Prota 3: Dyes and tannins/Colorants et tanins
Journ. Bot. 55: 36 (1917).
Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)
Mucuna urens auct. non (L.) Medik.
Horse-eye bean, hamburger bean (En). Œil de bourrique, grand pois pouilleux (Fr).
Origin and geographic distribution
Mucuna sloanei is very widespread, in Africa from Sierra Leone east to DR Congo, and south to Angola, also in the Caribbean region, tropical America and islands of the Pacific Ocean. Occasionally it is cultivated, e.g. in Nigeria.
A black dye is obtained from all parts of Mucuna sloanei, which is used in Nigeria to dye fibre and leather black. Cooked young fruits are eaten as a vegetable; in Nigeria Mucuna sloanei is occasionally cultivated for that purpose. The ripe seed is eaten pounded and cooked, preferably in soups. Oil extracted from the seed can be used in the preparation of resin, paint, polish, wood varnish, skin cream and liquid soap. The Edo people in Nigeria use leaf sap to stop diarrhoea. In tropical America the seed is used as a diuretic, and in Gabon and tropical America a seed decoction is used as a soothing medicine to relieve the discomfort of haemorrhoids. The seeds are also used for decoration and in games.
The dye of Mucuna sloanei has not been studied, but tannins, cyanogenic glycosides and indolic alkaloids have been reported in various Mucuna species and may also be present in this species, contributing to the colouring effect of the sap and leaves. Total lipid content of dry matter of Mucuna sloanei seed is about 7% (a different source gives an oil content of dried seeds of about 23%). Of the fatty acids, 83% is palmitic acid, oleic acid or linoleic acid. The dried seeds also contain (3%) of the amino acid L-dopa (levodopa), which stimulates the formation of the neurotransmitter dopamine in the brain.
Liana up to 6 m long, with angular almost glabrous branches. Leaves alternate, pinnately 3-foliolate; stipules caducous; petiole 5–11 cm long, rachis 2–3 cm long; petiolules 3–4 mm long; leaflets ovate to elliptical, 7–11 cm × 4–7 cm, apex acuminate, lateral leaflets asymmetrical, silky pubescent below. Inflorescence an axillary, umbellate raceme, 5– 10-flowered. Flowers bisexual, papilionaceous; pedicel c. 1 cm long; corolla up to 7 cm long, yellow-green to whitish yellow; stamens 10, 1 free and 9 united; ovary superior, 1-celled, style long. Fruit a flattened-cylindrical pod 10–14 cm × 4–5 cm × 1 cm, blackish, with 12–15 transversal deep furrows, bearing yellowish stinging hairs, 2–3-seeded. Seeds discoid, c. 3 cm in diameter and 2 cm thick, blackish to dark brown.
Mucuna belongs to the tribe Phaseoleae and is a large genus comprising about 100 species, distributed pantropically. In tropical Africa about 10 species are present.
Mucuna sloanei is found in wet localities in swamp forests, at borders of rivers and lakes, in savanna woodland and secondary vegetation.
In Nigeria cultivation of Mucuna sloanei is done using tall poles, as for climbing types of common bean.
Genetic resources and breeding
Mucuna sloanei is widespread and not in danger of genetic erosion.
Mucuna sloanei will probably remain of minor importance locally as a source of black dye. Ease of application, direct effect and intense coloration on various substrates using the leaf sap makes research worthwhile, e.g. to investigate possible applications as cosmetic colorants. The nutritional and medicinal values of Mucuna sloanei also need further investigation.
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Correct citation of this article:
Jansen, P.C.M., 2005. Mucuna sloanei Fawc. & Rendle In: Jansen, P.C.M. & Cardon, D. (Editors). PROTA 3: Dyes and tannins/Colorants et tanins. [CD-Rom]. PROTA, Wageningen, Netherlands.