Prota 11(1): Medicinal plants/Plantes mιdicinales 1
Journ. Bot. (Morot) 7: 299 (1893).
Origin and geographic distribution
Strophanthus thollonii occurs in south-eastern Nigeria, southern Cameroon, the Central African Republic and Gabon.
The Fang people and Bagielli pygmies in Gabon and Cameroon use the crushed or boiled seeds to prepare hunting poison. The seeds are used alone or together with those of Strophanthus gratus (Wall. & Hook.) Baill., or as part of a complex recipe of several plants, snake heads and mushrooms.
A large number of cardiac glycosides (cardenolides) have been isolated from Strophanthus thollonii. The seeds contain the highest concentration. Chemically, the water-soluble seed glycosides of Strophanthus thollonii are very similar to those of Strophanthus sarmentosus DC. The main glycosides isolated are based on 3 aglycones and include sarmentoside A, tholloside, bipindoside, locundioside and sarhamnoloside. They are all highly poisonous. The seeds also contain traces of ouabain.
Evergreen liana up to 20 m long, with clear or white exudate in all parts; stem up to 5 cm in diameter; bark grey; branches with many lenticels, dark maroon-brown or blackish. Leaves decussately opposite, simple and entire; stipules absent; petiole 213 mm long; blade narrowly elliptical to obovate, 317.5 cm Χ 17.5 cm, base cuneate to decurrent, apex acute to acuminate, margin slightly revolute, leathery, glabrous. Inflorescence a congested terminal dichasial cyme, on long or short branches or in the forks, glabrous, 15-flowered; peduncle 04 mm long; bracts ovate to narrowly triangular, 1.512 mm long, acute, early deciduous. Flowers bisexual, regular, 5-merous, fragrant; pedicel 210 mm long; sepals free, unequal, elliptical to narrowly elliptical, 1026 mm long, acute; corolla tube 2438 mm long, widening at c. 50% of its length into a cylindrical or cup-shaped upper part, at the mouth 1122 mm wide, white turning yellow at the base outside, pink and turning purple in the upper part outside, white and red- or purple-streaked inside, the white turning yellow, corona lobes narrowly triangular, 1027 mm Χ 24 mm, acute, slightly fleshy, sparsely pubescent, pink, turning purple in the centre, with white margins and apex, the white turning yellow, corolla lobes ovate, 1841 mm Χ 1019 mm, acute to slightly acuminate, white and turning yellow inside, dark pink or purple outside; stamens inserted at 1520 mm from the base of the corolla tube, exserted; ovary half-inferior, 2-celled, style 1723 mm long, ending in a pistil head surrounding the stigma. Fruit consisting of 2 ellipsoid follicles 1847 cm Χ 1.52.5 cm, tapering into a narrow apex, 2-valved, divergent at 140180Ί, wall rather thin and hard, smooth or slightly grooved, glabrous, with lenticels, dark maroon-brown or blackish purple, many-seeded. Seeds spindle-shaped, 1524 mm Χ 23 mm, densely short-hairy, at apex with a beak up to 3.5 cm long, glabrous for 1.515 mm in basal part, upper part with long hairs up to 4 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 thollonii resembles Strophanthus gratus (Wall. & Hook.) Baill., but chemically they are not related at all. They both lack the long petal tails, which are characteristic for the genus. Strophanthus thollonii flowers all year round, with a peak from November to January. Mature fruits can be found from December to January. Seeds are sometimes used to adulterate seed of Strophanthus hispidus DC.
Strophanthus gardeniiflorus Gilg is closely related to Strophanthus thollonii and is chemically similar. It is restricted to gallery forest in southern DR Congo, northern Zambia and eastern Angola at 10001500 m altitude. The seeds are used for arrow poison.
Strophanthus thollonii occurs on river banks in moist forest from sea-level up to 300 m altitude.
Genetic resources and breeding
Strophanthus thollonii occurs rather dispersed in its comparatively small distribution area, and is uncommon. Because of overharvesting, it has become locally threatened.
Strophanthus thollonii has so far mainly been used for making arrow poison, but this use is declining rapidly. Although it contains several glycosides, its medicinal use will remain limited unless further studies reveal new possibilities.
Beentje, H.J., 1982. A monograph on Strophanthus DC. (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen 824. Wageningen, Netherlands. 191 pp.
Neuwinger, H.D., 1996. African ethnobotany: poisons and drugs. Chapman & Hall, London, United Kingdom. 941 pp.
Bisset, N.G., 1989. Arrow and dart poisons. Journal of Ethnopharmacology 25: 141.
Brandt, R., Kaufmann, H. & Reichstein, T., 1966. Nigrescigenin, Identifizierung mit Sarmentosigenin A Glykoside und Aglykone. Helvetica Chimica Acta 49: 1844.
McKenzie, A.G., 2002. The rise and fall of strophanthin. International Congress Series 1242: 95100.
Weiss, E.K., Schindler, O. & Reichstein, T., 1957. Die Glykoside der Samen von Strophanthus tholloni Franch. 2. Mitteilung. Glykoside und Aglykone, 179. Mitteilung. Helvetica Chimica Acta 40(4): 9801015.
Correct citation of this article:
Beentje, H.J., 2006. Strophanthus thollonii Franch. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes mιdicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.