ABSTRACT
The increased interest in antioxidant activity of plant phytochemicals has necessitated their determination in rarely consumed fruits. The aim of this study was to determine the antioxidant capacity as well as the vitamin and mineral content of the selected commonly consumed and underutilized fruits. Samples of six selected commonly consumed fruits; pineapple (Ananas comosus) and banana (Musa acuminata) and underutilized fruits; soursop (Annona muricata), African canarium (Canarium schweinfurthii), african star apple (Chrysophyllum albidum) and tangerine (Citrus tangerina) were collected from the local market and analysed for antioxidant capacity using the free radical scavenging activity. The stable radical 1,1-diphenyl-2-picrylhydrazil (DPPH) and ferrous reducing antioxidant power (FRAP) assay were used.Antioxidant vitamins A,C,E and trace minerals were determined. The proximate analysis of the fruit pulps showed that C. albidum and C. schweinfurthii had the highest percentage of carbohydrate (22.41± 0.00 % and 21.37 ± 0.00 % respectively) while C. tangerina had the least (2.34 ± 0.00 %). C. schweinfurthii had the highest percentage of fat (19.41 ± 0.00 %) relative to the other fruit pulps. Tannins level was significantly (p<0 .05="" higher="" i="" in="">M. acuminata
(7.99 ± 0.00 mg/100g), terpenoids and saponin levels were also significantly (p<0 .05="" higher="" i="" in="">C. schweinfurthii (56.92 ± 0.15 mg/100g and 1.03 ± 0.02 mg/100g respectively) when compared to control and other underutilized fruit pulps. For flavonoid content, C. schweinfurthii and A. muricata had the highest values (32.27 ± 0.16 mg/100g and 30.13 ± 0.04 mg/100g respectively) while A. comosus had the least (7.20 ± 0.03 mg/100g). Vitamin C level was significantly (p<0 .05="" higher="" i="" in="">C. schweinfurthii and C. albidum (484.80 ± 2.1 mg/100g and 479.41 ± 0.7 mg/100g) respectively compared to the control. C. tangerina had the highest vitamin A levels (206.89 ± 4.9 mg/100g) while M. acuminata and A. comosus showed the highest level of vitamin E (74.48 ± 0.0 mg/100g and 59.42 ± 0.0 mg/100g) respectively. Selenium, zinc, potassium, calcium and iron levels were significantly (p<0 .05="" higher="" i="" in="">C. albidum and C. schweinfurthii relative to the other fruit pulps studied. C. albidum had the highest level of % inhibition (73.07%) relative to other fruit pulps while M. acuminata had the least % inhibition (31.12%). Ferric reducing power activity of the fruit pulps revealed significant increase in A. comosus and M. acuminata with increasing concentrations. M. acuminata had the highest reducing power activity (0.655 mg/ml) at the highest concentration (1mg/ml) while A. muricata had the least at (0.01mg/ml). In conclusion, among selected fruits, underutilized fruits have shown relatively higher level of antioxidant capacityand contain appreciable amount of essential nutrients, vitamins and minerals than the commonly consumed fruits. Especially African star apple and African canarium are good sources of antioxidants. The study further showed that no single plant food could provide all the required nutrients.
TABLE OF CONTENTS
Title Page
Abstract
Table of Contents
List of Figures
List of Tables
List of Abbreviations
CHAPTER ONE: INTRODUCTION
1.1 Antioxidants
1.1.1 Classification of antioxidants
1.1.1.1Primary or natural antioxidants
1.1.1.2Secondary or synthetic antioxidants
1.1.2 Antioxidant Vitamins
1.1.2.1Vitamin A
1.1.2.2 Vitamin C
1.1.2.3 Vitamin E
1.2Trace minerals
1.2.1 Selenium
1.2.2 Zinc
1.2.3 Iron
1.3 Phytochemicals
1.3.1 Phytochemical constituents of plants
1.3.1.1Terpenoids
1.3.1.2 Flavonoids
1.3.1.3Saponins
1.3.1.4Tannins
1.3.1.5Steroids
1.3.1.6Alkaloids
1.4Fruits
1.4.1 Fruit structure and development
1.4.2 Uses
1.4.3 Storage
1.4.4 Types of fruits
1.4.4.1Ananas Comosus (Pineapple)
1.4.4.2Musa Acuminata (Banana)
1.4.4.3Canariumschweinfurthii (African Canarium)
1.4.4.4Chrysophyllum Albidum (African Star Apple)
1.4.4.5Annona Muricata (Sour Sop)
1.4.4.6Citrus Tangerina (Tangerine)
1.5Aim and Objectives of the study
1.5.1Aim of the study
1.5.2Specific objectives of the study
CHAPTER TWO: MATERIALS AND METHODS
2.1 Materials
2.1.1 Plant materials
2.1.2 Chemical/Reagents
2.2 Methods
2.2.1 Sample preparation
2.2.2 Experimental design
2.2.3 Qualitative phytochemical analysis
2.2.3.1 Test for alkaloids
2.2.3.2 Test for flavonoids
2.2.3.3 Test for glycosides
2.2.3.4 Test for saponins
2.2.3.5 Test for tannins
2.2.3.6 Test for terpenoids
2.2.3.7 Carbohydrate
2.2.3.8 Protein
2.2.4 Quantitative phytochemical analysis
2.2.4.1 Tannin
2.2.4.2 Analysis of flavonoids
2.2.4.3 Saponins
2.2.4.3.1 Saponin standard curve
2.2.4.4 Alkaloids
2.2.5Proximate analysis
2.2.5.1 Determination of crude protein (Kjeldahl Method)
2.2.5.2 Determination of moisture content (Ovum Method)
2.2.5.3 Determination of ash content
2.2.5.4 Determination of crude fibre
2.2.5.5 Determination of fats (Soxhlet Method)
2.2.5.6 Determination of carbohydrate
2.2.6Evaluation of antioxidant scavenging activity of DPPH radical
2.2.7Ferric reducing antioxidant power (FRAP) assay
2.2.8 Vitamin analysis
2.2.8.1 Vitamin A
2.2.8.2 Vitamin C
2.2.8.3 Vitamin E
2.2.9 Mineral determination
2.2.9.1 Selenium determination
2.2.9.2 Iron
2.2.9.3 Calcium
2.2.9.4 Zinc
2.2.9.5 Magnesium
2.2.9.6 Sodium and potassium
2.2.10Statistical analysis
CHAPTER THREE: RESULTS
3.1 Phytochemical compositions of the fruit pulps of Ananas cosmosus, Musa acuminata,
Annona muricata, Canarium schweinfurthii, Chrysophylum albidum and Citrus
tangerina
3.1.1 Qualitative phytochemical constituents of the fruit pulps of Ananas cosmosus, Musa
acuminata, Annona muricata, Canarium schweinfurthii, Chrysophylum albidum and
Citrus tangerina
3.1.2 Quantitative phytochemical constituents of the fruit pulps of Ananas cosmosus, Musa
acuminata, Annona muricata, Canarium schweinfurthii, Chrysophylum albidum
and Citrus tangerina
3.2 Proximate compositions of the fruit pulps of Ananas cosmosus, Musa acuminata,
Annona muricata, Canarium schweinfurthii, Chrysophylum albidum and Citrus tangerina
3.3 Vitamin contents of the fruit pulps of Ananas cosmosus, Musa acuminata, Annona
muricata, Canarium schweinfurthii, Chrysophylum albidum and Citrus tangerina
3.4 Mineral contents (mg/100)of the fruit pulps ofAnanas cosmosus, Musa acuminata,
Annona muricata, Canarium schweinfurthii, Chrysophylum albidum and Citrus tangerina
3.5 Mineral contents (%)of the fruit pulps of Ananas cosmosus, Musa acuminata,
Annona muricata, Canarium schweinfurthii, Chrysophylum albidum and Citrus tangerina
3.6 Percentage Inhibition of the fruit pulpsof Ananas cosmosus, Musa acuminata,
Annona muricata, Canarium schweinfurthii, Chrysophylum albidum and Citrus Tangerine
3.6.1 Inhibition Concentration (IC50) values for DPPH radical scavenging activity of
the fruitpulps of Ananas cosmosus, Musa acuminata, Annona muricata,
Canarium schweinfurthii, Chrysophylum albidum and Citrus tangerine
3.7 Effective Concentration (Ec50) Values for Ferric Reducing Antioxidant Power
(FRAP) of fruit pulps of Ananas cosmosus, Musa acuminata, Annona muricata,
Canarium schweinfurthii, Chrysophylum albidum, and Citrus tangerina
CHAPTER FOUR: DISCUSSION
4.1 Discussion
4.2 Conclusion
4.3 Suggestions for Further Studies
REFERENCES
APPENDICES
CHAPTER ONE
INTRODUCTION
It is widely accepted that a plant-based diet with highintake of fruits, vegetables, and other nutrient-rich plant foods may reduce the risk of oxidative stress-related diseases (Riboli and Norat, 2003; Johnson 2004; Stanner et al 2004). Nutritionists are worried about the nutritive value of cooked food because the quality of most nutrients like protein, carbohydrates, vitamins and minerals are very poor (Reis et al., 1987). Fruits have been included in the human diet since prehistoric time and now in the developed and developing countries, there is the habit of taking fresh fruits after meal. In Nigeria, different kinds of seasonal fruits are available which are important sources of fiber, vitamins and minerals which provide essential nutrients for the good health of humans. Fruits are a major source of above mentioned food supplements.Fruits are referred to as juicy seed bearing structure of flowering plant that may be eaten as food (Hyson, 2002). Increased consumption of fruit and vegetables significantly reduces the incidence of chronic diseases, such as cancer, cardiovascular diseases and other aging-related pathologies. Fruits are not accorded theimportance they deserve in the diet of Nigerians due to ignorance of their nutritive value, cost and difficulty in storage and distribution (Sai, 1997). In developing nations, numerous types of edible wild plants are exploited as sources of food to provide supplementary nutrition to the inhabitants (Aberoumand and Deokule, 2009). Fruits offer protection against free radicals that damage lipids, proteins, and nucleic acids. Polyphenols, carotenoids (pro-vitamin A), vitamins C and E present in fruits have antioxidant and free radical scavenging activities and play a significant role in the prevention of many diseases (Veliogluet al., 1998; Spiller, 2001; Prakash and Kumar, 2011).Food and Agricultural Organization (FAO) reported that at least one billion people are thought to usewild food in their diet (Burhingame, 2000).
1.1 Antioxidants
An antioxidant is a substance, generally an organic compound, that is more readily oxidized than a second substance and hence can retard or inhibit the autoxidation of the second substance when added to it (Stenesh, 1989).Antioxidants are the body’s first line of defense against oxidative damage, and are critical for maintaining optimum health and wellbeing. Antioxidants are chemicals that interact with and neutralize free radicals, thus preventing them from causing damage. Oxidation is a chemical reaction that transfers electron from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. Free radicals
Antioxidants are capable of stabilizing, or deactivating, free radicals before they attack cells. Antioxidants are absolutely, critical for maintaining optimal cellular and systemic health and well-being (Traber and Atkinson, 2007). To protect the cells, organ and systems of the body against reactive oxygen species, humans have evolved a highly sophisticated and complex antioxidant protection system (Vertuaniet al., 2004). Although oxidation reactions are crucial for life, they can also be damaging; hence, plants and animals maintain complex systems of multiple types of antioxidants, such as glutathione, vitamins C and E as well as enzymes such as catalase, superoxide dismutase and various peroxidases. Low levels of antioxidants, or inhibition of the antioxidant enzymes, causes oxidative stress and may damage or kill cells. Antioxidants are also widely used as ingredients in dietary supplements in the hope of maintaining health and preventing diseases such as cancer and coronary heart disease. Although, initial studies suggested that antioxidant supplements might promote health, later large clinical trials did not detect any benefit and suggested instead that excess supplementation may be harmful. In addition to these uses of natural antioxidants in medicine, these compounds have many industrial uses, such as preservatives in food and cosmetics and preventing the degradation of rubber and gasoline. For many years chemists have known that free radicals cause oxidation which can be controlled or prevented by a range of antioxidants substances (Bjelakovic et al., 2007).............
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