Mucuna pruriens is a tropicallegume native toAfrica andtropical Asia and widely naturalized and cultivated.[2] Its Englishcommon names includemonkey tamarind,velvet bean,Bengal velvet bean,Florida velvet bean,Mauritius velvet bean,Yokohama velvet bean,cowage,cowitch,lacuna bean, andLyon bean.[2] The Tshivenda/Venda language name is Vhulada.
The plant is notorious for the extremeitchiness it produces on contact,[3] particularly with the young foliage and the seed pods. It also produces many medium-sized red swollen bumps along with the itching. It has agricultural and horticultural value and is used inherbalism.
Mucuna pruriens is an annual climbingshrub with long vines that can reach over 15 metres (50 feet) in length. When the plant is young, it is almost completely covered with fuzzy hairs, but when older, it is almost completely free of hairs. Theleaves are tripinnate, ovate, reverse ovate,rhombus-shaped or widely ovate. The sides of the leaves are often heavily grooved and the tips are pointy. In young specimens, both sides of the leaves have hairs. The stems of the leaflets are 2–3 millimetres (1⁄16–1⁄8 inch) long. Additional adjacent leaves are present and are about5 mm (1⁄4 in) long.
The flower heads take the form of axially arrayedpanicles. They are 15–32 centimetres (6–13 in) long and have two or three, or many flowers, which can be white, lavender, or purple. The accompanying leaves are about12.5 mm (1⁄2 in) long; the flower stand axes are from2.5–5 mm (1⁄8–3⁄16 in). The bell is7.5–9 mm (5⁄16–3⁄8 in) long and silky. Thesepals are longer or of the same length as the shuttles. The crown is purplish or white. The flag is1.5 mm (1⁄16 in) long. The wings are2.5–3.8 cm (1–1+1⁄2 in) long.
In the fruit-ripening stage, a 4–13 cm (2–5 in) long,1–2 cm (3⁄8–3⁄4 in) wide, unwinged,leguminous fruit develops. There is a ridge along its length and thehusk is covered in loose, orange hairs that cause a severeitch if they contact skin.[4][5] The pods carry up to seven seeds, which are shiny black or browndrift seeds. They are flattened uniform ellipsoids,1–1.9 cm (3⁄8–3⁄4 in) long,.8–1.3 cm (3⁄8–1⁄2 in) wide and 4–6.5 cm (2–3 in) thick. Thehilum, the base of thefuniculus (connection between placenta and plant seeds) is a surrounded by a significantarillus (fleshy seed shell). The dry weight of the seeds is 55–85 grams (2–3 ounces)/100 seeds.[6]
The seeds of the plant contain about 3.1–6.1%L-DOPA.[7]M. pruriens var.pruriens has the highest content ofl-DOPA. An average of 52.11% degradation ofl-DOPA into damagingquinones and reactive oxygen species was found in seeds ofM. pruriens varieties.[8]
The hairs lining the seed pods contain serotonin and the proteinmucunain, which cause severe itching when the pods are touched.[3][7][11] The calyx below the flowers is also a source of itchy spicules and the stinging hairs on the outside of the seed pods are used in some brands ofitching powder.[3][12] Scratching the exposed area can spread the itching to other areas touched, which can cause blindness if in the area of the eyes.[13] Once this happens, the subject tends to scratch vigorously and uncontrollably and for this reason the local populace in northernMozambique refer to the beans as "mad beans" (feijões malucos). The seed pods are known as "Devil Beans" inNigeria.[14]
In many parts of the world,M. pruriens is used as an importantforage,fallow andgreen manure crop.[15] Since the plant is a legume, itfixes nitrogen and fertilizes soil. InIndonesia, particularlyJava, the beans are eaten and widely known as 'Benguk'. The beans can also be fermented to form a food similar totempeh and known asBenguk tempe or 'tempe Benguk'.
M. pruriens is a widespread fodder plant in the tropics. To that end, the whole plant is fed to animals assilage, dried hay or dried seeds.M. pruriens silage contains 11–23% crude protein, 35–40% crude fiber, and the dried beans 20–35% crude protein. It also has use in the countries ofBenin andVietnam as a biological control for problematicImperata cylindrica grass.[15]M. pruriens is said to not be invasive outside its cultivated area.[15] However, the plant is invasive within conservation areas of South Florida, where it frequently invades disturbed land androckland hammock edge habitats. Cooked fresh shoots or beans can also be eaten. The plant contains relatively high (3–7% dry weight) levels ofl-DOPA,[16] which some people are sensitive to; it can cause nausea, vomiting, cramping, arrhythmias, and hypotension.
^G. V. Joglekar, M. B. Bhide J. H. Balwani. An experimental method for screening antipruritic agents.British Journal of Dermatology. Volume 75 Issue 3 Page 117 - March 1963
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