Acokanthera oblongifolia (PROTA)

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Plant Resources of Tropical Africa
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Acokanthera oblongifolia (Hochst.) Codd


Protologue: Bothalia 7: 449 (1961).
Family: Apocynaceae
Chromosome number: 2n = 22

Synonyms

  • Acokanthera spectabilis (Sond.) Hook.f. (1878),
  • Carissa spectabilis (Sond.) Pichon (1948).

Vernacular names

  • Dune poison bush, wintersweet (En).

Origin and geographic distribution

Acokanthera oblongifolia occurs in southern Mozambique and eastern South Africa.

Uses

Acokanthera oblongifolia is used medicinally to treat snakebites and as an emetic. To treat snakebites, a small amount of the leaves is eaten, a leaf decoction is drunk and the leaf pulp is rubbed into the wound, root powder is sniffed and roots or leaves are put on the swollen part as a dressing. Root scrapings are rubbed into the skin against itch. A wood or leaf decoction is drunk or administered as an enema as a cure for internal worms, and to combat evil spirits. The fruit is highly toxic, especially when unripe, but the ripe fruits have also caused fatalities in children. The stem bark and root bark are used as a potent arrow poison, for homicide, suicide and to kill stray dogs.

Properties

Numerous cardenolides were detected in the wood, leaves, seeds and fruit, the most important being acovenosides A and B, which both have cardio-vascular properties. Other cardenolides that were isolated are acovenoside C, spectabiline and acopieroside II. The last compound shows a higher activity than digitalin and digoxin as a cardiotonic. The seeds yielded acobioside A and 14-O-acetyl-acovenoside C; the latter showed marked cardiotonic activity in dogs.

Description

Evergreen shrub or small tree up to 6 m tall; young branches glabrous, conspicuously angled and ribbed. Leaves decussately opposite, simple and entire; stipules absent; petiole 4–12 mm long; blade elliptical, 6–12 cm × 1.5–5 cm, base cuneate or rounded, apex acute to obtuse, mucronate, leathery, glossy, glabrous, pinnately veined, lateral veins inconspicuous, with looping connections. Inflorescence a dense axillary cyme, many-flowered. Flowers bisexual, regular, 5-merous, fragrant; sepals free, ovate to lanceolate, 2.5–3 mm long, apex acuminate to acute, shortly hairy or glabrous outside, ciliate; corolla tube cylindrical, 14–20 mm long, glabrous or shortly hairy outside, inside sparsely hairy in the upper half and wrinkled below, white tinged pink, lobes broadly ovate, 3–7 mm long, apex rounded, glabrous to shortly hairy on both sides, ciliate or not, white; stamens inserted near the top of the corolla tube, included; ovary superior, ellipsoid, faintly ribbed, 2-celled, style slender, stigma minutely bifid. Fruit an ellipsoid to globose berry 2–2.5 cm long, purple when ripe, 1–2-seeded. Seeds ellipsoid, plano-convex, c. 1.5 cm long, smooth, glabrous.

Other botanical information

Acokanthera comprises 5 species and is restricted to Africa, with one species also found in Yemen. It is related to Carissa. Acokanthera oblongifolia fruits from February to April.

Ecology

Acokanthera oblongifolia occurs in dry forest and thickets on coastal dunes.

Genetic resources

There are no indications that Acokanthera oblongifolia is at risk of genetic erosion.

Prospects

The cardenolides isolated from Acokanthera oblongifolia are highly poisonous. Most of them have not been pharmacologically investigated, and more research is needed to evaluate the possible prospects of the various compounds. Acokanthera oblongifolia is easy to propagate, like the other Acokanthera species, and it would be a beautiful ornamental in gardens. However, this is not recommended because of its toxicity.

Major references

  • Hanna, A.G., Elgamal, M.H.A., Hassan, A.Z., Duddeck, H., Simon, A., Kovács, J. & Tóth, G., 1998. Complete 1H and 13C signal assignments of 5b-cardenolides isolated from Acokanthera spectabilis Hook.f. Magnetic Resonance in Chemistry 36(12): 936–942.
  • Kupicha, F.K., 1982. Studies on African Apocynaceae: the genus Acokanthera. Kew Bulletin 37(1): 41–67.
  • Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.

Other references

  • Coates Palgrave, K., 1983. Trees of southern Africa. 2nd Edition. Struik Publishers, Cape Town, South Africa. 959 pp.
  • Karawya, M.S., Abdel-Wahab, S.M. & Niazi, H.M., 1974. Assay of cardenolides in Acokanthera spectabilis. Planta Medica 25(1): 17–21.
  • van Wyk, B.E., van Heerden, F. & van Oudtshoorn, B., 2002. Poisonous plants of South Africa. Briza Publications, Pretoria, South Africa. 288 pp.

Author(s)

  • G.H. Schmelzer, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Schmelzer, G.H., 2007. Acokanthera oblongifolia (Hochst.) Codd. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 29 November 2017.