ABSTRACT
Vegetables viz. Corchorus olitorious Linn, Corchorus tridens Linn, Ceratotheca
sesamoides Endl, Vernonia amygdalina Del, Mormodica charantia Linn and Senna
occidentalis Linn were analyzed for their nutrient, anti-nutrient, vitamin, major, minor,
trace and ultra-trace metal contents. Standard analytical methods approved by the
(Association of Official Analytical Chemists) were used for the nutrient analysis.
Spectrophotometric methods were used for the determination of vitamins A and B in the
samples while iodine method was used for the determination of vitamin C respectively.
Instrumental neutron activation analysis (INAA) was used for the determination of major,
minor, trace and ultra-trace elements contents. The levels of various anti-nutrients in the
leaves were determined by appropriate methods. Results of the nutrient composition
analyses showed that moisture content ranged 46.90 – 75.53%; ash (2.48 – 11.95%); crude
protein (3.19 – 19.36%); crude lipid (3.33 – 6.67%); carbohydrate (5.69 – 10.38%) and
calorific value of (93.71 – 163.90Kcal/100g). These values conform to normal values found
in other exotic vegetables. Results of vitamins analyses revealed that vitamin A has the
highest concentration in Vernonia amygdalina Del (379.46mg/100g); Corchorus tridens
Linn (345.84mg/100g); Ceratotheca sesamoides Endl and least in Mormodica charantia
Linn (0.06mg/100g). Also, vitamin C amounts in the analyzed plants ranged 17.63 –
255.61mg/100g which lies within amounts found in some of the highly utilized leafy
vegetables. For the B vitamins, only B1 was found in relatively high amounts in Corchorus
olitorious Linn (154.125mg/100g) and Vernonia amygdalina Del (170.30mg/100g) while
the rest (B2 and B3) determined in this work were in small amounts (0.08 – 1.98mg/100g
and 0.50 – 7.916mg/100g) respectively. In addition to that, results of the analyses for antinutrients showed that cyanide content are low and less than the 10mg/kg Codex standard
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for cyanide in dried cassava. Likewise, the amounts of phytates, oxalates and tannins are
low. Moreover, results for the metal analyses in dry weight basis of the plant samples
indicates different pattern of concentrations in the various plants and their parts. Out of the
twenty nine elements determined; K, Ca, Na, Fe, Al were found in higher concentrations in
the range of 10040.0 – 67270.0, 2802.0 – 26950.0, 36.0 – 3520.0, 145.0 – 22215.0, and
52.0 – 2262.0ppm while Rb, Mn, and Zn at lower amounts in the range of 3.9 – 41.0, 3.19
– 326.78, 14.0 – 166.0ppm and the rest either at BDL levels or in traces. Student‟s t-test
statistical analysis (p<0.05) on the various parameters indicated varied relationships. The
results revealed that these plants contain nutrients, vitamins, and mineral elements and low
levels of toxicants. Therefore the plants should be included in diets and will enable
consumers, health professionals and regulatory bodies to document and make reference to
the data obtained in this work.
TABLE OF CONTENTS
Title page ……………………………………………………………………….. i
Declaration ……………………………………………………………………… ii
Certification……………………………………………………………………… iii
Dedication……………………………………………………………………….. iv
Acknowledgement……………………………………………………………… v
Abstract ………………………………………………………………………… vi
Abbreviations …………………………………………………………………… viii
Table of contents………………………………………………………………… x
List of tables…………………………………………………………………….. xx
List of figures…………………………………………………………………… xxii
List of appendices ………………………………………………………………. xxv
CHAPTER ONE………………………………………………………………… 1
1.0 INTRODUCTION………………………………………………………….. 1
1.1Aims and objectives………………………………………………………….. 8
1.2 Justification of the research………………………………………………… 8
CHAPTER TWO………………………………………………………………… 9
2.0 LITERATURE REVIEW………………………………………………….. 9
2.1 Corchorus olitorious Linn…………………………………………………… 9
2.2 Corchorus tridens Linn……………………………………………………… 11
2.3 Ceratotheca sesamoides Endl…………………………………………………. 11
2.4 Momordica charantia Linn………………………………………………… 12
2.5 Senna occidentalis Linn ……………………………………………………. 14
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2.6 Vernonia amygdalina Del…………………………………………………… 16
2.7 Chemical composition of leafy vegetables………………………………… 17
2.7.1 Moisture …..……………………………………………………………….. 17
2.7.2 Carbohydrate………………………………………………………………. 17
2.7.3 Protein………………………………………………………………………. 18
2.7.4 Lipids………………………………………………………………………. 18
2.7.5 Pigments…………………………………………………………………… 18
2.7.6 Mineral elements………………………………………………………….. 19
2.7.6.1Some major, minor and trace elements of interest………………………. 19
2.7.6.1.1Chromium……………………………………………………………… 19
2.7.6.1.2 Copper…………………………………………………………………. 20
2.7.6.1.3 Lead…………………………………………………………………… 21
2.7.6.1.4 Manganese…………………………………………………………….. 21
2.7.6.1.5 Nickel ………………………………………………………………… 22
2.7.6.1.6 Selenium……………………………………………………………… 22
2.7.6.1.7 Vanadium…………………………………………………………….. 23
2.7.6.1.8 Zinc……………………………………………………………………. 23
2.7.7 Vitamins…………………………………………………………………… 24
2.7.7.1Classification of vitamins………………………………………………… 25
2.7.7.1.1Fat soluble vitamins…………………………………………………….. 26
2.7.7.1.2 Water soluble vitamins………………………………………………… 27
2.7.8 Anti-nutritional factors……………………………………………………. 42
2.7.8.1Phytic acid……………………………………………………………….. 44
2.7.8.2 Oxalic acid………………………………………………………………. 50
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2.7.8.3 Tannins………………………………………………………………….. 51
2.7.8.4 Hydrocyanic acid……………………………………………………….. 55
2.7.8.4.1Toxicity of cyanides…………………………………………………….. 55
2.7.8.4.2Cyanogenic glycosides…………………………………………………. 57
2.8 Neutron activation analysis (NAA)…………………………………………. 58
2.8.1Priciples and practice of NAA ……………………………………………. 60
2.8.1.1 Reactor Neutron Activation Analysis………………………………….. 61
2.8.1.2Capture Reactions……………………………………………………….. 62
2.8.1.3Transmutation………………………………………………………… 63
2.8.2 Neutron source and energy spectra………………………………… 65
2.8.3Reaction rate……………………………………………………………. 66
2.8.4Decay modes of radioisotopes………………………………………… 69
2.8.5 Analysis procedure…………………………………………………… 71
2.8.6Calculation………………………………………………………………… 72
2.8.7Capabalities and limitations of neutron activation analysis…………. 76
2.8.8 Neutron flux convention………………………………………………… 81
2.8.9 HPGe detector efficiency………………………………………………… 83
2.8.3 Instrumentation in NAA…………………………………………………. 83
CHAPTER THREE ……………………………………………………………. 85
3.0 EXPERIMENTAL………………………………………………………… 85
3.1 Sample identification and collection…………………………………….. 85
3.2 Sample treatment ………………………………………………………… 85
3.3 Neutron activation analysis measurement………………………………. 85
3.4 Preparation of reagents………………………………………………….. 86
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3.4.1 Aqueous ammonia (6 M)………………………………………………… 86
3.4.2 Boric acid (2.5 %)………………………………………………………… 86
3.4.3 Orthophosphoric acid……………………………………………………. 86
3.4.4 Potassium Iodide (5 %)…………………………………………………… 87
3.4.5 Silver nitrate (0.02 M)…………………………………………………… 87
3.4.6 Hydrochloric acid (20 %)…………………………………………………. 87
3.4.7Ammonium thiocyanate (0.3 %)…………………………………………… 87
3.4.8 Starch solution (1 %)……………………………………………………… 87
3.4.9 Iron (III) Chloride (0.1 M)………………………………………………… 87
3.4.10 Hydrochloric acid (0.05 M)……………………………………………… 88
3.5.11 Hydrochloric acid (0.01 N)………………………………………………. 88
3.5.12 Hydrochloric acid (6 M)……………………………………………….. 88
3.5.13 Potassium permanganate (0.1 N)………………………………………. 88
3.4.14 Ethanol (50 %)………………………………………………………….. 88
3.4.15 Potassium permanganate (15 %)………………………………………… 88
3.4.16 Potassium permanganate (0.5 %)………………………………………… 89
3.5.17 Potassium dichromate (0.5%) …………………………………………… 89
3.5.18 Hydrogen peroxide (30 %)……………………………………………… 89
3.4.19 Sodium sulphate (40 %)…………………………………………………. 89
3.4.20 Ethanolic potassium hydroxide………………………………………….. 89
3.4.21 Sulphuric acid (0.02N) …………………………………………………… 90
3.4.22 Sulphuric acid (1.24%)…………………………………………………… 90
3.4.23 Sulphuric acid (1N)……………………………………………………….. 90
3.4.24 Methyl red Indicator………………………………………………………. 90
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3.4.25 Methylene blue Indicator…………………………………………………… 90
3.4.27 Potassium Cyanide (0.1N) …………………………………………………. 90
3.4.26 Iron (III) chloride (1.4%)………………………………………………….. 91
3.4.27 Calcium Chloride (5 %)…………………………………………………… 91
3.4.28 Sulphuric Acid (25 %)……………………………………………………… 91
3.5 Determination of proximate composition…………………………………… 91
3.5.1 Determination of moisture content………………………………………….. 91
3.5.2 Determination of ash content……………………………………………….. 92
3.5.3 Determination of crude fat………………………………………………….. 92
3.5.4 Determination of crude fiber……………………………………………….. 93
3.5.5 Determination of crude protein…………………………………………….. 93
3.5.6 Determination of Carbohydrate……………………………………………. 94
3.5.7 Determination of colorific value…………………………………………… 94
3.6 Determination of anti – nutritional content………………………………… 94
3.6.1 Determination of hydrogen cyanide……………………………………….. 94
3.6.2 Determination of oxalates………………………………………………….. 95
3.6.3 Determination of tannins…………………………………………………… 95
3.6.4 Determination of phytates………………………………………………….. 95
3.6.5 Determination of vitamins…………………………………………………. 96
3.6.5.1Vitamin A (β – Carotene)………………………………………………….. 96
3.6.5.2 Vitamin B1 (Thiamine)……………………………………………………. 96
3.6.5.3Vitamin B2 (Riboflavin)…………………………………………………… 96
3.6.5.4 Vitamin B3 (Niacin)……………………………………………………… 97
3.6.5.5Vitamin C (Ascorbic acid)………………………………………………… 97
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3.7 Data analysis…………………………………………………………………. 98
CHAPTER FOUR………………………………………………………………. 99
4.0 RESULTS…………………………………………………………………… 99
4.1 Elemental composition of Corchorus olitorious Linn, Corchorus tridens Linn,
Vernonia amygdalina Del, Ceratotheca sesamoides Endl, Mormodica charantia
Linn and Senna occidentalis Linn………………………………………… 99
4.2 Translocation factors of elements in the parts of Corchorus olitorious Linn,
Corchorus tridens Linn, Vernonia amygdalina Del, Ceratotheca sesamoides Endl
Momordica charantia Linn and Senna occidentalis Linn………………… 103
4.3 Bioavailability of calcium, iron, manganese and zinc in the leaves of of Corchorus
olitorious Linn, Corchorus tridens Linn, Vernonia amygdalina Del, Ceratotheca
sesamoides Endl Mormodica charantia Linn and Senna occidentalis
Linn………………………………………………………………………….. 104
4.4 Proximate composition of Corchorus olitorious Linn, Corchorus tridens Linn,
Vernonia amygdalina Del, Ceratotheca sesamoides Endl, Mormodica charantia
Linn and Senna occidentalis Linn leaves……………………………………. 105
4.5 Vitamin composition of Corchorus olitorious Linn, Corchorus tridens Linn,
Vernonia amygdalina Del, Ceratotheca sesamoides Endl, Mormodica charantia
Linn and Senna occidentalis Linn leaves………………………………….. 106
4.6 Antinutritional composition of of Corchorus olitorious Linn, Corchorus tridens
Linn, Vernonia amygdalina Del, Ceratotheca sesamoides Endl, Mormodica
charantia Linn and Senna occidentalis Linn leaves………………………. 107
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CHAPTER FIVE…………………………………………………………………… 131
5.0 Discussion……………………………………………………………………… 131
5.1 Elemental composition of Corchorus olitorious Linn, Corchorus tridens Linn,
Vernonia amygdalina Del, Ceratotheca sesamoides Endl, Mormodica charantia
Linn and Senna occidentalis Linn……………………………………….. 131
5.1.1 Aluminium………………………………………………………………….. 131
5.1.2 Calcium……………………………………………………………………… 132
5.1.3 Vanadium…………………………………………………………………… 133
5.1.4 Copper………………………………………………………………………. 133
5.1.5 Manganese…………………………………………………………………… 134
5.1.6 Sodium………………………………………………………………………. 135
5.1.7 Potassium……………………………………………………………………. 135
5.1.8 Lanthanum…………………………………………………………………… 136
5.1.9 Samarium……………………………………………………………………… 138
5.1.10 Scandium…………………………………………………………………… 138
5.1.11 Chromium…………………………………………………………………… 139
5.1.12 Iron…………………………………………………………………………. 140
5.1.13Cobalt……………………………………………………………………….. 141
5.1.14 Zinc………………………………………………………………………… 142
5.1.15 Bromine…………………………………………………………………….. 143
5.1.16 Rubidium…………………………………………………………………… 143
5.1.17 Barium……………………………………………………………………… 144
5.1.18 Hafnium……………………………………………………………………. 145
5.1.19 Thorium…………………………………………………………………… 146
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5.1.20 Europium…………………………………………………………………… 146
5.1.21Antimony…………………………………………………………………… 147
5.1.22 Ytterbium…………………………………………………………………. 148
5.1.23 Arsenic……………………………………………………………………. 148
5.1.24Lutetium…………………………………………………………………… 149
5.2 Variations in the distribution of the elements detected in the parts of Corchorus
olitorious Linn, Corchorus tridens Linn, Vernonia amygdalina Del, Ceratotheca
sesamoides Endl, Mormodica charantia Linn and Senna occidentalis
Linn……………………………………………………………………….. 150
5.2.1 Variation in the distribution of the elements detected elements in the roots, stems,
leaves and fruits of Corchorus olitorious Linn…………………………… 150
5.2.2 Variation in the distribution of the elements detected in the roots, stems, leaves and
fruits of Corchorus tridens Linn………………………………………… 157
5.2.3 Variation in the distribution of the elements detected in the roots, stems and leaves of
Vernonia amygdalina Del………………………………………………… 165
5.2.4 Variation in the distribution of the elements detected in the roots, stems and roots of
Ceratotheca sesamoides Endl……………………………………………… 170
5.2.5 Variation in the distribution of detected elements in the stems, leaves and fruits of
Momordica charantia Linn………………………………………………… 178
5.2.6 Variation in the distribution of the detected elements in the roots, stems, leaves and
fruits of Senna occidentalis Linn…………………………………………… 186
5.3 Translocation factors of the elements in the Corchorus olitorious Linn, Corchorus
tridens Linn, Vernonia amygdalina Del, Ceratotheca sesamoides Endl, Mormodica
charantia Linn and Senna occidentalis Linn……………………………… 196
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5.4 Bioavailability of the determined elements………………………………….. 198
5.5 Proximate composition of Corchorus olitorious Linn, Corchorus tridens Linn,
Vernonia amygdalina Del, Ceratotheca sesamoides Endl, Mormodica charantia
Linn and Senna occidentalis Linn leaves…………………………………. 201
5.5.1 Moisture…………………………………………………………………… 202
5.5.2 Ash content………………………………………………………………… 204
5.5.3 Crude protein……………………………………………………………….. 206
5.5.4 Crude Lipid………………………………………………………………… 207
5.5.5 Crude fiber of Corchorus olitorious Linn, Corchorus tridens Linn, Vernonia
amygdalina Del, Ceratotheca sesamoides Endl, Mormodica charantia Linn and
Senna occidentalis Linn leaves…………………………………………… 208
5.5.6 Carbohydrate content of Corchorus olitorious Linn, Corchorus tridens Linn,
Vernonia amygdalina Del, Ceratotheca sesamoides Endl, Mormodica charantia
Linn and Senna occidentalis Linn leaves…………………………………… 209
5.5.7 Calorific value of Corchorus olitorious Linn, Corchorus tridens Linn, Vernonia
amygdalina Del, Ceratotheca sesamoides Endl, Mormodica charantia Linn and
Senna occidentalis Linn leaves …………………………………………… 210
5.5.8 Vitamin content of Corchorus olitorious Linn, Corchorus tridens Linn, Vernonia
amygdalina Del, Ceratotheca sesamoides Endl, Mormodica charantia Linn and
Senna occidentalis Linn leaves…………………………………………. 211
5.5.8.1 Vitamin A (Retinol)……………………………………………………… 212
5.5.8.2 Vitamin B1 (Thiamin)…………………………………………………… 212
5.5.8.3 Vitamin B2 (Riboflavin)…………………………………………………. 213
5.5.8.4 Vitamin B3 (Niacin)……………………………………………………… 213
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5.5.8.5 Vitamin C (Ascorbic acid)……………………………………………….. 214
5.6.0 Anti-nutritional factors of Corchorus olitorious Linn, Corchorus tridens Linn,
Vernonia amygdalina Del, Ceratotheca sesamoides Endl, Mormodica charantia
Linn and Senna occidentalis Linn leaves……………………………… 215
5.6.1 Phytates……………………………………………………………………… 215
5.6.2 Oxalates……………………………………………………………………… 216
5.6.3 Tannins……………………………………………………………………… 216
5.6.4 Hydrogen cyanide…………………………………………………………… 216
CHAPTER SIX…………………………………………………………………… 192
6.0 CONCLUSION AND RECOMMENDATION…………………………… 218
6.1 Conclusion…………………………………………………………………… 218
6.2 Recommendation…………………………………………………………….. 227
References………………………………………………………………………… 229
Appendices………………………………………………………………………… 242
CHAPTER ONE
1.0 Introduction
Less utilized green leafy vegetables are plants consumed in relatively small quantities as a
side dish or relish with the staple food. Usually these vegetables are the leaves, roots or
stems of herbaceous plant. Their flower, calyces and immature seeds or fruits may also be
consumed. They are also used as boiled vegetables or added to soups and stews (Tomori
and Obijole, 2000) and their consumption is considered inferior in taste and nutritional
value when compared to their cultivated counterparts (Vainio-Matilla, 2000).
However, with persistence of malnutrition in the developing countries in spite of increased
basic food production, micronutrient deficiencies and other nutrition related diseases still
afflict over 2 billion people worldwide (Tomori and Obijole, 2000; Ejoh et al., 2005).
These had become a source of interest to nutritionist and other concerned scientific
researchers. In fact, several studies (Osaki et al., 2003, Fasakin, 2004; Alabi et al., 2005,
Antia et al., 2006; and Ekop, 2007) showed that many species of wild green leafy
vegetables are rich sources of nutrients.
Leafy vegetable are also known to add taste and flavor as well as substantial amount of
protein, fiber, minerals and vitamins to the diet (Oyenuga and Fetuga, 1975; Adeyemi,
1987, Fasakin, 2004; Alabi et al., 2005; Ejoh et al., 2005). Inaddition, some plants with
promising bioactive properties also contain useful minerals and food value for human and
animal consumption (Alabi et al., 2005).
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Moreover, leafy vegetables are the cheapest and most available sources of substantial
amount of vitamins A and C to the most vulnerable group, viz: rural populace. However, in
tropical Africa millions of people still suffer from vitamin A and C deficiency despite the
increased consumption of leafy vegetables (Ejoh et al, 2005). These leafy vegetables are
relatively inexpensive, easily and quickly cooked and rich in several nutrients especially –
carotene and vitamin C which are essential for human health (Tomori and Obijole, 2000).
Several vegetable species abound in Nigeria and most West African countries are used
partly as condiments or spices in human diets or as supplementary feeds for livestock such
as rabbits, poultry, swine and cattle (Aletor and Adeogun, 1995). These vegetables are
harvested at all stages of growth and fed either as processed, semi-processed or fresh to
man while they are usually offered fresh to livestock. The nutritional interest in some of
these vegetable species stems from their rich contents of essential amino acids, vitamins
and minerals. Further to their rich content of the mentioned nutrients above, it is established
that green vegetable leaves are also source of proteins because of their ability to synthesize
amino acids from a wide range of virtually every available primary materials such as water,
carbon dioxide, and atmospheric nitrogen (as in legumes).
However, the presence of inherent toxic factors or anti-nutritional components in plants has
been one major obstacle in harnessing the full benefits of the nutritional value of plant
foods, vegetables inclusive (Liener, 1969; Nwokolo and Bragg, 1977; Lewis and Fenwick,
1987). Although the presence of these anti-nutritional factors is always in trace quantities,
they have been established to play significant roles in the nutritional quality of food.
However, many food-processing techniques have been highlighted as possible means of
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reducing or eliminating the anti-nutrient levels in plant food sources to innocuous levels
that can be tolerated by animals particularly in monogastric nutrition (Fasuyi and Aletor,
2005).
Available medical literature reveals that plants have been used for curative purposes (Ming,
1999). There are many plants whose green leaves, roots and stems are used in herbal
preparations for the treatment of various ailments (Ekop, 2007). Most of the times the
potency of those plants is accounted for in terms of their organic constituents but, it is an
established fact that there is a high relationship between the chelation of metals and some
chemotherapeutic agents. The role of inorganic elements in animal and plant metabolism
has long been established but the effect and influence of these elements on administration
of medicinal plants has received relatively little attention (Gwarzo et al., 2006). Also there
is an increased awareness of the value of leafy vegetables in contributing to a balanced diet
particularly in areas where animal protein is deficient (Tomori and Obijole, 2000)
However, the consumption of vegetables and basic foodstuffs from plants and medicinal
plants traditionally has been largely indiscriminate without due regard to possible side
effects. Indeed, diet has long been considered as the major source of human exposure to
trace and ultra-trace elements and consequently their levels in basic food stuff determines
the quantity available to man. Because, it was postulated that, any element absent in plants
is probably not essential for man (Saiki et al., 1990, Tomori and Obijole, 2000, Gwarzo et
al., 2006). Nevertheless, some elements in the body can play a protective role in decreasing
the risk of some diseases. Consequently the levels of minerals in basic food stuff are of
great interest from toxicological and nutritional point of view.
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Other items obtainable on consumption of green leafy vegetables as earlier stated are the
anti-nutritional factors. When consumed in higher doses, they may pose problems to the
person concerned. For example, high values of cyanides has been implicated for cerebral
damage and lethargy in animals and man; Oxalate can form complexes with most essential
trace metals, thereby making them unavailable for enzymatic activities and other metabolic
activities (processes) (Akwaowo et al., 2000) and formation of kidney stones (Liebman and
Costa, 2000). In addition, presence of tannins, phytic acids and HCN may make the plants
potent poisons (Antia et al., 2006)
The data obtained however, from the analysis of chemical composition of food items is
important to both consumers and health professional alike. The recent campaigns, the
setting up of bodies and legislations by health ministries that regulates food and drug
administration highlighted this need. In addition, the data obtained from plants (vegetables)
are mainly used to monitor such aspects of life of man like medicine, nutrition, pollution
(environment) and toxicology of the substance in the long-term consumption of the plant.
Researchers have developed methods and instrumentations for the measurement of
constituents of food items and other materials of interest because of their impact on human
health. Their focus is on the measurement of analytes that are either beneficial or
detrimental to human health (Miller-Ihli, 1996, Paul et al., 2011and 2013).
In Nigeria, the National Agency for Food and Drugs Administration and Control
(NAFDAC) has been set up and charged with the responsibility of protecting public health
by promoting wholesomeness, quality and efficacy of processed foods, medicines,
cosmetics, medicinal devices, chemicals and prepackaged water through an effective
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quality assurance system and public enlightenment. In addition, there are inspectorates and
enforcement agencies as part of prevention of illnesses. These bodies or agencies are also
charged with the responsibility of formulating regulations and compilation of standard
specifications for compliance by manufacturers, importers and exporters of regulated
products and instituting labels depicting information about nutritional qualities of both
processed and unprocessed foods (NAFDAC, 2003; AOAC, 1993 and NFPA, 1994).
It is a common knowledge that administration of plants claimed to have medicinal
properties has largely been indiscriminate without due regard to possible side effects. It is
thus important to determine the chemical content of these plants for pharmacological assays
and other probable roles in the curative process. In addition to that, plants are generally the
major sources of food and minerals to both man and animals. The different species of plant
plays an important role in the diet of the inhabitants of arid, semi-arid and savanna
countries of Africa including Nigeria. They contain minerals in quantities compared
favorably with foods of W.H.O standard (Barminas et al., 1998). Of particular importance
among the parts of the plant are the leaves and the seeds containing trace elements at
varying levels depending on many factors such as species variety, stage of maturity and
environment (Daun and McGregor, 1991).
Therefore, since minerals, organic constituents and anti-nutritionals are very important to
man, accurate determination of them in wild plants, utilized and less utilized plants will
help nutritionist to recommend a list of plants for food supplementation and estimate daily
aggregate allowance from sources for meeting daily human requirements.
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From the environmental, pollution and toxicological point of view, many minerals
including those that are essential to life can be toxic at high doses or in certain compound
formulation. So the amount of minerals in living organism normally correlate significantly
with amounts in the environment. Also heavy metals do not degrade but accumulate in food
and are a serious threat to human health. In fact, there are certain plants known to have a
special ability which enable them to take elements with the tendencies of accumulating
same to dangerous levels, thus making the plants toxic (WHO, 1980; IRI, 1989; Szefer and
Szefer, 1994 and Last, 1995). Likewise, it is a known fact that different parts of plants
contain trace elements that are harmful to the body of man at a certain concentrations.
Sewage from homes, industrial effluents into aquatic environment, smoke from industries
and vehicles, parent materials from which the soil is formed; types of agrochemicals used
in farming and waste disposal systems all contribute to the elemental composition of plants.
Therefore, there is a greater tendency for the accumulation of a particular element as
suggested by Kovacs (1979) and Whitton (1989) and the extent of accumulation is a
reflection of the concentration of such materials in the environment as well as the species of
the plant in use. It is an established fact that metals in particular are present in both plants
and animals as components of simple salts and complexes performing various functions
(Yalwa, 2002). They are required by plants in amounts that result in their classification as
essential, beneficial and non-essential for their proper growth and development (Daniel,
1990).
Moreover, metals and in particular trace metals are a major class of contaminants in our
present world arising principally from natural and anthropogenic sources. The
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anthropogenic sources are primarily from industrialization and mining activities which are
of paramount importance to ecosystem sustainability (Okorie and Egila, 2012). In addition
to that, advancement in technology as well as increase in population have led to the
environmental concern emanating from indiscriminate dumping of refuse and discharge of
industrial effluents, petroleum waste and crude oil spills replete with most common trace
metals in our environments (Okorie and Egila, 2012).
Likewise, it is a fact that, mineral composition of plants found in a particular location
reflects the type of activities of man around the location, the soil type, chemical nature of
rocks underneath, specie of the plant, part of the plant, variety, stage of maturity and to
some extent the inherent property of plant (Pritchard,1999). It has also been found that most
plants in the vicinity of rivers fed with industrial sewage have been contaminated by toxic
micro metals and also plants growing on industrial effluent-contaminated soil accumulate
potentially toxic elements from the soil (Dike et.al, 2005).
However, Tomori and Obijole (2000) stated that, it is of interest to periodically assess the
mineral content of foods especially vegetables which supply micronutrients because of their
nutritional implications. Indigenous vegetables and the exotic ones (e.g Cabbage, Brocoli
and Lettuce etc) also play important roles in human diets. They supply the body with
minerals, vitamins and certain hormone precursors in addition to protein, taste, flavor, fiber
and energy (Fasakin, 2004 and Ndolovu and Afolayan, 2008).
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8
1.1.0 Objectives of the research
The objectives of this research are to:
i. Determine qualitatively and quantitatively the major, minor, trace and ultra trace
elements in Vernonia amygdalina Del, Corchorus olitorious Linn, Corchorus
tridens Linn, Ceratotheca sesamoides Endl, Senna occidentalis Linn and
Momordica charantia Linn.
ii. Determine the nutritive (proteins, lipids, carbohydrates, fibers and vitamins) and
anti-nutrive (cyanides, tannins, oxalates and phytates) factors in the above listed
plants.
iii. Assess the nutritional qualities of the plants and
1.2.0 Justification of the research
Previous research on the above mentioned plants were mainly on their phytochemistry,
bioactivities of their extract, their proximate composition and essential elements. Therefore,
this work shall focus on the multi-element analysis and nutritional quality of the plants.
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