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Pentarrhinum insipidum E.Mey.

Protologue
Comm. pl. Afr. austr.: 220 (1837).
Family
Asclepiadaceae (APG: Apocynaceae)
Chromosome number
2n = 22
Vernacular names
African heartvine (En).
Origin and geographic distribution
Pentarrhinum insipidum is widespread in Namibia, Zimbabwe and South Africa and again in the northern Tanzania-Kenya area, from where it extends into Ethiopia; it is known from one area in Sudan. Between those regions it is rare and has, for example, not yet been collected in northern Zambia or northern Malawi.
Uses
In southern Africa young leaves and fruits are used as raw or cooked vegetables. Sometimes the leaves are pounded with leaves of other species or with the tubers of several small Asclepiadaceae. The young fruits may be stored for 3 weeks before they deteriorate; older fruits (when the seeds inside have turned brown) become too hard to make good eating. They exude a copious amount of harmless latex and have a nutty, slightly peppery flavour.
In Tanzania a decoction of the leaves is used to wash boils, and after washing the boils are covered with hot leaves. In Malawi the roots are said to be used as medicine. The leaves might be a good fodder for domestic stock.
Properties
Pentarrhinum insipidum is certainly not poisonous, although it has been reported occasionally as being so. Fresh leaves contain per 100 g: water 85 g, energy 192 kJ (46 kcal), protein 3.5 g, fat 0.5 g, carbohydrate 6.7 g, fibre 2 g, Ca 370 mg, P 63 mg, Fe 9 mg, thiamin 0.2 mg, riboflavin 0.3 mg, niacin 1 mg, ascorbic acid 16 mg. Fresh young fruits contain per 100 g: water 88 g, energy 157 kJ (37 kcal), protein 2.3 g, fat 0.2 g, carbohydrate 6.6 g, fibre 1.5 g, Ca 72 mg, P 47 mg, Fe 0.8 mg (Arnold, T.H., Wells, M.J. & Wehmeyer, A.S., 1985).
Botany
Perennial, climbing, latex-containing herb, with elongated tuberous roots and strongly branched, annual shoots 2–3 m long, glabrous to sparsely pubescent. Leaves opposite, simple; petiole 2–5 cm long; blade ovate, 2.5–6.5 cm ื 2–5 cm, base cuneate to cordate, apex acuminate, margin entire. Inflorescence cymose, 5–15-flowered; peduncle 3–4 cm long. Flowers bisexual, regular, 5-merous, with aromatic scent; pedicel 0.5–2 cm long; calyx rotate, lobes triangular, up to 2.5 mm long, connate at base, pubescent outside; corolla with ovate to oblong lobes up to 6 mm ื 3.5 mm, connate at base, fully reflexed at anthesis, margin ciliate, green-yellowish; corona c. 3 mm long, fleshy, at apex with horn-like ornaments; anthers with connective appendages and wings; ovary superior, style apex flat. Fruit a pair of follicles, but usually only one developed, ellipsoid, 5–9 cm ื 1.5–2 cm, pale brown, smooth to densely covered with 2–4 mm long protuberances. Seeds ovoid, about 6 mm ื 2 mm, brown, margin winged, apex with a coma of 3–4 mm long hairs.
Pentarrhinum comprises only 2 species. The other species is Pentarrhinum abyssinicum Decne., which is more widely distributed but more scattered than Pentarrhinum insipidum, occurring from Cameroon to Namibia and from Ethiopia to Zimbabwe. In the literature, the name Pentarrhinum insipidum has sometimes erroneously been used for Pentarrhinum abyssinicum.
Ecology
Pentarrhinum insipidum is associated with shrubland and savanna, in dry or well-drained conditions, but does not tolerate extremes of dry and wet. It ranges from sea-level up to 2200 m altitude, but is most common between 600–1600 m.
Management
Pentarrhinum insipidum can easily be grown from seed and is a rapid producer of green material.
Genetic resources and breeding
Pentarrhinum insipidum is widespread in East and southern Africa and not in danger of genetic erosion.
Prospects
In southern Africa Pentarrhinum insipidum is an important vegetable from the wild. It is considered to have some potential for development as a commercial vegetable. Its medicinal value needs confirmation.
Major references
• Arnold, T.H., Wells, M.J. & Wehmeyer, A.S., 1985. Khoisan food plants: taxa with potential for future economic exploitation. In: Wickens, G.E., Goodin, J.R. & Field, D.V. (Editors). Plants for arid lands. Proceedings of the Kew International Conference on Economic Plants for Arid Lands. Allen & Unwin, London, United Kingdom. pp. 69–86.
• Liede, S. & Nicholas, A., 1992. A revision of the genus Pentarrhinum E. Meyer (Asclepiadaceae). Kew Bulletin 47(3): 475–490.
• Story, R., 1958. Some plants used by the bushmen in obtaining food and water. Memoirs of the Botanical Survey of South Africa No. 30. 113 pp.
Other references
• Burkill, H.M., 1985. The useful plants of West Tropical Africa. 2nd Edition. Volume 1, Families A–D. Royal Botanic Gardens, Kew, United Kingdom. 960 pp.
• van Wyk, B.E., van Oudtshoorn, B. & Gericke, N., 1997. Medicinal plants of South Africa. Briza Publications, Pretoria, South Africa. 304 pp.
• 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.
• Williamson, J., 1955. Useful plants of Nyasaland. The Government Printer, Zomba, Nyasaland. 168 pp. (Reprint: Williamson, J., 1975. Useful plants of Malawi. University of Malawi, Zomba, Malawi).
Author(s)
• P.C.M. Jansen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
• G.J.H. Grubben
Prins Hendriklaan 24, 1401 AT Bussum, Netherlands
• O.A. Denton
National Horticultural Research Institute, P.M.B. 5432, Idi-Ishin, Ibadan, Nigeria
Associate Editors
• C.-M. Messiaen
Bat. B 3, R้sidence La Guirlande, 75, rue de Fontcarrade, 34070 Montpellier, France
• R.R. Schippers
De Boeier 7, 3742 GD Baarn, 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:
Jansen, P.C.M., 2004. Pentarrhinum insipidum E.Mey. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/L้gumes. [CD-Rom]. PROTA, Wageningen, Netherlands.