ABSTRACT

Diabetes mellitus (DM) is a metabolic disorder characterized by a loss of glucose homeostasis, due to disturbance of carbohydrate, fats, and protein metabolism, resulting from defects in insulin production and action or both. In Nigeria, the number of people suffering from diabetes mellitus is rapidly increasing. There are several oral hypoglycemic drugs used in the treatment of DM but are not devoid of adverse effect. However, natural products from plant source have proven to be effective and safe in the treatment of DM. An ethnobotanical survey conducted in Imo state (Isiala Mbano & Owerri) and Abia state (Ikwuano) in South Eastern Nigeria revealed nine medicinal plants frequently mentioned by the traditional healers in the treatment of diabetes mellitus. Nine medicinal plants namely; Chlorophora excelsa (root), Strophanthus hispisdus (root), Picralima nitida (seed), Persea americana (seed), Loranthus micranthus (leaf), Ceiba pentandra (leaf), Synsepalum dolficicum (leaf), Anthocleista djalonensis (leaf) and Anacardium occidentale (leaf). The phytochemical properties of these plants were estimated using standard TLC method while the antioxidant activities were done using 1, 1-diphenyl-2-picrylhydrazl (DPPH), 2, 21-azino-bis-3-ethylbenzothiazoline-6-sulfonic-acid (ABTS), and Ferric Reducing Antioxidant Power (FRAP).Some of the samples had (Ceiba pentandra and Anacadium occidentale) a robust antioxidant potential while some of the samples exhibited moderate antioxidant potential. The thin layer Chromatography (TLC) profiling revealed the presence of phenolics, flavonoids, alkaloids, saponins with yellow-brown coloured zones at daylight indicating the presence of alkaloid, yellow coloured zone indicating the presence of flavonoids, and blue coloured zone indicating the presence of phenols. The presence of these compounds in the plantsindicates the presence of phytochemical in the plant extracts in support of their antioxidant and biological activity. The α-amylase inhibition test indicated that some of the plant extracts (Chlorophora excelsa, Picralima nitida, Synsepalum dolficicum, Anacardium occidentale) showed good α-amylase inhibitory effect and can act as good anti-diabetic agents and therefore at least supports their use in the treatment of Diabetes mellitus. The antioxidant activities seen in these plants need to be further explored in synergy with the possible anti-diabetic properties of the plants in the treatment of DM.

TABLE OF CONTENTS

Title page i

Certification ii

Dedication iii

Acknowledgements iv

Table of contents v

List of Tables viii

List of Figures ix

Abstract x

CHAPTER ONE 1

1.0 INTRODUCTION 1

1.1.      Background of this study 1

1.2.     Research justification 3

1.3.      Research objective 3

CHAPTER TWO 4

2.0 LITERATURE REVIEW 4

2.1.       Diabetes mellitus 4

2.1.1. Classification of Diabetes mellitus 4

2.1.2. Oral hyperglycemia drugs 6

2.1.3. Polyphenols 9

2.2.1. Phenolic acids 9

2.2.2. Flavonoids 9

2.3. Free radicals and oxidative stress 10

2.4. Hyperglycemia and oxidative stress 10

2.5. Antioxidant activities of plants 11

2.6.    Thin-layer chromatography 11

2.7. Medicinal plants investigated in the study 12

2.7.1. Anacardium occidentale 12

2.7.2. Anthocleista djalonensis 12

2.7.3. Ceiba pentandra 13

2.7.4. Chlorophora excelsa 14

2.7.5. Loranthus micranthus 15

2.7.6. Persea americana 16

2.7.7. Picralima nitida 18 

2.7.8. Strophanthus hispidus 18

2.7.9. Synsepalum dolficicum 19

CHAPTER THREE 21

3.0 MATERIALS AND METHODS 21

3.1. Plant materials 21

3.2. Plant collection and extract preparation 21

3.3. Quantitative determination of polyphenols 21

3.3.1. Determination of phenolic acid content 21

3.3.2. Determination flavonoid content 22

3.3.3 Determination of plant metabolites using Thin layer Chromatography (TLC) profiling 24

3.4. In vitroantioxidant activity of plant extracts 23

3.4.1. Ferric reducingantioxidant power (FRAP) 23

3.4.2. DPPH radical scavenging activity 24

3.4.3. ABTS radical scavenging Activity 24

3.5. Alpha-amylase inhibitory activity 24

3.5.1. Preparation of enzyme solution 24

3.5.2. Preparation of plant extract and enzyme substrate solution 24 

3.5.3. Calibration plot for D-maltose 24

3.5.4. Test for α-Amylase inhibitory activity 25

3.6. Antibacterial inhibition of plant extracts using disc susceptibility testing 26

CHAPTER FOUR 27 

4.0 RESULTS 27

4.1.1. Ethnobotanical information 27

4.2. Polyphenol content of the plant extracts 28

4.3. Antioxidant properties of plant extracts 29

4.4. Alpha amylase inhibitory activities 32

4.5. Thin layer chromatography (TLC) analysis 33

4.6. Antibacterial studies of the plant extracts 34

CHAPTER FIVE 35

5.1. DISCUSSION 35

5.2. CONCLUSION 38

5.3. RECOMMENDATION 39

5.4. Certificate and abstract note of scientific presentation 40

REFERENCES