ABSRACT

Two extracts from two plants were screened for antimicrobial activity using agar disc diffusion and micro dilution broth assays. The plants that were screened are Costus spicatus and Milicia excelsa  The methanol extracts of the plants were tested against five culture collection microorganisms consisting of two Gram positive organisms(Staphylococcus aureus ATCC25923 and Enterococcus faecalis ATCC7080), two Gram negative organisms(Escherichia coli ATCC25922 and Pseudomonas aeruginosa ATCC29853) and one acid fast bacillus(Mycobacterium smegmatis ATCC14468). The extract of only one of the plants exhibited moderate level of broad spectrum antimicrobial activity against these organisms. The antimicrobial activity was measured by the diameter of zone of inhibition and minimum inhibitory concentration (MIC). The mean diameter of zone of inhibition  of Costus spicatus at the concentration of 100mg/ml on Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis, and Escherichia coli were 15mm,18mm,13mm and 15mm respectively which showed the highest level of inhibition without any inhibition on Mycobacterium smegmatis.  The activities of some of the crude extracts were not comparable to the reference antibiotics at standard concentrations used per disc. The potential of these plants for development of cheap, culturally acceptable standardized herbal medicines is discussed. 

TABLE OF CONTENTS

Title Page i

Certification ii

Dedication iii

Acknowledgements iv

Table of Contents v

List of Tables vi

List of Figures vii

Abstract viii

CHAPTER ONE

1.0 INTRODUCTION 1

1.1 Aims and objectives 2

CHAPTER TWO

2.0 LITERATURE REVIEW 3

2.1 Antimicrobials from Plants 3

2.2 Groups of Antimicrobial Compounds Found in Plants 4

2.3    Plants That Contain Antimicrobials 8

2.4      Biology and Pathogenicity of Test Organisms 10

CHAPTER THREE

MATERIALS AND METHODS

3.1 Plant Materials 12

3.2 Extraction Procedure 12

3.3 Microorganisms 12

3.4 Preparation of Media 13

3.5 Preparation of Disc    13

3.6 Determination of Minimum Inhibitory Concentration 14

3.7 Agar Disc Diffusion Method 14

3.8 Phytochemical Screening 15

CHAPTER FOUR

3.0 RESULTS 16

CHAPTER FOUR

5.1 DISCUSSION 21

5.2 CONCLUSION 21

5.3     Contributions to Knowledge 22

5.4     Recommendation for Further Studies 22

REFERENCES

APPENDIX

LIST OF TABLES

TABLE          TITLE                                                                                                  PAGE

 1          Mean  Zone of Inhibition of Milicia excelsia 17

 2          Mean  Zone of Inhibition of Costus spicatus 18

 3         The minimum inhibitory concentration (MIC) and the minimum

                   bactericidal concentration (MBC) values of the extract of 

Costus spicatus 19

4 Phytochemical Constituents  of Plant Samples 20

LIST OF FIGURES

FIGURE               TITLE                                                                              PAGE

 1           Structure of an alkaloid                               5

 2           Structure of a condensed tannin                               5

 3           Structure of Flavonoid 6 

4           Structure of terpenoid 6

5     Structure of phenol 7

6                Structure of quinine 8