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Strophanthus amboensis (Schinz) Engl. & Pax

Protologue
Bot. Jahrb. Syst. 15: 376 (1892).
Family
Apocynaceae
Synonyms
Strophanthus intermedius Pax (1892).
Origin and geographic distribution
Strophanthus amboensis occurs from western DR Congo to Angola and Namibia.
Uses
In Angola a decoction of the roots or leaves of Strophanthus amboensis is taken against rheumatism. The Luvale people use an enema of the root to treat venereal diseases. The Luchazi people mix the pounded root with oil and apply the ointment to treat scabies. In Namibia the seeds are used in the preparation of arrow poison.
Properties
From the seeds about 10 cardiac glycosides (cardenolides) have been isolated of which the most important are based on the aglycone sarverogenin: mainly intermedioside and panstroside, and traces of amboside, leptoside, kwangoside and sarveroside. These glycosides are highly toxic. The aglycones sarverogenin and sarmentogenin have also been isolated. Sarverogenin has also been isolated from the root and bark after hydrolysis. Leptoside has a weak cardio-stimulant action.
Cell suspension cultures from the leaves, to which digitoxigenin was added, produced 6 transformation products, e.g. periplogenin.
Botany
Deciduous shrub up to 4 m tall or liana up to 20 m long, with clear or white exudate, all parts glabrous to hairy; stem up to 20 cm in diameter; bark pale grey; branches with few to many lenticels, pale brown or purple brown. Leaves decussately opposite, simple and entire; stipules absent; petiole 2–9 mm long; blade ovate to broadly ovate, 2–12.5 cm Χ 1–6.5 cm, base cuneate, rounded to slightly cordate, apex rounded or acuminate, papery or thinly leathery, with translucent dots. Inflorescence a terminal dichasial cyme, on long or short branches or in the forks, lax or congested, 1–12-flowered; peduncle 0–1 cm long; bracts ovate, narrowly ovate or narrowly triangular, 2–6 mm long, deciduous. Flowers bisexual, regular, 5-merous; pedicel 0.5–2 cm long; sepals free, slightly unequal, ovate or obovate, 3–11 mm long, obtuse or acute; corolla tube 15–27 mm long, widening at 15–35% of its length into a cylindrical upper part, at the mouth 6–13 mm wide, short-hairy, orange-yellow turning purple via dark red, white-streaked inside, corona lobes tongue-shaped, 2.5–7.5 mm long, obtuse, fleshy, minutely hairy, pink or violet, corolla lobes ovate, gradually narrowing into a narrow, spreading tail, lobes including the tail 25–75 mm long, hairy, reddish violet on the right outer side and whitish yellow on the left outer side, yellow on the inner side; stamens inserted at 5–7.5 mm from the base of the corolla tube, included; ovary half-inferior, 2-celled, style 5–7.5 mm long, ending in a ringlike pistil head surrounding the stigma. Fruit consisting of 2 ellipsoid follicles 12–27 cm Χ 1.5–2.5 cm, tapering into a broad and obtuse apex, 2-valved, divergent at 180–270°, wall thick and hard, many-seeded. Seeds spindle-shaped, slightly flattened, 8–16 mm Χ 2–4.5 mm, densely pubescent, at apex with a long beak up to 10 cm long, glabrous in lower half, upper half with long hairs up to 7 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 amboensis is a variable species. It flowers towards the end of the dry and the beginning of the rainy season; flowers appear before or with the leaves. Fruits mature at the beginning of the dry season.
Ecology
Strophanthus amboensis occurs in forest margins, woodland and thorn scrub, often in rock fissures, at 450–2000 m altitude.
Genetic resources and breeding
Strophanthus amboensis is rather widespread and not in danger of genetic erosion.
Prospects
Medicinal use of Strophanthus amboensis will be limited to local use in its area of distribution, unless further studies on the chemical constituents reveal new possibilities. Strophanthus amboensis has unusual and beautiful flowers, which makes it an interesting ornamental plant.
Major references
• Beentje, H.J., 1982. A monograph on Strophanthus DC. (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen 82–4. Wageningen, Netherlands. 191 pp.
• McKenzie, A.G., 2002. The rise and fall of strophanthin. International Congress Series 1242: 95–100.
• 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
• Hoffmann, L., 2005. Baum des Monats Februar. Wilde Mispel (Vangueria infausa) und Strophanthus amboensis. [Internet] Algemeine Zeitung online. Tourismus Namibia. Windhoek, Namibia. http://www.az.com.na/ index.php?page=news/ news.php&identifier=1079864137&id=10238 Accessed October 2005.
• Kawaguchi, K., Hirotani, M. & Furuya, T., 1988. Biotransformation of digitoxigenin by cell suspension cultures of Strophanthus amboensis. Phytochemistry 27: 3475–3479.
• Kawaguchi, K., Hirotani, M. & Furuya, T., 1989. Biotransformation of digitoxigenin by cell suspension cultures of Strophanthus intermedius. Phytochemistry 28: 1093–1097.
• Omino, E.A., 2002. Apocynaceae (part 1). In: Beentje, H.J. & Ghazanfar, S.A. (Editors). Flora of Tropical East Africa. A.A. Balkema, Rotterdam, Netherlands. 116 pp.
• Schindler, O., 1956. Die Glykoside der Samen von Strophanthus amboensis (Schinz) Engl. et Pax. 2. Mitteilung. Glykoside und Aglykone, 157. Mitteilung. Helvetica Chimica Acta 39(1): 64–79.
• Von Euw, J., Hess, H., Speiser, P. & Reichstein, T., 1951. Die Glycoside von Strophanthus intermedius Pax. Glycoside und Aglykone, 82. Mitteilung. Helvetica Chimica Acta 34(6): 1821–1833.
• Wall, M.E., 1955. Steroidal sapogenins. 25. Survey of plants for steroidal sapogenins and other constituents. Journal of the American Pharmacology Association 44(7): 438.
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 amboensis (Schinz) Engl. & Pax. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes mιdicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.