ABSTRACT

The antimicrobial activities and preliminary phytochemical screening of crude aqueous extract of Vernonia amygdalina Del. was carried out against isolates obtained from spoilt tomato paste which included Escherichia coli, Pseudomonas aeruginosa, Micrococcus spp, Acinetobacter spp, Lactobacillus spp, Aspergillus spp, Rhizopus spp and Penicillium spp. The extract exhibited antibacterial and antifungal activity against the test organisms. The phytochemical screening of Vernonia amygdalina showed the presence of tannins, cardiac glycosides, saponins, flavonoids, steroids, terpenes, anthraquinones and alkaloids. V. amydalina exhibited antimicrobial action action against test organisms judged by their various zones of inhibition; P. aeruginosa (9.50mm), Micrococcus spp (16.50mm), Escherichia coli. (12.33mm), Acinetobacter spp (10.33mm), Lactobacillus spp (13.50mm), Aspergillus spp (12.50mm), Rhizopus spp (10.33mm) and Penicillium spp (14.50mm). The crude extracts exhibited strong potency against the bacteria and fungi with Penicillium spp and Micrococcus spp being the most susceptible when compared to the control (Chloramphenicol). Since this crude extract was able to inhibit the growth of the organisms associated with tomato paste spoilage, it could as well be used for the preservation of tomato paste.

TABLE OF CONTENTS

Title page i

Certification ii

Dedication iii

Acknowledgement iv

Table of Contents v-vi

List of Tables vii

Abstract viii

CHAPTER ONE

1.1 Background of Study 1

1.2      Aim and Objectives             4

CHAPTER TWO

2.0 LITERATURE REVIEW 5

2.1 The Nature of Food Spoilage 6

2.2 Significance  of   Agents  of  Tomato  Spoilage 9

2.3 Plant antimicrobials in food applications 9

2.4 Application of Plant Antimicrobials in Shelf-Life Extension 

of Food 10

2.5 Vernonia amygdalina Del 11

2.6 Nutrient Composition/Nutritional Uses 12

CHAPTER THREE

3.0 MATERIALS AND METHODS 13

3.1 Collection of Plants Materials 13

3.2 Preparation of Plant Material and Plant Extracts 13

3.2.1 Cold Aqueous Extract 13

3.2.2 Preparation of media 13

3.2.3 Isolation of Bacteria 13

3.2.4 Isolation of Fungi 14

3.2.5 Purification (Subculture) of Bacterial Isolates 14

3.2.6 Purification of Fungal Isolates 14

3.3 Characterization and Identification of Bacterial Isolates 15

3.3.1 Antibacterial Assay 15

3.4 Phytochemical Screening of the Leaves Extracts 15

3.4.1 Test for Flavonoids 16

3.4.2 Test for Alkaloids 16

3.4.3 TestforSaponins 16

3.4.4 Test for Phenol 16

3.4.5 Test for Glycosides 16

3.4.6 TestforTannins 17

3.4.7 Test for volatile oils 17

3.4.8 Test for Steroids 17

3.4.9 Test for Terpenoids 17

3.4.10 Test for Anthraquinones 17

3.4.11 Test for Cardenolides Keller-KillianiTest 18

CHAPTER FOUR

4.0 RESULTS 19

CHAPTER FIVE

5.0 DISCUSSION 25

5.1      CONCLUSION 27

5.2 RECOMMENDATION 28

References 29

LIST OF TABLES

Table Title Page 

1 Morphological, biochemical and sugar fermentation profile of 

Bacterial isolates 20

2 Isolation and identification of fungal isolates 21

3 Mean Zone of inhibition of crude aqueous 

Extract of V. amygdalina leaves against bacterial isolates                         22

4 Mean Zone of inhibition of crude aqueous 

Extract of V. amygdalina leaves against fungal isolates                              23

5 Phytochemical Screening of Vernonia amygdalina (bitter leaves)

Ethanol and Aqueous leaves Extract 24