ANTIMICROBIAL ACTIVITY AND PHYTOCHEMICAL STUDIES OF TURRAEA ABYSSINICA, MEYNA TETRAPHYLLA AND LEONOTIS MOLLISSIMA KINUTHIA ESTHER WANJIRU A Thesis Submitted to the Graduate School in Partial Fulfilment of the Requirements for the Doctor of Philosophy Degree in Chemistry of Egerton University EGERTON UNIVERSITY NOVEMBER 2019 DECLARATION AND RECOMMENDATION Declaration This thesis is my original work and has not been submitted for examination in any institution. Signature: __________________ Date: ____________________ Kinuthia Esther Wanjiru SD11/0379/13 Recommendation This thesis has been submitted with our recommendation as the University Supervisors. Signature: _________________ Date: ___________________ Dr. Mwangi Elizabeth Muthoni, PhD Chemistry Department Egerton University Signature: _________________ Date: ___________________ Prof. Cheplogoi Peter Kiplagat, PhD (posthumous) Chemistry Department Egerton University ii COPYRIGHT © 2019, Kinuthia Esther Wanjiru All rights reserved. No part of this work may be reproduced, stored in a retrieval system, or transmitted in any forms or means, mechanical, photocopying, electronic process, recording, or otherwise copied for public or private use without the prior written permission from Egerton University iii DEDICATION This thesis is dedicated to my late parents Mr and Mrs Morrison Njenga, my husband George Kinuthia, our children, Anne Kinuthia, Beth Kinuthia, Grace Kinuthia and grandson Addy. iv ACKNOWLEDGEMENT I wish to extend my sincere thanks to the Almighty God for this far He has taken me and to all those who made this work a success. I would like to thank Egerton University for giving me a chance to pursue this degree. This gave me an opportunity to reach this scholarly level of achievement. My supervisors Dr. E.M. Mwangi and the Late Prof. P.K. Cheplogoi, for their help, guidance and the constructive criticism they gave me throughout. .Special thanks to National Commission for Science, Technology and Innovation (NACOSTI) for granting me the funds to accomplish this work. My special thanks to Dr Alice Njue for voluntarily stepping in to assist me when Prof Cheplogoi passed on. Many thanks to Prof. S.T. Kariuki of Botany Department, Egerton University for the identification of the plants, Dr. M.K. Langat of University of Surrey, UK for NMR analysis and Dairy Department, Egerton University for the bioassay tests. My very special thanks to all my Siblings, my husband George Kinuthia, our children Anne, Beth, Grace and our grandson Adrian for their prayers, encouragement and moral support. Thank you for creating a favourable environment for the good performance and success of this work. Finally my special thanks to my late parents, Mr and Mrs Morrison Njenga for educating me and showing me how much important Education is. v ABSTRACT Due to the high bills involved in the importation of modern medicinal drugs, about 80% of the African population use traditional medicine from plants to treat common infectious diseases caused by microorganisms. The main objective of this research was to determine the antimicrobial activity of crude extracts and isolated compounds from Turraea abyssinica, Meyna tetraphylla (Abyssinian coral tree) and Leonotis mollissima (Lion’s ear) from Meliaceae, Rubiaceae and Lamiaceae families respectively. They were studied in this research due to their wide use by local communities of Kenya for medicinal remedies. Plant materials were sampled from Kirinyaga East, Narok North, Baringo South, Tharaka Nthi Maua, Laikipia University and Mau Narok in Kenya. They were identified and voucher specimen kept for reference. All the plants crude extracts showed significant antimicrobial activity on all the test microorganism (Bacillus cereus, Staphylococcus aureus, Escherichia coli,Salmonella typhimurium and Candida albicans) at a concentration of 1 mg/ml despite been sampled from different regions of Kenya. They had lower MIC (Minimum Inhibition Concentration) as compared to the Amoxil® and Doxycycline® antibiotics that were used as positive control for comparison. From Turraea abyssinica stem bark dichloromethane crude extract (52.42 g), three compounds 176 (Sitosterol, 4.60 mg), 177 (Scopoletin, 6.00 mg) and 178 [2-(1’,2’-Dihydroxypropyl)tetradecanoic acid, 5.65 mg] were isolated. Of the three compounds only compound 176 showed significant activity on Bacillus cereus, Staphylococcus aureus, and Candida albicans) at a concentration of 2.5 mg/mL to 4.0 mg/mL. Meyna tetraphylla leaves dichloromethane crude extract (45.24 g) gave compounds 179 (Phaeophytin, 9.40 mg), 180 (Enantiomer, 5.80 mg), 118 (α-Amyrin, 5.65 mg) and 60 (Sitigmasterol, 5.82 mg). The Structures of the compounds were elucidated using 1D-and 2D NMR. Experiments. Compound (179) showed significant activity on Escherichia coli and Salmonella typhimurium at a concentration of 4.0 mg/mL while α-Amyrin (118) had significant activity on Salmonella typhimurium at a concentration of 4.0 mg/mL. Leonotis mollissima leaves dichloromethane crude extract (79.69 g) yielded compounds 181 (Sederin, 7.70 mg), 182 (20-hydroxylucidenic acid D2, 7.10 mg) and 183 [(13R)-19α,13α-epoxylabda- 6β(19).16(15)-dioldilactone, 21.20 mg]. Only compound (182) showed significant antimicrobial activity on Escherichia coli at a concentration of 0.4 mg/mL. This was a confirmation that the three plants contain compounds that can be isolated and used as drugs to treat various diseases including microbial infectious diseases. vi TABLE OF CONTENTS DECLARATION AND RECOMMENDATION .................................................................. ii COPYRIGHT ......................................................................................................................... iii DEDICATION......................................................................................................................... iv ACKNOWLEDGEMENT ....................................................................................................... v ABSTRACT ............................................................................................................................. vi TABLE OF CONTENTS ...................................................................................................... vii LIST OF TABLES ................................................................................................................... x LIST OF FIGURES ............................................................................................................... xii ABBREVIATIONS AND ACRONYMS ............................................................................. xiv CHAPTER ONE ...................................................................................................................... 1 INTRODUCTION ................................................................................................................ 1 1.1 Background information .................................................................................................. 1 1.2 Statement of the problem ................................................................................................. 2 1.3 Objectives ......................................................................................................................... 3 1.3.1 General objective ....................................................................................................... 3 1.3.2 Specific objectives ..................................................................................................... 3 1.4 Hypothesis ........................................................................................................................ 3 1.5 Justification ...................................................................................................................... 3 CHAPTER TWO ..................................................................................................................... 4 LITERATURE REVIEW ....................................................................................................... 4 2.1 Medicinal plants ............................................................................................................... 4 2.2 The Genus Turraea ........................................................................................................... 4 2.3 The Genus Meyna .......................................................................................................... 14 2.4 The Genus Leonotis ....................................................................................................... 15 2.5 Spectroscopy .................................................................................................................. 28 2.5.1 Nuclear Magnetic Resonance Spectroscopy ............................................................ 28 2.6 Microbial diseases .......................................................................................................... 30 2.7 Micro-organisms ............................................................................................................ 30 2.7.1 Escherichia coli ........................................................................................................ 30 2.7.2 Salmonella typhimurium ......................................................................................... 31 2.7.3 Staphylococcus aureus ........................................................................................... 31 2.7.4 Candidas albicans ...................................................................................................