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Adenium oleifolium Stapf

Protologue
Kew Bull. 1907: 53 (1907).
Family
Apocynaceae
Chromosome number
2n = 22
Synonyms
Adenium obesum (Forssk.) Roem. & Schult. subsp. oleifolium (Stapf) G.D.Rowley (1980).
Origin and geographic distribution
Adenium oleifolium occurs naturally in south-eastern Namibia, Botswana and South Africa.
Uses
An arrow poison is prepared from the latex, or from a decoction of the extremely bitter tuber. People living in the south-western Kalahari Desert prepare a salve from the plant, which is applied to snakebites and scorpion stings. Root sap is used to treat fever and colic. In larger doses it is purgative and toxic. Adenium oleifolium is occasionally grown as an ornamental.
Properties
Several cardiac glycosides have been isolated from Adenium oleifolium: hongheloside A (composed of oleandrigenin and D-cymarose), echujine (composed of the digitoxigenin, D-cymarose and 2 molecules of D-glucose), somaline (composed of digitoxigenin and D-cymarose) and odorotrioside G (composed of digitoxigenin, D-digitalose and 2 molecules of D-glucose). Tests with guinea pigs, cats and rats, which were injected with an alcoholic extract of the tuber or given the extract orally, all resulted in restlessness, generalized tremor, rapid breathing, convulsions and death.
Botany
Succulent, small shrub up to 40 cm tall, with thickened rootstock (tuber) 50–80 cm × 15–30 cm and white latex in all parts, soft pubescent on all parts; stem swollen at base. Leaves arranged spirally, clustered at the end of branchlets, simple, sessile; stipules minute or absent; blade linear, 4.5–14.5 cm × 0.3–1.4 cm, base cuneate, apex acute, entire, glaucous or pale green, leathery, hairy to glabrous. Inflorescence a terminal cyme; bracts narrowly oblong to narrowly ovate, 3–4 mm × 1–2 mm, acuminate, pubescent. Flowers bisexual, regular, 5-merous, showy, appearing with the leaves; pedicel 5–8 mm long, hairy; sepals lanceolate, 5–7 mm long, fused at base, white outside, hairy; corolla with tube 2.2–3.4 cm long, narrowly cylindrical at the base for 4–7 mm then campanulate to funnel-shaped, throat scales forming pockets between the lobes, lobes obovate, spreading, 1–1.3 cm long, acute, pale pink to red, more intense towards the margin, hairy outside, glabrous inside; stamens inserted at base of widened part of corolla tube, slightly exserted, anthers forming a cone covering the pistil, base sagittate, 5–7 mm long, with long apical appendices; ovary superior, composed of 2 free carpels, glabrous, styles fused, slender, with well-developed clavuncula. Fruit consisting of 2 cylindrical follicles, coherent at base, 8–11 cm long, long tapering at apex, spreading or recurved when mature, opening by a longitudinal slit, many-seeded. Seeds linear-oblong, 12–15 mm long, brown, striate, with tufts of long brownish hairs at both ends.
Adenium comprises 5 species, which are sometimes merged into a single one, Adenium obesum (Forssk.) Roem. & Schult. with 6 subspecies. Adenium oleifolium is characterized by its narrow leaves. The fruits take more than a year to mature. Seeds germinate readily, but the growth of the plants is slow.
Ecology
Adenium oleifolium grows in grassland with bushes, on stony ridges and limestone rock outcrops or in loose sand.
Genetic resources and breeding
Although the natural distribution of Adenium oleifolium is restricted, it seems not to be in immediate danger of genetic erosion. However, in Botswana it is rare and considered vulnerable.
Prospects
More research into the chemical composition and pharmacological activities of the compounds of Adenium oleifolium seems warranted. Possibilities to develop Adenium oleifolium as an ornamental seem limited because of its slow growth.
Major references
• Dimmitt, M.A. & Hanson, C., 1992. The genus Adenium in cultivation. Part 2: A. swazicum, A. boehmianum and A. oleifolium. Cactus and Succulent Journal 64(3): 110–111.
• Neuwinger, H.D., 1996. African ethnobotany: poisons and drugs. Chapman & Hall, London, United Kingdom. 941 pp.
• Plaizier, A.C., 1980. A revision of Adenium Roem. & Schult. and of Diplorhynchus Welw. ex Fic. and Hiern (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen 80–12. Wageningen, Netherlands. 40 pp.
• Rowley, G.D., 1983. The Adenium and Pachypodium handbook. Smart & Co. Ltd., Brackley, United Kingdom. 95 pp.
• von Koenen, E., 2001. Medicinal, poisonous and edible plants in Namibia. Klaus Hess Verlag, Göttingen, Germany. 336 pp.
Other references
• Codd, L.E., 1963. Apocynaceae. In: Dyer, R.A. & Codd, L.E. (Editors). Flora of southern Africa. Volume 26. Botanical Research Institute, Department of Agricultural Technical Services, Pretoria, South Africa. pp. 244–296.
Author(s)
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
G.H. Schmelzer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
A. Gurib-Fakim
Faculty of Science, University of Mauritius, Réduit, Mauritius
Associate editors
C.H. Bosch
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
M.S.J. Simmonds
Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, United Kingdom
R. Arroo
Leicester School of Pharmacy, Natural Products Research, De Montfort University, The Gateway, Leicester LE1 9BH, United Kingdom
A. de Ruijter
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Photo editor
A. de Ruijter
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Oyen, L.P.A., 2006. Adenium oleifolium Stapf. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
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