ABSTRACT
The chemical composition and the effect of different extraction solvents (water, acetone, ethanol and water-acetone (50:50)) on the leaf extracts’ antioxidant and antioxidant activities were also analyzed. The results revealed that the proximate composition had 4.5, 16.21, 11.09, 4.07, 9.17, 54.89 and 321.09 Kcal for moisture content, crude protein, crude fibre, fats, ash, carbohydrates and energy value respectively. Vitamins A, B1, B2, B3, B6, C and E were found to be present in the leaves with vitamin C had the highest cponcentration (110.14 mg/100g). Mineral content showed 59.73, 8.71, 17.55, 45.05, 116.83, 18.63 and 3.93 mg/100g for calcium, sodium, magnesium, phosphorus, potassium, iron and zinc respectively. Antinutrients values of 3.74, 0.92, 5.63, 8.92, 0.67 and 6.33 mg/100g for alkaloid, tannin, saponin, phytate, oxalate and glycoside respectively. The results showed that V. doniana leaves are rich in flavonoids and phenolic constituents. The highest total phenolic content of 451.03 mgGAE/g was obtained in water extract and highest total flavonoid extraction of 302.92 mgQE/g in ethanol extract. The antioxidant activities (FRAP and ABTS) were strongest in ethanol extract, (water 0.94, acetone 1.06, water-acetone (50:50) 0.77, ethanol 1.40), (water 61.03, acetone 32.78, water-acetone (50:50) 40.72, ethanol 66.31) respectively while the DPPH activities was strongest in water extract. (water 88.29, acetone 50.17, water-acetone (50:50) 51.13, ethanol 54.07). Utilization of Vitex doniana (uchakuru) leaves should be encouraged for use As food for its nutrients and antioxidant properties to enhances the nutritional and health status of the consumers.
TABLE OF CONTENTS
Title i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of Contents vi
List of Tables vii
List of Figures viii
List of Plates ix
List of Appendix x
Abstract xi
CHAPTER 1: INTRODUCTION
1.1 Background of the study 1
1.2 Statement of problem 2
1.3 Justification of the study 2
1.4 Objectives of the study 3
CHAPTER 2: LITERATURE REVIEW
2.1Uchakuru (Vitex doniana) 4
2.2 Uchakuru as an underutilized indigenious vegetable 5
2.3 Nutritional benefits of uchakuru leaves 8
2.4 Medicinal and health benefits of uchakuru leaves 9
2.5 Extracts of V. doniana leaf and extracting liquids 10
2.6 Anti-nutritional properties of uchakuru leaves 11
2.7 Antioxidant and phytochemical properties of V. doniana leaves 12
2.8 Relationship between antinutrients and antioxidants 15
2.8.1 Saponins 15
2.8.2 Phytate 16
CHAPTER 3: MATERIALS AND METHODS
3.1 Source of materials 17
3.2Sample preparation 17
3.2.1 Preparation of Vitex doniana((uchakuru) leaf extract 17
3.3 Proximate analysis 20
3.3.1 Moisture determination 20
3.3.2 Determination of crude protein 20
3.3.3 Crude fiber determination 21
3.3.4 Ash content determination 22
3.3.5 Determination of fat content 22
3.3.6 Total carbohydrate determination 22
3.3.7Determination of caloric value 23
3.4Vitamin analysis 23
3.4.1 Determinationvitamin A (retinol)concentration 24
3.4.2 Determination of vitamin B1 (thiamine)concentration 24
3.4.3 Determinationvitamin B2 (riboflavin)concentration 24
3.4.4 Determination of vitamin B3 (niacin) 25
3.4.5Determination of vitamin B6(pyridoxine ) 25
3.4.6Determination of vitamin C (ascorbic acid) concentration 25
3.4.7Determination of vitamin E (α -tocopharol) concentration 26
3.5Minerals analysis 26
3.5.1 Calcium determination 26
3.5.2Sodium determination 27
3.5.3Magnesium determination 27
3.5.4Determination of phosphorus 28
3.5.5Determination of potassium 28
3.5.6Iron determination 29
3.5.7Determination of zinc 29 3.6 Antinutrients analysis 30
3.6.1 Alkaloid determination 30
3.6.2 Tannin determination 30
3.6.3 Saponin determination 31
3.6.4 Phytate determination 31
3.6.5 Oxalate determination 31
3.6.6 Glycoside determination 32
3.7 Antioxidant analysis 32
3.7.1 Total phenolic determination 33
3.7.2 Total flavonoids content 33
3.7.3 Antioxidant activity determinations 33
3.7.3.1 DPPH (1, 1-diphenyl-2-picrylhydrazyl) radical scavenging assay 33
3.7.3.2 Ferric ion reducing antioxidant power (FRAP) assay 34
3.7.3.3 ABTS (2,2’-azinibis-(3-ethyl benzothiazoline-6sulphonic acid) assay 34
3.8 Experimental design 35
3.9 Statistical analysis 35
CHAPTER 4: RESULTS AND DISCUSSIONS
4.1 Proximate composition of uchakuru (V. doniana) leaves (dry matter basis) 36
4.2 Vitamin content of uchakuru leaves (dry matter basis) 39
4.3 Mineral content of uchakuru leaves (dry basis) 41
4.4 Antinutritional composition of uchakuru leaves (dry basis) 45
4.5 Antioxidants in uchakuru leaf extract 49
4.6 Antioxidant activity of uchakuru leaf extracts 51
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 56
5.2 Recommendation 56
References 57
Appendices 63
LIST OF TABLES
Table 4.1: Proximate composition of uchakuru leaves 37
Table 4.2: Vitamin content of uchakuru leaves 40
Table 4.3: Mineral content of uchakuru leaves 42
Table 4.4: Antinutritional / phytochemical composition of uchakuru leaves 47
LIST OF FIGURES
Figure 1: Flow chart for preparation of uchakuru(Vitex doninana) leaves extract with modifications to method described by Yakubu et al. (2016a) 19
Figure 2: Graphical representation of uchakuru leaf extract antioxidants and composition in mgQE/g and mgGAE 50
Figure 3: Graphical representation of uchakuru leaf extracts % DPPH Inhibition at various concentrations compared to vitamin C as standard 52
Figure 4: Graphical representation of uchakuru leaf extracts FRAP assay at various concentrations compared to Trolox 53
Figure 5: Graphical representation of uchakuru leaf extracts % ABTS Inhibition at various concentrations compared to trolox 54
LIST OF PLATES
Plate 1: Pictures of uchakuru (Vitex doniana) leaves 18
LIST OF APPENDIX
Appendix 1: Pictures of project student in the laboratory work 63
Appendix 2: Result of % DPPH inhibition of uchakuru leaf extract 64
Appendix 3: Result of FRAP assay of uchakuru leaf extract 65
Appendix 4: Result of % ABTS inhibition of uchakuru leaf extracts 66
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY.
Vegetables, especially leafy vegetables are important source of vitamins, minerals, fibres, and some essential amino acids. They have high content of water and abundance of cellulose. The cellulose is in a form which although not digested, serves a useful purpose in the intestine as roughages, thus promoting normal elimination of waste products (Osum et al., 2013).
Vitex doniana(uchakuru) is an indigenous fruit or leafy vegetable in Africa (Dako et al., 2014). It is readily recognized by its long-stalked gabbros leaves with the leaflets usually rounded at the apex, though sometimes they may be unrented or occasionally have very short triangular tip and the fruits are edible (Osum et al., 2013). V. doniana is one of the most consumed leafy vegetables collected from the wild (Achigan-Dako et al., 2011). The dried leaves are used to prepare sauces. In folk medicine, the leaves are employed in the treatment of stomach pains and in case of frequent stooling. They are usually chewed, extracted with water or used to prepare yam porridge. It is traditionally known that the efficiency or potency of V. doniana leaf extract increases with the intensity of the bitterness, it’s water extract is of primary interest. In addition, the plant is used in the treatment of mouth ulcers and sores. In this situation, the leaves are washed and chewed after which they are swallowed. The young leaves are used for stock in the Northern part of the country and also as pot herbs (Osum et al., 2013).
1.2 STATEMENT OF PROBLEM
Nigeria is blessed with different varieties of fruits and vegetables like vitex doniana (uchakuru), but most of them are underutilized due to lack of adequate information on their nutritional and health benefits. Also, some vegetables (like Uchakuru) are very high in anti-nutritional factors (like tannins, saponnins, alkaloids, phenols, etc.) which are chemical substances that inhibit the proper absorption of nutrients (Arokiyaraj et al., 2009; Adejumo et al., 2013). Consumption of these vegetables without proper preparation can lead to malnutrition especially among the rural dwellers who consume Uchakuru without proper utilization of the nutrients (Enechi and Odonwodu, 2003; Soetan and Oyewole, 2009; Achigan-Dako et al., 2011; Okoye, 2015).
1.3 JUSTIFICATION OF THE STUDY
Vegetables, especially leafy vegetables like Uchakuru are an important source of vitamins, minerals, fibre, and some essential amino acids (Osum et al., 2013), but most of these nutrients are not absorbed by the body due to presence of anti-nutritional factors (Soetan and Oyewole, 2009; Arokiyaraj et al., 2009; Adejumo et al., 2013). Nevertheless, some of the commonly considered anti-nutrient compounds like saponins and tannins are now being considered as potential antioxidants with health benefits and termed phytochemicals. Hence, depending on the consumer preferences retaining or eliminating these compounds could be facilitated (Awoyinka et al., 2016). Analysis of the chemical and antioxidant properties of vitex doniana (uchakuru) leaves extract will reveal its nutrients, anti-nutrients, antioxidants and health benefits and thereby encourage its proper utilization (Enechi and Odonwodu, 2003; Soetan and Oyewole, 2009; Adejumo et al., 2013).
1.4 OBJECTIVES OF THE STUDY
The main objective of this study was to obtain ‘chemical composition and the effect of extraction solvents on the antioxidant contents of vitex doniana (uchakuru) leaves obtained from Owelli-Court in Awgu Local Government Area of Enugu State.
The specific objectives were to:
i. Obtain and air dry Uchakuru leaves.
ii. Determine the proximate, vitamins, mineral and antinutrient composition of the dried leaves.
iii. Prepare water, acetone, ethanol and water-acetone (50:50) Uchakuru leaf extract, respectively.
iv. Determine the antioxidant and antioxidant activities of the leaf extracts.
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