| Mucuna pruriens | |
|---|---|
| Mucuna pruriens inflorescence | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Rosids |
| Order: | Fabales |
| Family: | Fabaceae |
| Subfamily: | Faboideae |
| Tribe: | Phaseoleae |
| Genus: | Mucuna |
| Species: | M. pruriens |
| Binomial name | |
| Mucuna pruriens (L.) DC. |
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| Synonyms | |
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Many, see text |
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Mucuna pruriens is a tropical legume known as velvet bean or cowitch and by other common names (see below), found in Africa, India and the Caribbean. The plant is infamous for its extreme itchiness produced on contact, particularly with the young foliage and the seed pods. It has value in agricultural and horticultural use and has a range of medicinal properties.
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The plant is an annual, climbing shrub with long vines that can reach over 15 m 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 M.pruriens plants, both sides of the leaves have hairs. The stems of the leaflets are two to three millimeters long. Additional adjacent leaves are present and are about 5 mm long.
The flower heads take the form of axially arrayed panicles. They are 15 to 32 cm long and have two to three, or many flowers. The accompanying leaves are about 12.5 mm long, the flower stand axes are from 2.5 to 5 mm. The bell is 7.5 to 9 mm 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 long. The wings are 2.5 to 3.8 cm long.
In the fruit ripening stage, a 4 to 13 cm long, 1 to 2 cm wide, unwinged leguminous fruit develops. There is a ridge along the length of the fruit. The husk is very hairy and carries up to seven seeds. The seeds are flattened uniform ellipsoid, 1 to 1.9 cm long, 0.8 to 1.3 cm wide and 4 to 6.5 cm thick. The hilum, the base of the funiculus (connection between placenta and plant seeds) is a surrounded by a significant arillus (fleshy seeds shell).
M.pruriens bears white, lavender, or purple flowers. Its seed pods are about 10 cm long[1] and are covered in loose orange hairs that cause a severe itch if they come in contact with skin. The chemical compounds responsible for the itch are a protein, mucunain,[1] and serotonin. The seeds are shiny black or brown drift seeds. It is found in tropical Africa, India and the Caribbean.
The dry weight of the seeds is 55 to 85 g/100 seeds.[2] With 2n = 20, 22 or 24 chromosomes.
In many parts of the world Mucuna pruriens is used as an important forage, fallow and green manure crop.[3] Since the plant is a legume, it fixes nitrogen and fertilizes soil.
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.[3] M.pruriens is said to not be invasive outside its cultivated area.[3] However, the plant is known to be invasive within conservation areas of South Florida where it frequently invades disturbed land and rockland hammock edge habitats.
M. pruriens is sometimes used as a coffee substitute called "Nescafe" (not to be confused with the commercial brand Nescafé). Cooked fresh shoots or beans can also be eaten. This requires that they be soaked from at least 30 minutes to 48 hours in advance of cooking, or the water changed up to several times during cooking, since otherwise the plant can be toxic to humans. The above described process leaches out phytochemical compounds such as levodopa, making the product more suitable for consumption. If consumed in large quantities as food, unprocessed M. pruriens is toxic to non-ruminant mammals including humans.
Traditionally, M. pruriens has a sexual function improving effect in rats.[4] It is used in Ayurvedic medicine.
The plant and its extracts have been long used in tribal communities as a toxin antagonist for various snakebites. Research on its effects against Naja (Cobra),[5] Echis (Saw scaled viper),[6] Calloselasma (Malayan Pit viper) and Bangarus (Krait) [7] have shown that it has potential use in the prophylactic treatment of snakebites.
M. pruriens seeds have also been found to have antidepressant properties in cases of depressive neurosis when consumed.[8] and formulations of the seed powder have shown promise in the management and treatment of Parkinson disease.[9]
Dried leaves of M. pruriens are sometimes smoked.[1] The herb contains L-DOPA, a precursor to the neurotransmitter dopamine. The L-DOPA content increases when extracts are prepared. L-DOPA converts into dopamine, an important brain chemical involved in mood, sexuality, and movement.
The hairs lining the seed pods and the small spicules on the leaves contain 5-hydroxytryptamine (serotonin) which cause severe itching (pruritus) when touched.[10][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 itching powder.[12] Water should not be used if contact occurs, as it only dilutes the chemical. Also, one should avoid scratching the exposed area since this causes the hands to transfer the chemical to all other areas touched. Once this happens, one tends to scratch vigorously and uncontrollably and for this reason the local populace in Northern Mozambique refer to the bean as the mad bean (Feijão Malucos). The local populace in Northern Mozambique use raw, unrefined moist tobacco to treat the itching. In India the application of cow dung is very effective to treat the itching caused by the spicules of this herb.
M.pruriens seeds contain high concentrations of levodopa, a direct precursor of the neurotransmitter dopamine. It has long been used in traditional Ayurvedic Indian medicine for diseases including Parkinson's Disease.[13][14][15] In large amounts (e.g. 30 g dose) it has been shown to be as effective as pure levodopa/carbidopa in the treatment of Parkinson's Disease, but no data on long-term efficacy and tolerability is available.[16]
In addition to levodopa, it contains serotonin (5-HT), 5-HTP, nicotine, N,N-DMT (DMT), bufotenine, and 5-MeO-DMT. As such, it could potentially have psychedelic effects, and it has purportedly been used in ayahuasca preparations.[17]
The mature seeds of the plant contain about 3.1-6.1% L-DOPA,[10] with trace amounts of 5-hydroxytryptamine (serotonin), nicotine, DMT-n-oxide, bufotenine, 5-MeO-DMT-n-oxide, and beta-carboline.[18] One study using 36 samples of the seeds found no tryptamines present in them.[19]
The leaves contain about 0.5% L-DOPA, 0.006% dimethyltryptamine (DMT), 0.0025% 5-MeO-DMT and 0.003% DMT n-oxide.[20]
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Synonyms of M. pruriens, M. pruriens ssp. pruriens and M. pruriens var. pruriens:
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Synonyms of M. pruriens var. hirsuta:
Synonyms of M. pruriens var. sericophylla:
Synonyms of M. pruriens var. utilis:
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