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Pentarrhinum abyssinicum Decne.

Protologue
DC., Prodr. 8: 553 (1844).
Family
Asclepiadaceae (APG: Apocynaceae)
Origin and geographic distribution
Pentarrhinum abyssinicum occurs in Cameroon, DR Congo, Rwanda, Burundi, Ethiopia, Kenya, Tanzania, Malawi, Zambia, Angola, Namibia and Zimbabwe.
Uses
In Kenya roots are chewed and the juice swallowed to treat stomach-ache. The roots can also be boiled and the decoction drunk for this purpose.
Botany
Perennial, climbing, latex-containing herb, with fibrous roots and strongly branched, annual shoots 2–2.5 m long, glabrous to pubescent; trichomes c. 0.3 mm long. Leaves opposite, simple and entire; petiole 1.5–3.5 cm long; blade ovate, 2.5–7 cm × 2–5 cm, base cordate to lobate, apex acute to acuminate. Inflorescence an axillary cyme, 5–15-flowered; peduncle 1.5–4.5 cm long. Flowers bisexual, regular, 5-merous, with aromatic scent; pedicel 0.5–2.5 cm long; calyx rotate, lobes ovate, up to 2.5 mm long, connate at base, pubescent outside; corolla with ovate lobes up to 4–5 mm × c. 3 mm, connate at base, fully reflexed at anthesis, margin glabrous or ciliate, yellowish green; corona 2–3 mm long, taller than gynostegium; anthers with connective appendages and wings; ovary superior, style apex flat. Fruit a pair of follicles, but usually only one developed, ellipsoid, c. 7 cm × c. 1.5 cm, long-beaked, brown, densely covered with 3–4 mm long protuberances, c. 40 seeds per fruit. Seeds ovoid, 6–7 mm × 4.5–5 mm, brown, margin not winged, apex with a coma of 1.5–2 mm long hairs.
Pentarrhinum comprises about 6 species nowadays, but is likely to become larger as species are being transferred to it from Cynanchum. The other widespread species is Pentarrhinum insipidum E.Mey., which occurs in Namibia, Zimbabwe and South Africa and again in northern Tanzania and Kenya, 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. In the literature, the name Pentarrhinum insipidum has sometimes erroneously been used for Pentarrhinum abyssinicum Decne.
Another Pentarrhinum species is used medicinally in East Africa. Pentarrhinum somaliense (N.E.Br.) Liede (synonym: Cynanchum somaliense (N.E.Br.) N.E.Br.) occurs throughout East Africa. A plant extract is taken to ease childbirth and to treat abdominal pains. In Ethiopia fruits are eaten by all age groups.
Ecology
Pentarrhinum abyssinicum occurs in open woodland, forest margins and grasslands, at 1000–2000 m altitude.
Genetic resources and breeding
Pentarrhinum abyssinicum is widespread and relatively common and it is therefore not threatened by genetic erosion.
Prospects
Pentarrhinum abyssinicum will probably remain of local importance as a medicinal plant, unless chemical and pharmacological research proves differently.
Major references
• Kokwaro, J.O., 1993. Medicinal plants of East Africa. 2nd Edition. Kenya Literature Bureau, Nairobi, Kenya. 401 pp.
• Liede, S. & Nicholas, A., 1992. A revision of the genus Pentarrhinum E. Meyer (Asclepiadaceae). Kew Bulletin 47(3): 475–490.
• Liede, S., 1997. Phylogenetic study of the African members of Cynanchum (Apocynaceae - Asclepiadoideae). Systematic Botany 22(2): 347–372.
Other references
• Addis, G., Urga, K. & Dikasso, D., 2005. Ethnobotanical study of edible wild plants in some selected districts of Ethiopia. Human Ecology 33(1): 83–118.
Author(s)
G.H. Schmelzer
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, Réduit, Mauritius
Associate editors
R. Arroo
Leicester School of Pharmacy, Natural Products Research, De Montfort University, The Gateway, Leicester LE1 9BH, United Kingdom

Correct citation of this article:
Schmelzer, G.H., 2010. Pentarrhinum abyssinicum Decne. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(2): Medicinal plants/Plantes médicinales 2. [CD-Rom]. PROTA, Wageningen, Netherlands.