Phytochemical and Elemental Analysis of Nettles Found In
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Phytochemical and Elemental Analysis of Nettles found in KwaZulu-Natal, South Africa By NOMFUNDO THOBEKA MAHLANGENI 2016 Phytochemical and Elemental Analysis of Nettles found in KwaZulu-Natal, South Africa NOMFUNDO THOBEKA MAHLANGENI 2016 A thesis submitted to the School of Chemistry and Physics, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Westville, for the degree of Doctor of Philosophy. This thesis has been prepared according to Format 4 as outlined in the guidelines from the College of Agriculture, Engineering and Science which states: This is a thesis in which chapters are written as a set of discrete research papers, with an overall introduction and final discussion where one (or all) of the chapters have already been published. Typically, these chapters will have been published in internationally recognized, peer- reviewed journals. As the candidate’s supervisor(s), I have approved this thesis for submission. Supervisor: Signed: .......................................... Name: ..................................... Date: Co-supervisor: Signed: ........................................... Name: ..................................... Date: ii ABSTRACT There is a rich diversity of indigenous edible plants in South Africa. Rural communities have for years, been collecting indigenous edible medicinal plants for food and for their medicinal properties. However, a combination of a shortage of food and lack of diversity in the diet has resulted in many South Africans suffering from malnutrition. Malnutrition, food insecurity and nutrient deficiencies which help propogate non-communicable diseases are amongst the top concerns in South Africa. Knowledge on the elemental composition, nutritional and medicinal value of medicinal plants would allow for safe consumption of these plants and improve overall health. The aim of this study was to investigate the secondary metabolites in the Laportea and Obetia nettles found in KwaZulu-Natal (South Africa) and to conduct an elemental investigation into the nutritional composition of these nettles to determine their suitability for consumption and their contribution to recommended dietary allowances. The study showed that cooked and raw leaves of nettles (L. peduncularis, L. alatipes, and O. tenax) were rich sources of macronutrients and essential elements which are comparable to common vegetables. The nettles, L. alatipes and O. tenax, have higher macronutrient content than elemental content relative to the nettles, L. peduncularis and U. dioica, after cooking. Soil quality indicators (geo-accumulation indices and enrichment factors) showed moderate to no contamination of nettle growth soils around KwaZulu- Natal. Statistical analysis showed the association of these metals in the different sites. Phytochemical analysis of the nettles showed that the nettles were rich in β-carotene and sterols owing to their use as natural anti-diabetic agents. This study provides information on the nutritional value of nettles and shows that they can serve as an affordable alternative to commercially available herbs and it also lends scientific credence to the ethno-medicinal use of nettles. iii SUMMARY OF ISOLATED COMPOUNDS 18' 4' 17 19 20 5' 16 3' 7 9 11 13 15 14' 12' 10' 8' 1' 2' 2 1 6 6' 13' 8 10 12 14 15' 11' 9' 7' 5 3 17' 16' 19' 20' 4 18 C-1 242 1 21 24 22 18 26 20 24 12 23 25 11 17 19 13 27 16 1 14 2 9 15 10 8 7 3 5 HO C-2 4 6 iv ABBREVIATIONS 13C NMR - C-13 nuclear magnetic resonance spectroscopy 1H NMR - proton nuclear magnetic resonance spectroscopy ANOVA - analysis of variance BAF- bioaccumulation factor CA- cluster analysis CEC- cation exchange capacity CRM- certified reference material d - doublet dd - double doublet DPPH - 2,2-diphenyl-1-picrylhydrazyl DRI - dietary reference intake EDTA- ethylenediaminetetraacetic acid Ex – exchangeable EF- enrichment factor FRAP – ferric reducing antioxidant potential GC-MS - gas chromatography-mass spectrometry v Hz - Hertz ICP-OES- inductively coupled plasma-optical emission spectrometry Igeo- geo-accumulation factors IR- infrared NIPI- Nemerow integrated pollution index r- correlation coefficient PC- principal component PI- pollution index RDA- recommended dietary allowance RI- response index SD- standard deviation SOM- soil organic matter TF- translocation factor TLC- thin-layer chromatography UL- tolerable upper intake level UV- ultraviolet vi DECLARATIONS Declaration 1: Plagiarism I, Mahlangeni Nomfundo Thobeka declare that 1. The research reported in this thesis, except where otherwise indicated, and is my original research. 2. This thesis has not been submitted for any degree or examination at any other university. 3. This thesis does not contain other persons’ data, pictures, graphs or other information, unless specifically acknowledged as being sourced from other persons. 4. This thesis does not contain other persons' writing, unless specifically acknowledged as being sourced from other researchers. Where other written sources have been quoted, then: a. Their words have been re-written but the general information attributed to them has been referenced b. Where their exact words have been used, then their writing has been placed in italics and inside quotation marks, and referenced. 5. This thesis does not contain text, graphics or tables copied and pasted from the Internet, unless specifically acknowledged, and the source being detailed in the thesis and in the References sections Signed ......................................................................... vii Declaration 2: Publications & Conferences Publication 1 Title: The distribution of macronutrients, anti-nutrients and essential elements in nettles, Laportea peduncularis susp. peduncularis (river nettle) and Urtica dioica (stinging nettle) Authors: Nomfundo T. Mahlangeni, Roshila Moodley, Sreekantha B. Jonnalagadda Journal: Journal of Environmental Science and Health, Part B, 2016, 51(3): 160-169. Publication 2 Title: Heavy metal distribution in Laportea peduncularis and growth soil from the eastern parts of KwaZulu-Natal, South Africa Authors: Nomfundo T. Mahlangeni, Roshila Moodley, Sreekantha B. Jonnalagadda Journal: Environmental Monitoring and Assessment, 2016, 188(2): 1-14. Publication 3 Title: Elemental analysis of edible mountain nettle (Obetia tenax) and the influence of soil on its chemical composition Authors: Nomfundo Thobeka Mahlangeni, Roshila Moodley, Sreekantha Babu Jonnalagadda Journal: Manuscript accepted for publication: Analytical Letters Conference Title: 29th EFFoST International Conference, Food Science Research and Innovation: Delivering sustainable solutions to the global economy and society, Athens, Greece, 10-12 November, 2015 Poster: The distribution of macronutrients, anti-nutrients and essential elements in nettles, Laportea peduncularis susp. peduncularis (River nettle) and Urtica dioica (Stinging nettle). (Nomfundo T. Mahlangeni, Roshila Moodley, Sreekantha B. Jonnalagadda) viii In all of the publications I have performed all the experimental work and written the manuscripts. The co-authors were involved in discussion of the results and were responsible for verifying the scientific content and accuracy of the results as well as editing the manuscripts. I have been the corresponding author on two of the manuscripts contained in this thesis. Signed: …………………………… ix ACKNOWLEDGEMENTS Firstly, would like to thank God for giving me the strength, patience and confidence to embark on such a journey. I would also like to convey my sincere gratitude to my supervisor, Prof. S.B. Jonnalagadda, for the opportunity to study under him and for the knowledge and wisdom, support and constant encouragement. And also my co-supervisor, Dr. R. Moodley, for her being a teacher, nurturer and a great mentor from my early stages of being a researcher. It has been a long journey on which she gladly walked with me. I would also like to acknowledge the following individuals who encouraged me, gave me words of wisdom and helped me through my research; my best friend Bongisiwe, Kimona, Olumuyiwa, Olusola, Samuel, Victoria, Judie, Esther, Gracious; my brothers and sisters Nerena, Letticia, Lydia, Mr and Mrs Lodder. I would like to thank my colleagues in the natural products research group for moral support, Lamla, Saba and the rest of the team. I would like to acknowledge, the technical team in the School of Chemistry & Physics for their assistance: Vashti Reddy, Anita Naidoo, Greg Moodley, Dilip Jagjivan, Unathi Bongoza and Edward Khathi (School of Life Sciences). I would also like to acknowledge the National Research Foundation (NRF) for financial support. Lastly, I would like to thank my family; my mother, Mrs T.F. Mahlangeni, for her love, support, wisdom and encouragement throughout the research, my sister Phakamile, and my brother Andile for their support and patience and my nieces and nephews (Senamile, Aphiwe, Asanda, Sandiselwe, Nosipho, Minenhle and Lwanele) for their love and support. x CONTENTS Phytochemical and Elemental Analysis of Nettles found in KwaZulu-Natal, South Africa ........................ ii ABSTRACT ................................................................................................................................................. iii SUMMARY OF ISOLATED COMPOUNDS ............................................................................................ iv ABBREVIATIONS ...................................................................................................................................... v DECLARATIONS