Prota 11(1): Medicinal plants/Plantes mιdicinales 1
Engl. & Prantl, Nat. Pflanzenfam. Nachtr. 2: 59 (1900).
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.
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.
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.
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 15 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, 12(5) flowered; peduncle 06(17) mm long; bracts linear or narrowly ovate, 28 mm long, sometimes deciduous. Flowers bisexual, regular, 5-merous, fragrant; pedicel 39(17) mm long; sepals free, slightly unequal, ovate or narrowly ovate, 519 mm long, acute; corolla tube (13.5)1738 mm long, widening gradually at 2040% of its length into a cup-shaped upper part, at the mouth (11)1525(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, 523 mm long, acute, not fleshy, red or purple-red, corolla lobes ovate, ( 10)1438(48) mm Χ (7.5)1024(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 5.510.5 mm from the base of the corolla tube, included; ovary half-inferior, 2-celled, style 815 mm long, ending in a ringlike pistil head surrounding the minute stigma. Fruit consisting of 2 ellipsoid follicles 1135 cm Χ 12.5 cm, long-tapering towards a narrow apex and ending in an obtuse tip, 2-valved, divergent at an angle of 160240°, wall thick and hard, glabrous, with many lenticels, dark brown or purple-brown, many-seeded. Seeds spindle-shaped, flattened, 8.519.5 mm Χ 2.54 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.
Strophanthus welwitschii occurs in woodland, often in rocky localities and gallery forest, at 3001800 m altitude.
Genetic resources and breeding
Strophanthus welwitschii is not uncommon in its distribution area and not in danger of genetic erosion.
Medicinal use of Strophanthus welwitschii will remain limited in its area of distribution, unless further studies reveal new possibilities.
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McKenzie, A.G., 2002. The rise and fall of strophanthin. International Congress Series 1242: 95100.
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: 152160.
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.