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Euphorbia subsalsa Hiern

Protologue
Cat. afr. pl. 1(4): 948 (1900).
Family
Euphorbiaceae
Origin and geographic distribution
Euphorbia subsalsa occurs in Angola and Namibia.
Uses
A powder is prepared by pounding the sun-dried stem, from which the thorns are burnt off. This powder is smeared on incisions of the skin to ease pain when making tattoos.
In northern Namibia latex of Euphorbia subsalsa is occasionally added to arrow poison made from the bitter root sap or latex of Adenium boehmianum Schinz, or arrow or spear poison made from the seeds or latex of Fockea multiflora K.Schum. to increase their efficacy. The Himba people of Namibia mainly use the latex to kill wild animals by poisoning the drinking water.
Botany
Monoecious shrub up to 60(–120) cm tall, branching from the base; branches 4-angled, angles with wavy teeth up to 2 cm apart; stem up to 1 cm in diameter, not or distantly constricted into segments, pale green with a longitudinal stripe, with white latex; spine shield elongated, often joined into a horny margin, with 2 pairs of spines closely set on each spine shield, the lower pair 6–16 mm long, sturdy, the upper pair 2–5 mm long, brown or dark grey. Leaves rudimentary, scale-like, minute, soon falling; stipules modified into small spines on the upper part of the spine shield. Inflorescence an axillary, almost sessile, simple cyme, consisting of clusters of flowers, each cluster called a ‘cyathium’; cyme branches 0–2, short; bracts 2; cyathia c. 3 mm in diameter, with a shortly cup-shaped involucre, green, 5-lobed with broadly ovate, fringed, emarginate lobes, glands 5, elliptical, not touching, yellow, female flower 1, surrounded by many male flowers. Flowers unisexual; male flowers sessile, perianth absent, stamen shortly exserted; female flowers almost sessile, perianth 3-lobed, ovary superior, glabrous, 3-celled, styles 3, fused at base. Fruit an almost sessile, obtusely 3-lobed capsule 2.5–3.5 mm in diameter, glabrous, brown, 3-seeded. Seeds ovoid, c. 2 mm long, with small warts.
Euphorbia comprises about 2000 species and has a worldwide distribution, with at least 750 species occurring in continental Africa and about 150 species in Madagascar and the Indian Ocean islands. Euphorbia subsalsa belongs to subgenus Euphorbia, section Euphorbia, a large group which is characterized by succulent, angular stems, stipules modified into small spines, a spine shield with an additional pair of spines (sometimes fused into a single spine), axillary inflorescences and seeds without a caruncle. Euphorbia subsalsa and the species mentioned below are characterized by the small size of the plants and the branched, 4-angled, succulent stems with 4 spines per spine shield and almost sessile fruits.
Euphorbia kaokoensis (A.C.White, R.A.Dyer & B.Sloane) L.C.Leach is endemic to Namibia. It was formerly considered a variety of Euphorbia subsalsa, but is distinguished by its 5–7-ribbed branches, longer and more densely set spines; its medicinal uses are similar to those of Euphorbia subsalsa. Euphorbia tenuispinosa Gilli occurs in Kenya and Tanzania; the Galla people in Kenya use the latex as the main ingredient of arrow poison. Euphorbia schinzii Pax occurs in Botswana, Zimbabwe and northern South Africa; references to its presence in Kenya probably concern Euphorbia angustiflora Pax. In Zimbabwe root powder is rubbed into scarifications on the breasts as a galactagogue. Euphorbia uhligiana Pax occurs in Kenya and Tanzania. A stem decoction is drunk to treat colds. Sap is applied to wounds to heal them. In Kenya a bitter root and stem decoction is taken to treat fever, including malaria. Euphorbia virosa Willd. occurs in Angola, Namibia and the Cape Province of South Africa. In northern Namibia latex is added to arrow poison made from the bitter root sap or latex of Adenium boehmianum Schinz. Latex or powder of dried branches is used to poison hyenas and jackals, and also to poison waterholes. Black rhinoceros is reported to browse the plant. The latex contains esters of diterpene alcohols of the tigliane type. Honey from Euphorbia virosa is unpalatable because it causes a burning sensation when eaten.
Ecology
Euphorbia subsalsa occurs in shrubland, often dominated by mopane (Colophospermum mopane (Benth.) J.Léonard), at about 1000 m altitude. It occurs mainly on calcareous soils.
Management
Euphorbia subsalsa is only harvested from the wild.
Genetic resources and breeding
Although Euphorbia subsalsa occurs in a relatively small area, there are no signs that it is threatened by genetic erosion. As a (semi-)succulent Euphorbia species, its trade is controlled under CITES appendix 2.
Prospects
The latex of Euphorbia subsalsa is apparently very poisonous and it will remain of local importance only, unless chemical or pharmacological research demonstrates interesting properties.
Major references
• Eggli, U. (Editor), 2002. Illustrated handbook of succulent plants: Dicotyledons. Springer, Berlin, Germany. 554 pp.
• Neuwinger, H.D., 1996. African ethnobotany: poisons and drugs. Chapman & Hall, London, United Kingdom. 941 pp.
• SEPASAL, 2008. Euphorbia subsalsa. [Internet] Survey of Economic Plants for Arid and Semi-Arid Lands (SEPASAL) database. Royal Botanic Gardens, Kew, Richmond, United Kingdom. http://www.kew.org/ ceb/sepasal/. Accessed February 2008.
• van Wyk, B.E. & Gericke, N., 2000. People’s plants: a guide to useful plants of southern Africa. Briza Publications, Pretoria, South Africa. 351 pp.
Other references
• Beentje, H.J., 1994. Kenya trees, shrubs and lianas. National Museums of Kenya, Nairobi, Kenya. 722 pp.
• Brown, N.E., Hutchinson, J. & Prain, D., 1909–1913. Euphorbiaceae. In: Thiselton-Dyer, W.T. (Editor). Flora of tropical Africa. Volume 6(1). Lovell Reeve & Co., London, United Kingdom. pp. 441–1020.
• Gelfand, M., Mavi, S., Drummond, R.B. & Ndemera, B., 1985. The traditional medical practitioner in Zimbabwe: his principles of practice and pharmacopoeia. Mambo Press, Gweru, Zimbabwe. 411 pp.
• Heine, B. & Heine, I., 1988. Plant concepts and plant use; an ethnobotanical survey of the semi-arid and arid lands of East Africa. Part 3. Rendille plants (Kenya). Cologne Development Studies 8. Breitenbach, Saarbrücken, Germany. 120 pp.
• Kokwaro, J.O., 1993. Medicinal plants of East Africa. 2nd Edition. Kenya Literature Bureau, Nairobi, Kenya. 401 pp.
• SEPASAL, 2008. Euphorbia virosa. [Internet] Survey of Economic Plants for Arid and Semi-Arid Lands (SEPASAL) database. Royal Botanic Gardens, Kew, Richmond, United Kingdom. http://www.kew.org/ ceb/sepasal/. Accessed February 2008.
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
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:
Schmelzer, G.H., 2008. Euphorbia subsalsa Hiern. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.