The study examined the nutrients and phytochemicals composition of some lesser – known vegetables in Nigeria (Mucuna pruriens and Phyllantus nuriri) and their effects on iron and beta carotene status of rats. Leaf extract was collected from each vegetable. The leaves were separately plucked, sorted and extraneous materials were removed. Then they were washed with deionized water and were pulverized to get the concentrates. Standard methods were used to determine the proximate, some minerals, and vitamins composition as well as phytochemical constituents of the extracts. Animal study was carried out to ascertain the bioavailabihty of these nutrients. Twenty male adult rats were used for the study. They were divided into four groups according to their body weights. The animals were housed individually in metabolic cages. The rats were fed standard rat chow. The extracts were made to provide 0.11 mg/day iron to the rats. The study lasted for twenty eight days. The rat study showed that feeding rats with rat chow supplemented with Mucuna pruriens and Phyllantus nuriri extract improved the hemoglobin levels. Mucuna pruriens contained 11.47% carbohydrates, 3.20% protein, 1.25% ash and 3.82% crude fibre, while Phyllantus nuriri contained 15.47% carbohydrate, 3.87% protein, 3.02% ash and 3.20% crude fibre. The vegetables had significant quantities of calcium (23.45mg and 34.71mg), iron (7.45mg and 11.27mg), Vitamin C (26.16mg and 20.13mg/100mg), vitamin E (3.06mg and 3.62mg) and 3 – carotene (3.62 and 3.65mg) per l00g sample. Anti – nutrients and toxicant levels of the vegetables were low. Mucuna pruriens had 0.004mg phytate and 0.62mg oxalate while Phyllantus nuriri had 1.28mg phytate and 1.31 mg oxalate. Phytochemicals were present in these vegetables. Mucuna pruriens contained 0.003% alkaloids, 0.54% tannins, 7.01% saponins, 3.16% flavonoids, 12.47% cyanogenic glycosides and 1.06% phenols. Phyllantus nuriri had 1.68% alkaloids, 0.68% tannins, 3.95% saponins, 6.22% flavonoids, 1.17% cyanogenic glycosides and 0.21% phenols. The hemoglobin level for Phyllantus nuriri group was 23.73%, while the Mucuna pruriens group was 16.57%. The serum iron, red blood cell count and beta – carotene levels of rats were significantly improved. The recommendations are that the consumption of these vegetables could be useful in addressing some micronutrients and diet – related non – communicable diseases because of their rich and micronutrient and phytochemical constituents. Nutrition educators should use the information from this study to counsel families on the consumption of these lesser – known vegetables. Students should also be assisted to carryout the same study on humans to see the nutritional effect. Organoleptic evaluation of these vegetables should be carried out to evaluate acceptability.
1.1 Background to the Study
Green leafy vegetables constitute an indispensable constituent of human diet, especially in local delicacies. It is estimated that over 60 species of green leafy vegetables are used as food. Apart from the well-known and easily cultivated green leafy vegetables serving as sources of micronutrients, several wild and ornamental plants are traditionally ‘important supplement sources of food nutrients. They are used for various purposes ranging from food for man and animals, to therapeutic and manure for plants. Some of the vegetables are underutilized.
Seasonality partly precipitates micronutrient deficiency, especially during off-season when green leafy vegetables are unavailable. The anti-nutrient content of vegetables, limit the availability of micronutrient present in the vegetables. The issue of micronutrient deficiencies and their consequences on health, learning capability and productivity of affected people constitute a major public health problem globally and is of increasing prominence in Nigeria. The current rate of micronutrient deficiency is 24% among mothers and 48% among pregnant women in Nigeria (FMOH, 2006). There have been several attempts by Nutritionists the world over to proffer adequate solutions to this problem. Part of the efforts is to document the nutrient composition of some green leafy vegetables, which still grow as wild crop or semi-wild crop or unpopular vegetables in many areas in Nigeria ecosystem, which could contribute to the micronutrient intake of the populace.
Mucuna pruriens leaves and Phyllanthus nuriri leaves are unpopular vegetables in Nigeria. Mucuna is a leguminous plant (NAS, 1979). A number of species are available in Nigeria for example M. utilis (“Agbara-orji ”), M. Flagellipes-(“ukpo’), M Sloanie (“ukpa ’). The leaf of Mucuna pruriens is commonly known as “agbara nkita” among the Ibos of Eastern Nigeria. The leaves of mucuna are used as medicine or for therapeutic purposes. In the local communities, these leaves are used for the treatment of anaemia (Ezekwesili, 2005).
Phyllanthus nuriri leaf is another wild vegetable, which comes under the botanical family called Euphorbiaceae. The most common species of this family in most West African nations are Phyllanthus amaru and Phyllanthus nuriri popularly called “chancea piedra” in many parts of the world. Among the Ibos of eastern Nigeria it is called “okwonwa”. In the local communities, it is used in the treatment of anaemia and malaria (Uzoma, 2004).