2781

12(3): Medicinal and poisonous plants 3

Mucuna Adanson

Fam. pl. 2: 325 (1763).

LEGUMINOSAE

x = 11; Mucuna pruriens: 2n = 20, 22, 24

Mucuna comprises about 100 species in the tropics and subtropics of both hemispheres. A few species are widespread, partly as a result of human activities, but far more species have a very limited distribution. In the region covered by Thailand, Indo-China and Peninsular Malaysia 13 species occur, in Java 5 and in the Philippines 13, whereas 11 species are found in the islands of the Pacific Ocean.

Traditional medicinal uses of Mucuna have been recorded throughout the tropics, but are in general limited. Seeds are used as an aphrodisiac and purgative, and to treat Parkinson's disease, roots as a tonic, leaves to treat fever and headache, bark against rheumatic complaints, and sap to heal wounds and cuts, and to treat fever. The irritant hairs on the outside of the fruits of various Mucuna species (e.g. Mucuna gigantea) are mentioned as being used in criminal poisoning, whereas apparently minor doses are credited as a vermifuge of very doubtful quality. Mucuna pruriens is widely grown as a cover crop and green manure.
In Java the seeds of Mucuna macrophylla Miq. (synonym: Mucuna junghuhniana (O. Kuntze) Prain) are made into bead chains regarded as charms, to ward off diseases in children. The seeds are also included in a prescription for flatulence.

The use of Mucuna pruriens seeds for the symptomatic treatment of Parkinson's disease as supported by modern research is closely linked to the high concentration of the amino acid L-dopa (levodopa; L-3,4-dihydroxyphenylalanine), which stimulates the formation of the neuro-transmitter dopamine in the brain. Dopamine lessens tremors experienced in Parkinson's disease. However, opinions differ on the side effects and efficacy in the long run of L-dopa. The L-dopa content in Mucuna pruriens seeds collected in Java is not related to their cultivation status and ranges from 1.6—2.8%. Neither is it correlated to the presence of violently itching hairs predominating in wild forms. Mucuna macrophylla, Mucuna gigantea and Mucuna diabolica Backer ex Keuch. yielded L-dopa at concentrations of 1.6—1.9%, 1.7—2.0% and 2.2—2.3%, respectively.
A seed extract of Mucuna pruriens showed in-vivo prophylactic protection against snake (Echis carinatus) venom in mice. In-vitro tests on human plasma and bovine prothrombin revealed that the extract activated prothrombin. Main cause of death after the bite of Echis carinatus is haemorrhage and this could be partially counteracted by the increase in procoagulant activity as observed in vitro.
An ethanol extract of Mucuna pruriens exhibited antipyretic and analgesic activity in rats when given intragastrically at a dose of 1 g/kg. A leaf decoction decreased blood cholesterol and lipid levels. It has been recorded that Mucuna pruriens increases sperm count and motility.

Large lianas, sometimes annual or short-lived perennial climbers, rarely erect shrubs. Leaves alternate, pinnately trifoliolate; stipules caducous; lateral leaflets variably asymmetrical; stipels often caducous. Inflorescence axillary on leafy shoots or on old branches, subumbellate, condensed-paniculate or falsely racemose; bracts and bracteoles caducous. Flowers bisexual, showy; calyx 4—5-lobed, 2-lipped with upper pair of lobes connate; corolla papilionaceous, standard rounded with a median claw and a pair of inflexed lateral auricles at base, wings and keel usually much longer, clawed and with small auricle; stamens 10, 9 fused and 1 free; ovary superior, 1-celled, style long, filiform, bent. Fruit an ovoid, oblong or linear pod, valves thick, often ribbed or ornamented with raised lamellae and frequently with irritant bristles, septate or apparently so between the seeds, usually dehiscent. Seeds discoid to globose or oblong, compressed, hilum usually extending around three quarters of the circumference, but sometimes short and surrounded by a rim-aril. Seedling with hypogeal germination; first leaves scale-like or simple.
Seedlings of Mucuna gigantea and Mucuna macrophylla may attain a height of more than 1 m in 3 weeks time. Nodulating ability is reported for numerous Mucuna species. Seeds of Mucuna gigantea can be dispersed by sea currents.
Mucuna is divided into 2 subgenera. Most species belong to subgenus Mucuna, having a woody habit and large, discoid seeds with hilum extending around three quarters of the circumference, whereas a few (e.g. Mucuna pruriens) belong to subgenus Stizolobium, being an annual or short-lived, hardly woody perennial with oblong-ovoid seeds having a very short hilum surrounded by a rim-aril. An overall revision of Mucuna for South-East Asia is still lacking and an up-to-date account for Indonesia and Papua New Guinea is badly needed in view of the great number of endemics recorded in the literature for these countries.

Mucuna can be found on a wide range of soils in habitats as diverse as coral beaches, coastal swamps, riverine forest, moist evergreen rain forest, dry thickets, limestone cliffs and open country, from sea-level up to well over 2000 m altitude.

Propagation of Mucuna pruriens (velvet bean) is mostly by seed. Seed requires no scarification, but dry seed requires soaking in water for 24 hours. The germination rate of fresh seed is up to 100%, and seed stored in a cool, dry place may remain viable for 2 years. After sowing, velvet bean requires 1—2 weedings. It is little affected by diseases and pests. Seed yields can be as high as 1500 kg/ha on good soils. Cell suspension cultures of Mucuna pruriens were able to endogenously accumulate L-dopa up to 6% on a dry weight basis.

In view of their wide distribution and presence in forest margins and secondary regrowth, the Mucuna species treated here do not appear to be threatened by genetic erosion. Germplasm collections of Mucuna are maintained, for instance at Bogor (Indonesia) where there are 55 accessions of Mucuna pruriens, and at Laguna (the Philippines) where there are 29 accessions of Mucuna spp.

Research on the phytochemistry and pharmacological properties of Mucuna has led to important discoveries, such as the presence and activities of L-dopa, which is still important in the therapy for Parkinson's disease. More research may reveal other interesting medicinal properties, which was recently the case concerning activity against the effects of snakebites.

[35]Allen, O.N. & Allen, E.K., 1981. The Leguminosae. A source book of characteristics, uses and nodulation. MacMillan Publishers, London, United Kingdom. 812 pp.
[239]Faridah Hanum, I. & van der Maesen, L.J.G. (Editors), 1997. Plant Resources of South-East Asia No 11. Auxiliary plants. Backhuys Publishers, Leiden, the Netherlands. 389 pp.
[297]Guerranti, R., Aguiyi, J.C., Errico, E., Pagani, R. & Marinello, E., 2001. Effects of Mucuna pruriens extract on prothrombin by Echis carinatus venom. Journal of Ethnopharmacology 75: 175—180.
[731]Perry, L.M., 1980. Medicinal plants of East and Southeast Asia. Attributed properties and uses. MIT Press, Cambridge, Massachusetts, United States & London, United Kingdom. 620 pp.
[751]Pras, N., Woerdenbag, H.J., Batterman, S., Visser, J.F. & van Uden, W., 1993. Mucuna pruriens: improvement of the biotechnological production of the anti-Parkinson drug L-dopa by plant cell selection. Pharmacy, World and Science 15(6): 263—268.
[819]Sastrapradja, D.S., Sastrapradja, S., Aminah, S.H. & Lubis, I., 1975. Species differentiation in Javanese Mucuna spp. with particular reference to seedling morphology. Annales Bogorienses 6(1): 57—68.
[997]Wilmot-Dear, C.M., 1991. A revision of Mucuna (Leguminosae - Phaseoleae) in the Philippines. Kew Bulletin 46(2): 213—251.
[1000]Wilmot-Dear, C.M., 1992. A revision of Mucuna (Leguminosae: Phaseoleae) in Thailand, Indochina and the Malay Peninsula. Kew Bulletin 47(2): 203—245.

K.R. Dahal & J.L.C.H. van Valkenburg

Mucuna biplicata
Mucuna gigantea
Mucuna hainanensis
Mucuna pruriens

Dahal, K.R. & van Valkenburg, J.L.C.H., 2003. Mucuna Adanson. In: Lemmens, R.H.M.J. and Bunyapraphatsara, N. (Editors): Plant Resources of South-East Asia No 12(3): Medicinal and poisonous plants 3. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea

The following species in this genus are important in this commodity group and are treated separatedly in this database:
Mucuna biplicata
Mucuna gigantea
Mucuna hainanensis
Mucuna pruriens