ABSTRACT
The study investigated the nutrients and phytochemical compositions of some leafy vegetables in Nigeria (Hibiscus cannabinus, Adansonia digitata, Sesamum indicum and Cassia tora leaves) and the effects of their extracts on blood glucose and lipid profile of alloxan induced diabetic rats. Two kilogrammes of each of the vegetables were bought fresh, sorted by removing extraneous material, washed with deionized water and separately pulverized using Gallenkamp mixer Kenwood –MPR 201. A half of the vegetables was used for chemical analysis and a half for methanol extract production. Standard methods were used to determine in triplicate the proximate, some minerals, vitamins, antinutrients, food toxicants, and phytochemical constituents of the fresh leaves and their methanol extracts. Animal study was carried out to ascertain the effect of the nutrients on blood glucose and lipid profile of alloxan- induced diabetic rats. Forty five male adult albino rats (150-200g) divided into nine groups of five rats each on basis of body weights were used for the study. The group of rats fed rat chow and glibanclamide drug served as standard control. The other groups were fed rat chow and graded doses of each vegetable extract (500mg and 1000mg/kg bodyweight) daily for twelve days. Water was given ad libitum. The proximate principles were lower in the fresh leaves than in the extract except for crude fibre. The leaves had 80.20% - 95.09% moisture, 1.62% – 3. 89% protein, 0.05% – 0.06% fat, 0.06% – 1.35% ash, 1.56% – 4.16 crude fibre and 1.04% – 13.71% carbohydrate. Mineral values were 236.68 – 437.11mg sodium, 0.87 – 2.67mg potassium, 0.63 - 4.97mg calcium, 172.50 – 235.70mg phosphorus, 0.51 – 0.59mg zinc, 0.26 – 0.59mg iron, 3.37 – 3.44mg copper and 0.24 – 0.28mg magnesium. The leaves contained 11.57 - 22.28 µg beta carotene, 1.25 - 2.88mg thiamin, 0.87 - 2.82mg riboflavin, 15.60 - 29.37mg vitamin C, niacin 0.74 - 1.61mg and 25.89 -31.43mg vitamin E. All the vegetables had traces of oxalate, 0.01mg - 0.05mg phytate, 0.37mg - 0.43mg tannins.
Hydrocyanides levels of the vegetables were low (0.01 - 0.02mg). Food toxicants (cadmium and lead) levels of the leaves were (0.01 - 0.03mg and 0.02 - 0.14mg, respectively). The values were within safe levels for cadmium and lead allowed by World Health Orginisation (WHO) standard for food substances (SAFS). The phytochemicals of the vegetables were in small quantities relative to the nutrients. The phytochemical levels were higher in the extracts than in the fresh leaves. The leaves contained 0.06 - 0.12mg saponins; 0.01mg - 0.04mg flavonoids, 0.03mg – 0.21mg alkaloids, 0.01 – 0.02mg glycosides; 0.09mg - 0.21mg terpenes and 0.09mg - 0.16mg phytosterols. The extracts had 5.40% – 9.84% moisture, 14.56% - 26.42% protein, 0.68% – 1.23 % fat; 4.34% – 8.51% ash, 0.62% – 0.83% crude fibre and 54.64% - 74.44% carbohydrate. Mineral values for the extracts were 873.64 – 1423.44mg sodium, 1122.61 – 1425.30 mg potassium, 1571.94 – 1924.34 calcium, 138.37 – 224.19mg phosphorus, 0.18 – 0.27mg/100g zinc, 18.74 – 34.19mg iron, 0.28 – 0.83mg copper, and 229.37 – 341.55mg/ magnesium. The extracts contained 7.60 – 13.70µg β carotene, 1.22mg - 2.40mg thiamin, 0.54 – 2.32mg riboflavin, 14.86 – 26.34mg vitamin C, 0.84 – 9.52mg niacin and 21.30mg - 25.72 mg vitamin E. The antinutrients contents of the extracts were 0.66mg - 1.78mg phytate, 4.57 - 7.07mg tannins and 0.22mg - 0.48mg hydrocyanides. 0.01mg - 0.03mg cadmium and 0.02mg – 0.21mg lead. Phytochemicals value for the extracts were 2.40 - 3.73mg saponins, 0.09 - 0.29mg flavonoids, 4.91mg - 6.77mg alkaloids, 2.40 - 3.84mg glycosides, 1.09mg - 2.30mg terpenes and 1.26mg - 2.50mg phytosterols. Feeding the rats with rat chow supplemented with graded doses of Hibiscus cannabinus, Adansonia digitata, Sesamum indicum and Cassia tora leaves extracts reduced blood glucose concentrations and improved lipid profiles. The Adansonia digitata and Cassia tora leaf extracts fed at higher doses (1000mg) decreased blood glucose concentrations of rats (33.63% and 23.92%, respectively) more than those fed standard antidiabetic drug glibenclamide (17.23% ). They improved lipid profile of the rats by (26.92% and 25.46%). They decreased the total cholesterol (TC) and triglyceride (TG)) 54.72 and 67.70% respectively more than those fed standard drug (21.15% TC and 45.83% TG). The vegetables extracts could be used for management of diabetes and some other related non – communicable diseases due to their rich nutrients, antioxidants and phytochemical constituents.
TABLE OF CONTENTS
Title page
List of Tables
List of Figures
ABSTRACT
CHAPTER ONE: INTRODUCTION
1.1 Background to the Study
1.2 Statement of the Problem
1.3 General objective of the Study
1.4 Specific Objectives
1.5 Significance of the Study
CHAPTER TWO: LITERATURE REVIEW
2.1 Vegetables
2.1.1 Classification of Vegetables
2.1.2 Uses of vegetables in foods
2.1.3 Importance of Vegetables
2.1.4 Health benefits of Vegetables
2.1.5 Vegetables in diabetes management
2.1.6 Effect of processing on green leafy Vegetables
2.1.7 Recommended daily intake of Vegetables
2.2.0 Nutrient composition of green leafy Vegetables
2.2.1 Moisture content of vegetables
2.2.2 Carbohydrates content of vegetables
2.2.3 Protein content of vegetables
2.2.4 Fats in green leafy vegetables
2.2.5 Ash in vegetables
2.2.6 Minerals in vegetables
2.2.7 Vitamins in vegetables
2.3.0 Antioxidants
2.3.1 Antioxidants in vegetables
2.3.2 Antioxidants in prevention and management of diabetes
2.4.0 Phytochemicals
2.4.1 Classes of phytochemicals
2.4.2 Mechanism of action of phytochemicals
2.4.3 Specific phytochemicals in vegetables and their actions
2.4.4 Recommended nutrient intake of phytochemicals
2.4.5 Phytochemicals index
2.4.6 Health benefits of phytochemicals
2.4.7 Phytochemicals in diabetes management
2.5.0 Antiphysiological factors in green leafy vegetables
2.5.1 Antinutrients
2.6 Toxicants in vegetables
2.7 Hibiscus cannabinus plant and leaves
2.7.1 Nutrient composition of Hibiscus cannabinus leaves
2.7.2 Phytochemical content of Hibiscus cannabinus leaves
2.7.3 Hypoglycemic activity of Hibiscus cannabinus leaves
2.8. Adansonia digitata plant and leaves
2.8.1 Nutrient composition of Adansonia digitata leaves
2.8.2 Phytochemical content Adansonia digitata leaf
2.8.3 Adansonia digitata in the management of diabetes mellitus
2.9 Sesamum indicum plant and leaves
2.9.1 Nutrient composition of Sesamum indicum leaves
2.9.2 Phytochemical content of Sesamum indicum leaves
2.9.3 Sesamum leaves in diabetes management
2.10 Cassia tora plant and leaves
2.10.1 Uses of Cassia tora leaves
2.10.2 Constituents and chemical properties of Cassia tora leaves
2.10.3 Medicinal potentials of Cassia tora leaves
2.11 Blood glucose
2.11.1 Blood glucose regulation
2.12.0 Diabetes mellitus
2.12.1 Classification of diabetes
2.12.2 Prevalence of diabetes mellitus
2.12.3 Aetiology of diabetes mellitus
2.12.4 Common symptoms of diabetes mellitus
2.12.5 Diabetes treatment
2.12.6 Diabetes complications
2.13 Alloxan
2.14 Lipid profile
2.14.1 Cholesterol
2.14.1.1 Types of Cholesterol
CHAPTER THREE: MATERIALS AND METHODS
3.1.0 Materials
3.1.1 Procurement of materials
3.1.2 Preparation of vegetables
3.1.3 Preparation of vegetable extracts
3.2.0 Chemical analysis
3.2.1 Moisture determination
3.2.2 Crude protein Determination
3.2.3 Fat determination
3.2.4 Ash determination
3.2.5 Crude fibre
3.2.6 Carbohydrate determination
3.2.7 Mineral contents
3.2.8 Vitamins determination
3.2.9 Antinutrients determination
3.2.9.1 Oxalate
3.2.9.2 Pytate
3.2.9.3 Tannins
3.2.9.4 Hydrocynide
3.2.10 Toxicant determination
3.2.10.1 Cadmium and lead
3.2.11 Phytochemical determination
3.2.11.1 Saponins
3.2.11.2 Flavonoid determination
3.2.11.3 Alkonoids
3.2.11.4 Glycocides
3.3.0 Animal Experiment
3.3.1 Sourcing of animals and housing
3.3.2 Diet composition
3.3.3 Induction of diabetes
3.3.4 Feeding trial
3.3.5 Blood sample collection
3.3.6 Biochemical indices determination
3.3.6.1 Determination of blood glucose levels
3.3.6.2 Determination of serum total cholesterol Levels
3.3.6.3 Determination of serum Triglycerides
3.3.6.4 Determination of serum High Density Lipoprotein (HDL)
3.3.6.5 Determination of serum low Density Lipoprotein (LDL)
3.4.0 Statistical analysis
CHAPTER FOUR RESULTS
4.1 Proximate composition of fresh Hibiscus cannabinus, Adansonia, digitata, Sesamum indicum and Cassia tora leaves (wet weight basis)
4.2 Mineral contents of fresh Hibiscus cannabinus, Adansonia, digitata, Sesamum indicum and Cassia tora leaves (wet weight basis)
4.3 Vitamin contents of fresh Hibiscus cannabinus, Adansonia digitata, Sesamum indicum and Cassia tora leaves (wetweight basis)
4.4 Antinutrient and food toxicant content of fresh Hibiscus cannabinus, Adansonia, digitata, Sesamum indicum and Cassia tora leaves on wet weight basis
4.5 Phytochemcial composition of fresh Hibiscus cannabinus, Adansonia digitata, Sesamum indicum and Cassia tora leaves on wet weight basis
4.6 Proximate composition of the methanol extract of Hibiscus cannabinus, Adansonia, digitata, Sesamum indicum and Cassia tora leaves on wet weight basis
4.7 Mineral contents of methanol extracts of Hibiscus cannabinus, Adansonia, digitata, Sesamum indicum and Cassia tora leaves
4.8 Vitamin contents of the methanol extracts of Hibiscus cannabinus, Adansonia, digitata, Sesamum indicum and Cassia tora leaves
4.9 Anti nutrient and food toxicant contents of methanol extract of Hibiscus cannabinus, Adansonia digitata, Sesamum indicum and Cassia tora leaves
4.10 Phytochemcial contents of methanol extracts of Hibiscus cannabinus, Adansonia, digitata, Sesamum indicum and Cassia tora leaves
4.11 Blood glucose levels of rats fed rat chow and glibenclamide drug, rat chow and 500mg, 1000mg of Hibiscus cannabinus, Adansonia digitata, Sesamum indicum and Cassia tora leaf extracts
4.12 Mean serum total cholesterol (TC) levels (mg/dl) of rats fed rat chow and glibenclamide drug, rat chow and 500mg, 1000mg of Hibiscus cannabinus, Adansonia digitata, Sesamum indicum and Cassia tora leaf extracts
4.13 Mean serum triglyceride (TG) levels (mg/dl) of rats fed rat chow and glibenclasmide drug, rat chow and 500mg, 1000mg of Hibiscus cannabinus, Adansonia digitata, Sesamum indicum and Cassia tora leaf extracts
4.14 Mean serum high density lipoprotein (HDL) levels of rats fed rat chow and glibenclamide drug, rat chow and 500mg, 1000mg of Hibiscus cannabinus, Adansonia
digitata, Sesamum indicum and Cassia tora leaf extracts
4.15 Mean serum low density lipoprotein (LDL) levels of rats fed rat chow and glibenclamide drug, rat chow and 500mg, 1000mg each of Hibiscus cannabinus, Adansonia digitata, Sesamum indicum and Cassia tora leaf extracts
CHAPTER FIVE: DISCUSSION, CONCLUSION AND RECOMMENDATIONS
5.1 Discussion
5.1.1 Proximate composition
5.1.2 Mineral composition
5.1.3 Vitamins
5.1.4 Antinutrients, antiphisiololgical factors and food toxicants
5.1.5 Phytochemicals
5.1.6 Blood glucose levels
5.1.7 Total cholesterol levels
5.1.8 Triglyceride levels
5.1.9 High density lipoprotein
5.1.10 Low density lipoprotein
5.2 Conclusion
5.3 Recommendations
REFERENCES
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background to the Study
Vegetables include those leafy outgrowths of plants or parts of plants that are used in making soup or eaten with the principal part of the meal (Onimawo & Egbekun, 1998). Green leafy vegetables and fruits occupy an important place among the food crops as these provide adequate amounts of many vitamins and minerals for humans. They are rich source of carotene, ascorbic acid, riboflavin, folic acid and minerals like calcium, iron and phosphorous (Nnam, Onyechi & Madukwe, 2012). They are important protective foods and highly beneficial for the maintenance of good health and prevention of diseases (Kubmarawa, Andenyang & Magomya, 2009). Studies have shown that phytochemicals found in large quantities in fruits and vegetables are responsible for this protective effect (Sundarrayanan, Kumia & Sekar, 2011).
Over the past 25 years epidemiological studies have shown a diminished risk of chronic diseases in populations consuming diets high in fruits and vegetables (Kearo, Popkin & Frison, 2010). Countries like South Korea, a high income country that have undergone rapid social change and economic development since the 1970s, still have lower rate of obesity and other non-communicable diseases than the countries with comparable average income. This is because South Korea has protected its traditional food systems. These foods are relatively high in vegetables and fruits (Lee, Popkin & Kim 2002). Equally numerous empirical and investigative reports have indicated that current non-communicable diseases (NCDS) trend in Africa can be attributed to rapid shift from traditional foods which contain mostly vegetables to western food products resulting in elevated intake of saturated fats and food preservatives with reduced intake of dietary fibre, vital nutrients and phytochemicals when compared to basic dietary guidelines (Nahurung, 1997; Gupta, 2011). The shift
Past generations whose diets consisted mainly of herbs, fruits, vegetables, nuts and starchy tubers lived longer than the present generation (Sathanaraynan, Thomas, Fashik & Sekher, 2009). They were not victims of the many health problems faced by the present population (Uguru, 2005). Life expectancy was better in the past because vegetables were a major component of the diet (Sathanaraynan at al., 2009). Vegetables should be adequately included in the diet to help to fight against the deadly scourge diseases. According to Socrates, a Greek philosopher, Fruits and vegetables are the earliest source of food to mankind (Largen, 1984). Equally Tutare (2000) reported that there are over 200 varieties of vegetables to which majority of Nigerians are not accustomed to. The major reason for less exploitation and utilization of fruits and vegetables in Nigeria is due to ignorance of their contribution to adequate nutrition (Kubmarawa et al., 2009; Nnam, 2011).
Leafy vegetables are known to add taste and flavour as well as substantial amounts of protein, fibre, minerals and vitamins to the diet, (Nahurung, 1997; Willel, 2002; Sundarrayanan et al., 2011). The amounts of the nutrients and constituents in the more commonly used leafy vegetable species in Nigeria have been studied to some extent (Oguntona, 1998; Kubmarawa, 2009; Ene-obong, 2001). However the lesser known regional and local vegetables remain virtually neglected. Lack of information on the specific nutrients in a large number of locally consumed vegetable species with which Nigeria is richly endowed is partly responsible for their under exploitation especially in areas beyond the traditional localities where they are found and consumed.
During the last decade the concept of health promotion using fruits and vegetables has become legitimate part of health care (Nielsen, 2010). There is an increasing preference expressed by many patients in recent time towards the popular use of alternative therapies that include food supplements
There is dearth of information on the efficacy of Hibiscus cannabinus (rama), Adansonia digitata (baobab), Sesamum inducum (karkashi ) , Cassia tora (tabsa) leaves as remedy to manage diabetes. The thrust of this study was to explore the detailed nutrients and phytochemicals composition of these foods and their use in animal models to treat diabetes mellitus.
1.2 Statement of the Problem
Increasing incidence of chronic diet related non communicable diseases (NCDS) is one of the health challenges world over (Nnam, Onyechi & Madukwe, 2012). The diseases which include cardiovascular diseases (CVDS), diabetes mellitus, obesity, hypertension and cancers are increasingly becoming public health problems in Nigeria (Nnam et al., 2012). NCDs account for 60% of global deaths. It is predicted that by 2020 NCDS would account for 73% deaths and 60% disease burden (Ene-Obong, 2010). The causes are linked to poverty, globalization and adoption of western dietary patterns.These are facilitated by advertisement for consumption of unhealthy foods and lack of physical exercise (Onyechi and Ibeanu, 2010; Nnam et al., 2012).
Diabetes mellitus is one of the chronic non communicable diseases.Diabetes is a serious complex chronic condition and a major cause of ill health worldwide (Willel, 2012). This metabolic disorder is characterized by hyperglycemia and disturbances of carbohydrate, protein and fat metabolism. These could be as a result of an absolute or relative lack of the hormone insulin (Sathanaraynan, Thomas.....
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