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Euphorbia ingens E.Mey. ex Boiss.

Protologue
A.DC., Prodr. 15(2): 87 (1862).
Family
Euphorbiaceae
Chromosome number
2n = 40
Synonyms
Euphorbia similis A.Berger (1907).
Vernacular names
Candelabra tree, common tree euphorbia (En).
Origin and geographic distribution
Euphorbia ingens occurs from the Caprivi strip (Namibia), Zambia and Botswana east to Mozambique and south to eastern South Africa and Swaziland.
Uses
The latex is very toxic, causing intense irritation and blistering to the skin and mucous membranes. If the latex comes into contact with the eyes, it causes temporary or even permanent blindness. Medicinally, the latex is taken in very small amounts, often on sugar, as a drastic purgative and to treat alcohol dependency. Pulverized root or a few drops of latex in porridge is eaten to treat bronchitis. In Zimbabwe the stems of Brachystegia spiciformis Benth. are chewed and the fibres dipped in the latex of Euphorbia ingens; the fibres are then dried and burnt and the smoke inhaled to treat asthma and bronchitis. In South Africa the Venda people use the latex to treat chronic ulcers, warts and cancer. There are several cases recorded of overdoses, causing vomiting, violent abdominal pain and excessive purging, and even death.
In Zimbabwe and South Africa a bundle of grass soaked in latex is thrown into water as a fish poison.
The wood is light and tough and is used to make boats, planks and doors. Before cutting, the trunk is scorched to prevent the toxic latex from splashing. The flowers of Euphorbia ingens and several other tree-sized Euphorbia spp. produce much nectar, but the honey, known as ‘noors honey’, causes a burning sensation in the mouth, which is intensified by drinking water. Euphorbia ingens is planted as an ornamental in succulent gardens or rock gardens in South Africa and the United States.
Properties
The latex and roots of Euphorbia ingens contain ingenol, a tetracyclic diterpene ester of the ingenane type, based on the parent alcohol 16-hydroxyingenol and several derivatives. Ingenol and its derivatives show tumour-promoting, anti-HIV and anti-leukaemia activities. Much research is directed toward synthesis and biological evaluation of ingenol analogs and derivatives. The irritant ingenol esters of the latex have ID50 values of 0.004–0.02 μg in mice-ear tests.
An extract of the pounded branches in water was given to chickens before or during a Newcastle disease outbreaks. The rate of mortality reduction ranged between 38% for chickens given the extract during Newcastle disease outbreak as a therapeutic measure and 100% for chickens given the extract as a prophylactic measure.
Different concentrations of latex were used in mortality tests with several aquatic animals. The latex was found to be a short-lived and effective fish poison. Within 12 hours all the fish and half the frogs died, whereas crabs and snails appeared not to suffer any detrimental effects. The poison degraded and became harmless to fish within 48 hours.
Botany
Monoecious, succulent small tree up to 12(–15) m tall, with abundant latex; bole stout; bark grey, roughly fissured; branches persistent from c. 3 m upwards, almost erect, rebranching, forming a large, broadly rounded crown; terminal branches fleshy, 6–12 cm in diameter, constricted at irregular intervals into oblong segments 10–15 cm long, 4-angled, wings up to 3 cm wide, margins of angles straight to wavy, with shallow tubercles 1–2 cm apart; spine shields obtusely triangular, c. 6 mm × 5 mm, soon becoming corky, with 2 pairs of spines, 1 pair stout, c. 5 mm long, 1 (stipular) pair triangular, c. 1.5 mm long, flexible, soon falling. Leaves at the end of branches, in 4 rows, sessile; stipules transformed into small spines; blade obovate, c. 3 mm × 3 mm, soon falling, in young plants up to 8 cm × 2 cm. Inflorescence an axillary cyme, 1–3 together crowded at the end of branches, consisting of clusters of flowers, each cluster called a ‘cyathium’, peduncle 8–20 mm long, branches 2, c. 5 mm long; bracts 2, c. 5 mm long; cyathia c. 5 mm × 10 mm, with a cup-shaped involucre, lobes c. 2.5 mm long, glands 5, transversely elliptical, c. 2 mm × 4 mm, golden-yellow, each involucre containing 1 female flower surrounded by many male flowers. Flowers unisexual; male flowers sessile, perianth absent, stamen c. 5.5 mm long; female flowers with pedicel c. 5 mm long in fruit, perianth irregularly 3-lobed, lobes filiform, 2–4 mm long, ovary superior, glabrous, 3-celled, styles 3, 3–3.5 mm long, fused at base, apex 2-fid. Fruit an obtusely 3-lobed capsule c. 7 mm × 10 mm, fleshy, green becoming red, hardening before dehiscence, 3-seeded. Seeds almost globose, c. 4 mm × 3 mm, greyish brown speckled with pale brown, smooth.
The flowers of Euphorbia ingens are pollinated by butterflies, bees and other insects, and the seeds are dispersed by birds, which feed on the fruits. Birds also like nesting in these trees; hole-nesting birds such as woodpeckers often use dead sections.
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 ingens belongs to section Euphorbia, a large group which is characterized by succulent, usually angular stems, stipules modified into small spines (or absent), a spine shield with an additional pair of spines (sometimes fused into a single spine), axillary inflorescences and seeds without a caruncle. Euphorbia ingens is very similar to Euphorbia candelabrum Trémaux ex Kotschy from East and northeastern Africa, and may be conspecific. The branches of trees in southern Africa are usually more distinctly and shortly segmented, the tubercle teeth along the angles are usually further apart and the branch tips are fewer-flowered.
Euphorbia conspicua N.E.Br. is a small tree up to 15 m tall endemic to western Angola; it is also very similar to Euphorbia candelabrum. The latex is taken as a purgative to treat constipation, and also to treat breast inflammation, epilepsy, coughs and tuberculosis.
Ecology
Euphorbia ingens occurs in dry mopane and wooded grassland, often on rocky outcrops, from sea-level up to 1600 m altitude. It can survive in areas that go through long periods of drought or are generally very dry.
Management
As an ornamental Euphorbia ingens is a hardy succulent and needs little or no maintenance. It does best in the open sun.
Genetic resources and breeding
Euphorbia ingens is relatively common in its distribution area; small trees are only browsed by rhinoceros, and therefore it is not threatened by genetic erosion. All succulent Euphorbia spp. are listed in CITES appendix 2.
Prospects
The latex of Euphorbia ingens is highly poisonous and medicinally it should therefore be used with great care. Only few chemical analyses have been done, and virtually no pharmacological tests. Because the latex contains ingenol and derivatives more research is warranted.
Major references
• Carter, S. & Leach, L.C., 2001. Euphorbiaceae, subfamily Euphorbioideae, tribe Euphorbieae. In: Pope, G.V. (Editor). Flora Zambesiaca. Volume 9, part 5. Royal Botanic Gardens, Kew, Richmond, United Kingdom. pp. 339–465.
• Coates Palgrave, K., 1983. Trees of southern Africa. 2nd Edition. Struik Publishers, Cape Town, South Africa. 959 pp.
• Kellerman, T.S., Coetzer, J.A.W. & Naudé, T.W., 1988. Plant poisonings and mycotoxins of livestock in southern Africa. Oxford University Press, Cape Town, South Africa. 243 pp.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• van Wyk, B.E., van Heerden, F. & van Oudtshoorn, B., 2002. Poisonous plants of South Africa. Briza Publications, Pretoria, South Africa. 288 pp.
Other references
• Bossard, E., 1996. La médecine traditionelle au Centre et à l’Ouest de l’Angola. Ministério da Ciência e da Tecnologia, Instituto de Investigação Cientifico Tropical, Lissabon, Portugal. 531 pp.
• Carter, S., 1985. Euphorbia candelabrum, a question of validity (Euphorbiaceae). Taxon 34(4): 699–701.
• Grace, O.M., Prendergast, H.D.V., Jäger, A.K. & van Staden, J., 2002. Bark medicines in traditional healthcare in KwaZulu-Natal, South Africa: an inventory. South African Journal of Botany 69(3): 301–363.
• Kaoma, C. & Chiteta, K., 2001. Effect of Euphorbia ingens on Newcastle disease in local chickens. Agricultura Tropica et Subtropica 34: 87–91.
• Le Roux, L.-N., 2004. Euphorbia ingens. [Internet] South African National Biodiversity Institute, Cape Town, South Africa. http://www.plantzafrica.com/ plantefg/euphorbingen.htm Accessed February 2008.
• Opferkuch, H.J., Adolf, W., Sorg, B., Kusumoto, S. & Hecker, E., 1981. The chemistry of ingenol 1. Ingenol and some of its derivatives. Zeitschrift für Naturforschung, Teil B Anorganische Chemie – Organische Chemie 36(7): 878–887.
• Opferkuch, H.J. & Hecker, E., 1982. The active principles of the spurge family Euphorbiaceae 4. Skin irritant and tumor promoting di terpene esters from Euphorbia ingens. Journal of Cancer Research and Clinical Oncology 103(3): 255–268.
• Ross, M.J. & Steyn, G.-J., 2004. Preliminary results on the ichthyocidal properties of Euphorbia ingens (Euphorbiaceae). African Journal of Aquatic Science 29(2): 265–269.
• SEPASAL, 2008. Euphorbia ingens. [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.
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
Photo editor
A. de Ruijter
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Schmelzer, G.H., 2008. Euphorbia ingens E.Mey. ex Boiss. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
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