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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.


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 from traditional foods to western food products has been dubbed the nutrition transition and is directly implicated in the rise of type 2 diabetes, cardiovascular and other NCDs (Uguru, 2005).

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 and herbal/folklore preparation with anti diabetic activity. This is because of the much scientific evidence available to support their efficacies in the control of diabetes related metabolic disorders and long term complications (WHO, 1980; Shittu, Bankole &   Ashiro, 2007). The diabetes blog is all over research linking increased consumption of vegetables with protective health benefits ( Treatment   with   diets   has   fewer side effects. Moreover   foods   are cheap and readily available even in the rural community.

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 & Sekher, 2009; Rajjkiran, Nusrath & Sujatta, 2011).  Currently, there are over 150 million diabetic patients worldwide.  The number is likely to increase to 300 million or more by the year 2025 (Rajikeran et al., 2011). No  modern medicine has reached the satisfactory level in the treatment of diabetes.  The International Diabetes Federation (IDF) (2013) reported that diabetes is no longer a disease of the poor as four out of five people (80%)  have diabetes in the world live in low and middle income countries. A country by country summary table by IDF 2012 showed that 3,165.31 million Nigerians between the ages of 20 and 79 years have diabetes, while 2,532.25million Nigerians living with the conditions are unaware and undiagnosed. Nigeria lost 88.681million persons in 2012 due to diabetes related illnesses and has a 4.83% comparative prevalence according to World Health Organization (WHO) standard. As the global burden of diabetes accelerates the call to address the world wide care of diabetics intensifies daily. It has been estimated that by 2025 the incidence of diabetes mellitus would double.  There are several drugs for the treatment of diabetes. They however have prominent side effects (Gupta, Medratia, Singh & Sharm, 2006) and most often out of reach for most diabetics. The next option is dietary treatment using foods that are locally available with hypoglycemic effect (Onyechi and Ibeanu, 2010).  There has been increasing demand for the use of natural plant products with anti diabetic activity (Fuentes, Sagua, Morale & Bongue, 2005). This is because of their   wide biological activities, high safety margins and low costs (Fuentes et al., 2005).

Use of plant products to treat diabetes mellitus is of growing interest as most plant foods contain many bioactive substances with therapeutic potentials.  Many leafy vegetables and their extracts are effective in the treatment of many non-communicable diseases (NCDs) (Fuentes et al., 2005; Nnam et al., 2012).  WHO also recommends the evaluation of traditional plant extracts, for the treatment of diabetes as such extracts have fewer side effects and possess better glycemic control over the synthetic medicines (WHO, 2007).  Nnam et al. (2012) reported that some leafy vegetables have medicinal properties and can be used for the sick and convalescence.  Anecdotal evidence suggests that there is antidiabetic activity in Hibiscus cannabinus (rama), Adansonia digitata (baobab), Sesamum indicum (karkashi) and Cassia tora ( tabsa) leaves.  The leaves are major soup vegetables in different parts of northern Nigeria where they are grown and utilized. The present study focused on the scientific investigation of the nutrient, phytochemical composition and anti diabetic activity of Hibiscus cannabinus (rama), Adansonia digitata [baobab], Sesamum indicum (karkashi) and Cassia tora (tabsa) leaves. The study would provide evidence based information for further research work on the hypoglycemic potentials of the vegetables.

 1.3 Objectives of the Study        

General objective

The general objective of the  study was to determine the nutrients and  phytochemical composition of  some leafy vegetables (Hibiscus cannabinus, Adansonia digitata, Sesamum indicum, Cassia tora leaves) used for preparing soups in Adamawa State of Nigeria and their anti diabetic activity in alloxan-induced diabetic rats.

Specific Objectives

The specific objectives of this study were to determine:

1.      some nutrients, antinutrients and food toxicant content of Hibiscus cannabinus,                Adansonia digitataSesamum inducumCassia tora leaves and their extracts; 

2.        some  phytochemical   constituents of  the leaves ( alkaloids, carotenoids,  phytosterol,  glycosides,  terpenoids ,  flavonoids,   phenols,   saponins ) and their extracts; and

3.      the  effect  of   the vegetable extracts   on  blood glucose , serum  cholesterol, high density lipoprotein,  low density lipoprotein and triglycerides in alloxan - induced diabetic  rats . 

1.4   Significance of the Study                                                     

The result of this work will be of great significance to the scientific community because it would provide evidence based information on the vegetables for Nutritionists and Dietitians preparing diets for diabetic patients in various communities. The vegetables are cheap and abundant and information on their contribution to dietary management of diabetes would be very meaningful.     The result could be useful information to Pharmacists to elucidate the medicinal potentials of the vegetables.

The result if positive would create awareness to the general public on the use of the vegetables as remedy to manage diabetes. It would also increase their consumption in many parts of the country where the vegetables are less known and consumed even when they are available in large quantities in the places. The result would also provide valuable information for use in compiling the food composition table on Nigerian foods.

Equally, the result if positive would attract Scientists for further biochemical investigations as well as determine mechanism of action of their active constituents responsible for antidiabetic activities and properties.

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