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
1.1 BACKGROUND INFORMATION - - - - - - - - - - - - - - - .. 1
1.2 STATEMENT OF THE PROBLEM - - - - - - - - - - - - - - - 4
1.3 PURPOSE OF STUDY - - - - - - - - - - - - - - - - - - .. 4
1.4 SCOPE AND LIMITATIONS OF THE STUDY - - - - - - - - - - - - 5
1.5 HYPOTHESES - - - - - - - - - - - - - - - - - - - - .. 5
1.6 OBJECTIVES OF THE STUDY - - - - - - - - - - - - - - - - 5
1.6.1 GENERAL OBJECTIVE - - - - - - - - - - - - - - - - - .. 5
1.6.2 SPECIFIC OBJECTIVE - - - - - - - - - - - - - - - - - .. 5
CHAPTER TWO - - - - - - - - - - - - - - - - - - - - - .. 6
2 LITERATURE REVIEW - - - - - - - - - - - - - - - - - - .. 6
2.1 ELEMENTAL CHEMICAL COMPOSITION OF PLANTS - - - - - - - - - 6
2.1.1 Zinc - - - - - - - - - - - - - - - - - - - - - - . 7
2.1.2 Selenium - - - - - - - - - - - - - - - - - - - - - .. 8
2.1.3 Chromium - - - - - - - - - - - - - - - - - - - - . 10
2.1.4 Vanadium - - - - - - - - - - - - - - - - - - - - .. 11
2.2 MEDICINAL PLANTS - - - - - - - - - - - - - - - - - - 12
2.2.1 Trigonella foenum-graecum L (FENUGREEK) - - - - - - - - - - - .. 13
2.2.2 Glycyrrhiza glabra L. - - - - - - - - - - - - - - - - - .. 14
2.2.3 Prunus africana (HOOK F) KALKMAN - - - - - - - - - - - - - 16
2.2.4 Azadirachta indica A - - - - - - - - - - - - - - - - - - 18
2.2.5 Urtica massaica L. - - - - - - - - - - - - - - - - - - . 20
2.2.6 Zanthoxylum usambarensis (ENGL.) KOKWARO - - - - - - - - - - 21
2.2.7 Maytenus obscura (A.RICH) CUF - - - - - - - - - - - - - - . 23
2.2.8 Maytenus putterlickiodes (LOES.) EXELL & MENDONÇA - - - - - - - - 24
2.2.9 Mondia whytei (HOOK F.) - - - - - - - - - - - - - - - - 25
2.2.10 Maerua edulis (GILG & GILG-BEN) - - - - - - - - - - - - - 26
2.3 ANALYTICAL METHODS FOR DETERMINATION OF TRACE ELEMENTS - - - . 27
2.3.1 Energy Dispersive X-ray Fluorescence Theory - - - - - - - - - - - 28
CHAPTER THREE - - - - - - - - - - - - - - - - - - - - 33
3 MATERIALS AND METHODS - - - - - - - - - - - - - - - - . 33
3.1 SAMPLE COLLECTION AND PRETREATMENT - - - - - - - - - - - . 33
3.2 EDXRF STANDARDS - - - - - - - - - - - - - - - - - - 33
3.3 EDXRF INSTRUMENTATION - - - - - - - - - - - - - - - - . 34
3.4 SAMPLE PREPARATION AND ANALYSIS - - - - - - - - - - - - - - - ..34
3.5 SAMPLE PREPARATION AND ANALYSIS - - - - - - - - - - - - . 34
3.6 STATISTICAL ANALYSIS - - - - - - - - - - - - - - - - - . 35
CHAPTER FOUR - - - - - - - - - - - - - - - - - - - - .. 36
4 RESULTS, DISCUSSION, CONCLUSION AND RECOMMENDATION - - - - - .. 36
4.1 RESULTS AND DISCUSSION - - - - - - - - - - - - - - - - .. 36
4.1.1 Elemental Levels in Reference Material - - - - - - - - - - - - - ..36
4.1.2 Zinc levels - - - - - - - - - - - - - - - - - - - - 37
4.1.3 Vanadium levels - - - - - - - - - - - - - - - - - - - 40
4.1.4 Chromium levels - - - - - - - - - - - - - - - - - - .. 43
4.1.5 Selenium levels - - - - - - - - - - - - - - - - - - - .. 45
4.2 CONCLUSION - - - - - - - - - .ERROR! BOOKMARK NOT DEFINED.
4.3 RECOMMENDATIONS - - - - - - - - - - - - - - - - - - . 47
4.3.1 Recommendations from this study - - - - - - - - - - - - - - . 48
4.3.2 Recommendation for further work - - - - - - - - - - - - - - . 48
REFERENCES - - - - - - - - - - - - - - - - - - - - - 49
APPENDIX - - - - - - - - - - - - - - - - - - - - - - .. 61
LIST OF TABLES
Table 2.1: RDA for trace elements of interest - - - - - .… - - - - - - 12
Table 4.1 Elemental analysis of Bowen kale compared to certified values (mg/kg) - - 36
Table 4.2: Zinc levels (mg/kg) - - - - .. - - - - - .37
Table 4.3: Vanadium levels (mg/kg) - - - - - - - - - - - - - - 40
Table 4.4: Chromium levels (mg/kg) - - - - - - - - - - - - - - 43
Table 4.5: Selenium levels (µg/kg) - - - - - - - - - - - - - - - 45
LIST OF FIGURES
Figure 2.1: Trigonella foenum-Graecum plant - - - - - - - - - - - - - - 13
Figure 2.2: Trigonella foenum-Graecum seeds - - - - - - - - - - - - - . 13
Figure 2.3: Glycyrrhiza glabra plant - - - - - - - - - - - - - - - - - .15
Figure 2.4: Glycyrrhiza glabra roots - - - - - - - - - - - - - - - - 15
Figure 2.5: Prunus africana trunk - - - - - - - - - - - - - - - - .. 17
Figure 2.6: Azadirachta indica plant - - - - - - - - - - - - - - - - - .19
Figure 2.7: Azadirachta indica fruits - - - - - - - - - - - - - - - - . 19
Figure 2.8: Urtica massaica plant - - - - - - - - - - - - - - - - - 20
Figure 2.9: Zanthoxylum usambarensi plant - - - - - - - - - - - - - - - .22
Figure 2.10: Zanthoxylum usambarensis seed pods - - - - - - - - - - - - 22
Figure 2.11: Maytenus obscura plant - - - - - - - - - - - - - - - - . 23
Figure 2.12: Maytenus putterlickiodes plant. - - - - - - - - - - - - - - ..24
Figure 2.13: Mondia whytei plant - - - - - - - - - - - - - - - - - - 26
Figure 2.14: Mondia whytei roots - - - - - . - - - - - - - - - - - - 26
Figure 2.15: Maerua edulis plant - - - - - - - - - - - - - - - - - . 27
Figure 2.16: Electronic set up of the EDXRF system…. - - - - - …….30
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