Mucuna pruriens

Mucuna pruriens is an annual climbing shrub 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. The leaves 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 about 5 mm (1⁄4 in) long.

The flower heads take the form of axially arrayed panicles. 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 about 12.5 mm (1⁄2 in) long; the flower stand axes are from 2.5–5 mm (1⁄8–3⁄16 in). The bell is 7.5–9 mm (5⁄16–3⁄8 in) long and silky. The sepals are longer or of the same length as the shuttles. The crown is purplish or white. The flag is 1.5 mm (1⁄16 in) long. The wings are 2.5–3.8 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 the husk is covered in loose, orange hairs that cause a severe itch if they contact skin.^[4][5] The pods carry up to seven seeds, which are shiny black or brown drift 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. The hilum, the base of the funiculus (connection between placenta and plant seeds) is a surrounded by a significant arillus (fleshy seed shell). The dry weight of the seeds is 55–85 grams (2–3 ounces)/100 seeds.^[6]

Mucuna pruriens seeds contain dimethyltryptamine (DMT), DMT-N-oxide, 5-MeO-DMT, bufotenin, serotonin, unidentified β-carbolines, L-DOPA (levodopa), mucunine, mucunadine, prurienene, prurieninine, mucuadine, mucuadinine, mucuadininine, prurienidine, and nicotine, among other constituents.^{[7][8][9][10]} Aproteine and mucunaine are found in the hairs on seedpods and cause skin irritation.^[7] Tryptamines like DMT are present in not only the seeds but also the pods, leaves, and roots of the plant.^[7][9][10] The seeds of Mucuna pruriens contain about 3.1 to 6.1% L-DOPA.^[11] M. pruriens var. pruriens has the highest content of L-DOPA.^{[citation needed]} An average of 52% degradation of L-DOPA into damaging quinones and reactive oxygen species was found in seeds of M. pruriens varieties.^[12] The amounts of individual tryptamines in the plant are very low compared to L-DOPA, for instance 0.0001 to 0.001%.^[10]

The hairs lining the seed pods contain serotonin and the protein mucunain, which cause severe itching when the pods are touched.^[3][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 of itching powder.^[3][14] Scratching the exposed area can spread the itching to other areas touched, which can cause blindness if in the area of the eyes.^[15] Once this happens, the subject tends to scratch vigorously and uncontrollably and for this reason the local populace in northern Mozambique refer to the beans as "mad beans" (feijões malucos). The seed pods are known as "Devil Beans" in Nigeria.

In many parts of the world, M. pruriens is used as an important forage, fallow and green manure crop.^[16] Since the plant is a legume, it fixes nitrogen and fertilizes soil. In Indonesia, particularly Java, the beans are eaten and widely known as 'Benguk'. The beans can also be fermented to form a food similar to tempeh and known as Benguk tempe or 'tempe Benguk'.

M. pruriens is a widespread fodder plant in the tropics. To that end, the whole plant is fed to animals as silage, 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 of Benin and Vietnam as a biological control for problematic Imperata cylindrica grass.^[16] M. pruriens is said to not be invasive outside its cultivated area.^[16] However, the plant is invasive within conservation areas of South Florida, where it frequently invades disturbed land and rockland hammock edge habitats. Cooked fresh shoots or beans can also be eaten. The plant contains relatively high (3–7% dry weight) levels of l-DOPA,^[17] which some people are sensitive to; it can cause nausea, vomiting, cramping, arrhythmias, and hypotension.

Tryptamines present in Mucuna pruriens such as dimethyltryptamine (DMT), 5-MeO-DMT, bufotenin, and serotonin are normally orally inactive due to rapid metabolism by the enzyme monoamine oxidase.^[10] However, these constituents can become orally active when combined with monoamine oxidase inhibitors (MAOIs).^[10] Consequently, although levels of tryptamines in the plant are low, it has been recommended that people taking MAOIs do not consume Mucuna pruriens due to potential for adverse effects.^[10]

• 
  19th-century Japanese illustration
• 
  Flowers (colored engraving)
• 
  Mature seed pods
• 
  Seeds of different colors