Comparative proximate analysis of some green leafy vegetables from selected communities in Rivers...

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International Journal of Basic and Applied Sciences Vol. 4. No. 2 2015. Pp. 55-61 ©Copyright by CRDEEP. All Rights Reserved. Full Length Research Paper

Comparative Proximate Analysis of Some Green Leafy Vegetables from Selected Communities of Rivers and Imo State, Nigeria. Igwe1, K., Ofoedu2, C.E., Okafor2, D.C., Odimegwu2, E.N., Agunwah2, I.M. and Igwe2, V.S. 1Department of Biochemistry, Federal University of Technology, P.M.B 1526 Owerri, Nigeria. 2Department of Food science and Technology, Federal University of Technology, PMB 1526 Owerri, Nigeria *Corresponding Author: Igwe K

Absract The proximate composition of some edible green leafy vegetables; Okro leaf (Abelmoschu sesculentus), Pumpkin leaf (Telfairia occidentalis), Bitter leaf (Vernonia amygdalina) and Water leaf (Talinum triangulare) from selected oil producing communities (Umusoya, Eleme, Omagwa, Rukpokwu, and Bomu) of River State was investigated. The values obtained were compared to the proximate composition of edible green leafy vegetables from non oil-producing areas (Owerri, Mgbidi, Mbano, Mbaise, and Orlu) of Imo state. Values from the polluted and unpolluted areas indicated significant difference (P<0.05) in moisture content of the vegetables as it ranges from to for polluted areas and to for non polluted areas, while there was no significant

difference (P>0.05) for polluted and unpolluted bitter leaf. For Ash content, values in the polluted areas ranged from to

while in the unpolluted areas it ranged from to and both showed significant difference (P<0.05). The protein content in

the polluted areas ranged from to and to in the unpolluted areas and both showed significant difference

(P<0.05). Also, lipid content in the polluted areas ranged from while the unpolluted areas ranged from

and both showed significant difference (P<0.05). The crude fibre content in the polluted areas ranged from while the

values in the non polluted areas ranged from . Results from the study indicated that indiscriminate crude oil pollution on soil has significant effect on plant proximate composition and quality of vegetables produced, as a result of bioaccumulation of hydrocarbon substance in their aerial parts of the vegetables. Keywords: Bitter leaf, pumpkin leaf, water leaf, okro leaf, oil pollution, proximate composition Introduction Vegetable is one of the staple food components that its production has continue to increase in most countries of the world. Vegetable production constitutes about 4.64% of the total staple food production between 1970 and 2003 in Nigeria (CBN, 2003). In Nigeria, green leafy vegetable widely consumed by every household includes pumpkin leaf, bitter leaf, water leaf, okra leaf, among others.Vegetable crops are grown and consumed worldwide as a source of nutrient and fibre in the human diet. The consumption of a variety of vegetables by man is believed to contribute significantly to the improvement of human health, in terms of prevention and or cure of diseases because plants have long served as a useful and rational source of therapeutic agent (Roberts and Tyler, 1999) Bitter leaf (Vernonia amygdalina) is a widely used local plant in Nigeria for both nutritional and therapeutic purposes. It grows in a range of ecological zones in Africa and produces large mass forage and is drought tolerant (Bonsi et al., 1995). The bitter taste is due to anti-nutritional factors such as alkaloids, saponins, tannins and glycosides (Butter and Biuley, 1973). The macerated leaves of the plants are consumed as vegetables and condiments while the water extract serves as tonic for the prevention of certain illnesses. (Arhoghro et al., 2000) Water leaf (Talinum triangulare) belongs to the plant family portulaceae. It is a short-lived perennial herb, growing to 30-60cm in height. The leaf is greenish in colour with succulent stem and alternate leaf arrangement (Udoh and Akpu, 2007). In Nigeria, its wide acceptance across various ethnic groups has earned it several local names, such as “gare” in Yoruba, mmon-mmongikong in Efik/Ibibio among others; which is consistent with its high moisture content (Udoh and Akpan, 2007) Okra (Abelmoschus esculentus) is one of the most important vegetables grown in the tropics. In Nigeria, it is produced predominantly by present farmers usually in home. The crop is put to several uses locally. The immature green pods and fresh leaves are used as potherbs. The fresh okra fruits are high in Vitamin A and C; and in calcium (NARP, 1993). Significant levels of carbohydrate, potassium, magnesium and other vitamins are also present (Norman, 1992).



In Nigeria, Pumpkin leaf (Telferia occidentalis) is consumed in different parts of the country because of the numerous nutritional and medicinal attributes ascribed toit. It has different traditional names; among Igbos, it is known as ugu, iroko or akporoko in Yoruba, ubong in Efik, umee in urhobo and umeke in Edo (Akoroda, 1990). Oyolu ( 1978) reported that the leaves together with the edible shoots contain 85% moisture,11% crude protein, 25% carbohydrates, 3% oils, 11% ash and as much as 700ppm of iron, while (Longe et al., 1983) reported that the minerals namely: calcium, potassium, magnesium, iron, sodium and phosphorus are concentrated in the testa, pulp and husk. However, contamination of land is of paramount importance to man in that it is on this portion that man’s existence depends. Large amount of diverse chemicals enter the environment via industrial discharge and other anthropogenic activities (Adoki and Orugbani, 2007). Soil and water represent the first lines of oil pollution. The oil mineral producing areas in Nigeria are in danger because the land is damaged and made infertile due to oil spills and other factors, and this prevents growth of crops for varying periods of time.The damaging effects are due to suffocation and toxicity of the crude oil (Odu, 1970). Crude oil also contains hydrocarbons that exert adverse effects on soil conditions, microorganisms and plants when beyond 3% concentration; oil becomes increasingly deleterious to soil biota and crop growth (Udo and Fayemi, 1975). Crude oil makes it unsatisfactory for plant growth (Dejong, 1980). This is due to insufficient aeration of the soil because of displacement of the soil particles by crude oil (Rowell, 1977).

The release of crude oil into the environment by oil spills through accidents, pipeline sabotage has caused serious harm to farmlands thereby reducing available land for productivity. The effects of oil pollution on vegetables vary according to the type and amount of oil involved. Crude oil is phytotoxic because it creates unsatisfactory conditions for plant growth ranging from heavy metal toxicity to inhibited aeration of the soil. Crude oil spills affect vegetables adversely by creating conditions which make nutrients like nitrogen and oxygen needed for growth unavailable to them (Onyeike and Onwuka, 1999). Therefore, this study was aimed at determining and comparing the proximate composition of edible green leafy vegetables from selected oil producing communities of areas in River state and selected non-oil producing communities of areas in Imo state.

Figure 1. Bitter leaf (Vernonia amygdalina) Figure 2. Okra leaf (Abelmoschus esculentus)

Figure 3. Water leaf (Talinum triangulare) Figure 4. Pumpkin leaf (Telfairia occidentalis)

Materials and Method Sample Collection and Preparation Fresh leaves of Pumpkin leaf (Telfairia occidentalis), Water leaf (Talinum triangulare), Bitter leaf (Vernonia amygdalina) and Okro leaf (Abelmoschus esculentus)were collected from petroleum polluted farmland in Rivers state and non petroleum polluted farmland in Imo state.



The fresh leafy vegetables were handpicked, washed with distilled water to remove dust particles. The samples were then cut into

sizeable pieces using knife and sun dried. They were later placed in an oven at temperature of 50 for 2days for complete dryness.

The dried samples were then ground using blender into fine powdery form. Each of the samples was stored in well labeled plastic containers for analysis. Table 1. Proximate Composition (%) of Selected Edible Green Leafy Vegetables

Means with different superscript along the columns show significant difference at (P<0.05)

Proximate Analysis The Proximate analysis (Moisture, Fat, Protein, Ash, Crude fibre and Carbohydrate contents) was carried out according to the methods of A.O.A.C. (2004). Statistical Analysis Triplicate determinations were done. The significant differences obtained from the result were calculated using fisher’s least significant difference (FLSD) test in one way analysis of variance (ANOVA) which was used to separate the means of the measured parameters.

Results and Discussion The proximate composition of the selected green leafy vegetables is presented on Table 1. The results (Table 1 & Fig. 5) showed that

the polluted vegetables are significantly different (P 0.05) in percentage Moisture content from the unpolluted vegetables. This is

observed in all the test samples except in Bitter leaf where there is no statistical difference (P 0.05) between the polluted and

unpolluted Bitter leaf. The high moisture levels in the polluted vegetables suggest that the vegetables analysed may not be stored for a long time due to high water activity. High moisture content helps in maintaining the protoplasmic contents of cells (Gbadamosi, 2011). It also supports a greater activity of water-soluble enzymes and co-enzymes needed for metabolic activities of these leafy vegetables (Iheanacho, 2009). However, high moisture may cause quality problem as the samples may be susceptible to bacterial spoilage during storage (Onyeike et al., 2003); microorganisms that cause spoilage are known to thrive in foods containing high

moisture content (Emebuand Anyika, 2011). However, there was significant difference (P 0.05) in Ash content between all the

samples of polluted vegetables and the unpolluted vegetables. The significant high ash contents (Table 1 & Fig. 6) in edible green leafy vegetables from selected non oil-producing areas in Imo State compared with values from selected oil-producing areas in Rivers State may be attributable to crude oil pollution and contamination of the soils. The high ash contents of samples from control areas may suggest higher level of mineral elements in these samples as against values in edible green leafy vegetable samples from crude oil contaminated farmlands. As a result of crude oil pollution in these farmlands, mineral elements are not readily available for absorption by the roots of vegetable crops in the polluted areas. Since uptake of water, salts and mineral elements are carried out by the plant roots; vegetable grown in non-crude oil polluted farmlands may accumulate these minerals in their tissues leading to increase in ash content. It has been demonstrated that these edible green leafy vegetables and root crops are capable of accumulating high levels of minerals from the soil (Cobb et al., 2000).

Group Moisture Ash Protein Lipid Fibre Carbohydrate

Polluted Okro leaf

Unpolluted okro leaf

d

Polluted pumpkin leaf

Unpolluted pumpkin leaf

Polluted bitter leaf

Unpolluted bitter leaf

Polluted water leaf

Unpolluted water leaf



Crude protein content (Table 1 & Fig. 7) of edible green leafy vegetables harvested from the control areas were significantly different

(P 0.05)and also generally higher, compared with those from oil-producing areas probably due to favorable soil fertility and

environmental conditions. It has been reported that Imo state soils were high in nitrate (Iheanacho, 2009). The decrease in protein content may be as a result of oxidative stress induced by the presence of crude oil in these vegetables. This may have interfered with the protein synthesis or an increase in protein oxidation and destruction of plant cells which may possibly lead to a decrease in protein content of these vegetables. The result of this study corroborates that of Nwaogu et al., (2010). In his work with Puccinellia maritama, Amakari (1981) showed that plant cell membranes are disrupted by crude oil pollution and thus cell organelles such as ribosomes



which are the sites of protein synthesis are affected in crude oil damaged cells. These samples cannot contribute to the daily protein requirement of 23-56g for humans (National Research Council (1974) Recommended daily dietary allowance). The low levels of protein in these samples would therefore require dietary supplementation with animal proteins or complementary proteins from legumes especially in diets meant for children and pregnant women.

Lipid content (Table 1 & Fig. 8) was generally low in the samples irrespective of location. However, polluted vegetables were significantly different (P<0.05) and higher in lipid content than the non polluted vegetables. The increase in lipid content observed in these vegetables may be due to the ability of these vegetables to absorb and bio-accumulate crude oil in their aerial parts. This also corroborates the work of Wyszkowiski and Ziolkowski (2008) which reported that contamination of soil with petroleum substances may not weaken the vegetative development of crops but can cause accumulation of hydrocarbon in plants. Petroleum hydrocarbons can also have a direct effect by producing oily films on aerial parts of the plants, thus reducing plant transpiration and respiration thereby decreasing permeability, thus causing disorders in the metabolic processes which may result in some modification in the chemical compositions of plants (Wyszkowiski and Ziolkowski, 2008). This may be responsible for the increase in lipid content of vegetables from oil-producing farmlands. The low level of lipid contents in all samples analysed from oil producing and control areas may be of benefit to individuals suffering from hyperlipidaemia because of the role of fat in potentiating one’s risk of developing certain kinds of cancer, heart disease and diseases associated with damage of coronary artery (Onunogbu, 2002). Lipid is major determinant of palatability of food (Antia et al., 2006)

However, the results in Table 1 & Fig. 9, showed that the Crude fibre content of unpolluted edible green leafy vegetables are

significantly different (P 0.05) from the polluted samples and this is observed for all the test samples. This suggests that crude oil

pollution affects the crude fibre content in these vegetables thereby causing a significant reduction in crude fibre content. Fibre in leafy vegetables plays a number of roles in the body. Fibre is known to cleanse the digestive tract, remove potential carcinogens from the body, as well as keep blood sugar levels under control (Emebu and Anyika, 2011). Carbohydrate content (Table 1 & Fig. 10) are generally high in all the samples irrespective of location. Polluted vegetables are

significantly higher (P 0.05) in carbohydrate than the unpolluted vegetables. The high level of carbohydrate in edible green leafy



vegetables from oil-producing areas and controls indicate that they contribute significantly to the energy content of the food materials. The main function of carbohydrate is to provide the body with fuel and energy that is required for daily activities and exercise. The human body needs constant supply of energy to function properly, and lack of carbohydrate in the diet may result in tiredness or fatigue, poor mental function, and lack of endurance and stamina. However, crude oil contaminants, apart from increasing the concentration of hydrocarbon in the soil can also lead to the predominance of organic carbon over the content of nitrogen in the humus horizon, which can consequently lead to large supply of energy and proportionately decrease in the availability of nitrogen (Wyszkowiski and Ziolkowski, 2008). Thus, strong competition for nitrogen occurs between microorganisms that are degrading the hydrocarbons and the plant root systems. This competition may result to acute shortage of nitrogen for plants, thereby minimizing or inhibiting the plant growth. This may also be responsible for the decrease in plant protein content and slight increase in carbohydrate content of polluted vegetables as observed in this research.

Conclusion From this study, proximate composition of edible green leafy vegetables from selected oil-producing areas of River State showed a reduction in the crude protein, ash, and crude fibre of these polluted vegetables. This observed reduction can be an indication of oxidative and metabolic stress due to crude-oil pollution in these areas. Also, increase in lipid, carbohydrate and moisture content in these polluted vegetables is an indication of the bioaccumulation of hydrocarbon substance in their aerial parts. Results from the study also indicated that indiscriminate crude oil pollution on soil has significant effect on plant growth, yield and the quality of vegetables produced.

Recommendation Further work should be done by compounding processed diets from the leafy vegetables and fed to laboratory animals to examine the effects on nutritional parameters.

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Comparative proximate analysis of some green leafy vegetables from selected communities in Rivers...

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