fruit is used by children as chewing gum.

Medicinal Uses

Although very poisonous, the plant has been used medicinally in Africa, particularly to combat poisoning and parasites. All parts of the plant, except for the pulp of the ripe fruit, contain large amounts of cardiac glycosides (cardenolides), of which about 15 have been identified. These glycosides are responsible for the plant's activity as an arrow poison, but they also act as cardiac stimulants. The main compounds are acovenoside A, acovenosigenin, acolongifloroside K and ouabagenin. To treat snakebites and spider bites, a small amount of the leaves is eaten, a leaf or root decoction is drunk and the leaf or root pulp is rubbed into the wound. Alternatively, the root powder is sniffed and a dressing made of the roots or leaves is put on the swollen part. An infusion of the roots is taken to expel tapeworm; to treat excessive and irregular menstruation; as a treatment for syphilis. The powdered root is sniffed as a cure for headaches. A leaf infusion is taken to treat abdominal pain, colds, measles and blood poisoning. The powdered leaf is sniffed, or an infusion of the leaves is used as a nasal spray, in order to combat headaches. Small pieces of the stem are chewed to relieve toothache.

Known Hazards

The fruit is poisonous when unripe and contains alkaloids that can affect the heart. The fruit should only be used when very ripe. Wood from this plant should not be used for cooking food, as it can make the food poisonous.

Distribution

A tropical plant. It grows on high hill-slopes and dry plateaux from East Africa to South Africa. It grows up to 2,400 m above sea level. It can grow in arid places. It grows in area with a rainfall between 600-1,000 mm. In Tanzania it grows between 1,500-2,100 m above sea level and can be on termite mounds. It grows in Miombo woodland in Africa. It suits hardiness zones 9-11.

Where It Grows

Africa, Asia, Botswana, Central Africa, China, Congo, East Africa, Eswatini, India, Kenya, Malawi, Mozambique, South Africa, Southern Africa, Swaziland, Tanzania, Zambia, Zimbabwe,

Cultivation

It can be grown from seeds or semi-ripe cuttings.

Propagation

Seed - it requires no pre-treatment, but has a very limited viability and so should be sown as soon as it is ripe. Cuttings of half-ripe wood.

Notes

There are about 15 Acokanthera species. If this wood is used to cook food it can make the food poisonous.

Nutrition

Synonyms

Also Known As

Common poison-bush, Kibaichiago, Kikwei, Kiruru, Luzekwa, Mekweu, Msunguti, Murichu, Mururu, Musungu-sungu, Ngweo, Ol-morijoi, Ordeal poisonwood, Rumbara, Usungu

References (26)

• Barwick, M., 2004, Tropical and Subtropical Trees. A Worldwide Encyclopedic Guide. Thames and Hudson p 6
• Bethwell, O.O., 2007. Acokanthera oppositifolia (Lam.) Codd. [Internet] Record from Protabase. Schmelzer, G.H. & Gurib-Fakim, A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. < http://database.prota.org/search.htm>. Accessed 13 October 2009
• Bircher, A. G. & Bircher, W. H., 2000, Encyclopedia of Fruit Trees and Edible Flowering Plants in Egypt and the Subtropics. AUC Press. p 7 (As Acokanthera longiflora)
• Bothalia 7:448. 1961
• Burkill, H. M., 1985, The useful plants of wet tropical Africa. Vol. 1

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