Alpha Amylase Inhibitory Activities And Antioxidative Properties Of Some Medicinal Plants Used In The South East, Nigeria For The Treatment Of Diabetes Mellitus

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