Species of
Mucuna Adans are legumes in the tribe phaseoleae
(Natarajan et al., 2012). The species are climbing vines and erect shrubs distributed worldwide. According to
Natarajan et al., (2012) the genus
Mucuna contains about 120 species while
De Moura et al., (2016) reported 115 species in the genus distributed world-wide with 19 species occurring in Africa. It is native to India and China and has the character of high diseases resistance and grows well in dry soil with low fertility condition
(Ravishankar et al., 2016). They possess mainly trifoliate leaves (
De Moura et al., 2016). Mucuna flowers show a remarkable variation in colour of the corolla, ranging from white (
M. pruriens) to black
(Tozzi et al., 2005). Based on fruit and seed morphology, two subgenera which are
Mucuna subg.
Mucuna and
Mucuna subg.
Stizolobium (P. Browne) Baker have been traditionally recognized in
Mucuna (
Wilmot-Dear, 1984). Most of the
Mucuna species have wide economic importance in agriculture as forage and green manure, weed biological control and as a coffee substitute
(Ravishankar et al., 2016). Ukachukwu and Obioha (2000) reported that rural population of Nigeria consume seeds of
Mucuna cochinchinensis during scarcity of common legumes.
Osei-Bonsu et al., (1996) also reported that
M. cochinchinensis and
M. utilis are used as soup thickeners in Southern Ghana as the soup is eaten along with starchy food. Seeds of
Mucuna urens are used as soup thickener and vegetable oil by Igbo community of Southeastern Nigeria
(Afolabi et al., 1985; Ukachukwu et al., 2002). Seeds of
M. sloanei and
M. flagellipes Hook.f. are cracked by hitting with a hard object before cooking, then hulled, ground, mixed with red palm oil to obtain yellow powder and marketed as soup thickener (
Ezueh, 1997). Consumption of
Mucuna as food has also been reported from Mozambique and Malawi
(Infante et al., 1990; Gilbert, 2002). According to
Adebowale and Lawai (2005) and
Ezeagu et al., (2003), Mucuna species generally have high protein content of 24% to 1.44%, lipids ranging from 2.86% to 9.8%, crude fibre (5.3-1.5%), ash (2.9-5.5%) and carbohydrate ranging from 59.2% to 64.88%. The anti-nutritional factors found in
Mucuna species include L-dopa, phenolics, tannin, haemagglutinins, trypsin and chymotrypsin inhibitors, phytic acid, saponins and cyanogenic compounds (
Vadivel and Janardhanan, 2000). However, most of these anti-nutritional factors are eliminated to low levels during processing.
Ukachukwu and Obioha (1997) reported detoxification by cooking for 90 minutes or toasting for 60 minutes. The studies of
Ravishankar et al., (2016) on genetic relationship of
M. macrocarpa,
M. imbricata and two hybrids named as IIHR hybrid and Dhanwantari showed that
M. macrocarpa was genetically close to
M. atropurpurea and
M. gigantea whereas
M. imbricata and hybrids IIHR hybrid and Dhanwantari were genetically more close to two varieties of
M. pruriens which are var
. pruriens and var.
hirsuta.
Mucuna pruriens (L.) DC. is commonly known as ‘Velvet bean’. It is native to Africa and Asia with a vigorous climbing habit. The velvet bean has long, slender branches, alternate leaf arrangement, lanceolate leaf shape and white flowers with a bluish-purple butterfly-shaped corolla. The pods of
M. pruriens are pubescent and contain 4 to 6 seeds
(Lampariello et al., 2012). There are varieties of
M. pruriens which are var
. pruriens and var.
utilis.
Mucuna pruriens is by far the most investigated species for the study of intra species genetic and chemo-diversity.
Mucuna pruriens is the source of an established herbal drug used for the management of Parkinson’s disease, male infertility, nervous disorders and also as an aphrodisiac. It has been shown that its seeds are of high medicinal importance
(Lampariello et al., 2012). It is the natural source of levodopa in large amounts used mostly for the treatment of Parkinson’s disease (
Maldonado, 2018).
Agharkar (1991) and
Singh et al., (1996) reported that
M. pruriens is a constituent of more than two hundred indigenous drug formulations. It is widespread and common in bushes and low forests areas of India. All parts of
M. pruriens are importantfor medicine (
Pandey, 1999).
Mucuna pruriens roots are bitter, thermogenic, anthelmintic, diuretic, emollient, stimulant, aphrodisiac, purgative, febrifuge, tonic,
etc. It is considered useful to relieve constipation, nephropathy, strangury, dysmenorrhoea, amenorrhoea, elephantiasis, dropsy, neuropathy, consumption, ulcers, helminthiasis, fever and delirum (
Shalini, 1997;
Upadhyay, 2000). Leaves are popular culinary herbs and fodder crops which are useful in the treatment of ulcers, inflammation, cephalagia and general debility. The trichomes of
Mucuna pods contain mucuna in and serotonin and as a result, pod causes itching, blisters and dermatitis. Pods are also used as vegetable and pod hairs (trichomes) are used as anthelmintic. Hairs mixed with honey have been used as vermifuge. As ointment prepared with hairs act as a local stimulant and mild vesicant (
Shastry, 1995). Besides, medicinal properties,
Mucuna fixes nitrogen and is as a green manure and cover crop. Seeds contain L-DOPA (4-3, 4-dihydroxy phenylalanine), glutathione, lecithin, gallic acid, glycosides, nicotine, prurenine, prurenidine, dark brown viscous oil. Demand for
M. pruriens increased in Asian drug markets and internationally after the discovery that
Mucuna seeds contain L-dopa, an anti-parkinson’s disease drug (
Farooqi, 1999).
Ravishankar et al., (2016) stated that there was paucity of information on phylogeny with high degree of taxonomical confusion in the genus
Mucuna. Besides, it is uncertain which variety of
M. pruriens is the source of natural Levodopa used in the treatment of Parkinson’s disease.
Cultivated varieties of M. pruriens
There are four cultivated varieties
Mucuna pruriens which are:
M. pruriens var.
pruriens, M. pruriens var.
hirsuta (Wight and Arn.) Wilmot-Dear,
M. pruriens var.
sericophylla (Perkins) Wilmot-Dear,
M. pruriens var.
utilis (Wall. ex Wight) Baker ex Burck (
Buckles, 1995;
https://www.tropicalforages.info/pdf/mucuna_pruriens.pdf). These varieties are distributed worldwide. The commonest among all varieties are
var. pruriens and
var. utilis (Eilitta et al., 2003). The basionym
M. pruriens var.
utilis has other nomenclature based on the perceptions of other authors. Some synonyms of
M. pruriens var.
utilis are:
Carpopogon capitatus Roxb,
Macranthus cochinchinensis Lour,
Mucuna aterrima Holland,
Mucuna pruriens var.
biflora Trimen,
Mucuna deeringiana (Bort) Merr
(Eilitta et al., 2003). Fruits of
Mucuna pruriens var.
utilis have long pale silky hairs with seeds often streaked in different colours while fruits of
Mucuna pruriens var.
pruriens have orange-brown irritant bristles with seeds uniform in colour
(Carsky et al., 1998).
Mucuna flagellipes is a legume popularly known as ‘ukpo’ by the Igbo-speaking people of Southeastern Nigeria (
Enwere, 1998). It possesses pods containing 1 to 3 seeds with a hard coating which is white when immature and turns black when mature and dry (
Enwere, 1998).
Mucuna flagellipes is a liana of high economic importance (
Ezueh, 1997). It is very useful in Southeastern Nigeria as a soup thickener. Using the seeds involves cracking, boiling, deshelling and grinding the seeds to powder before adding to thicken the soup. In some villages, the seeds are special delicacy. The cracked seeds are spiced to taste and served as a delicious meal. (
Ezueh 1997;
Eneobong and Corovale, 1992). The seed flour of
M. flagellipes is used as soup thickener in most Igbo-speaking communities of Southeastern Nigeria. Preparation of the seed is usually associated with long cooking time which is required to soften the cotyledon before grinding as well as reduce the anti-nutritional components of the seed
(Onuegbu et al., 2003).
Toxicity of the Mucuna grains
Mucuna grains can be toxic for human and non-ruminant animals if consumed when the anti-nutritive substances in them are untreated. The most important toxic compounds are the non-protein amino acids, L-dopa and hallucinogenic tryptamines. Grain treatment has best been done by boiling in water for one hour, pressure-cooking for 20 minutes, or boiling in water for 30 minutes after soaking in water for 48 hours. Despite the presence of anti-nutritional compounds however, there is evidence that velvet bean grains can be fed to ruminant animals to supplement their diet without apparent problems (
https://www.tropicalforages.info/pdf/mucunapruriens.pdf;
Onuegbu et al., 2003).
