EVALUATION OF THE ANTIDIABETIC EFFECTS OF WATER AND METHANOLIC EXTRACTS OF AVOCADO (PERSEA AMERICANA) SEED ON ALLOXAN INDUCED DIABETIC RATS

ABSTRACT

The high prevalence, complications and cost of conventional drugs in the management diabetes necessitated the search for alternative treatment. As a result, this study seeks to evaluate the composition, anti-diabetic potential toxicity and tissue-protective effects of both the water and methanolic extracts of Persea americana (avocado pear) seed on alloxan-induced diabetic albino rats were investigated. This study was conceived and designed based on information on the local use of the seed in diabetes treatment. Proximate and anti-nutritional constituents of the seed were determined and 100g of the sample was extracted with 1000ml of both water and methanol using the maceration method. The extracts were evaporated to dryness using a rotary evaporator and stored at 4^oC until use. The effects of different doses (200mg/kg.b.wt., 300/kg.b.wt.) of both water and methanolic extracts of P. americana seed on alloxan-induced diabetic albino rats were compared with those of a reference drug, insulin. The glucose level and weight of the rats were measured weekly for 21 days. The liver function tests and the histopathologies of the liver, and kidneys, were investigated. Results of the proximate investigation shows that the seed is rich in carbohydrate (49.03± 0.02 g/100g), lipid (17.90±

0.14 g/100g), protein (15.55± 0.36 g/100g) moisture (15.10± 0.14 g/100g) and ash (2.26±0.23 g/100g). Anti nutritional components such as total oxalate (14.98±0.03 mg/100g), tannin (6.98±0.04 mg/100g) and phytic acid (3.18±0.16 mg/1 00g). Results also showed that both the water and methanolic extracts exhibited significant anti-diabetic effects on the experimental rats. However, the methanolic extracts showed a better anti diabetic effect than the water extracts. The extracts showed no significant effects on the liver function parameters (bilirubin, conjugate bilirubin, AST, ALP and ALT) compared with the normal control but rather reversed the histopathological damage that occurred in alloxan-induced albino diabetic rats. In conclusion, the present study provides a pharmacological basis for the traditional use of P. americana seeds extracts in the management of Diabetes mellitus. It seems P. americana seed contains substantial amount of nutrients that could warrant its utilization in animal feed or food. However, further studies are required to indentify the active ingredient responsible for the anti-diabetic properties of the seed extract.

TABLE OF CONTENT

Title Page

Certification

Dedication

Acknowledgement

Abstract

Table of Contents

List of Tables

List of Figures

CHAPTER ONE

1.0       Introduction

1.1       Background

1.2       Global Burden of Diabetes

1.3       Statement of Problem

1.4       Aims and Objectives of the Study

CHAPTER TWO

2.0       Literature Review

2.1       Diabetes Mellitus

2.1.1    Types of Diabetes Mellitus

2.1.2    Prevention / Treatment of Diabetes Mellitus

2.2       Medicinal Plants

2.3       Evaluation of Drug Toxicity

2.3.1    Liver Function

2.3.1.1 Total Bilurubin

2.3.1.2 Conjugated Bilurubin

2.3.1.3 Aspartate Transaminase (AST)

2.3.1.4 Alanine Transaminase (ALT)

2.3.1.5 Alkaline Phosphatase (ALP)

2.3.2    Histology of Liver and Kidney

CHAPTER THREE

3.0       Materials and Methods

3.1       Experimental Design

3.2       Chemicals and Reagents

3.3       Sample Collection and Preparation

3.4       Proximate Analysis

3.4.1    Protein Content

3.4.2    Crude Fat Content

3.4.3    Moisture Content

3.4.4    Ash Content Measure

3.4.5    Carbohydrate Content

3.5       Anti-nutritional Components

3.5.1    Tannin Content Determination

3.5.2    Oxalate Determination

3.5.3    Phytic Acid

3.6       Animal Experiment

3.6.1    Induction of Diabetes

3.6.2    Administration of Extracts

3.6.3    Blood Sample Collection

3.6.4    Liver Function Tests

3.6.4.1 Total Bilirubin Test

3.6.4.2 Conjugated Bilirubin Test

3.6.4.3 Alanine Aminotransferase (ALT) Test

3.6.4.3 Aspartate Aminotransferase (AST) Test

3.6.4.5 Alkaline Phosphatase (ALP) Test

3.6.5    Histological Study

3.6.5.1 Histology Sample Preparation

3.7       Statistical Analysis of Data

CHAPTER FOUR

4.0       Results

4.1       Proximate Analysis

4.2       Anti-Nutritional Analysis

4.3       Animal Experiment Results

4.3.1    Glucose Analysis Results

4.3.2.   Results of Body Weight Analysis

4.3.3.   Liver Function Test Results

4.3.4    Histology Results

CHAPTER FIVE

5.0       Discussion

5.1       Proximate and Anti-nutrients

5.2       Effects of Extracts on Body Weight

5.3       Effects of Seed Extracts on Blood Glucose

5.4       Effects of Seed Extracts on Liver Function Parameters

5.5       Histological Effects of Extracts on the Kidney and Liver

5.6       Conclusion

References

Appendix

.

LIST OF TABLES

CHAPTER ONE

1.0              INTRODUCTION

1.1              BACKGROUND

During the past decade, the traditional systems have gained importance in the field of medicine. The World Health Organization estimates that 4 billion people, 80% of the world population (WHO, 2002), presently use herbal medicine for some aspect of primary health care (Orisataoki and Oguntibeju, 2010). Eighty percent (80%) of African populations use some form of traditional herbal medicine (WHO, 2002.) and the worldwide annual market for these products approaches US$ 60 billion (Willcox and Bodeker, 2004). Herbal medicine is a major component in all indigenous people's traditional medicine. Medicinal plants have continued to attract attention in global search for effective methods of using plants parts (e.g. seeds, leaves, stems, roots, barks etc) for the treatment of many diseases affecting humans (Sofowora, 2008). This is as a result of the continuous need for less expensive means of disease control.

Medicinal plants are plants which can be used for therapeutic purposes or which are precursors for the synthesis of useful drugs (Sofowora, 2008). Many important drugs used in healthcare today are directly derived from plants due to its bioactive constituents such as; alkaloids, tannins, steroids, etc. Examples include L-Dopa derived from Mucuna spp used for anti-parkinsonism, another is Caffeine, a CNS stimulant derived from Camellia sinensis and Quinine from Cinchona ledgeriana and used for Antimalarial, antipyretic.

As a matter of fact, well into the 20^th century, much of the pharmacopoeia of scientific medicine was derived from the herbal lore of native people. Many drugs commonly used today are of herbal origin. Undisputedly, the history of herbology is inextricably intertwined with that of modern medicine. Many drugs listed as conventional drugs were originally derived from plants.

Salicyclic acid, a precursor of aspirin, was originally derived from white willow bark and the meadowsweet plant (Zand, et al., 2003).

Plants are very unique as their existence is very essential for the sustenance of the rest of the food chain. Based on the observations made through successive generations, superstition as well as traditional medicinal folklore, man has found and has been using herbs, barks, fruits, leaves, seeds, roots and stems of different plants of various climatic regions for therapeutic purposes (Sofowora, 2008).

1.2              GLOBAL BURDEN OF DIABETES

Diabetes mellitus is a metabolic disease caused by a deficiency in the secretion or action of insulin (Nelson and Cox, 2005). This disorder is characterized by major symptoms as; polyuria (frequent and abundant urine), glycosuria (presence of glucose in urine) and hyperglycemia (glucose rate on an empty stomach higher than 1.2g/l in plasma blood and confirmed in at least two occasion) (N’guessan et al., 2009). Basically, there are two major clinical classes of diabetes

.The type 1 diabetes or insulin dependent diabetes mellitus (IDDM) and type 2 diabetes or non insulin dependent diabetes mellitus (NIDDM) also called insulin resistant diabetes. According to the International Diabetes Federation (IDF) 2014 updates, out of the world seven billion population, 387million people, aged 20–79 years wor ldwide are diabetic, (IDF, 2014) giving a comparative prevalence of 8.3%, while 46.3% cases are undiagnosed. In every 7 seconds, a person dies of diabetes, 4.9 million deaths in 2014. Seventy seven percent (77%) of people with diabetes live in low and middle income countries. Africa has recorded cases of 2,150,274 (5.05%) diabetic patients with over 13million undiagnosed cases. In Nigeria, there are estimated 374,651 diabetic cases, with another 172,339 undiagnosed cases. These figures account for about 4.64% Nigerian adults between ages 20-79 living with diabetes (IDF, 2014). In 2014, about 105,090 Nigerians died as a result of diabetes (IDF, 2014). An average diabetic Nigerian spent about 43527.16 naira (US $178.39) in 2014 due to diabetes treatment (IDF, 2014). With this alarming prevalence rate, diabetes mellitus poses a major challenge globally and accounts for a number of disabilities and deaths globally.