Mucuna Pruriens, The Conventional Herbal Drug

Since time immemorial various plant and plant parts have been used as traditional medicine, Ayurveda developed over generations within different societies before the era of modern medicine. According to WHO(2008), traditional medicine is the sum total of the knowledge, skills and practices based on the theories, beliefs and experiences indigenous to different cultures, whether explicable or not, used in the maintenance of health as well as in the prevention, diagnosis and improvement or treatment of physical and mental illness. In some of the Asian and African countries, about 70-80% of the population still relies on traditional medicine for their primary health care needs.

Mucuna pruriens usually known as velvet bean or cow-itch or cowage belonging to the Fabaceae family(Rajeshwar et al., 2005) is a traditional medicinal plant used in Indian medicine. It includes 150 species of annual and perennial legumes(Lampariello et al., 2012). The tropical legume Mucuna pruriens is widely naturalized and cultivated and native to Africa and tropical Asia. It is contemplated a feasible source of dietary protein (Janardhanan et al., 2003; Pugalenthi et al., 2005) owing to its high protein content (23-35%) toting up with its digestibility, compared to other pulses such as soya bean, rice bean and lima bean (Gurumoorthi et al., 2003). It can thus be considered a good source of food.

Mucuna pruriens is an annual climbing hedge plant with long vines that can reach over 15 meters (50ft) in length. The plant is totally covered with fuzzy hairs at the young stage, but it is almost completely free of hairs when it grows older (Sahaji, 2011). “Cowitch” and “cowage” are general English names of Mucuna types with copious long stinging orange hairs on the pods that cause a severe itch if they come in contact with the skin (Andersen et al., 2015). The itch is caused by a protein known as mucuna in (Reddy et al., 2008) contained in the hair coating the seed pods. Nonstinging variants of M. pruriens are commonly called “velvet bean” and they have oppressed, silky hair.

The dynamic annual climbing legume of M. pruriens extensively known as velvet bean, originally from southern China and eastern India, was once widely cultivated as a green vegetable crop (Duke, 1981). It is at present used in the tropics as a popular green crop as food, feed and cover crop (Eilitt?, 2003). M. pruriens have been reported to be consumed traditionally as food by certain tribal groups in a number of countries. In many countries like Asia, America, Africa and the Pacific Islands the velvet bean is being cultivated and used as a vegetable for human consumption; especially the pods; the young leaves are used as animal fodder.

The plant has long, slim branches; leaves are trifoliate, alternate or spiraled; flowers borne singly or in twos or threes in long pendant clusters, varying from white to dark purple, butterfly-shaped corolla. The pods are furry, chunky and stringy, averaging 4 inches long, containing four to six seeds. They are pubescent with dense black velvety hairs that cause irritating blisters when contacted with the skin. The seeds are subglobose, usually marbled, but sometimes full-colored, white, brown or black. In India, the mature seeds of velvet bean are traditionally consumed by a South Indian hill tribe, the Kanikkars, after boiling repeatedly to remove toxic principles. In the recent years, the Dravidian tribes in the Tirunelveli district have started cultivating it for use as a pulse. Mucuna spp. has been reported to exhibit reasonable tolerance to abiotic stresses, including drought, low soil fertility, and high soil acidity. They are however sensitive to cold and develop feebly in cold, wet soils (Duke, 1981). The genus flourishes unsurpassed under tropical conditions, in areas below 1500m above sea level and in areas with abundant rainfall. M. pruriens, like other legumes, pertains the ability to fix atmospheric nitrogen by establishing a symbiotic relationship with the soil microorganisms.

Although the Mucuna beans are suggested for having good nutritional value, it has been reported that velvet bean also contains several anti-nutritional factors such as L-dopa, phenols, tannins, hemagglutinin, trypsin and chymotrypsin inhibitors, anti-vitamins, protease inhibitors, phytic acid, flatulence factors, saponins and hydrogen cyanide (Vadivel, 2000). Velvet bean contains high concentrations of L-dopa (4-7%), due to which it is used as a commercial source of L-dopa, used in the treatment of Parkinson’s disease. It is also reported that possibly because of the presence of toxic chemicals, the plant exhibits less vulnerability to insect pests (Duke, 1981). M. pruriens is reported to hold nematicides effects as well as remarkable allelopathic activity, which may function to restrain competing for plants (Gliessman et al. 1981).

Regardless of its anti-nutritional properties, diverse species of Mucuna are grown as a minor food crop. The seeds of velvet bean contain approximately 23.4% of protein and are rich in minerals (Duke, 1981). In Brazil, the seed starch has been studied as a food thickener and adhesive base. The immature pods and leaves of velvet bean are used as green vegetables in South-East Asia. Some parts of Asia and Africa also consume the seeds after roasting (Vadivel, 2000). Mucuna beans have also been used as an alternative to coffee after being roasted and ground, for at least several decades in Central America, for which the seeds are commonly known as “Nescafe” in this region (Duke, 1981).