INVESTIGATION OF WILD GARLIC PLANT EXTRACTS AS POTENTIAL DEVULCANIZING AGENTS By Mooketsi Mpuputla A thesis submitted in fulfillment of the requirements of the degree for Magister Scientae in chemistry at the Nelson Mandela University January 2020 Supervisor: Dr. B.G. Hlangothi Co-supervisor: Prof. C. Woolard Co-supervisor: Dr. P.S. Hlangothi DEDICATION The work present in this study is dedicated to my son, Hlompo. Though a young growing man and you might have not known it, but I want to thank you for being the wind beneath my wings, reminding me that I have the ability to reaching greater successes, being the role model of the successes that you too are to one day fulfill – this is your first step my son I LOVE YOU i DECLARATION ii ACKNOWLEDGEMENTS Firstly, I wish to thank my Heavenly Father, God, for all He has done for me the past years throughout my studies. Thanking Him for His endless strength provided and ability to continue in my journey of studies, from undergrad until this very point. I wish to sincerely extend my gratitude to my supervisor, Dr. B.G. Hlangothi. Thank you for the opportunity and trust in me to work on this project. The road was not easy, but because of your endless support and encouragement, we have made it as a team. THANK YOU SO MUCH!! My co-supervisor, Prof. C.D. Woolard, thank you so for your support and research expertise in the field of rubber and science technology. Thank you for your time to listen and share new ideas. You are much appreciated!! Dr. S.P. Hlangothi, I wish to thank you for your continuous support and role that you have played in supporting and motivating me through my education and research. I could never forget the things you have pulled together for me in order to complete this degree too. My friends, peers, and colleagues in the BGH and CRST research groups, thank you all so much for your moral support and inputs. Mr Lukhanyo Bolo for his assistance with thermal analysis, guidance and valuable input throughout my research. I wish to thank the technical staff, Mr H. Schalkenkamp, Mr E. Bashman, and Mrs K. Muller for their assistance. Ms E. Storm from the Horticulture Department for plant harvesting and the Botany Department at the Nelson Mandela University for plant identification. My parents, I thank you so much for your love and support. I appreciate your patience and understanding that it has not only been about what you wish for me but mostly what I want to achieve. My family, at large, thanks for your endless prayers, believing in me and continuous support iii Contents Dedication .................................................................................................................... i Declaration ...................................................................................................................ii Acknowledgements ..................................................................................................... iii Abstract .......................................................................................................................ix LIST OF ABBREVIATIONS .........................................................................................xi LIST OF FIGURES Page ........................................................................... xiii LIST OF TABLES ..................................................................................................... xvii LIST OF SCHEMES ................................................................................................ xviii CHEMICAL STRUCTURES OF SOME IMPORTANT SPECIES .............................. xix CHAPTER 1: ............................................................................................................... 1 INTRODUCTION ......................................................................................................... 1 1.1. Aims and objectives ....................................................................................... 4 CHAPTER 2: ............................................................................................................... 5 LITERATURE REVIEW ............................................................................................... 5 2.1. THE FAMILY ALLIACEAE ............................................................................. 5 2.2. THE GENUS TULBAGHIA ............................................................................. 5 2.3. TULBAGHIA VIOLACEA ................................................................................ 7 2.3.1 Pharmacological studies of Tulbaghia violacea ....................................... 9 2.3.2 Bioactive components of T. violacea ..................................................... 11 2.4. VULCANIZATION ........................................................................................ 14 2.4.1 SULFUR VULCANIZATION REACTION SCHEME ............................... 18 2.4.2 MODEL COMPOUND VULCANIZATION .............................................. 19 2.5. DEVULCANIZATION ................................................................................... 22 iv CHAPTER 3: ............................................................................................................. 27 EXPERIMENTAL METHODS and MATERIALS ....................................................... 27 3.1. REQUIREMENTS ........................................................................................ 27 3.1.1. Chemicals and solvents ......................................................................... 27 3.1.2. Other materials ...................................................................................... 28 3.1.3. Collection of plant material .................................................................... 28 3.2. Instrumentation ............................................................................................ 28 3.2.1 High-Performance Liquid Chromatography (HPLC) .............................. 28 3.2.2 Reverse-Phase Chromatography .......................................................... 29 3.2.3 Gel Permeation Chromatography (GPC) ............................................... 29 3.2.4 Nuclear Magnetic Resonance (NMR) .................................................... 29 3.2.5 Fourier Transform Infrared Spectroscopy (FTIR) ................................... 30 3.2.6 Rotavapor .............................................................................................. 30 3.2.7 Hot Plate Magnetic Stirrer ..................................................................... 30 3.2.8 Differential Scanning Calorimetry (DSC) ............................................... 30 3.2.9 Thermographic Analysis ........................................................................ 31 3.2.10 Balances ............................................................................................ 31 3.3. Experimental procedures ............................................................................. 31 3.3.1. Plant extract preparation ....................................................................... 31 3.3.2. TLC and phytochemical test of extracts ................................................. 32 3.3.3. Analysis of crudes by HPLC .................................................................. 32 3.3.4. Purification of MBTS .............................................................................. 33 3.3.5. Purification of MBT ................................................................................ 34 3.3.6. Thermogravimetric Analysis (TGA) ........................................................ 34 3.3.7. Differential Scanning Calorimetry (DSC) ............................................... 34 v 3.3.8. Vulcanization of model compound ......................................................... 34 3.3.9. HPLC analysis of curatives and vulcanized products ............................ 36 3.3.10. Gel Permeation Chromatography ....................................................... 37 3.3.11. Devulcanization of Squalene vulcanizates ......................................... 37 CHAPTER 4 .............................................................................................................. 39 RESULTS AND DISCUSSION .................................................................................. 39 4.1. Extraction and analysis of crude extracts of Tulbaghia violacea. ................. 39 4.1.1. Plant extraction ...................................................................................... 39 4.1.2. Identification of sulfides ......................................................................... 40 4.1.3. Phytochemical analysis of sulfides ........................................................ 42 4.1.4. FTIR analysis of crudes ......................................................................... 43 4.1.5. HPLC analysis of crude extracts and quantification of DADS ................ 45 4.2. MBTS accelerated sulfur vulcanization of squalene ..................................... 50 4.2.1. TLC and NMR analysis of vulcanizates ................................................. 50 4.2.2. FTIR analysis of vulcanizates ................................................................ 51 4.2.3. RP-HPLC analysis vulcanizates ............................................................ 52 4.2.4. GPC analysis of vulcanizates ................................................................ 54 4.2.5. Thermal analysis and reactions of curatives .......................................... 58 4.3. devulcanization of squalene products