ABSTRACT

Two extracts from two Nigeria medicinal plants, Colocasia esculenta and Caladium bicolor were screened for antibacterial activities using disc diffusion and micro dilution broth assays. Methanol extracts of each of the plants were tested against four microorganisms consisting of two Gram positive bacteria (Staphylococcus aureus and Streptococcus faecalis) and two Gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The antibacterial activity was measured by the diameter zone of inhibition and minimum inhibitory concentration (MIC). The extracts exhibited moderate broad spectrum antibacterial activities against the microorganisms. The diameter of zone of inhibition ranges from 10mm-15mm at 2000mg/ml of crude extract per disc. The MIC values were between 125mg/ml-100mg/ml. The activities of some of the crude extracts were comparable to the reference antibiotics (Gentamicin) at standard concentration per disc. These findings have shown the potentials of these extracts for antibacterial activities against clinical isolates.

TABLE OF CONTENTS

Title Page i

Certification ii            

Dedication iii

Acknowledgements iv

Table of Contents v

List of Tables vii

List of Figure viii

Abstract ix   

CHAPTER ONE 1

1.1 Introduction 1

1.2 Aims and objectives 2

CHAPTER TWO 3

2.0      Literature review 3

2.1 Examples of plants used as medicine 4

2.2 Active chemical constituents of medicinal action of plant 6

2.3 Clinical isolates 10

2.4 Description of the plants 16

2.4.1 Colocasia esculenta 16

2.4.2 Caladium bicolor 16

CHAPTER THREE 18

MATERIALS AND METHODS 18

3.1 Collection and identification of plant materials 18

3.2 Preparation of  plant extracts 18

2.2.1 Methanol extract 18

3.3 Test organism 20

3.4 Preparation of plant extract concentration 20

3.4.1 Disc diffusion assay 20

3.5 Control experiment using Gentamycin and Dimethyl Sulphuroxide 21

3.6 Preparation of culture media and antibacterial activity 21

3.7 Determination of Minimum inhibitory concentration 22

CHAPTER FOUR 23

RESULTS 23

4.1 Percentage yield of plant extracts 23

4.2 Antibacterial activity of plant extracts 23

4.3 Minimum inhibitory concentration test results of the plant extracts 24

CHAPTER FIVE 27

DISCUSSION AND CONCLUSION 27

5.1 Discussion 28

5.2 Conclusion 29

References