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Strophanthus sarmentosus DC.

Protologue
Bull. Sci. Soc. Philom. Paris 3: 123, t. 8, fig. 1 (1802).
Family
Apocynaceae
Chromosome number
2n = 18
Vernacular names
Spider tresses, poison arrow vine (En).
Origin and geographic distribution
Strophanthus sarmentosus occurs from Senegal east to the Central African Republic, northern DR Congo and southern Uganda, and south to Angola (Cabinda).
Uses
In West Africa the seed is used to make arrow poison, especially in the drier parts where Strophanthus hispidus DC. is scarce or absent. Strophanthus sarmentosus seeds are usually mixed with parts of other plants and boiled in water, after which the decoction is concentrated into a poisonous syrup in which the arrow tips are dipped. The plant enters into local medicine throughout West Africa. In Senegal a root decoction is taken to treat gonorrhoea and leprosy. A macerate of pounded roots is taken on an empty stomach to treat painful joints and hernia. The powdered roots cooked together with the grains of Digitaria exilis (Kippist) Stapf are taken to treat flatulence with constipation, without causing painful purging. In Guinea the crushed seeds are applied to the head to kill lice, and in Liberia they are applied to scabies. In Côte d’Ivoire a leaf decoction is used as an eye drop to treat conjunctivitis and trachoma. A decoction of the twigs is taken to treat rheumatoid arthritis, while the leaf sap is drunk and the bark macerate used as an enema to treat venereal diseases. They are considered diuretic and soothing. A leaf decoction is taken as emetic and to treat diarrhoea, whereas a root decoction is taken as vermifuge or to restore strength. In Senegal and Côte d’Ivoire the latex is applied to wounds and sores as a cicatrisant. In Senegal the plant is therefore used in circumcision ceremonies. In Benin a leaf decoction mixed with other plants is taken as a remedy against snakebites. In Congo the stems and leaves are used to make steam baths and infusions against rheumatism. In the 1950s a seed extract was used to combat rheumatoid arthritis in the United States and Europe. In Nigeria the stems are used to make bows and the bark to make ropes, hats and mats.
Production and international trade
In the early 1950s the fruits of Strophanthus sarmentosus, mixed with those of other Strophanthus spp., were collected and exported on a large scale from West Africa as raw material for the production of cortisone. Since then, easier methods of making this compound have been found, and collection stopped as quickly as it had started.
Properties
The composition of cardiac glycosides (cardenolides) in Strophanthus sarmentosus seeds is very variable. Four chemical types are distinguished, based on the weakly polar chloroform-soluble glycosides, of which 2 are widespread. The first type occurs throughout the distribution area of Strophanthus sarmentosus, and its main constituents are the sarverogenin glycosides panstroside and sarveroside. The second type occurs only in West Africa, with main constituents the sarmentogenin glycosides sarnovide and sarmentocymarin. The third type is rare and occurs only in southern Mali. Its main constituents are musaroside and sarmutoside, which yield the aglycone sarmutogenin. The fourth type occurs from west Côte d’Ivoire to Sierra Leone and is characterized by a very low level of glycosides, mainly of the aglycone sarverogenin, with sarveroside sometimes replaced by intermedioside. The water-soluble glycosides of the 4 types are strongly polar and so far 18 have been identified. These polar glycosides are mainly derivatives of 7 aglycones of different oxidation states, with as main compounds sarmentoside A, tholloside, sarhamnoloside, locundioside and bipindoside. The seed also contains traces of ouabain. All other plant parts also contain glycosides but except for the latex, only in traces. Most of the isolated glycosides are highly toxic.
Sarmentoside A increased the force and rate of rabbit heart contractions in vitro; this cardio-active property was similar to digoxin, a Digitalis glycoside. The aglycone sarmentogenin was used in the 1950s to manufacture cortisone, as it contains a 11-ketocorticosteroid. Cortisone was at that time a new medicine for arthritis and cardiac rheumatism, and it was thought that large amounts were needed to treat patients, but it was later found that doses needed were much lower. Due to the fame of Strophanthus for cortisone production, more research into the botany and chemistry was done, especially on other corticosteroids and sex-hormones. As the concentration of sarmentogenin for cortisone production was found to be very variable in the seeds of Strophanthus sarmentosus, other methods were developed to obtain 11-ketocorticosteroids more easily from other plant species, e.g. from the sapogenin diosgenin from Dioscorea spp., and from hecogenin from Agave spp. The demand for the seed of Strophanthus sarmentosus then collapsed.
Adulterations and substitutes
The seeds of Strophanthus hispidus are more commonly used in West Africa for arrow poison than those of Strophanthus sarmentosus, except in the dry regions, where the former is rare or absent. In the forest regions, especially east of Cameroon, Strophanthus gratus (Wall. & Hook.) Franch. is preferred over Strophanthus sarmentosus.
Description
Deciduous shrub with long trailing stems or liana up to 40 m long, with clear or white exudate, stem up to 15 cm in diameter; bark pale brown, corky and deeply fissured; branches with many lenticels, dark brown or reddish brown, with many up to 1 cm high corky protuberances. Leaves decussately opposite or in whorls of 3, simple and entire; stipules absent; petiole 2–17(–20) mm long; blade elliptical to ovate, 2–15 cm × 1.5–7 cm, base rounded to cuneate, apex acuminate, margin often undulate or slightly revolute, glabrous. Inflorescence a congested terminal dichasial cyme, on short branches or less often on long branches or in the forks, 1–5(–11)-flowered; peduncle 0–6(–10) mm long; bracts ovate, 4.5–13.5 mm long, sepal-like. Flowers bisexual, regular, 5-merous, fragrant; pedicel 2–12 mm long; sepals free, slightly unequal, ovate to elliptical, 5–20 mm long, acute; corolla tube 15–40 mm long, widening at 22–35% of its length into a cup-shaped upper part, at the mouth 15–30 mm wide, white and turning yellow in the lower part 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 and often undulate, 5–22 mm long, tip acute, white, pink-or purple-streaked, the white turning yellow, corolla lobes ovate, 7–20 mm × 6–18 mm, gradually or rather abruptly narrowing into the 1–2.5 mm wide pendulous tail, lobes including the tail 4–14 cm long, white and turning yellow on both sides, outside near the base pink or purple, tails pale yellow; stamens inserted at 7–13.5 mm from the base of the corolla tube, included; ovary half-inferior, 2-celled, style 9–17.5 mm long, ending in a pistil head surrounding the minute stigma. Fruit consisting of 2 ellipsoid follicles 10–28 cm × 1.5–4.5 cm, tapering into a broad and obtuse apex, 2-valved, divergent at 180°, wall thick and hard, glabrous, slightly grooved, with many lenticels, many-seeded. Seeds spindle-shaped, 8–20 mm × 2–4 mm, densely hairy, at apex with a long beak up to 8 cm long, glabrous in lower half, upper half with long hairs up to 10 cm long.
Other botanical information
Strophanthus comprises 38 species, of which 30 occur in continental Africa, 1 in Madagascar and 7 in Asia, from India to South-East Asia. Two varieties of Strophanthus sarmentosus are distinguished, the very common var. sarmentosus with shortly hairy flowers and the rare var. glabriflorus Monach., restricted to Guinea, with glabrous flowers.
Growth and development
Strophanthus sarmentosus flowers in the dry season, just before the leaves expand. Fruits mature in the dry season. Cultivated plants have reached ages of over 55 years.
Ecology
Strophanthus sarmentosus occurs in rain forest, gallery forest and thickets, from sea-level up to 1400 m altitude.
Management
Though Strophanthus sarmentosus is not cultivated, it is sometimes spared when clearing woodland and tended. Compared to Strophanthus hispidus, Strophanthus sarmentosus does not grow easily from rooted stems, and produces less fruit in cultivation than in the wild.
Harvesting
Fruits are harvested before maturity, as otherwise they open and the seeds disperse.
Handling after harvest
For arrow-poison use, the almost mature fruits are kept in a pot until they open. The seeds are then cleaned by removing the tuft of hair by stirring or burning, and they are roasted to preserve their chemical properties by destroying the enzyme, which converts the glycosides into biologically inactive compounds when the seeds are stored for a long time or become damp.
Genetic resources
Strophanthus sarmentosus has a wide distribution, but is not common. Although it is represented in botanic gardens in both tropical and temperate regions, no concerted efforts to conserve genetic resources or breeding programmes are known.
Prospects
The medicinal of use of Strophanthus sarmentosus will remain limited unless further studies on the chemical constituents reveal new possibilities. Strophanthus sarmentosus can be grown as an ornamental, as it has beautiful flowers, but as propagation is not easy, it will probably remain of minor importance.
Major references
• Beentje, H.J., 1982. A monograph on Strophanthus DC. (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen 82–4. Wageningen, Netherlands. 191 pp.
• Burkill, H.M., 1985. The useful plants of West Tropical Africa. 2nd Edition. Volume 1, Families A–D. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 960 pp.
• Hegnauer, R., 1964. Chemotaxonomie der Pflanzen. Band 3. Birkhäuser Verlag, Basel, Switzerland. 743 pp.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
Other references
• Arbonnier, M., 2004. Trees, shrubs and lianas of West African dry zones. CIRAD, Margraf Publishers Gmbh, MNHN, Paris, France. 573 pp.
• Beentje, H.J. & Cooke, D., 2000. Strophanthus sarmentosus: Apocynaceae. Curtis’s Botanical Magazine 17(4): 202–207.
• Burkill, H.M., 2000. The useful plants of West Tropical Africa. 2nd Edition. Volume 5, Families S–Z, Addenda. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 686 pp.
• Neuwinger, H.D., 1996. African ethnobotany: poisons and drugs. Chapman & Hall, London, United Kingdom. 941 pp.
• Owonubi, M.O. & Iwalewa, E.O., 1997. Cardio-activity of sarmentoside-A from Strophanthus sarmentosus seeds. Nigerian Journal of Natural Products and Medicine 1: 16–18.
Sources of illustration
• Beentje, H.J., 1982. A monograph on Strophanthus DC. (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen 82–4. Wageningen, Netherlands. 191 pp.
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, Réduit, 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
Photo editor
A. de Ruijter
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Beentje, H.J., 2006. Strophanthus sarmentosus DC. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
Distribution Map wild


1, flowering branch; 2, fruit, one follicle removed; 3, seed.
Redrawn and adapted by Iskak Syamsudin



flowering branch


flowering branch


inflorescence