ABSTRACT
Kenya is endowed with nature where hundreds of medicinal plants are available. During
photosynthesis and respiration process in plants, animals and other organisms, ions of metal elements
play a major role with a few of the elements being essential to the body as nutrients. Trace elements
Zn, Cr, V and Se with known immunological response and healing properties were analysed from
selected medicinal plants available in Kenya. These plants were; Prunus africana, Urtica massaica,
Maytenus obscura, Maytenus putterlickiodes, Azadiracta indica (Neem), Mondia whytei,
Zanthoxylum usambarense, Maerua edulis, Trigonella foenum-graecum (fenugreek) and Glycyrrhiza
glabra. The concentrations of elements were determined using Energy Dispersive X-ray
Fluorescence Spectrometer (EDXRF). The levels of zinc varied from 25.94±1.89 to 70.58±4.70
mg/kg (mean 45.94± 12.42 mg/kg). Vanadium from 1.69±0.18 to 9.99±0.86 mg/kg with an average
level of 5.89± 2.09 mg/kg. Chromium from 1.44±0.30 to 6.94±0.59 mg/kg with a mean of 3.49±1.32
mg/kg. For selenium the levels varied from 53.21±5.45 to 124.01±4.41 µg/kg with a mean of 90
±19.17 µg/kg. The levels of the trace elements were compared with recommended dietary intake
(RDI) and were found to provide these essential elements as part of therapeutic utility. The levels in
different plant parts were found not to be statistically significantly different (P>0.05) except for
vanadium levels in urtica massaica (P=0.05). The results of this study will be used to sensitize the
public on the presence of essential trace elements in the studied medicinal plants and to contribute to
the advancement of knowledge.
TABLE OF CONTENTS
TITLE PAGE - - - - - - - - - - - - - - - - - - - - - - i
DECLARATION - - - - - - - - - - - - - - - - - - - - - ii
DEDICATION - - - - - - - - - - - - - - - - - - - - - iii
ACKNOWLEDGEMENTS - - - - - - - - - - - - - - - - - - iv
ABBREVIATIONS AND ACRONYMS - - - - - - - - - - - - - - - v
TABLE OF CONTENTS - - - - - - - - - - - - - - - - - - - - vi
LIST OF TABLES - - - - - - - - - - - - - - - - - - - - viii
LIST OF FIGURES - - - - - - - - - - - - - - - - - - - - ix
ABSTRACT - - - - - - - - - - - - - - - - - - - - - - - x
CHAPTER ONE - - - - - - - - - - - - - - - - - - - - - 1
1 INTRODUCTION - - - - - - - - - - - - - - - - - - - - 1
11 BACKGROUND INFORMATION - - - - - - - - - - - - - - - 1
12 STATEMENT OF THE PROBLEM - - - - - - - - - - - - - - - 4
13 PURPOSE OF STUDY - - - - - - - - - - - - - - - - - - 4
14 SCOPE AND LIMITATIONS OF THE STUDY - - - - - - - - - - - - 5
15 HYPOTHESES - - - - - - - - - - - - - - - - - - - - 5
16 OBJECTIVES OF THE STUDY - - - - - - - - - - - - - - - - 5
161 GENERAL OBJECTIVE - - - - - - - - - - - - - - - - - 5
162 SPECIFIC OBJECTIVE - - - - - - - - - - - - - - - - - 5
CHAPTER TWO - - - - - - - - - - - - - - - - - - - - - 6
2 LITERATURE REVIEW - - - - - - - - - - - - - - - - - - 6
21 ELEMENTAL CHEMICAL COMPOSITION OF PLANTS - - - - - - - - - 6
211 Zinc - - - - - - - - - - - - - - - - - - - - - - 7
212 Selenium - - - - - - - - - - - - - - - - - - - - - 8
213 Chromium - - - - - - - - - - - - - - - - - - - - 10
214 Vanadium - - - - - - - - - - - - - - - - - - - - 11
22 MEDICINAL PLANTS - - - - - - - - - - - - - - - - - - 12
22
1 Trigonella foenum-graecum L (FENUGREEK) - - - - - - - - - - - 13
222 Glycyrrhiza glabra L - - - - - - - - - - - - - - - - - 14
223 Prunus africana (HOOK F) KALKMAN - - - - - - - - - - - - - 16
224 Azadirachta indica A - - - - - - - - - - - - - - - - - - 18
225 Urtica massaica L - - - - - - - - - - - - - - - - - - 20
226 Zanthoxylum usambarensis (ENGL) KOKWARO - - - - - - - - - - 21
227 Maytenus obscura (ARICH) CUF - - - - - - - - - - - - - - 23
228 Maytenus putterlickiodes (LOES) EXELL & MENDONÇA - - - - - - - - 24
229 Mondia whytei (HOOK F) - - - - - - - - - - - - - - - - 25
2210 Maerua edulis (GILG & GILG-BEN) - - - - - - - - - - - - - 26
23 ANALYTICAL METHODS FOR DETERMINATION OF TRACE ELEMENTS - - - 27
231 Energy Dispersive X-ray Fluorescence Theory - - - - - - - - - - - 28
CHAPTER THREE - - - - - - - - - - - - - - - - - - - - 33
3 MATERIALS AND METHODS - - - - - - - - - - - - - - - - 33
31 SAMPLE COLLECTION AND PRETREATMENT - - - - - - - - - - - 33
32 EDXRF STANDARDS - - - - - - - - - - - - - - - - - - 33
33 EDXRF INSTRUMENTATION - - - - - - - - - - - - - - - - 34
34 SAMPLE PREPARATION AND ANALYSIS - - - - - - - - - - - - - - - 34
35 SAMPLE PREPARATION AND ANALYSIS - - - - - - - - - - - - 34
36 STATISTICAL ANALYSIS - - - - - - - - - - - - - - - - - 35
CHAPTER FOUR - - - - - - - - - - - - - - - - - - - - 36
4 RESULTS, DISCUSSION, CONCLUSION AND RECOMMENDATION - - - - - 36
41 RESULTS AND DISCUSSION - - - - - - - - - - - - - - - - 36
411 Elemental Levels in Reference Material - - - - - - - - - - - - - 36
412 Zinc levels - - - - - - - - - - - - - - - - - - - - 37
413 Vanadium levels - - - - - - - - - - - - - - - - - - - 40
414 Chromium levels - - - - - - - - - - - - - - - - - - 43
415 Selenium levels - - - - - - - - - - - - - - - - - - - 45
42 CONCLUSION - - - - - - - - - ERROR! BOOKMARK NOT DEFINED
43 RECOMMENDATIONS - - - - - - - - - - - - - - - - - - 47
431 Recommendations from this study - - - - - - - - - - - - - - 48
432 Recommendation for further work - - - - - - - - - - - - - - 48
REFERENCES - - - - - - - - - - - - - - - - - - - - - 49
APPENDIX - - - - - - - - - - - - - - - - - - - - - - 61
LIST OF TABLES
Table 21: RDA for trace elements of interest - - - - - … - - - - - - 12
Table 41 Elemental analysis of Bowen kale compared to certified values (mg/kg) - - 36
Table 42: Zinc levels (mg/kg) - - - - - - - - - 37
Table 43: Vanadium levels (mg/kg) - - - - - - - - - - - - - - 40
Table 44: Chromium levels (mg/kg) - - - - - - - - - - - - - - 43
Table 45: Selenium levels (µg/kg) - - - - - - - - - - - - - - - 45
LIST OF FIGURES
Figure 21: Trigonella foenum-Graecum plant - - - - - - - - - - - - - - 13
Figure 22: Trigonella foenum-Graecum seeds - - - - - - - - - - - - - 13
Figure 23: Glycyrrhiza glabra plant - - - - - - - - - - - - - - - - - 15
Figure 24: Glycyrrhiza glabra roots - - - - - - - - - - - - - - - - 15
Figure 25: Prunus africana trunk - - - - - - - - - - - - - - - - 17
Figure 26: Azadirachta indica plant - - - - - - - - - - - - - - - - - 19
Figure 27: Azadirachta indica fruits - - - - - - - - - - - - - - - - 19
Figure 28: Urtica massaica plant - - - - - - - - - - - - - - - - - 20
Figure 29: Zanthoxylum usambarensi plant - - - - - - - - - - - - - - - 22
Figure 210: Zanthoxylum usambarensis seed pods - - - - - - - - - - - - 22
Figure 211: Maytenus obscura plant - - - - - - - - - - - - - - - - 23
Figure 212: Maytenus putterlickiodes plant - - - - - - - - - - - - - - 24
Figure 213: Mondia whytei plant - - - - - - - - - - - - - - - - - - 26
Figure 214: Mondia whytei roots - - - - - - - - - - - - - - - - - 26
Figure 215: Maerua edulis plant - - - - - - - - - - - - - - - - - 27
Figure 216: Electronic set up of the EDXRF system… - - - - - ……30
