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Strophanthus thollonii Franch.

Protologue
Journ. Bot. (Morot) 7: 299 (1893).
Family
Apocynaceae
Origin and geographic distribution
Strophanthus thollonii occurs in south-eastern Nigeria, southern Cameroon, the Central African Republic and Gabon.
Uses
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.
Properties
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.
Botany
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 2–13 mm long; blade narrowly elliptical to obovate, 3–17.5 cm Χ 1–7.5 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, 1–5-flowered; peduncle 0–4 mm long; bracts ovate to narrowly triangular, 1.5–12 mm long, acute, early deciduous. Flowers bisexual, regular, 5-merous, fragrant; pedicel 2–10 mm long; sepals free, unequal, elliptical to narrowly elliptical, 10–26 mm long, acute; corolla tube 24–38 mm long, widening at c. 50% of its length into a cylindrical or cup-shaped upper part, at the mouth 11–22 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, 10–27 mm Χ 2–4 mm, acute, slightly fleshy, sparsely pubescent, pink, turning purple in the centre, with white margins and apex, the white turning yellow, corolla lobes ovate, 18–41 mm Χ 10–19 mm, acute to slightly acuminate, white and turning yellow inside, dark pink or purple outside; stamens inserted at 15–20 mm from the base of the corolla tube, exserted; ovary half-inferior, 2-celled, style 17–23 mm long, ending in a pistil head surrounding the stigma. Fruit consisting of 2 ellipsoid follicles 18–47 cm Χ 1.5–2.5 cm, tapering into a narrow apex, 2-valved, divergent at 140–180Ί, wall rather thin and hard, smooth or slightly grooved, glabrous, with lenticels, dark maroon-brown or blackish purple, many-seeded. Seeds spindle-shaped, 15–24 mm Χ 2–3 mm, densely short-hairy, at apex with a beak up to 3.5 cm long, glabrous for 1.5–15 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 1000–1500 m altitude. The seeds are used for arrow poison.
Ecology
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.
Prospects
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.
Major references
• Beentje, H.J., 1982. A monograph on Strophanthus DC. (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen 82–4. Wageningen, Netherlands. 191 pp.
• Neuwinger, H.D., 1996. African ethnobotany: poisons and drugs. Chapman & Hall, London, United Kingdom. 941 pp.
Other references
• Bisset, N.G., 1989. Arrow and dart poisons. Journal of Ethnopharmacology 25: 1–41.
• 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: 95–100.
• 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): 980–1015.
Author(s)
• H.J. Beentje
Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, United Kingdom


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:
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.