ANTIDIABETIC ACTIVITIES OF THE METHANOLIC ROOT BARK EXTRACT OF AFZELIA AFRICANA IN ALLOXAN-INDUCED DIABETIC MICE

ABSTRACT

The methanolic root bark extract of Afzelia africana was tested for antidiabetic activities

in-vivo. The acute toxicity of the extract was tested in mice and the result showed that the extract

has low toxicity. Investigation on the phytochemical constituents of the plant extract revealed the presence of flavonoids, tannins, alkaloids, steroids and saponins.

The plant extract was tested for antidiabetic activities in alloxan – induced diabetic mice at doses; 62.5 mg/kg, 125 mg/kg, 250 mg/kg, 500 mg/kg and 1000 mg/kg over a period of 6 hours. The extract was found to have antidiabetic activity. Optimum activity was noted at the dose of 250 mg/kg and 6 hours post treatment.  The antidiabetic activity of the extract did not differ significantly (p>0.05) from that of glibenclamide.

Column and thin layer chromatography revealed the presence of five fractions in the plant extract with fraction 3 found to be the active fraction.

The free radical scavenging activity of the active fraction determined by in- vitro DPPH (1, 1-diphenyl 2-picryl hydrazine) and FRAP (Fehling’s reducing antioxidant power) Methods revealed that it has an antioxidant activity.

CHAPTER ONE INTRODUCTION

Diabetes mellitus, commonly referred to as diabetes (as it will be in this article) was first identified as a disease associated with “sweet urine”, and excessive muscle loss in the ancient world. An elevated level of blood glucose (hyperglycemia) leads to spillage of glucose into the urine, hence the term sweet urine.

It is a metabolic disease characterized by high blood glucose levels, either, because the body does not produce enough insulin or because the body cells do not properly respond to insulin that is produced (Rother, 2007). Insulin is a hormone produced by the beta cells of the pancreas. Its primary function is to transport glucose to cells. When the blood glucose is elevated (for example after eating food), insulin is released from the pancreas to normalize the glucose level. If this function cannot be met as in diabetic cases glucose accumulates in the blood leading to many complications (Rother, 2007).

The discovery of a role for the pancreas in diabetes is generally ascribed to Joseph Von Mering and Oskar Minkowski, who in 1889 found that dogs whose pancreas were removed developed all the signs and symptoms of diabetes and died shortly afterwards (Von Mering and Minkowski, 1890). The classical symptoms of Diabetes mellitus are polyuria, polydipsia, polyphagia  and  weight  loss  (Cooke  and  Plotnick,  2008).  Diabetes  mellitus  is  a  relatively common endocrinopathy in dogs and cats. It is more important in these species, though it has been reported in horses, dairy cattle, pigs and sheep (Aiello et al., 1998). In dogs and cats, most spontaneous cases occur in middle aged animals. In dogs, females are affected twice as often as male and the incidence appears to be increased in certain breeds of dogs such as miniature poodles, Dachshunds, Shnauzers, Terriers and Beagles, but any breed may be affected (Aiello et al., 1998).

In humans, diabetes mellitus is a major cause of death worldwide. In the year 2000, according to WHO, at least 171 million people worldwide suffered from diabetes, or 2.8% of the population (WHO, 1999). Type 2 diabetes is by far the most common, affecting 90 to 95% of the U.S diabetic population. The incidence of diabetes in developing countries follows the trend of urbanization and lifestyle changes, perhaps most importantly a “Western-style” diet. This has suggested an environmental (i.e. dietary) effect.

From an economic perspective, the National Diabetes Information Clearing house estimates that diabetes costs $132 billion in the United States alone every year. The per capita cost resulting from diabetes in 1997 amounted to $10,071.00; while health care costs for people without diabetes incurred a per capita cost of $2,699.00. During the same year, 13.9 million days of hospital  stay were attributed  to  diabetes  while 30.3  million physician  office visits  were diabetes related. These numbers reflect only the population in the United States. Globally, the statistics are staggering. The American Diabetes Association cites the 2003 assessment of the National Centre for Chronic Disease Prevention and Health Promotion that one in three Americans born after the year 2000 will develop diabetes in their lifetime (Narayan et al.,2003). According to the American Diabetes Association, approximately 18.13% (8.6 million) of Americans aged 60 and older have diabetes (Seniors and Diabetes, 2006). Diabetes mellitus prevalence increases with age and the number of older persons with diabetes are expected to grow as the elderly population increases in number. The National Health and Nutrition Examination Survey (NHANES III) demonstrated that, in the population over 65 years old, 18%

– 20% have diabetes, with 40% having either diabetes or its precursor form of unpaired glucose tolerance (Harris et al., 1998).

1.1       STATEMENT OF THE PROBLEM

   Ethnomedical products are sometimes exaggerated and based on trial and error hence the need to justify the practice of traditional medicine.

   Despite the availability of synthetic drugs, diabetes has remained a major cause of death world wide (The Diabetes Control and Complications Trial Research Group, 1993), thus there is need to search for a more potent antidiabetic agent of natural origin.

   Plant drugs are frequently considered to be less toxic more free from side effects than synthetic agents.

   Plant drugs are cheaper to obtain than synthetic agents as they are readily available in nature.

1.2       RESEARCH OBJECTIVES

1. To validate the ethnomedical use of methanolic root-bark extract of Afzelia africana in the treatment of diabetes mellitus. 2. To establish the toxicity of the extract on laboratory animals.

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