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Research Article
Nutritional Content of Melochia corchorifolia (Linn.) Leaves

K.J. Umar, L.G. Hassan, S.M. Dangoggo, M. Inuwa and M.N. Almustapha

International Journal of Biological Chemistry, 2007, 1(4), 250-255.

Abstract

Melochia corchorifolia leaves were analysed for their proximate and mineral composition. On Dry Weight (DW) basis, the leaves had the following proximate composition: crude protein (23.31±2.27%), crude lipid (13.33±2.89%), ash (10.00±0.10%), crude fibre (23.33±2.89%) and available carbohydrate (30.03±2.83%). M. corchorifolia leaves had high moisture content (62.16±6.11% Wet weight) with low energy value (275.66±23.20 kcal/100 g). The mineral composition in mg/100 g DW are: K (7.250±37.50), Ca (750.37±10.58), Mg (108.33±5.77) and P (101.89±0.08), Na (94.00±1.15), Cu (33.50±2.55), Fe (19.91±3.01), Mn (9.68±0.59) and Zn (6.73±0.62). When the minerals detected were compared with US Recommended Dietary Allowances, K, Cu, Fe and Mn were found to be adequate for both adults and children. Furthermore, the leaves have nutrient density >100% except for phosphorus, which is low for pregnant and lactating mothers.

ASCI-ID: 34-37

Energy (in kcal) = (2.44xg protein) + (8.37xg lipid) + (3.57xg available carbohydrate) (Asibey-Berko and Tayie, 1999).

Mineral Analysis
Sample Digestion
One gram of the powdered sample was digested with 25.0 cm3 concentrated HNO3 using Tecator digestion block until evolution of brown fume stopped. One centimeter cube of perchloric acid was added to the mixture and the content was further heated to a clear solution. After heating, 30 cm3 of hot distilled water was added to the digest and heated to boiling. The solution was then filtered hot into a clean 50 cm3 volumetric flask, cooled and made up to the mark with distilled water (Tayie and Asibey-Berko, 2001). Two more duplicate digest solutions and a blank were prepared.

Mineral Quantification
K and Na were analysed by flame spectrometry (with Corning 400 spectrophotometer) KCl and NaCl were used to prepare the standards. Phosphorus was determined colorimetrically with Jenway 6100 spectrophotometer using phosphovanado-molybdate method with KH2PO4 as the standard. Calcium and Magnesium were analysed by titrating the samples solutions against EDTA solution using Calcon and Erochrome Black T indicators (AOAC, 1990). The concentrations of Cu, Fe, Mn and Zn were determined with a Unicam 969 model atomic absorption spectrophotometer with standard air-acetylene flame.

Nutrient Density
To evaluate the nutritional significance of mineral elements, Nutrient Density (ND) of the sampleswas computed using the equation:

ND (%) = [(Np/Ep)/(Nr/Er)]x100

Where
Np = Nutrient concentration (mineral element in the food).
Ep = Energy supplied by food.
Nr = Recommended daily intakes of nutrient.
Er = Recommended energy intake (3000 kcal day-1 for an adult male given by WHO/FAO (Cole, 1980).

RESULTS AND DISCUSSION

The proximate analysis of Melochia corchorifolia leaves is presented in Table 1. As with most fresh leafy vegetables, the leaves have high moisture content. The leaves also had high percentage of crude lipid when compared to most values (0.33-4.57%) obtained in some edible green leafy vegetables (Guil-Guerrero et al., 1998; Ishida et al., 2000; Agbo, 2004; Gupta et al., 2005). However, high crude lipid was also reported in some tropical vegetables (8.3-27.0% DW) (Ifon and Bassir, 1980; Sena et al., 1998).

The ash content was high in the leaves, but within the range of 9.2±1.5 to 28.0±1.1% reported in green leafy vegetables of Nigeria (Ifon and Bassir, 1980; Ladan et al., 1996).

M. corchorifolia leaves contain high amount of crude protein (23.31±2.27% DW) which is within the range of 17.2±0.1 to 27.03% DW reported for some Nigerian leafy vegetables (Ifon and Basir, 1980). This suggest that this leafy vegetable could be utilised as cheap source of protein supplement. When compared to the recommended dietary allowances for adult (34-56 g day-1) and children (13-19 g day-1), it further indicates the potential of this plant as a protein source.

Dietary fibre is an important component of food in human nutrition as it promotes gut motility and reduces serum cholesterol level, breast cancer and hypertension (Anhwange et al., 2004; Hassan and Umar, 2004). This ability is due to reduction in the rate of absorption of glucose and fat by fibre (Ekop et al., 2004). In this analysis, M. corchorifolia leaves were found to have high fibre content (23.33±2.89% DW). This value is comparable to the fibre content of Gynandropsis gynandra leaves (Hassan et al., 2005).

The estimated available carbohydrate is low compared to the RDA value (130 g) for adults and children (Hassan and Umar, 2006). According to Ifon and Bassir (1980), leafy vegetables may not be important sources of carbohydrate as they are eaten along with other carbohydrate rich food such as cereals. Main function of carbohydrate in the body is for energy supply. The plant leaves energy value 275.66±23.20 kcal/100 g DW (1153.30 J/100 g DW) was within the range of 84-2500 kJ/100 g reported for plant foods (Saka and Msonthi, 1994). This value is low compared to adult energy requirement (3000 kcal day-1) (Cole, 1980).

Table 2 shows the mineral profile of M. corchorifolia leaves. Potassium is the most abundant (7.250±37.50 mg/100g DW), followed by calcium, magnesium and then phosphorous with values in mg/100g DW of 750.37±0.58, 108.33±5.77 and 101.89±0.08, respectively. With the exception of potassium, all the above mentioned elements in M. corchorifolia leaves are lower compared to those reported in Gynandropsis gynandra leaves (Hassan et al., 2005) and some tropical leafy vegetables (Aletor and Adeogun, 1995). Sodium content is the lowest among the macro elements determined. This observation agrees with many other reported results, that have shown sodium to be present in low concentration particularly when compared to potassium.

Microelements play a vital role in human nutrition, as they are dietary essential. However, high concentration above the safe level is toxic to the body. Iron is the second most abundant found among the trace element analysed. When compared with other green leafy vegetables, M. corchorifolia leaves have lower value than 110-325 mg/100 g DW found in some Nigerian leafy vegetables (Ifon and Bassir, 1979; Ladan et al., 1996), but within the range of 4.3-119.1 mg/100 g found in underutilized leafy vegetables of Republic of Niger (Sena et al., 1998).

Table 1: Proximate composition of Melochia corchorifolia leaves
Values are mean±Standard deviation of three determinations

Table 2: Mineral Composition of Melochia corchorifolia Leaves
*: The data are mean value±standard deviation (SD) of three replicated, **: Source: Thangadurai et al. (2001)

Iron is an essential trace element for haemoglobin formation, normal functioning of the central nervous system and in the oxidation of carbohydrates, proteins and fats (Adeyeye and Otikiti, 1999). Comparing the amount found in this study with the reference value (Table 2), the level of Fe in the leaves are adequate to supply the daily iron requirement for adult, children, pregnant and breast-feeding mothers. Furthermore Copper is the most abundant microelement found in the plant leaves. High content could be due to intake of the element by the plant from the soil. The Cu in the leaves is higher than the reported values (1-2.5 mg/100 g) for some tropical leafy vegetables (Ifon and Bassir, 1979; Barminas et al., 1998; Sena et al., 1998). Copper is an essential trace element which exists as an integral part of copper proteins ceruloplasmin which is a copper-transport protein.

Manganese acts as activator of many enzymes (McDonald et al., 1995) while zinc is involved in normal function of immune system. The Mn content in leaves is within the range reported for some tropical plants (Ifon and Bassir, 1979; Sena et al., 1998) and considered to be adequate if bioavailable when compared with recommended dietary allowances (Table 2). Zinc on the other hand is low compared to recommended dietary allowances.

For all the elements analyses, except phosphorus for pregnant and lactating mothers, the percentage of Nutrient Densities (ND), were higher than 100% (Table 3). According to Karakaya et al. (1995), food material with ND of 100% supplies the nutrient need in the same proportion, as the caloric needs. Also if this index is above 100%, then the food provides the nutrients in greater proportion than the caloric need. On the other hand, values of ND below 100% indicate that food fails to provide a proportionate amount of the nutrient. Thus, the result confirm that Melochia corchorifolia leaves are adequate rich sources of mineral elements, without evaluating the effect of other antinutrient factors.

Table 3: Mineral nutrient density of melochia corchorifolia leaves

CONCLUSION

From the result it can be seen that Melochia corchorifolia leaves could be used as protein supplement, sources of dietary lipids, fibre and minerals. Furthermore as potassium depresses blood pressure while sodium enhances, based on the results, the plant leaves could be recommended for hypertensive patients.

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