ABSTRACT
The roots of Dennettia tripetala and Milicia excelsa were analyzed for the presence of phytochemicals. Five different solvents, which include methanol, ethanol, ethyl acetate, butanol and water, were used for the extraction of the phytochemicals.The root of Dennettia tripetala contained alkaloids, terpenoids, flavonoids, saponins, phenols, steroids and glycosides in varying degrees of abundance in the different solvents with tannins not detected in all the solvents. Milicia excelsa contained all the phytochemicals in Dennettia tripetala, in addition to tannins, in different degrees of abundance in the various solvents. The root of Dennettia tripetala contained 1.83 % alkaloids, 3.64 % flavonoids, 1.41 % saponins, 0.67 %phenols, 0.36 % steroids and 0.08 % glycosides whereas that of Milicia excelsa contained 2.19 %alkaloids, 6.40 % flavonoids, 0.87 % saponins, 0.34 % phenols, 0.36 % tannins, 0.15 % steroids and 0.09 % glycosides. Results of the Principal Component Analysis (PCA) of the phytochemicals revealed that, in Dennettia tripetala, there was strong positive correlation between alkaloids and glycosides (0.995)and also phenols and saponins (1.000) while the strong negative correlations were between alkaloids and flavonoids (-0.980), flavonoids and glycosides (-0.956), phenols and steroids (-1.000) and also saponins and steroids (-1.000). In Milicia excelsa, the strong positive correlations were between alkaloids and flavonoids (0.908), phenols and saponins, glycosides (0.866) and also steroids and tannins (1.000) whereas the strong negative correlations were between phenols and steroids (-0.866), saponins and tannins, steroids (-1.000) as well as tannins and phenols (-0.866). An assay of the antioxidant potentials of various extracts of both plants, using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method, revealed that the ethanolic extracts of Dennettia tripetala and Milicia excelsa as well as the methanolic extract of Dennettia tripetala showed high percent inhibition ranging from 83.34 to 89.75 at 0.01 mg/mL of the extracts; results which showed to be better than standard ascorbic acid (67.89) at the same concentration. Other extracts of both plants, at higher concentrations, gave percent inhibitions ranging from 35.80 for the butanolic extract of Milicia excelsa at 0.025 mg/mL to 95.96 for the methanolic extract of the same plant at 0.5 mg/mL. A comparison of the half maximal inhibitory concentration (IC50) values of the extracts showed that ethyl acetate extracts of both plants had the best IC50 values at 0.014 and 0.150 for Dennettia tripetala and Milicia excelsa respectively which were better than ascorbic acid standard whose IC50 value was 1.060. All the other extracts of both plants also had IC50 values better than ascorbic acid except for ethanol in both plants and methanol in Milicia excelsa. The extracts were tested for antimicrobial activity against a gram positive cocci, staphylococcus aureus, and a gram negative rod, klebsiella sp. The results revealed that the ethanolic extract of Dennettia tripetala and the butanolic extracts of both plants showed activity against the test organisms at two concentrations, 400 mg/mL and 200 mg/mL, with the inhibition zone diameters (IZD) ranging from 8.2 mm to 12.0 mm and 6.5 mm to 14.0 mm for the ethanolic and butanolic extracts respectively. The minimum inhibitory concentration (MIC) of the extracts ranged from 41.5 mg/mL to 48.3 mg/mL for the ethanolic extracts and 164.8 mg/mL to 111.7 mg/mL for the butanolic extracts. The presence of these secondary metabolites in varying and substantial amounts in the roots of the plants as well as the antioxidant and antimicrobial potentials of the roots of the plants lends scientific credence to the ethnomedicinal use of these plants parts for the treatment of various diseases and ailments.
TABLE OF CONTENTS
Title page i
Certification iii
Dedication iv
Acknowledgement v
Abstract vi
Table of contents vii
List of tables ix
CHAPTER ONE: INTRODUCTION
1.1 General Background 1
1.2 Phytochemicals 2
1.3 Antibiotics 2
1.3.1 Penicillins 2
1.3.2 Cephalosporins 3
1.3.3 Tetracyclines 4
1.4 Antimicrobial Assay 5
1.5 Antioxidants 5
1.5.1 Antioxidant Assays 6
1.6 Botanical Profiles of the Plants 6
1.7 Ethnomedicinal Uses of the Plants 8
1.8 Objectives of the Study 8
1.9 Scope of the Study 9
1.10 Significance of the Study 9
CHAPTER TWO: LITERATURE REVIEW
2.0 General Background 10
2.1 Classes of Phytochemicals 11
2.1.1 Alkaloids 11
2.1.2 Terpenoids 12
2.1.3 Tannins 13
2.1.4 Saponins 13
2.1.5 Flavonoids 14
2.1.6 Steroids 15
2.1.7 Essential Oils 16
2.1.8 Phenolics 16
2.2 Review of Previous Works on Plants and Phytochemicals 17
CHAPTER THREE: EXPERIMENTAL
3.1 Sample Collection 23
3.2 Chemicals and Reagents 23
3.3 Apparatus and Equipment used 24
3.4 Extraction of the Phytochemicals 24
3.5 Identification of the Phytochemicals 25
3.6 Quantification of the Phytochemicals 26
3.7 Antioxidant Assay 31
3.8 Antimicrobial Assay of Extracts 32
3.8.1 Preparation of Turbidity Standard 33
3.8.2 Preparation of Inoculum 33
3.8.3 Inoculation Procedure 34
3.9 Data Analysis, Results and Interpretation 35
CHAPTER FOUR: RESULTS, DISCUSSIONS AND CONCLUSION
4.1 Results of Phytochemical Analysis 36
4.1.1 Percentage Yield of the Various Phytochemicals 36
4.1.2 Qualitative Phytochemical Analysis of Various Extracts of Dennettia
Tripetala and Milicia Excelsa 37
4.1.3 Quantitative Analysis of the Phytochemicals 39
4.1.4 Statistical Correlation of the Phytochemicals 41
4.1.5 Results of Antioxidant Analysis 44
4.1.5.1 Antioxidant Assay of the Various Extracts of Dennettia Tripetala 44
4.1.5.2 Antioxidant Assay of the Various Extracts of Milicia Excelsa 45
4.1.6 IC50 Values for the Various Extracts 58
4.1.7 Results of Antimicrobial Analysis 61
4.1.7.1 Antimicrobial Activities of the Extracts of the Root of Dennettia Tripetala 61
4.1.7.2 Antimicrobial Activities of the Extracts of the Root of Milicia Excelsa 63
4.2 Discussions 69
4.3 Conclusion 76
References 77
Appendix 92
LIST OF TABLES
4.1 Percentage Yield of the Various Phytochemicals 36
4.2 Phytochemical Analysis of the Various Extracts of Dennettia Tripetala 37
4.3 Phytochemical Analysis of the Various Extracts of Milicia Excelsa 38
4.4 Quantitative estimation (g/100 g) of alkaloids, flavonoids, phenols,
saponins, steroids, tannins and glycosides in the roots of Denettia
tripetala and Milicia excelsa. 39
4.5 Correlation Matrix of the Different Phytochemicals in the Roots of
Dennettia Tripetala 41
4.6 Correlation Matrix of the Different Phytochemicals in the Roots of
Milicia Excelsa 42
4.7 DPPH Radical-Scavenging Activity (% inhibition) of Various Extracts
of Dennettia Tripetala 44
4.8 DPPH Radical-Scavenging Activity (% inhibition) of Various Extracts
of Milicia Excelsa 45
4.9 DPPH Radical-Scavenging Activity (% inhibition) of Ascorbic Acid Standard 46
4.10 IC50 Values for Various Extracts of the Root of Dennettia Tripetala 58
4.11 IC50 Values for Various Extracts of the Root of Milicia Excelsa 59
4.12 Inhibition Zone Diameter (IZD) of ethanolic extract of the root of
Dennettia tripetala against tested organisms 61
4.13 Inhibition Zone Diameter (IZD) of butanolic extract of the root of
Dennettia tripetala against tested organisms 62
4.14 Inhibition Zone Diameter (IZD) of butanolic extract of the root of
Milicia Excelsa against tested organisms 63
CHAPTER ONE
INTRODUCTION
1.1 GENERAL BACKGROUND
Plants and plant parts are a known source of herbal medicine and natural health-enhancing products for many centuries. Various plant parts such as leaves, fruits, seeds, bark, flowers, rhizomes and roots have at one time or the other been utilized for medicinal purposes. It is estimated that about 75% of useful bioactive plant-derived pharmaceuticals used globally are discovered by systematic investigation of leads from traditional medicines1.The search for antimicrobial agents have over the years led researchers to in-depth study and analysis of various plants and their parts2, 3.
Over the years, infections caused by strains of bacteria that are resistant to orthodox drugs, also called multi-drug resistant (MDR) bacteria, have either found cure or control by the use of bioactive compounds isolated from plants. These bioactive compounds are known as phytochemicals. They can help prevent the spread of or totally eliminate infections. These phytochemicals can either be used alone as antimicrobial agents or in combination with commercially available antibiotics asstudies have shown that a higher activity against microorganisms can be achieved by combining certain phytochemicals with commercially available antibiotics4.For example, Pseudomonas aeruginosa, a microorganism which has exhibited resistance to 19 different antibiotics was observed for synergistic effects when phytochemical extracts from clove, jambolan, pomegranate and thyme were used together with known antibiotics. Results showed that bacterial growth was inhibited at phytochemical concentrations of 50µg/mL even to as low as 10µg/mL and, interestingly also, for antibiotics that previously did not show any activity by themselves against the microorganism5.
1.2 PHYTOCHEMICALS