chlorantha Stem Bark

Ayoade A. Adesokan^* and Musbau A. Akanji

Department of Biochemistry, University of Ilorin,
Ilorin, Nigeria

ABSTRACT

The antimalarial bioactivity of aqueous extract of stem back of Enantia chlorantha was investigated in Plasmodium berghei infected mice. Stem bark of Enantia chlorantha was analysed for its phytochemicals. Twenty five (25) albino mice were infected by intraperitoneal injection of standard inoculum of chloroquine sensitive Plasmodium berghei (NK 65 strain). The animals were randomly divided into 5 groups of 5 mice each. Group A served as the control while groups B and C were administered 1.75 and 5 mg/kg body weight of artesunate and chloroquine respectively. Groups D and E received 100 and 400 mg/kg of extract of E. chlorantha orally. The results showed the presence of alkaloids saponins, phenolics, flavonoids and glycosides. There was 100 per cent parasite clearance in the 400mg/kg extract and chloroquine groups, and 98.6 per cent clearance in the group that received 100mg/kg body weight of extract. There was no parasite clearance in the artesunate group. There was 100 per cent mortality in the negative control group; 40 per cent mortality in the artesunate, chloroquine and 100mg/kg body weight extract group and 60 per cent mortality in the 400mg/kg extract group. The Mean Survival Time for the control group was 9.0 days; artesunate 22 and chloroquine 19.8 days, while the groups that received 100 and 400 mg/kg body weight of extract recorded 19.6 and 17.0 days respectively.

The results showed that aqueous extract of Enantia chlorantha possess potent antimalarial activities comparable to that of chloroquine and may be ascribed to the significant presence of alkaloids and phenolics.

Keywords:Antimalarial bioactivity, Enantia chlorantha, Stem bark, Plasmodium berghei, Mice.

Introduction

Malaria remains the major cause of morbidity and mortality in the tropical regions of the world with over 300 million new cases reported annually (WHO, 2005). Almost 90 per cent of the deaths from malaria occur in sub-Saharan Africa, where the vulnerable groups are children under 5 years and the pregnant women (WHO, 1999).

WHO experts say that the number of people infected with malaria is still increasing at the rate of about 5 per cent annually, and this has been attributed largely to increasing incidence of resistance to antimalarial drugs formerly effective against the pathogen. Antimalarial drug resistance has become one of the greatest challenges against malaria control. There is widespread multi-drug resistance to common antimalarial drugs (Muregi et al., 2003; WHO, 2005).

In Africa, more than 80 per cent of the people use traditional herbal remedies for the treatment of many ailments including malaria (Akerele, 1984; Wright and Phillipson, 1990).

Rodent plasmodia such as Plasmodium yoeli and Plasmodium berghei are commonly used as malaria models in mice and have tremendous impact on the investigation of antimalarial activity of plant extracts.

The need to search and develop more effective antimalarial drugs that are inexpensive and readily available to people in the developing countries like Nigeria has necessitated this study.

Materials and Methods

Plant Materials

The stem bark of Enantia chlorantha [family–Annonaceae], was harvested in the month of April at Ifetedo along Ife–Ondo road, and was authenticated at the Department of Botany, Obafemi Awolowo University, Ile-Ife, Nigeria with voucher number: oliv. IFE No 13968.

Aqueous Extraction

Stem bark of the plant was air-dried to constant weight and ground into powdered form with an electric blender (Blender/Miller III, model MS 223) Taiwan, China. Aqueous extract was prepared as described previously (Akanji and Adesokan, 2005).

Phytochemical Analysis

A portion of the stem powder was subjected to phytochemical analysis, using standard chemical tests as described earlier (Odebiyi and Sofowora, 1978; Trease and Evans, 1989).

Experimental Animals

Albino mice, weighing 20-25g, were obtained from the small Animal Holding Unit of the Department of Pharmacology, College of Health Sciences, University of Ilorin, Ilorin, Nigeria. The animals were housed in wire mesh cages under standard conditions, and the study conducted in accordance with the recommendations from the declaration of Helsinki on guiding principles in the care and use of animals.

Drugs and Reagents

Artesunate used in this study was manufactured by Mekopharm Chemical Pharmaceutical Joint Stock Company, Vietnam, while the chloroquine was from Mayer and Baker Pharmaceutical Company Limited. Nigeria. Other reagents were of analytical grade.

Malaria Parasite

Plasmodium berghei (chloroquine sensitive NK 65 strain) was obtained from the Institute for Advanced Medical Research and Training (IMRAT), College of Medicine, University of Ibadan, Ibadan, Nigeria.

Inoculation of Experimental Mice

Albino mice were infected by intraperitoneal injection of standard inoculum (0.2 ml of 1 x 10⁷ infected erythrocytes) from a single donor mouse previously infected with Plasmodium berghei (29.8 per cent parasitaemia).

Animal Groupings

The animals were randomly divided into 5 groups of 5 mice each, after confirmation of parasitaemia 72 h post-inoculation. Group A, (control) was left untreated but administered appropriate volume of distilled water. Group B received artesunate orally at a dose of 1.75mg/kg body weight daily for 4 days and group C 5mg/kg body weight of chloroquine base for the same period. Groups D and E were administered aqueous extract of Enantia chlorantha through oropharyngeal canula at the doses of 100 and 400mg/kg body weight respectively.

Estimation of Percentage Parasitaemia

Percentage parasitaemia was estimated at the end of the observational period of 28 days using the formula:

Parasitized RBC

—————————————————— x 100

Parasitized RBC + Non-parasitized RBC

Estimation of Percentage Mortality

The number of deaths was recorded for the animals in each group for the experimental period and the percentage mortality calculated thus:

Number of dead animals in a group

—————————————————— x 100

Total number of animals in the group

Estimation of Mean Survival Time (MST)

The number of days each animal survived was recorded for the animals in each group and the mean survival time calculated using the formula:

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