ABSTRACT
Leaves of Hibiscus sabdariffa L. obtained from a farm within North – Bank Market in Makurdi Metropolis of Benue State, Nigeria were studied to assess the level of some trace metals (Mg, Mn, and Zn). The trace metals were analysed using atomic absorption spectrometry. The result obtained indicated that the level of Mg was highest in the sample, the level of Mn was intermediate while Zn has the lowest value. In the sample analysed, the concentrations were also above the maximum limit for NAFDAC’S required daily intake (RDI) and FAO/WHO required daily allowance. Their concentrations were 866.82 ± 211.18 mg/100g dry weight for Mg; 103.38 ± 15.12 mg/100g dry weight for Mn; and 32.91 ± 3.54 mg/100g dry weight for Zn. In view of the reported nutritional and functional properties, of the leaves of Hibiscus sabdariffa L., the plant could be a source of active dietary constituents in the role of prevention of chronic and degenerative diseases as well as to challenge the micronutrient deficiency.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of Study
The term fruit and vegetables may be defined as edible plant foods excluding cereal grains, nuts, seeds, coffee, tea, cacao and herbs and spices, provided a similar but more detailed definition for fruit and vegetables, noting the exclusion of nuts, seeds, peanuts, peanut butter, grains and vegetables when used as grains and the inclusion of olives, avocados, pickles, coconut and products and mixed dishes that contain any amount of fruit and vegetable. They also provided a narrow definition of fruit and vegetables that has specific conditions relating to macronutrient content, processing and serving sizes, but this definition is not practical for use in relation to epidemiological studies (IARC, 2003).
The culinary term vegetable refers to edible part(s) of a plant consumed raw or cooked, generally with a main dish, in a mixed dish, as an appetizer or in a salad. Vegetables include edible stems and stalks, roots, tubers, bulbs, leaves, flowers, some fruits, pulses (mature beans and peas), fungi (mushrooms, truffles), algae (sea weed) and sweet corn and hominy (cereal grains used as vegetables) (IARC, 2003).
The culinary term vegetable excludes other cereal grains, nuts, peanuts (a type of pulse) and culinary fruits. The distinction as to which botanical fruits are considered to be culinary vegetables depends on cultural use in meal patterns and the flavours they impart (IARC, 2003).
Botanical fruits used as vegetables (e.g., eggplant, okra, zucchini) tend to be savory in taste, while those used as fruits are generally sweet (due to a higher sugar concentration) or tart as in cranberries, lemons and limes (due to a higher acid content) (IARC, 2003).
Trace metals (elements) are metals in extremely small quantities almost at the molecular level that reside in or are present in animal and plant cells and tissues. Some are necessary part of good nutrition. They include Iron, Zinc, Copper, Chromium, Cobalt, Molybdenum, Manganese, Selenium and others (Adebayo et al., 2006).
Trace elements refer to chemical elements present only in minute amounts in a particular sample or environment, or chemical elements required only in minute amounts by living organisms for normal growth. The human body is composed of elements which can be roughly divided into abundant elements and trace elements. Abundant elements consists of the major element that are involved in the formation of covalent bonds and are important constituents of tissues (oxygen, carbon, hydrogen, nitrogen etc.) and semi-major elements, which often exists in the ionic state and are involved in functions of the living body through maintenance of osmotic pressure and membrane potentials (potassium, sodium etc.) (Wada, 2001). Major elements account for 96% of the total body weight. Deficiency of major elements can lead to nutritional disorders and their presence in excess can cause obesity. Deficiencies or excess states of semi-major elements often results in water and electrolyte abnormalities. Examples of trace elements includes: - Manganese (Mn), Iodine (I), Cobalt (Co), Zinc (Zn), Copper (Cu), Boron (B) and Iron (Fe). The trace elements reported to be essential are Iron (Fe), Copper (Cu), Zinc (Zn), Manganese (Mn), Iodine (I), Tin (Sn), Silicon (Si), Uranium (U) and Arsenic (As) (Wada, 2001). Several trace elements such as Fe, Zn, Cu, Cr, Co and Mn are essential, while Pb, As, Cd, Ni and Hg are toxic at certain levels.
The Roselle or Sorrel plant (Hibiscus sabdariffa L.) is a species of Hibiscus native to the old world tropics, used for the production of bast fibre and as an infusion. It is an annual or perennial herb or wood-based sub shrub. The plant is considered to have anti-hypertensive properties, specifically sorrel plant (Hibiscus sabdariffa L.) is an acid tasting herb of the Malvaceas family (McLean, 1973; James, 2003; Yadong et al., 2005). The plant is an annual crop widely grown in the northern part of Nigeria, with promising nutritional potential. It is one of the under-exploited food crops of Nigeria. Sorrel plant bears edible calyces, seeds and leaves. The different parts of the plant appear to have potentials exploitation by the food processing industry (McLean, 1973; James, 2003). In northern Nigeria, sorrel is known as yakuwa or sure (pronounced suuray) in Hausa or karassu in Kanuri, in Benue sorrel is known as Ashwe in Tiv language. It is also used in stews usually in addition to spinach. In some Hausa communities, it is steamed and made into salad using kuli-kuli (traditional roasted peanut cakes with oil extracted), salt, pepper, onion and tomatoes. The recipe varies according to different levels of household income.
Hibiscus sabdariffa L.is rich in mineral elements. These mineral elements are inorganic element. Their bioavailability and metabolic functions are related to the forms in which they are found. Example in the presence of oxalates and citrate, calcium cannot be absorbed when combined with oxalate. Chelating agent have a selective attraction with various mineral element releasing one mineral element for another for which it has a greater attraction and sometimes creating deficiencies of one element which is present in otherwise adequate amount
Roselle in addition to these essential minerals contains various anti-nutrients which are almost responsible for the anti-nutritional factors although they occur in low levels. Anti-nutrients are non-essential nutrients that are not required by the human body for sustaining life. They are also natural or synthetic compounds that interfere with the absorption of nutrients commonly found in food sources and beverages (Ross, 2003).
Globally, many researchers have noted the food potentials of the different parts of sorrel plant (Mclean, 1973; Duke and Atchley, 1984; Nnam and Onyeke, 2003; Rich, 2004 and Yadong et al., 2005). The calyx could be processed to produce jam, marmalade, jelly, ices, ice cream, herbal tea, wine, juice, syrup, sauces, gelatin and butter. Sorrel calyx has some medicinal uses such as the treatment of bilious attacks, decreasing the viscosity of the blood, reducing blood pressure and as diuretic for stimulating intestinal peristalsis. It can also be used to treat cancer, cough, and scurvy (Yadong et al., 2005). The leaves could be useful in producing curries, as vegetable in soup, eaten raw in salads, as a purée in eating rice and fish. Sorrel leaves have some medicinal uses (Duke and Atchley, 1984). It has diuretic effects and could lower temperature during fever. It acts as an emollient and sedative for digestive and kidney functions. It sooths cough and decreases the rate of absorption of alcohol (Rich, 2004). Products from the seeds are food condiments, coffee, essential oil, foo foo, porridge, animal feed, oily soups, and sauces. The seed has medicinal uses as diuretic, laxative and tonic for addressing debility challenges of patients. It may appear that no standard recipe has been evolved for the development of the products as novel food from the under-exploited food crop.
1.2 Statement of the Problem
Preliminary evaluation of sorrel leaf shows that they have rich nutrient potentials and may become useful in commercial food production. The different parts of the plant have however, limited use. Proximate and nutrient analysis of edible vegetables plays a crucial role in assessing their nutritional significance (Pandey et al., 2006). Diversifying the utilization of this indigenous nutritious plant through the development of new products from the different parts of the plant would provide some new value-added products into the family menu. This will improve the nutrient intake and nutritional status of the populace.
1.3 Aim and Objective of the study
The aim of this research work is to assess the levels of essential trace elements in the leaves of sorrel plant (Hibiscus sabdariffa L.).
The objective is to compare the levels of essential trace elements in the leaves of sorrel plant (Hibiscus sabdariffa L.).
1.4 Significance of the Study
The results of the study will encourage food industries to exploit the leaves parts of sorrel plant raw materials for making some commercial products. The results of the study can extend the food uses of sorrel leaves as a positive step in the dietary diversification programme. Sorrel plant can contribute to the economic improvement of Nigeria through the production, use and sale of different food products from its leaves. The development of products from sorrel leaves will stimulate nutritionists and food scientists to investigate other indigenous food plants for commercial purposes.
1.5 Scope of the Study
The research is strictly limited to the determination of the concentration levels of zinc (Zn), Manganese (Mn) and Magnesium (Mg) in Hibiscus sabdariffa L. leaves obtained from North bank market in Makurdi metropolis.
