Agrobotanical, nutritional and bioactive potential of unconventional legume - Mucuna

K R Sridhar and Rajeev Bhat

Microbiology and Biotechnology, Department of Biosciences, Mangalore University, Mangalagangotri 574 199, Karnataka, India
sirikr@yahoo.com

Abstract

Unconventional legumes are promising in terms of nutrition, providing food security, agricultural development and in crop rotation in developing countries. The wild legume, Mucuna consists of about 100 varieties/accessions and are in great demand as food, livestock feed and pharmaceutically valued products. Mucuna seeds consist of high protein, high carbohydrates, high fiber, low lipids, adequate minerals and meet the requirement of essential aminoacids. The seeds also possess good functional properties and in vitro protein digestibility. Hydrothermal treatments, fermentation and germination have been shown to be most effective in reducing the antinutrients of Mucuna seeds. Several antinutritional compounds of Mucuna seeds serve in health care and considerable interest has been drawn towards their antioxidant properties and potential health benefits.

All parts of Mucuna plant are reported to possess useful phytochemicals of high medicinal value of human and veterinary importance and also constitute as an important raw material in Ayurvedic and folk medicines. Mucuna seeds constitute as a good source of several alkaloids, antioxidants, antitumor and antibacterial compounds. Seeds are the major source of L-DOPA, which serve as a potential drug in providing symptomatic relief for Parkinson's disease. As cultivar differences in Mucuna influences the quantity of L-DOPA and lectin in seeds, future investigations should direct towards the selection of germplasm with low L-DOPA and lectin for human and animal consumption, while high L-DOPA for pharmaceutical purposes. Inexpensive means of processing techniques needs to be implemented to exploit the nutraceutical potential of Mucuna for the benefit of poor and rural development in developing countries.

Keywords: Antioxidants, antitumor activity, bioactive compounds, fodder, food, L-DOPA, Mucuna, nutrition, wild legumes

Introduction

Bridging the gap between teeming population and food production is one of the important tasks of developing countries. Expensive staple foods and policy constraints on food imports are the major factors worsening the food situation in developing countries (Weaver 1994). Protein-energy deficiency has been recognized as the most common form of malnutrition in regions where people depend mainly on starch-based diets (FAO 1994, Pelletier 1994, Weaver 1994, Michaelsen and Henrik 1998). Livestock production, animal husbandry and maintenance of soil fertility play important role in rural development and in turn the economy of developing countries. Livestock nutrition is also one of the critical constraints to increase animal productivity in developing countries (ILRI 1995) and perpetual gap persists between the demand and supply of digestible crude protein and total digestible nutrients to livestock in Asian continent (Singh et al 1997). Supplementation of animal protein for monogastric animals is expensive and not easily affordable (Umoren et al 2005). Poppi and Mclennan (1995) have advocated increasing the quality of legume-based pasture diets to uplift the livestock production. Legume pastures have been projected as an economically viable alternative for proteins and calories in developing countries (Famurewa and Raji 2005, Rao 1994). Feed supplementation with native legumes is viable and provides additional proteins, minerals, energy in dry seasons and improves the overall nutritional status in developing countries (Guillion and Champ 1996). Some underutilized wild legumes adapted to adverse conditions have been explored for their nutritional advantages (Amubode and Fetuga 1983, USNAS 1975, Udedibie 1991, Siddhuraju et al 1995, 2000, Vijayakumari et al 1997, Vadivel and Janardhanan 2001a, Bhagya et al 2006, Sridhar and Seena 2006, Quiceno and Medina 2006). To fulfill the growing demands of plant-based proteins for humans and livestock, research is underway on the possibilities of employing underutilized legumes as inexpensive and elegant source of protein than conventional sources viz., soybean (Glycine max), groundnut (Arachis hypogea) and animal-based proteins (Chel-Guerrero et al 2002, Krause et al 1996, Siddhuraju et al 1995). Legumes have long shelf life and provide more proteins, abundant carbohydrates, high fiber, low fat (except oilseeds) and possess high concentration of polyunsaturated fatty acids. Legumes are also known for certain bioactive compounds, whose beneficial effects need to be explored for efficient exploitation. Thus, underexplored legumes assume importance in terms of nutrition, food security, agricultural development, enhancement of economy and rotation of crops to improve soil fertility. In view of rural development, the current review emphasizes the importance of unconventional legume, Mucuna as a source of food, feed and pharmaceutically valued compounds.
 

Mucuna

The legume family (Fabaceae) is the third largest among flowering plants, consisting of approximately 650 genera and 20,000 species (Doyle 1994) and is the second most important plant source of human and animal nutrition (Vietmeyer 1986). Figure 1 shows Mucuna pruriens in natural habitat (southwest India) with pods, ripened and dried seeds.

Many of the legumes possess multiple uses such as food, fodder and pharmaceuticals. Some legume seeds are known for anti-cancerous compounds that retard or arrest the cancer growth. For instance, an alkaloid 'genistein' derived from kudzu beans (Pueraria Montana Lour.) has the unique property to retard cancer growth (Brink 1995) and 'trigonelline' of jackbean (Canavalia ensiformis) possesses anticancerous properties (Morris 1999).  Similarly, 'canavanine' extracted from jackbean (Canavalia ensiformis) is also reported to be cytotoxic to human pancreatic cancer cells (Swaffer et al 1995). Legumes also serve as weed control (e.g. Cassia, Mucuna, Sesbania) as well as source of natural pesticide (e.g. rotenoids) (Balandrin et al1985). Many varieties and accessions of the wild legume, Mucuna are in great demand in food and pharmaceutical industries. Nutritional importance of Mucuna seeds as a rich source of protein supplement in food and feed has been well documented (Siddhuraju et al 2000, Siddhuraju and Becker 2001a, Bressani 2002). Mucuna seeds constitute excellent raw material for indigenous Ayurvedic drugs and medicines due to the presence of 3,4-dihydroxy-L-phenylalanine (L-DOPA), which provides symptomatic relief in Parkinson's disease (Shaw and Bera 1993, Prakash and Tewari 1999). The decoction of Mucuna seeds also lowers the cholesterol and lipids of plasma in rats (Iauk et al 1989). Standley and Steyermark (1946) have reported the use of one of Mucuna species as dye (Mucuna argyrophylla Standl.). Mucuna is also being extensively used as cover crop, mulch and to control weeds in agriculture.

In Mucuna (synonym, Stizolobium) (Hutchinson and Dalziel 1954), about 100 varieties have been identified and described (Duke 1981, Buckles 1995). Mucuna has Latin names (Mucuna pruriens Baker; Mucuna prurita Hook), English names (cow-hitch plant or cowhage) and common names (velvet bean, devil bean). The species nomenclature 'pruriens' in Latin refers to itching sensation due to the result of contact with pod hairs. Mucuna cochinchinensis cultivated in some parts of Southern Nigeria and Senegal was first found in French Cochin-China (Hashim and Idrus 1977). Since then it has spread to other tropical countries (India, Indonesia, Philippines and Peninsular Malaysia) (Hutchinson and Dalziel 1954, Ukachukwu and Obioha 1997). Mucuna is grown as a minor food crop by tribals and ethnic groups of Asia and Africa (Dako and Hill 1977, Iyayi and Egharevba 1998). It was cultivated widely for the first time in Floridan region during 1890's as cover crop for the purpose of maintenance of soil fertility and feed for monogastric animals (pigs) and ruminants. However, cultivation and utilization of Mucuna declined rapidly due to affordable inorganic fertilizers and it was replaced by soybean (Elittä and Carsky 2003). After realizing a rapid deterioration in soil fertility and side effects of chemical fertilizers during 1980's, re-exploitation of Mucuna in tropical regions began (Buckles 1995). Significant impact of Mucuna in weed control (e.g. Imperata cylindrica) led to renewed interest on its utilization and gained the support of various organizations (Chikoye and Ekeleme 2000, Carsky et al 2001). Traditional use of Mucuna as food crop by farmers at field level gained popularity due to good yield (Gilbert 2002, Ukachuwu et al 2002). Except for the pioneering research on Mucuna by Buckles (1995), no detailed reports are available on utilization of Mucuna as food and feed. Sure and Read (1921) have detailed the biological analysis of seed of Georgia velvet bean (Stizolobium deeringianum). Ferris (1917) and Fain and Tabor (1921) have mentioned on the use of Mucuna as ruminant feed. Scott (1916) and Lamaster and Jones (1923) have reported use of Mucuna seeds as feed for dairy cows. Tweedie and Carew (1963) also reported the use of velvet beans as ruminant feed. Mucuna plant has been used in mixed cropping with maize and cowpea and the yield and chemical composition of fodder have been described by Singh and Relwani (1978). Harms et al (1961) reported the influence of feeding various levels of velvet beans to chicks and laying hens. Species differentiation between Mucuna with reference to seedling morphology has been described by (Sastraprajada et al 1975). Mucuna pruriens has been extensively used as cover crop for enhancement of water infiltration, softening the soil, improvement of soil fertility and to suppress the weeds (Acanthospermum hispidum, Euphobia hirta, Senescio vulgaris, Oxygonum sinuatum, Schkuria pinnata, Richardia brasiliensis, Bidens pilosa, Sonchus oleraceae) (Osei-Bonsu et al 1994, Mwangi et al 2006).
 

Agrobotanical features

Mucuna and their accessions are herbaceous twining annual plants. They possess trifoliolate leaves (leaflets are broadly ovate, elliptic or rhomboid ovate and unequal at the base); flowers white to dark purple and hang in long clusters (pendulous racemes); pods are sigmoid, turgid and longitudinally ribbed, seeds ovoid (4-6 per pod) and black or white. Mucuna pods are covered with reddish-orange hairs, which readily dislodge and cause intense skin irritation and itch due to presence of a chemical called mucunain. Kuo et al (2004) compared the external features of Mucuna based on morphological characteristics (small branches, leaves, length of leaves, racemes, calyx and pods) of four accessions (Mucuna gigantea, Mucuna macrocarpa, Mucuna membranacea and Mucuna pruriens var. utilis). Gurumoorthi et al (2003a) evaluated the agrobotanical traits of seven accessions of Mucuna (90 days-old plants) (Thachenmalai, black seed coat; Thachenmalai, white seed coat; Mundanthurai, white seed coat; Mundanthurai, black seed coat; Kailasanadu, white seed coat; Valanad, black seed coat; Mylaru, white seed coat) collected from five agroecological regions of Southern India and recorded a wide diversity in Mucuna accessions. Black seed coat bearing Thachenmalai accession exhibited high fertility index, biomass production and seed yield followed by Valand accession. The leghaemaoglobin of the seven accessions varied between 0.18 mM (Mundanthurai white accession) and 0.52 mM (Kailasanadu). Mundanthurai (black accession) registered the highest germination (99.75%), while it ranged between 79.75 % and 96% in rest of the accessions. Thachenmalai (black accession) and Mylaru flowered in 60 days of sowing against 61-67 days in other accessions. The authors inferred that genetic diversity existing between Mucuna accessions is not influenced by environment. However, a major finding by Capo-chichi (2002) is that the evaluation of some of the commonly utilized Mucuna accessions can be considered as mere varieties of Mucuna pruriens.

Mucuna grown in Taiwan consist of three species and one variety (Mucuna gigantea, Mucuna macrocarpa, Mucuna membranacea and Mucuna pruriens var. utilis)(Xu et al 1996, Li and Yang 2002, Kuo et al 2004). In West Africa, Mucuna flagellipes, Mucuna sloanei, Mucuna prurines var. pruriens, Mucuna pruriens var. utilis and Mucuna cochinchinensis are well established. In Malaysia, Mucuna bracteata are frequently planted in large plantations and small-holdings of oil palm and rubber as cover crops along with some of the other legumes (Calopogonium caeruleum and Pueraria javanica) (Ministry of Agriculture 2000). A yield of approximately 5000 kg seeds per hectare has been reported in well-managed irrigated fields from India (Singh et al1995, Farooqi et al1999). Maximum seed yield of 1.995 tonnes/ha (spacing of 1.0 m × 1.0 m, 10,000 plants/ha) has been reported by Krishnamurthy et al (2003) based on the results obtained from a field experiment (Zandu Foundation for Health Care Research Farm, Ambach, South Gujarat, India) on growing Mucuna pruriens (L.) DC. var. utilis.
 

Mucuna as food and feed

Food

Seeds of Mucuna constitute source of food for tribals and some ethnic groups of Asia and Africa (Dako and Hill 1977, Iyayi and Egharevba 1998). The immature pods and leaves serve as vegetables, while seeds as condiment and main dish by ethnic groups in Nigeria (Adebowale and Lawal 2003b). Farmers of Kenyan coast exclusively use Mucuna seeds in beverage preparation, while those dwelling at North-rift region use finely powdered roasted seeds for consumption (Saha and Muli 2000). Mature seeds are consumed by some of the Indian tribals (Mundari, Dravidian groups, Northeastern and Kanikkas) (Arora 1981, Jain 1981). Reports are available on the use of Mucuna seeds as food by Sri Lankan population (Ravindran and Ravindran 1988). Ukachukwu and Obioha (1997) reported that rural population of Nigeria (Enugu and Kogi) consumes seeds of Mucuna cochinchinensis during famine or scarcity of common legumes (Ukachukwu and Obioha 1997). Survey by Onweluzo and Eilittä (2003) revealed that in Enugu and Kogi, about 55% of population consumes Mucuna on cultivation, while about 40% cultivate for consumption as well as for marketing.

Mucuna seeds are usually toasted for 5-10 min before grinding and flouring to supplement as thickener in sauce or soup. Osei-Bonsu et al (1996) reported that people of Southern Ghana consume Mucuna cochinchinensis and Mucuna utilis (pounded, cracked or boiled up to 40 min) daily. After draining the cooked water, softened seeds are hulled, ground into paste and mixed with other ingredients (e.g. chillies, egg plant, onions, meat or fish) to prepare soup (Asadua and Nkwan), which is eaten along with starchy staples. The beans are also useful in preparation of oil soups (stew) (Osei-Bonsu et al 1996). The most popular recipes are stew, sauce (Akpoko ji/nkashi/Una) gel (Opka), roasted snacks (Akpaka Ide), porridge, Moi-Moi and fried cake. Consumption of these products did not cause any adverse effect on human health. Mucuna sloanei is used by the Igbo community in Sub-Saharan Africa as condiment or part of the main dish (Afolabi et al 1985, Ukachukwu et al 2002). Seeds of Mucuna urens are used as thickener of soup and vegetable oil by Igbo community of Southeastern Nigeria (Afolabi et al 1985, Ukachukwu et al 2002). Seeds are also used in beverages and thickening agents in recipes of several food items (Haq 1983, Wanjekeche et al2003). Finely powdered and roasted dry seeds of Mucuna serve as supplement of coffee of African tribals. Preparations of toasted and ground seeds of Mucuna cochinchinensis and Mucuna utilis are very popular among senior citizens of Nsukka and Igala regions of Africa (Ene-Obong and Carnovale 1992, Ukachukwu and Obioha 1997). Seeds of Mucuna accessions (Mucuna sloanei and Mucuna flagellipes) 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). Egounlety (2003) reported the methods of pretreatment of Mucuna pruriens var. utilis seeds for preparation of three foods stuffs (Mucuna tempe, Mucuna condiment and Mucuna fortified weaning food) through fungal (Rhizopus oligosporus) or bacterial (Bacillus sp.) fermentation and changes in biochemical composition of seeds on fermentation have been detailed. Fermentation of Mucuna with R. oligosporus resulted in pleasant cheese-like aroma that was retained up to 48 hr. In condiment preparation, as fermentation proceeds, the product attains dark colour. Egounlety (2003) recommended the use of Mucuna seeds as a good substrate for fungal or natural fermentation and for the production of Mucuna tempe and Mucuna fortified weaning foods at household level to overcome protein-energy malnutrition. Diallo et al (2002) reported formulation of four recipes (coffee, porridge, ragout and tau) from seeds of Mucuna pruriens. For preparation, seeds were soaked in freshwater over 48 hr (seed coat will be removed manually after 24 hr) replacing water once in every 12 hr followed by cooking up to 60-90 min in water. Consumption of such preparations by about 300 trained women volunteers did not result in any negative health effects (Diallo et al 2002). Use of polysaccharide gums extracted from Mucuna flagellipes in preparation of raw beef burgers containing graded levels (0.25, 0.5, 0.75 and 1.0%) has been reported by Onweluzo et al (2004). Beef burgers containing Mucuna gums significantly lowered shrinkage, elevated water holding capacity (WHC) and stability under ambient conditions (27±1°C; relative humidity, 90.6%). Overall acceptability score indicated that the Mucuna gum-stabilized beef burgers were acceptable and the seeds serve as effective stabilizers. Tempe, a fermented soybean food product is produced traditionally in Indonesia. Similarly, tempe is also produced in Japan using Mucuna seeds (Higasa et al 1996).

Feed

Mucuna pruriens has been compared to Gliricidia sepium (a recommended legume for supplementation of the grass-based diet) in dairy livestock feeding (Muinga et al 2003). Feeding experiment performed on Jersey cows revealed that Mucuna forage (2 kg DM/day) could be used to supplement dairy cows along with grass as basal diet. Mucuna and Gliricidia forages resulted in daily milk yield 5.2 and 5.5 kg/cow respectively. Ravindran and Ravindran (1988) stated that nutritive value of Mucuna can be improved further as livestock feed ingredient on soaking, germination and heat treatment to inactivate and reduce/destroy its antinutritional components (Aletor and Aladetimi 1989, Agunbiade and Longe 1996). Castillo-Caamal et al (2003) showed that the sheep fed with treated Mucuna seeds increased the weight and the growth response confirms the benefits with increased intake of nutrients and antinutrients.

Studies have been carried out on weaner pigs by feeding raw Mucuna seed meal by Esonu et al (2001). Feeding of raw seed meal resulted in deleterious effects on the performance as well as blood constituents of pigs. Emenalom et al (2004) studied the pathophysiological responses of weaner pigs fed with raw and cracked-soaked and cooked Nigerian Mucuna pruriens seed meals. Raw seed meal was poisonous to pigs, but relatively safe after thermal treatments. Raw and cracked-soaked and cooked meal in pig diets (15%, 20, 30 and 40%) against control diet indicated that the seeds are poisonous at 15% dietary inclusion and significantly affects the hematological and serum biochemical indices with 40% mortality. These clinical effects were pronounced in smaller pigs (17-18 kg) than bigger ones (21 kg) indicating that body weight as an important factor to overcome the toxic effects of raw Mucuna seed meal. Pre-heated Mucuna seed meal proved safe for pigs at different dietary inclusion without improvement of most of the hematological and serum biochemical parameters. Poor weight gain of pigs receiving increased levels of the processed Mucuna seed diets indicates incomplete detoxification.

Supplementing 10% dry-roasted Mucuna seeds in broiler diet resulted in better growth of birds than raw seeds (Del Carmen et al 1999). Iyayi and Taiwo (2003) investigated the effect of incorporation of Mucuna pruriens seed meal on the performance of laying hens and broilers (18 week-old black Nera birds). In diets 1, 2, and 3, 40% soybean meal was replaced with autoclaved, raw and roasted (RMSM) Mucuna seeds respectively. None of the Mucuna diets showed the effect on egg (size, weight, length and width) and no meat or blood spots on the eggs. Similarly, egg yolk index did not significantly change on feeding Mucuna diet. In another set of experiment with broiler chicks (160 day-old), soybean meal was replaced with RMSM in conventional broiler diet (0, 33.3, 66.7 and 100%) at starter and finisher phases. None of the combination of RMSM affected the efficiency of feed utilization or weights of gizzards and hearts of birds. Addition of 6% RMSM had no effect on the organ weights, while weights of air sacs, small and large intestine and caeca reduced, while weights of liver and spleen were increased at 12 and 18% RMSM. Results of this study revealed that: (i) Laying hens ate normally with diets containing autoclaved or roasted Mucuna compared to raw Mucuna seed diet; (ii) If processed Mucuna seeds incorporated at 6% level of diet, it produced good egg quality against sole soybean meal diet; (iii) Processed Mucuna seeds are promising plant protein source to replace soybean meal in feeding broilers. Incorporation of RMSM at 6% in diets was optimum for the production of broilers from the starter to finishing phase. However, RMSM over 6% cause reduction in performance of the birds due to antinutritional factors and disrupted the digestive tract and other organs. The RMSM at 18% resulted in degenerative syndromes in the organs of the birds.

Siddhuraju and Becker (2001a) reported that fish fed up to 13% of Mucuna seed diet (raw or autoclaved) produced growth performances similar to respective control group and in feed utilization of common carp. However, the sensitivity of common carp to the antinutritional factors (total phenolics, L-DOPA or non-starch polysaccharides) of Mucuna seed meal resulted in low growth performance. Study by Siddhuraju and Becker (2003a) showed that use of all the processed Mucuna pruriens seeds significantly improve the growth performance and feed utilization of tilapia fish compared to raw seeds and the values are comparable with control diet. All diets containing raw Mucuna seeds significantly lowered the plasma cholesterol. However, significant negative influence on the hepato-somatic index was found in fish fed with raw as well as treated Mucuna seed meals. The raw seed meal at the 25% dietary protein included in the fish feeding experiment significantly reduced the growth performance and nutrient utilization. But at 25% dietary protein, processed Mucuna seeds resulted good feed utilization and growth.
 

Nutritional properties

Studies have been carried out on the seed characteristics and chemical composition of three morphotypes of Mucuna urens (L.) Medikus (horse eye bean, Nigeria) by Adebooye and Phillips (2006) and their results revealed that all three morphotypes are good source of crude protein (19.97-20.57%), carbohydrate (73.29-75.49%), fat (1.84-5.05%) and vitamins (11.24-17.10%). Ezeagu et al (2003) studied the proximate composition of 12 Mucuna accessions from Nigeria and found high protein (24.50-29.79%), fat (4.72-7.28%), carbohydrate (59.20-64.88%), crude fibre (3.65-4.43%), starch (39.22-41.17%) and gross energy (16.64-17.17 kJ/g). Proximate composition of eight accessions of Mucuna seeds is projected in Table 1.

Proximal value

Crude protein

Four Indian accessions of Mucuna consist of high amount of crude protein (20.2-29.6%) (Vadivel and Janardhanan 2000, Vijayakumari et al 2002). Crude protein of eight Mucuna accessions ranged between 24 and 31.44% (Table 1), which surpasses many wild legumes (Atylosia scarbaeoides, 17.3%; Erythrina indica, 21.5%; Neonotonia wightii, 15.1%; Rhynchosia filipes, 16.9%; Tamarindus indica, 14%; Arinathan et al 2003) and edible legumes (Cajanus cajan, 19.4%; Cicer arietinum, 20.7%; Vigna trilobata, 20.2%, and V. unguiculata, 15.9%; Jambunathan and Singh 1980, Nwokolo 1987, Arinathan et al 2003).

Crude lipid

Crude lipid of Mucuna seeds showed wide variations. Some investigators reported as low as 2.8-4.9% (Ravindran and Ravindran 1988, Siddhuraju et al 2000), while others up to 8.47-14.0% (Janardhanan and Lakshmanan 1985, Vijayakumari et al 2002). Vadivel and Janardhanan (2000) reported crude lipid in intermediary range (6.3-7.4%). Adebowale et al (2005a) showed that the ether extract of whole seed, cotyledon and seed coat consists of 9.6, 9.8 and 3.0% crude lipid respectively. Crude lipid of eight Mucuna accessions ranged between 4.1-14.39% (Table 1)

Crude fibre

Crude fibre of Mucuna seed accessions ranged between 5.3 and 11.5% (Janardhanan and Lakshmanan 1985, Ravindran and Ravindran 1988, Mohan and Janardhanan 1995). The dietary fibre was in the range of 6.7-19.5% (Siddhuraju et al 2000, Vadivel and Janardhanan 2000, Vijayakumari et al 2002), while the neutral detergent fibre and acid detergent fibre ranged between 10.3-25.9% and 9.3-20.4% respectively (Bressani 2002, Del Carmen et al 2002, Ayala-Burgos et al 2003). Table 1 reveals that crude fiber of eight accessions ranged between 4.19 and 6.79%. High crude fibre in diet is known to enhance the digestibility, decrease the blood cholesterol and reduce the risk of large bowel cancers (Anderson et al 1995, Salvin et al 1997).

Ash and vitamins

Ash in Mucuna seeds ranges from 2.9-5.5% (Janardhanan and Lakshmanan 1985, Ravindran and Ravindran 1988, Vadivel and Janardhanan 2000). Kay (1979) reported thiamine (13.9 ppm) and riboflavin (1.8 ppm) as major vitamins in seeds.

Carbohydrates

The low digestible and high resistant starch and soluble sugars in Mucuna pruriens var. utilis ranged from 9.2-10.5% in whole seeds and 10.1-11.5% in dehulled seeds (Siddhuraju et al 2000). Among the 12 accessions studied by Ezeagu et al (2003), total sugar ranged between 1.51 and 3.19 g/100 g with highest concentration in Mucuna preata. Ezeagu et al (2003) reported carbohydrate in the range of 59.20-64.88 g/100 g with highest concentrations in Mucuna veracruz (64.88 g/100 g). Structural, physicochemical, retrogradation behavior and functional properties of Mucuna seed starch were determined by Adebowale and Lawal (2003b, 2003c) and found that temperature has a pronounced impact on the swelling capacity and solubility and heat moisture conditioning reduced the solubility and swelling capacity of the native starch. Carbohydrates of legumes are known to reduce the plasma cholesterol and gradually elevate the levels of blood glucose (Leeds 1982, Walker 1982). Carbohydrates of eight accessions ranged between 42.79-64.88% (Table 1)

Minerals

Legumes form a rich source of minerals particularly potassium, magnesium, iron, zinc and calcium (Salunkhe et al 1985). Among the minerals of Mucuna utilis seeds,potassium was highest (778-1846 mg/100 g) followed by calcium (104-900 mg/100 g), iron (1.3-15 mg/100 g), zinc (1.0-15 mg/100 g), manganese (0.56-9.26 mg/100 g) and copper (0.33-4.34 mg/100 g). Some accessions of Mucuna are the rich source of phosphorous (98-498 mg/100 g) and magnesium (85-477 mg/100 g) (Janardhanan and Lakshmanan 1985, Ravindran and Ravindran 1988, Siddhuraju et al 2000, Vadivel and Janardhanan 2000). Ezeagu et al (2003) reported minerals of 12 Mucuna accessions of Nigeria, wherein potassium was the major element (Mucuna georgia, 300 mg/100 g; Mucuna jaseada, 846 mg/100 g) with high calcium (0.07-0.14%), phosphorus (0.44-0.56%) and iron (4.08-14.85 mg/100 g). Reports on seeds of Mucuna pruriens revealed high potassium (806-2790 mg/100 g) (Mary Josephine and Janardhanan 1992), while low potassium (356-433 mg/100 g) is also reported by Adebowale et al (2005a). Mineral composition of seed legumes is dependent on the soil edaphic factors including the genetic origin and geographical source (Vadivel and Janardhanan 2001b). It is known that iron, selenium, zinc and manganese strengthen the immune system as antioxidants (Talwar et al 1989). Similarly, magnesium, zinc and selenium are also known to prevent cardiomyopathy, muscle degeneration, growth retardation, alopecia, dermatitis, immunologic dysfunction, gonadal atrophy, impaired spermatogenesis, congenital malformations and bleeding disorders (Chaturvedi et al 2004). The variations in the mineral composition of some Mucuna seed accessions have been projected in Table 2, wherein potassium constitutes the major element.

Fatty acids and amino acids

Only a few studies are available on the fatty acid composition of Mucuna seeds (Table 3). The fatty acid profile consists of high unsaturated fatty acids such as oleic acid (6.9-28.7%) and linoleic acid (21.4-49.5%) (Mohan and Janardhanan 1995, Siddhuraju et al 2000). Among the antinutritionally important and undesirable fatty acids, behenic acid (C_22:0) (0.73 to 3.76%) was reported in Mucuna seeds.