Toxicological Studies of Aqueous Leaf Extract of Mucuna pruriens on Albino Rats

Enechi Osmond C.* Emmanuel N. Tufon and Ogugua Victor N.

Department of Biochemistry, University of Nigeria, Nsukka, Nigeria

ABSTRACT:

The leaves of Mucuna pruriens have been used traditionally for the treatment of various ailments but little information has been documented about its toxicological studies of the aqueous leaf extract of mucuna pruriens on albino rats to ascertain its hepatotoxic effect when used in traditionally medicine. Preliminary phytochemical analysis was carried out by the method of Harboune (1973). The ALT and AST concentrations were measured using Human test kits (Germany). Total protein and bilirubin were measured using standard biochemical methods as described in Amadi et al. 2004. The phytochemical analysis indicated the presence of flavonoids, tannins, terpenoids, alkaloids, saponins and trace amounts of cyanogenic glycosides. The leaf extract of graded doses of 400 and 800mg/kg body weight given orally to the rats caused no significant increase or decrease (p>0.05) in the serum ALT, AST, total protein and bilirubin concentrations when compared to the controls. From the results of our study, we therefore conclude that the aqueous leaf extract of mucuna pruriens had no hepatotoxic effect at the investigated doses and thus can be used in traditional medicine. However, further research needs to be carried out on higher doses and duration.

KEYWORDS: Toxicology, Mucuna pruriens, Hepatotoxic, Phytochemistry.

INTRODUCTION:

About 80% of the world’s population relies on herbal medicines (William, 2002). Traditional medicine has remained popular in all regions of the developing countries. In most African countries, it is believed that the first line of treatment for 60% of children with high fever resulting from malaria is the use of herbal medicines at home (WHO, 2003). At present, the World Health Organization is taking an official interest in herbal medicines in order to facilitate its aim of making health care available for all. However, there are no hundred percent certainties that some of these herbs are without negative side effects. There is thus the need for continuous scientific investigation on herbs to determine any toxicological effects (Warrier, 1995). Although the leaves of mucuna pruriens have been used for centuries for the treatment of various ailments such as dropsy, ulcers, inflammation and pains (Taylor, 2005; Oudhie, 2001), little information has been documented about the effect of the aqueous leaf extract of mucuna pruriens on albino rats to ascertain its hepatotoxic effect when used in traditional medicine.

MATERIALS AND METHODS:

Collection and Preparation of Plant Materials:

The leaves of Mucuna pruriens were harvested from Uzo Ayinyu, Obukpa Nsukka Local Government Area of Enugu State, Nigeria by plucking them fresh and green. They were botanically identified by Mr. Njokuocha of the herbarium section, Department of Botany, University of Nigeria Nsukka, Nigeria.

The leaves were dried under shade at room temperature (25^oC) for 14 days and pulverized using a 40-mesh sieve and then macerated in water (0.4L) and filtered after 6 hours. The filtrate was collected as the aqueous extract, wrapped with an aluminum foil to prevent the penetration and interaction of light with the extract. The extract was then refrigerated.

Procurement and management of experimental animals:

Twenty four (24) albino male Wister rats were purchased from the laboratory Animal Unit of the Department of Physiology, Faculty of Veterinary Medicine, University of Nigeria, Nsukka. They were held in stainless wire-rat-cages in a clean fly proof experimental animal house and were fed ad libitum with 25% crude protein commercial chick’s mash diet (Top Feed Nigeria Ltd). The rats were given access to unlimited supply of clean water using animal drinkers. The animals were divided into three groups of eight rats each. The experimental groups were given orally 400mg/kg body weight (Group 2) and 800mg/kg body weight (Group 3) of the extract per day for 14 days while the control group (Group 1) were given normal saline (0.9% NaCl). Animals were sacrificed on day 15.

Blood Samples Collection:

Blood samples were collected from the retro-bulbar medial cantus of the eye of the rats. A micro-capillary tube was carefully inserted into the medial cantus of rats to puncture the retro-bulbar plexus and thus enable the outflow of blood into a sterilized anticoagulant free test tube. The blood was then centrifuged at 3000rpm for 5 minutes and the serum collected and used for the biochemical assays.

Phytochemical analysis:

The phytochemical analysis was done using the method of Harborne (1973). Phytochemical tests were carried out to detect the presence of alkaloids, flavonoids, cyanogenic glycosides, saponins, tannins and terpenoids.

Alanine aminotransferase (ALT) Measurement:

Alanine aminotransferase (ALT) was measured using a Human test kit (Germany). ALT reagent (1ml) was added to 0.1ml of serum and read immediately at 344nm.

Aspartate aminotransferase (AST) measurement:

Aspartate aminotransferase (AST) was measured using a Human test kit (Germany). AST reagent (1ml) was added to 0.1ml of serum and read immediately at 344nm.

Total Protein Determination:

Total protein was determined by the Biuret’s method as described by Amadi et al. (2004). Three test tubes were labeled blank, standard and sample. Distilled water (0.02ml) was added to the blank tube, 0.02ml of standard was added to the tube labeled standard and serum (0.02ml) was added to the sample tube. To each tube Biuret’s reagent (1.0ml) was added, mixed and incubated for 30 minutes at 25^oC. The absorbance of the sample and standard were measured against the blank at 540nm.

Bilirubin Determination:

Bilirubin was determined using standard biochemical method as summarized below. Two test tubes were labeled blank and sample. Sulfanilic acid (0.2ml) was added to both tubes and one drop of nitrite to the sample tube only. Nacl solution 0.9% (2.0ml) was then added to both tubes, mixed and left to stand for 5 minutes at 25^oC. The absorbance was then read against the blank at 540nm.

Statistical Analysis:

Data entry and analysis were done using SPSS version 12.0 and values were represented as mean ± SD. The difference between groups were compared for statistical significance using sample t-test with the level of significance set at p<0.05.

RESULTS:

The result of the phytochemical analysis of Mucuna pruriens is summarized on Table 1

Table 1: phytochemical composition of the leaf extract of Mucuna pruriens

Phytochemicals	Composition
Flavonoids	+++
Saponins	+++
Tannins	++
Terpenoids	++
Alkaloids	+++
Cyanogenic glycosides	+

Key; +++= High; ++= Moderate; += Low

Results obtained from the ALT, AST, total protein and bilirubin concentrations (table 2) show no significant increase or decrease in the test animals compared to the control groups after 14 days of administration of the extract (p>0.05)

Table 2: The effect of the extract on the serum concentrations of ALT, AST, total protein and bilirubin after 14 days of administration in albino rats; Mean ± SD

Groups	Parameters
Groups	ALT (U/L)	AST (U/L)	Total protein (g/dl)	Bilirubin (µmol/L)
Group 1 (Control)	24.65 ± 1.08	64.13 ± 5.09	6.99 ± 0.61	0.38 ± 0.03
Group 2 (400mg/kg b.w.)	22.9 ± 0.78	66.87 ± 4.87	7.00 ± 0.19	0.34 ± 0.09
Group 3 (400mg/kg b.w.)	25.85 ± 2.34	68.05 ± 5.88	7.07 ± 0.55	0.36 ± 0.06

DISCUSSION:

As indicated in Table 1, the leaf extract of Mucuna pruriens is rich in phytonutrients such as flavonoids, saponins, tannins, terpenoids, alkaloids while cyanogenic glycosides in trace amounts. The biological functions of flavonoids include protection against allergies, inflammation, free radicals, microorganisms, ulcer and tumors (Okwu and Omodamiro, 2005; Duke, 1992; Enechi and Odonwodo, 2003). The presence of flavonoids, alkaloids, tannins and saponins in the leaf of Mucuna pruriens may contribute to the vast pharmacological properties of the plant and justifies its use in the treatment of various ailments in traditional medicine. The results of the liver function test show that there was no significant increase or decrease (p>0.05) in the serum concentration of ALT, AST, total protein and bilirubin after 14 days of administration of the extract when compared to the control group. The liver function enzymes are found within organs and tissues and are released into the blood following cellular necrosis or damage (Havel, 2004).

In conclusion from our results, the aqueous leaf extract of mucuna pruriens had no hepatotoxic effect at the doses used in this study and thus can be used in traditional medicine. However, further research needs to be carried out on higher doses and duration.

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Received on 27.04.2011

Accepted on 29.06.2011

Research J. Pharmacology and Pharmacodynamics. 3(5): Sept –Oct. 2011, 253-255