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Mareya micrantha (Benth.) Müll.Arg.

A.DC., Prodr. 15(2): 792 (1866).
Mareya spicata Baill. (1860).
Vernacular names
Number one (En).
Origin and geographic distribution
Mareya micrantha occurs from Guinea east to Cameroon and south to DR Congo.
The leaves and fruits are very bitter and poisonous, causing drastic purging when eaten. A leaf decoction or leaf sap is widely known as a violent purgative and abortifacient. Even when diluted, a decoction of fresh leaves is never given to pregnant women, children or old persons. A leaf decoction is mainly used to treat diseases which require drastic action, such as tapeworm infections, gonorrhoea and leprosy. In Sierra Leone, however, a decoction of dried leaves is given to children as a worm treatment. Burnt leaves mixed with clay are applied to scabies and measles. A leaf decoction or fermented leaves with rum and coconut are taken to treat malaria, cough and general weakness. A leaf infusion is taken as an analgesic to treat headache and stomach-ache; externally a paste of the leaves is applied to fractures, stiffness, sprains, sores and ulcers including guinea-worm sores, lumbago, kidney-pain or rheumatic pains. The powdered roots are applied to snakebites and stings of venomous animals. The pounded bark mixed with white clay is applied to treat river blindness, and a leaf decoction is taken internally for the same purpose.
The name ‘number one’ is an indication of the dangerous toxicity of the plant. The fruits were formerly used as ordeal poison; an overdose will cause complete exhaustion by purging.
The stems of Mareya micrantha are commonly used as yam stakes. In Guinea it is cultivated as a hedge plant.
Preliminary analysis of the leaves showed the presence of anthraquinone glycosides and cucurbitacin-like substances. Aqueous leaf extracts suppressed cardiac contractility of isolated frog and rat hearts in a concentration-dependent way. In another test an aqueous leaf extract elicited concentration-dependent contractions of the longitudinal muscle of isolated guinea-pig ileum. Leaf extracts caused hypotension in dogs, and a root extract caused paralysis of the respiratory centre in rats. The methanol and hot and cold aqueous extracts of the leaves showed antibacterial activity against Enterobacter aerogenes, Agrobacterium tumefaciens, Bacillus subtilis, Clostridium sporogenes, Escherichia coli and Staphylococcus aureus. Ethanolic leaf extracts showed low antiplasmodial activity against a chloroquine-resistant strain of Plasmodium falciparum and no anti-amoebic activity in vitro. The extract showed considerable cytotoxicity to mammalian cells.
The wood is white, soft and perishable.
Monoecious shrub or small tree up to 8(–12) m tall; twigs short-hairy. Leaves alternate, simple; stipules small, triangular, soon falling; petiole 0.5–7.5 cm long; blade ovate, ovate-oblong to oblanceolate, (5–)10–25 cm × 2–9 cm, base cuneate, apex shortly acuminate, slightly toothed in upper part, glabrous or slightly short-hairy. Inflorescence a slender axillary raceme up to 25 (–40) cm long with male flowers in clusters in upper part and female flowers solitary or accompanied by several male flowers in lower part. Flowers unisexual, petals absent; male flowers with pedicel 1.5–2.5 mm long, calyx splitting into 3–4 lobes, c. 1.2 mm long, obtuse, green, stamens 10–20(–24), longer than calyx lobes, free; female flowers almost sessile, sepals 3–5, c. 1 mm long, imbricate, greenish, disk flattened, lobed, ovary superior, ovoid, short-hairy, 3-celled, styles 3, fused at base, recurved, papillose. Fruit a 3-lobed capsule 3–4 mm in diameter, slightly depressed above, short-hairy, pale brown to reddish, 3-seeded. Seeds ovoid, c. 2 mm in diameter, smooth, brownish.
Mareya comprises 3–4 species, which mainly occur in West and Central Africa. Mareya brevipes Pax, a shrub occurring in Central Africa and Uganda, is also used medicinally. In Gabon the seeds are eaten as a strong purgative. Mareya congolensis (J.Léonard) J.Léonard is endemic in DR Congo. The bark is chewed as a purgative.
Mareya micrantha occurs in primary and secondary forest, from sea-level up to 500 m altitude.
Genetic resources and breeding
Mareya micrantha is a common shrub throughout its distribution area and is therefore not threatened by genetic erosion.
Mareya micrantha has many medicinal uses despite its toxicity, and the pharmacological tests show interesting activities. Not much is known about its chemistry though, and it seems worthwhile to identify the compounds responsible for the activities.
Major references
• Abo, J.-C., Aka, K.J., Ehile, E.E. & Guédé-Guina, F., 2000. Effets d’un extrait aqueux brut de Mareya micrantha et de ses différentes fractions sur l’activité mécanique du cœur isolé de rat. Revue de Médecines et Pharmacopées Africaines 14: 7–17.
• 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.
• 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.
• MacFoy, C.A. & Cline, E.I., 1990. In vitro antibacterial activities of three plants used in traditional medicine in Sierra Leone. Journal of Ethnopharmacology 28(3): 323–327.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
Other references
• Awohee, D.E., 1987. Purgative drugs of natural origin and preliminary investigation into the pharmacognostical characters of the leaves of Mareya micrantha. B.Pharm degree thesis, Faculty of Pharmacy, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana. 94 pp.
• Guédé-Guina, F., Tsai, C.S., Smith, M.O., Vangah Manda, M., Washington, B. & Ochillo, R.F., 1995. The use of isolated functional heart to pharmacologically characterize active ingredients in the aqueous extracts of Mareya micrantha. Journal of Ethnopharmacology 45(1): 19–26.
• Keita, S.M., Arnason, J.T., Baum, B.R., Marles, R., Camara, F. & Traoré, A.K., 1995. Etude ethnopharmacologique traditionnelle de quelques plantes médicinales antihelminthiques de la République de Guinée. Revue de Médecines et Pharmacopées Africaines 9(2): 119–134.
• Léonard, J., 1996. Révision des espèces zaïroises des genres Mareya Baill. et Mareyopsis Pax & K. Hoffm. (Euphorbiaceae). Bulletin du Jardin Botanique national de Belgique 65: 3–22.
• Raponda-Walker, A. & Sillans, R., 1961. Les plantes utiles du Gabon. Paul Lechevalier, Paris, France. 614 pp.
• Tessier, A.M. & Paris, R.R., 1978. Study of some African toxic Euphorbiaceae containing cucurbitacins. Toxicological European Research 1(5): 329–336.
• Tsai, C.S., Guédé-Guina, F., Smith, M.O., Vangah Manda, M. & Ochillo, R.F., 1995. Isolation of cholinergic active ingredients in aqueous extracts of Mareya micrantha using the longitudinal muscle of isolated guinea-pig ileum as a pharmacological activity marker. Journal of Ethnopharmacology 45(3): 215–222.
• Zirihi, G.N., Mambu, L., Guédé-Guina, F., Bodo, B. & Grellier, P., 2005. In vitro antiplasmodial activity and cytotoxicity of 33 West African plants used for the treatment of malaria. Journal of Ethnopharmacology 98: 281–285.
G.H. Schmelzer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

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. Mareya micrantha (Benth.) Müll.Arg. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.