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Strophanthus welwitschii (Baill.) K.Schum.

Protologue
Engl. & Prantl, Nat. Pflanzenfam. Nachtr. 2: 59 (1900).
Family
Apocynaceae
Origin and geographic distribution
Strophanthus welwitschii occurs throughout Central Africa and in the western part of southern Africa, in DR Congo, eastern Tanzania, Zambia and Angola.
Uses
In DR Congo a seed decoction is administered orally to treat respiratory diseases in children. In Angola a root infusion is drunk to treat gonorrhoea, but excessive usage is dangerous and can even be fatal. Root powder mixed with oil is rubbed in to treat scabies. The seeds are used to produce arrow poison.
Properties
The amount of cardiac glycosides (cardenolides) in the seeds varies throughout the area of distribution; seeds from Zambia are less bitter than those from Angola and contain hardly any glycosides. Seeds from Angola contain intermedioside, panstroside, inertoside and leptoside. All glycosides except inertoside are highly toxic.
Botany
Deciduous shrub or small tree up to 5 m tall or liana up to 8 m long, with clear or white exudate; stem up to 10(–40) cm in diameter; bark dark brown or grey; branches with many lenticels, branchlets minutely hairy. Leaves decussately opposite or rarely in whorls of 3 or 4, simple and entire; stipules absent; petiole 1–5 mm long; blade ovate to narrowly elliptical, up to 8.5 cm Χ 4 cm, base cuneate to rounded, apex rounded to acute or acuminate, margins undulate or slightly revolute, thinly leathery, with a line of translucent dots near the midrib. Inflorescence a terminal dichasial cyme, on long or short branches or in the forks, glabrous or hairy, 1–2(–5) flowered; peduncle 0–6(–17) mm long; bracts linear or narrowly ovate, 2–8 mm long, sometimes deciduous. Flowers bisexual, regular, 5-merous, fragrant; pedicel 3–9(–17) mm long; sepals free, slightly unequal, ovate or narrowly ovate, 5–19 mm long, acute; corolla tube (13.5–)17–38 mm long, widening gradually at 20–40% of its length into a cup-shaped upper part, at the mouth (11–)15–25(–35) mm wide, white, sometimes suffused with pink near the base, pale or reddish purple in the upper part outside, creamy and red- or purple-streaked inside, corona lobes narrowly triangular, 5–23 mm long, acute, not fleshy, red or purple-red, corolla lobes ovate, ( 10–)14–38(–48) mm Χ (7.5–)10–24(–29) mm, acute, spreading or recurved, minutely hairy inside, inside white, turning dark pink, outside white turning pale pink on left side, pale purple turning purple-red on the right side; stamens inserted at 5.5–10.5 mm from the base of the corolla tube, included; ovary half-inferior, 2-celled, style 8–15 mm long, ending in a ringlike pistil head surrounding the minute stigma. Fruit consisting of 2 ellipsoid follicles 11–35 cm Χ 1–2.5 cm, long-tapering towards a narrow apex and ending in an obtuse tip, 2-valved, divergent at an angle of 160–240°, wall thick and hard, glabrous, with many lenticels, dark brown or purple-brown, many-seeded. Seeds spindle-shaped, flattened, 8.5–19.5 mm Χ 2.5–4 mm, densely hairy, at apex with a long beak up to 11 cm long, glabrous in lower half, upper half with long hairs up to 9.5 cm long.
Strophanthus comprises 38 species, of which 30 occur in continental Africa, 1 in Madagascar and 7 in Asia, from India to South-East Asia. Strophanthus welwitschii flowers towards the end of the dry and the beginning of the rainy season when forming new leaves. Mature fruits are present in the dry season.
Ecology
Strophanthus welwitschii occurs in woodland, often in rocky localities and gallery forest, at 300–1800 m altitude.
Genetic resources and breeding
Strophanthus welwitschii is not uncommon in its distribution area and not in danger of genetic erosion.
Prospects
Medicinal use of Strophanthus welwitschii will remain limited in its area of distribution, unless further studies reveal new possibilities.
Major references
• Beentje, H.J., 1982. A monograph on Strophanthus DC. (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen 82–4. Wageningen, Netherlands. 191 pp.
• Neuwinger, H.D., 1998. Afrikanische Arzneipflanzen und Jagdgifte. Chemie, Pharmakologie, Toxikologie. 2nd Edition. Wissenschaftliche Verlagsgesellschaft mbH, Stuttgart, Germany. 960 pp.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Watt, J.M. & Breyer-Brandwijk, M.G., 1962. The medicinal and poisonous plants of southern and eastern Africa. 2nd Edition. E. and S. Livingstone, London, United Kingdom. 1457 pp.
Other references
• Disengomoka, I. & Delaveau, P., 1983. Medicinal plants used for child’s respiratory diseases in Zaire. Journal of Ethnopharmacology 8: 257–264.
• McKenzie, A.G., 2002. The rise and fall of strophanthin. International Congress Series 1242: 95–100.
• Von Euw, J., Heitz, G.A.O., Hess, H., Speiser, P. & Reichstein, T., 1952. Glykoside und Aglykone, 89. Die Glykoside von Strophanthus welwitschii. Helvetica Chimica Acta 35: 152–160.
Author(s)
• A. de Ruijter
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, Rιduit, 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

Correct citation of this article:
de Ruijter, A., 2006. Strophanthus welwitschii (Baill.) K.Schum. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes mιdicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.