J. A. Ondo et al. / Agricultural Sciences 3 (2012) 697-701
698
Table 1. Studied plants and edible parts.
Usual plant name Edible part Scientific name of plant
Pepper Fruits Capsicum frutescens
Nkoumou Leaves Gnetum africanum
Okra Fruits Abelmoschus calei
Eggplant Fruits Solanum melongena
Lemon grass Leaves Cymbopogon citratus
Yam Tubers Dioscorea spp
Leaves
Cassava
Tubers
Manihot esculenta Crantz
Amaranth Leaves Amaranthus cruentus
Roselle with small red leaves Leaves Hibiscus sabdariffa
Roselle with large green leaves Leaves Hibiscus sabdariffa
Appropriate quality assurance procedures and precau-
tions were carried out to ensure reliability of the results.
Double distilled deionized water was used throughout the
study. Glassware was properly cleaned, and the reagents
were of analytical grade. Standard plant reference mate-
rials (DC 73349) from China National Analysis Center for
Iron were analyzed as a part of the quality assurance-
quality control protocol (accuracies within 100% ± 10%).
Blank and drift standards were run after ten determina-
tions to maintain instrument calibration. The coefficient
of variation of replicate analyses was determined for the
measurements to calculate analytical precision.
2.2. Daily Intake of Elements
The estimated daily intake (EDI) of elements depended
on both the element concentration in crops and the amount
of consumption of the respective food crop. In this study,
the daily intake was considered for each edible part of
plants. The estimated daily intake (EDI) of Mg, Ca, K and
Na through edible parts of food crops was calculated
according to the following Eq.1 [8]:
DIMMK I (1)
where [M]: macro-element concentration in plants (mg·kg−1),
K: conversion factor used to convert fresh part consumed
of plant weight to dry weight, estimated to 0.085, I: daily
intake of consumed plants in kg. The average daily food
crops intakes for adults and children were considered to
be 0.345 and 0.232 kg/person/day, respectively [9].
2.3. Statistical Analysis
Pearson’s correlation coefficients were calculated and
one-way ANOVA method to test the significant differ-
ences of macro-element content in edible parts of crop
foods regions was employed, the level of significance was
set at p < 0.05. Statistical analyses were performed with
the software XLSTAT (version 2010).
3. RESULTS AND DISCUSSION
3.1. Metal Concentrations in Edible Parts of
Food Crops
Elemental composition of samples, reported on dry
weight basis, is given in Ta b l e 2 . On comparative basis,
the tubers had less Mg and K levels than the fruits (p <
0.042 and p < 0.049, respectively). Ca and Na presented
no significant differences for the three plant parts. Fur-
thermore, certain edible parts showed interesting element
uptake. Thus, Abelmoschus calei (fruits), Amaranthus
cruentus and green Hibiscus sabdariffa (leaves) had the
highest levels of Mg (5154, 5374 and 4247 mg/kg re-
spectively); Solanum melongena (fruits), Amaranthus
cruentus and green Hibiscus sabdariffa (leaves) had the
highest levels of Ca (15,049, 21,384 and 32,721 mg/kg
respectively); Capsicum frutescens had the highest levels
of K (11,902 mg/kg) green Hibiscus sabdariffa (leaves)
had the highest levels of Na (745 mg/kg). When Gnetum
africanum was the most consumed vegetable in the East
region of Gabon, it was the poorest of food crops studied
because it accumulated the lowest macro-element con-
centrations. The trend of accumulation in the edible parts
of plants was generally: Ca > K > Mg > Na.
Macro-elements are essential minerals required for the
diverse physiological and biochemical functions in the
human body. They are absorbed by human and animals
via foods as plants. The levels of macro-elements and
others minerals in plants are influenced by their interac-
tions and the soil nature and chemical composition [10].
Milk and other dairy products are excellent sources of
calcium, both qualitatively and quantitatively. However,
in some countries, milk consumption is limited due to the
undesirable effects of lactose intolerance [11]. Green lea-
fy vegetables, seeds and legumes are good alternative
sources of calcium, in addition to cow milk and fish with
bones. Thus, Amaranthus cruentus, green Hibiscus sab-
dariffa and Solanum melongena could be considered good
or excellent source of calcium because its concentrations
were higher than 1000 mg/kg [12].
The magnesium chief function in the body includes
bone mineralization, building of proteins, and a magne-
sium deficiency results in osteoporosis [13]. Therefore,
magnesium role with regard to bone quality and nutrition
is really indispensable. In this study, fruits and leaves had
higher Mg concentrations than tubers. Mg, as a constitu-
ent of chlorophyll, is contained in large quantities of green
leafy vegetables. Mainly centered on plant foods, the
African traditional diet appears to have sufficient Mg
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