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Euphorbia poissonii Pax

Protologue
Bull. Mus. natn. Hist. nat., Paris 8: 62 (1902).
Family
Euphorbiaceae
Vernacular names
Candle plant (En).
Origin and geographic distribution
Euphorbia poissonii occurs from southern Burkina Faso and Ghana east to Cameroon. It possibly also occurs in Guinea, Côte d’Ivoire and Mali.
Uses
The latex of Euphorbia poissonii is very caustic and toxic, and very irritating to the skin and mucous membranes. It can cause blindness when in contact with the eyes. Despite its toxicity, it is used medicinally. In Nigeria a few drops of latex are applied to Guinea-worm sores and to skin papilloma. A few drops of latex with sugar cane or in palm wine or soup are taken as a purgative. In Cameroon the latex extracted from the leaves is applied to treat lumbago. It is also placed in a carious tooth to relieve toothache or to help to loosen the tooth and render extraction easier.
Throughout West Africa the latex is used as fish poison. A piece of stem is mixed with the seeds of Strophanthus to prepare arrow poison. In Nigeria the latex is said to be added sometimes to tobacco snuff to increase its pungency. The Hausa people use the latex on cereals to catch guinea fowl. The latex is also used in bait to kill rodents and birds, and is used for removing hairs from hides. The latex is applied as glue on branches to capture birds. The latex is highly poisonous when added to food, drinking water and kola nuts, and in Nigeria homicides are sometimes committed through Euphorbia poissonii poisoning.
In West Africa Euphorbia poissonii is sometimes planted in gardens as an ornamental plant or as a hedge around fields and graveyards. In Europe and the United States it is kept as a pot plant in succulent collections. The flowers are much visited by bees and other insects.
Euphorbia poissonii closely resembles Euphorbia unispina N.E.Br., and they have similar uses.
Production and international trade
Several compounds isolated from Euphorbia poissonii are internationally traded. Resiniferatoxin was sold on the internet in 2007 for US$ 35 (1 mg) to US$ 525 (25 mg); tinyatoxin was sold for US$ 60 (1 mg) to US$ 240 (5 mg). Euphorbia poissonii is also traded on the internet as an ornamental plant.
Properties
The latex of Euphorbia poissonii contains esters of the diterpene tigliane type alcohols 12-deoxyphorbol and 12-deoxy-16-hydroxyphorbol, the diterpene daphnane type alcohol resiniferonol, and several esters of the macrocyclic diterpene alcohol 19-hydroxyingol, e.g. the pentacyclic euphorianin. Most compounds isolated are mono- and di-esters of 12-deoxyphorbol. Daphnane esters are generally known for their potent skin irritant properties, whereas tigliane esters are toxic and tumour promoters; however, some of the tigliane compounds, especially 12-deoxyphorbol derivatives, possess anticancer activities.
The variety of irritant compounds present in high concentrations is reflected by the irritant activity of the latex, which is more than 30 times stronger in Euphorbia poissonii latex (ID50 = 0.1 μg / 5 μl) than in the latex of e.g. Euphorbia unispina, although after 24 hours both activities have almost the same value. The isolated aromatic esters of the daphnane type are more potent irritants in mouse ear tests than the aromatic tigliane esters, especially resiniferatoxin (ID50 = 0.00021 nMol / 5 μg) and tinyatoxin (ID50 = 0.0012 nMol / 5 μg). Of the 6 isolated aromatic tigliane esters, the highly irritant 12-deoxyphorbol-13-O-phenylacetate-20-O-acetate (ID50 = 0.075 nMol / 5 μg) is the major compound; candletoxin A, candletoxin B and DPP ( 12-deoxyphorbol 13-phenylacetate) are also strongly irritant. The irritant activity of resiniferatoxin and tinyatoxin is rapid. It reaches a maximum within 4 hours and then fades to inactivity after 24 hours.
Resiniferatoxin and tinyatoxin are highly toxic, as they bind to pain receptors in the same way as capsaicin, but much more powerfully. They stimulate the neurons to fire repeatedly until the neuron dies, causing searing pain and sending the victim into severe anaphylactic shock. Resiniferatoxin is used in the treatment of incontinence associated with an overactive bladder. It also has antifeedant and analgesic properties. Efforts have been made to synthesize this compound. In laboratory tests, DPP induced the expression of HIV-1 in latently infected T cells and rendered them sensitive to killing by an immunotoxin. DPP is 20- to 40-fold more potent than the related phorbol ester prostratin, and the combination of high potency and antitumour promoting activity makes DPP an attractive candidate for therapy of HIV-1 infection.
During further phytochemical studies on the latex, derivatives of 19-hydroxyingol were isolated. These compounds showed cytotoxic activities against 6 human solid tumour cell lines (lung carcinoma, breast carcinoma, colon adrenocarcinoma, kidney carcinoma, prostate adenocarcinoma and pancreatic carcinoma). Moreover, most of the 12-deoxyphorbol ester derivatives showed selective cytotoxicity for the human kidney carcinoma cell line with potencies for one compound exceeding those of the anticancer drug adriamycin by 10,000 times.
A root extract of Nigerian material, screened for molluscicidal activity on the freshwater snail Bulinus globulus, was reported as being inert.
Description
Monoecious, candelabriform shrub up to 2 m tall; branches cylindrical, 3–3.5(–4) cm in diameter, silvery grey, covered with prominent rounded tubercles and horny spine shields up to 8 mm in diameter, grey, with 1 spine on young plants or spine rudimentary, with white latex. Leaves arranged spirally at stem apex in 8–10 ranks, simple and entire, soon falling; stipules, if present, modified into small spines, soon falling; petiole short, thick; blade obovate to spoon-shaped, 5–14 cm × 3–7 cm, base long-cuneate, apex deeply notched, fleshy, glabrous, pinnately veined. Inflorescence an axillary cyme, numerous at the ends of branches, consisting of clusters of flowers, each cluster called a ‘cyathium’; peduncle and branches short; bracts 2, ovate, c. 2 mm long, membranous; cyathia c. 8 mm in diameter, with a shortly funnel-shaped involucre, green, 5-lobed with broadly ovate, fringed lobes, glands 5, elliptical, touching, green, each involucre containing 1 female flower surrounded by many male flowers. Flowers unisexual; male flowers sessile, perianth absent, stamen shortly exserted, red; female flowers with curved pedicel 5–12 mm long in fruit, perianth 3-lobed, ovary superior, glabrous, 3-celled, styles 3. Fruit a deeply 3-lobed capsule 5–6 mm in diameter, lobes almost globose, glabrous, 3-seeded. Seeds ovoid, c. 2 mm long, smooth, pale grey with a few darker markings.
Other botanical information
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 poissonii 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 a pair of spines (sometimes fused into a single spine), axillary inflorescences and seeds without caruncle. Euphorbia poissonii closely resembles Euphorbia unispina N.E.Br., and they have overlapping medicinal uses.
Euphorbia sapinii De Wild. occurs from Cameroon and the Central African Republic south to western DR Congo, and is closely related to Euphorbia poissonii and Euphorbia unispina. In the Central African Republic and DR Congo the latex is rubbed onto the skin of dogs to treat scabies. The latex is also an ingredient for spear poison; it is used as a fish poison and sometimes as an ordeal poison in the form of eye drops.
Growth and development
Euphorbia poissonii flowers at the end of the dry season, before new leaves are formed.
Ecology
Euphorbia poissonii occurs on rocks and dry stony soils, usually in open woodland with grass, at 400–700 m altitude.
Propagation and planting
Euphorbia poissonii can be propagated by seed or by stem cuttings. Stem cuttings should be at least 20 cm long and preferably cut from the base of a branch where the cut surface is woody. After cutting they should be allowed to dry for at least 2 weeks for a callus to form on the cut end.
Management
Euphorbia poissonii latex is harvested from wild plants or from those planted near villages.
Harvesting
Harvesting of the leaves is seasonal because the plants are leafless in the dry season.
Genetic resources
Euphorbia poissonii has a relatively large area of distribution and is locally common. Therefore it is not likely to be threatened by genetic erosion. Trade in all succulent Euphorbia spp. is controlled under CITES appendix 2.
Prospects
Although Euphorbia poissonii has useful biological activities, its use for medicinal purposes is limited by the toxicity of the latex. However, the prospects of some of its compounds are good; for example, resiniferatoxin is going through phase II clinical trials and DPP can be used in the therapy of persistent HIV-1 infection.
The taxonomy and distribution areas of Euphorbia poissonii, Euphorbia unispina and some other closely related species need to be reviewed as they resemble each other closely.
Major references
• Adjanohoun, E.J., Aboubakar, N., Dramane, K., Ebot, M.E., Ekpere, J.A., Enow-Orock, E.G., Focho, D., Gbilé, Z.O., Kamanyi, A., Kamsu, K.J., Keita, A., Mbenkum, T., Mbi, C.N., Mbiele, A.L., Mbome, I.L., Mubiru, N.K., Nancy, W.L., Nkongmeneck, B., Satabié, B., Sofowora, A., Tamze, V. & Wirmum, C.K., 1996. Contribution to ethnobotanical and floristic studies in Cameroon. CSTR/OUA, Cameroon. 641 pp.
• Arbonnier, M., 2002. Arbres, arbustes et lianes des zones sèches d’Afrique de l’Ouest. CIRAD, MNHN, UICN. 573 pp.
• Burkill, H.M., 1994. The useful plants of West Tropical Africa. 2nd Edition. Volume 2, Families E–I. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 636 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.
• Dalziel, J.M., 1937. The useful plants of West Tropical Africa. Crown Agents for Overseas Governments and Administrations, London, United Kingdom. 612 pp.
• Evans, F.J. & Schmidt, R.J., 1977. The succulent euphorbias of Nigeria. 2. Aliphatic diterpene esters of the lattices of Euphorbia poissonii Pax and E. unispina. Lloydia 40: 225–229.
• Evans, F.J. & Schmidt, R.J., 1979. The succulent euphorbias of Nigeria. 3. Structure and potency of the aromatic ester diterpenes of Euphorbia poissonii Pax. Acta Pharmacologica et Toxicologica 45(3): 181–191.
• Keay, R.W.J., 1958. Euphorbiaceae. In: Keay, R.W.J. (Editor). Flora of West Tropical Africa. Volume 1, part 2. 2nd Edition. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. pp. 364–423.
• Neuwinger, H.D., 1996. African ethnobotany: poisons and drugs. Chapman & Hall, London, United Kingdom. 941 pp.
Other references
• Aubréville, A., 1950. Flore forestière soudano-guinéenne. Société d’Editions Géographiques, Maritimes et Coloniales, Paris, France. 533 pp.
• Eggli, U. (Editor), 2002. Illustrated handbook of succulent plants: Dicotyledons. Springer, Berlin, Germany. 554 pp.
• Fakunle, C.O. & Ekong, D.E.U., 1978. A new diterpene ester from Euphorbia poisonii. Tetrahedron Letters 19(24): 2119–2120.
• Fakunle, C.O., Connolly, J.D. & Rycroft, D.S., 1989. A novel penta-ester of 19-hydroxyingol from the latex of Euphorbia poisonii. Fitoterapia 60(5): 466–467.
• Fatope, M.O., Zeng, L., Ohayagha, J.E. & McLaughlin, J.L., 1996. New 19-acetoxyingol diterpenes from the latex of Euphorbia poisonii (Euphorbiaceae). Bioorganic and Medicinal Chemistry 4(10): 1679–1683.
• Fatope, M.O., Zeng, L., Ohayagha, J.E., Shi, G. & McLaughlin, J.L., 1996. Selectively cytotoxic diterpenes from Euphorbia poisonii. Journal of Medicinal Chemistry 39(4): 1005–1008.
• Graham, J.G., Quinn, M.L., Fabricant, D.S. & Farnsworth, N.R., 2000. Plants used against cancer – an extension of the work of Jonathan Hartwell. Journal of Ethnopharmacology 73(3): 347–377.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Schmidt, R.J. & Evans, F.J., 1976. A new aromatic ester diterpene from Euphorbia poisonii. Phytochemistry 15(11): 1778–1779.
• Schmidt, R.J. & Evans, F.J., 1977. Candletoxins A and B, two new aromatic esters of 12-deoxy-16-hydroxy-phorbol, from the irritant latex of Euphoria poisonii Pax. Cellular and Molecular Life Sciences 33(9): 1197–1198.
• Schmidt, R.J. & Evans, F.J., 1978. Two minor diterpenes from Euphorbia poisonii latex. Phytochemistry 17(8): 1436–1436.
• Smith, R.J. & Evans, F.J., 1980. Skin irritant effects of esters of phorbol and related polyols. Archives of Toxicology 44: 279–289.
Author(s)
A.T. Tchinda
Institut de Recherches Médicales et d’Etudes des Plantes Médicinales (IMPM), Ministère de la Recherche Scientifique et de l’Innovation, B.P. 6163, Yaoundé, Cameroun


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:
Tchinda, A.T., 2008. Euphorbia poissonii Pax. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
Distribution Map wild


plant habit


flowering and fruiting branch