1 INTRODUCTION:

Vigna unguiculata is a plant which is cultivated in India and belongs to the family Fabaceae/ Papilionaceae.^1,2It is a warm-season, annual legume that exhibits a wide range of growth habits.³Varieties may be short and bushy, prostrate, or tall and vine like.⁴ The plant is known by a variety of names, but cowpea is the most popular worldwide name. In the United states, it is called black-eyed beans, black-eyed peas or sourthern peas, whereas in Indian and Brazil, it is referred to as lobia and caupi respectively.⁵In tamil, it is called caramunnipayira/ karamani.¹ It is found almost in India, Haryana, Punjab, Gujarat and Uttar Pradesh. It is usually grown on marginal lands in Tripura, Assam valley, Andaman and Nicobar islands, cowpea is grown on a limited scale in rice fallow where black pepper and coconut palms are grown together, which is grown as fodder crop. It is warm season, annual legume.The upright stems are hollow and hairless.(Fig.5), Flowers are purple or white bell shaped⁴(Fig.4).

It is grown throughout the year under rainfed and irrigated conditions of kerala and in similar climatic conditions.³ In Cambodia, pulse is prescribed in liver complaints with jaundice.¹Drug induced diuresis is beneficial in many life threatening disease conditions such as congestive heart failure, nephritic syndrome, cirrhosis, renal failure, hypertension and pregnancy toxaemia.⁶Diuretics are the drugs that increase the rate of urination.⁷ Cowpea is known also as containing a low amount of fat and high level of fiber which can prevent heart disease by reducing the low density lipoprotein.⁸. These plants have intermediate growth habit, and take 100 days to mature, where the second half is the productive period.³ These are herbaceous, erect or suberect, climbing, prostrate, growing 15-80 cm high. 3-6 inch; long, slender, round, two valved pods⁴.(Fig.1) The plants starts flowering in about 40-50 daysand the first harvest can be done after 55 days.¹ These are medium length, pendant pods, medium sized, kidney shaped or roundish seeds (Fig.3), The active constituents present in cowpea which is responsible for diuretic activity is Saponin which inhibited contraction of smooth muscle caused by acetylcholine⁹ Leaves are alternate, trifoliate with petioles 5-25 cm long. (Fig.2) The lateral leaflets are opposite and asymmetrical , while the central leaflet is symmetrical and ovate. The cowpea was protected against Field Insects Pests with the use of Cashew Nut Shell Liquis (CNSL), whose efficacy as seed protectant against C. maculatus L. On cowpea seeds in storge was reported¹⁰ some varieties of cowpea are used specifically for wildlife purposes¹¹.

Fig 1- Whole plant

Fig 2- Leaves

Fig 3-Legumes

Fig 4- Flower

Fig 5- Root

Habitat:^12,13

Cowpea is commonly cultivated as a nutritious and highly palatable food source in the Middle East, Africa, and throughout the tropics and subtropics. Nowadays it is cultivated throughout and across Asia, Oceania, southern Europe, Africa, southern USA. Cowpea grows best in hot conditions. It can grow in moderate shade, but in agro forestry or orchard applications, shade should not be too heavy. It is better adapted to sandy soils and droughty condition. An eight foot taproot can develop in roughly 8 weeks. Seeds mature in 90-140 days. Flowering occurs roughly in 48 days.

TAXONOMIC CLASSIFICATION^17,
18

Botanical name : Vigna unguiculata

Family : Fabaceae/ Papilionaceae

Sub family : Faboideae

Order : Fabales

Tribe : Phaseoleae

Sub tribe : Phaseolinae

Kingdom : Plantae

Sub kingdom : Vascular plants

Division : Magnoliophyta

Class : Magnoliopsida

Sub class Rosidae

Origin : Bangladesh

Genus : Vigna

Species : unguiculata.

HISTORY:

Vigna unguiculata is native to India and belongs to the family Fabaceae/ Papilionaceae. It is grown in various parts of India.¹ The seeds are diuretic, used to stregthen the stomach, boiled and eaten, considered good food and to destroy worms in the stomach.¹⁴All the parts of plants are used as food which are nutritious, thus providing proteins and vitamins, whereas immature pods and peas are used as vegetables while several main dishes and snacks are prepared from grains. This is because crop is considered as nutrition to man¹⁵It is also useful in toning the spleen, stomach and pancreas helps induce urination and relieves damp conditions like leucorrhea.¹⁶ It increases water retension properties.³

PHYTOCHEMISTRY:

Presence of phytoconstituents like saponins, flavanoids and terpenoids have been previously found to be responsible for diuretic and laxative activities in plants.^3,19-22Saponin present in this plant is responsible for diuretic activity.⁹ Plant is rich in vitamin A and C. It contains appreciable amount of thiamine, riboflavin, niacin, vitamin B6 and pantothenic acid and also foliate.¹⁶Milk which are extracted from cowpea contains proteins 1.2-3, total solid, sugars 0.2-0.6g/100ml and energy 17.9-42.4 k cal.³It also has small amount of Iron, Sodium, Zinc, Selenium, Manganese and copper¹⁶.

USES:

The various parts of the plant Vigna unguiculata (leaves, stem, root, seeds and legumes) are used as a diuretic which will increase the water retension.³Seeds are used as laxative, diuretic, ingestible, appetiser, galactogogue, tonic and antibilious and pulse to strengthen the stomach.¹Whole plant- Diuretic effect. It is used as allopathic medicine which may help to suppress weeds.¹³

MEDICINAL PROPERTIES OF COWPEA:

ANTI-OXIDANT ACTIVITY:²³

The anti oxidant activity of seed extracted with methanol was tested using a linoleic acid peroxidation model, FRAP, ORAC and TRAP assays, as well as DPPH, Hydroxyl, Nitric oxide and superoxide radical scavenging activity. Extracts of seeds were assessed for their potential scavenging anti radical activity against some common radicals like hydroxyl, nitric oxide and superoxide and values expressed as IC 50 µg/ml. It concluded that cowpea showed significant management or prevention of degenerative diseases associated with free radical damage, in addition to their traditional role of preventing protein malnutrition.

ANTI-DIABETIC ACTIVITY:²⁴

Vigna unguiculata seed oil has anti diabetic activity which was investigated albino rats by administration of single dose of alloxan monohydrate (110mg/kg body wt) to diabetes induced rats for a period of 21 days. The effect of oil on blood glucose level was measured in the diabetic rats. It was compared with standard anti diabetic agent, glipizide. It was concluded that seed oil of cowpea may be very useful for the improvement of the complications of diabetes.

ANTI BACTERIAL ACTIVITY:²⁵

Aqueous and ethanolic extracts of seeds of Vigna unguiculata collected from local area and were studied for anti bacterial activity. It was tested against gram +ve bacteria- Bacillus substilis and gram –ve bacteria- E.coli by agar well diffusion method. Different concentrations (100, 200, 300µg/ml) were incorporated into wells. The standard drug used was tetracycline (300µg/ml) was poured into an extra well. The results showed the highest positive anti bacterial activity with an inhibition diameter of 22mm against E. coli. It was concluded that Vigna unguiculata showed anti bacterial activity against E.coli, a gram – ve bacteria.

CONCLUSION:

Vigna unguiculata is a multipurpose plant species widely used as food and medicine. Every part of the Vigna unguiculata plant is reported to be useful. The edible parts are India and where found to show interesting pharmacological properties including anti oxidant, anti diabetic and anti bacterial activity. It is hoped that this review will be a strong stimulus for research and development efforts towards better understanding and utilization of the plant Vigna unguiculata.

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Received on 21.08.2015 Modified on 28.09.2015

Res. J. Pharmacognosy and Phytochem. 7(4): Oct-Dec. 2015; Page 219-222

DOI: 10.5958/0975-4385.2015.00033.3