International Journal of Current Research and Review
ISSN: 2231-2196 (Print)ISSN: 0975-5241 (Online)
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IJCRR - vol 06 issue 01, January, 2014

Pages: 28-33

Date of Publication: 30-Nov--0001

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Author: Roger Ondo Ndong, Armelle Lyvane Ntsame Affane, Hugues Martial Omanda, Philippe Padoue Nziengui, Richard Menye Biyogo, Jean Aubin Ondo, Aime-Jhustelin Abogo Mebale

Category: Healthcare

Abstract:The rate of urbanization in developing countries imposes to develop standards for efficient food security. This study was conducted in 2013 in Libreville, Gabon to evaluate the metal concentration in three leafy vegetables commonly consumed in West Africa. Amaranthus cruentus (Amaranth), Hibiscus sabdariffa (Roselle) and Manihot esculentus (Cassava) were sampled in seven markets of Libreville (Gabon) and analyzed for their concentration in Al, Ca, Fe, K, Mg and P using ICP-AES. The concentration ranges found were 11-173 mg/kg, 5897-24911 mg/kg, 135-1220 mg/kg, 1531-9728 mg/kg, 1470-7146 mg/kg and 186-1277 mg/kg for Al, Ca, Fe, K, Mg and P, respectively. These results indicated that amongst the leafy vegetables studied, Amaranthus cruentus was the best source of nutrients (Ca, Fe, K, Mg and P). However concerns could be raised for the some high aluminum content found in these leafy vegetables which may be detrimental to human and animal health.

Keywords: leafy vegetables, nutrients, aluminum, daily intake, target hazard quotient.

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Population growth forecasts for year 2030 indicate that the world population will increase and reach 9 billion inhabitants. This growth will particularly occur in the urban areas of developing countries, creating a situation of exploding alimentary needs. In response to this considerable challenge, urban agriculture, which was almost insignificant thirty years ago, has developed in cities and has reached a phase of rapid expansion in developing countries. Therefore, it is important to assess the nutritional quality of cultivated vegetables (Ondo et al., 2013). The consumption of vegetable and fruits has increased through urban agriculture, which provides fresh produces throughout the year (Kawashima and Soares, 2003). This has led to improve and balance people’s diets since fresh produces represent important source of proteins, vitamins and minerals for humans (Akbar et al., 2010). Indeed, humans require more than 22 mineral elements, all of which can be supplied by an appropriate diet. Each mineral has a particular function within the body. For example, calcium (Ca) functions as a constituent of bones and teeth, regulation of nerve and muscle function. Calcium absorption requires calcium-binding proteins and is regulated by vitamin D, sunlight, parathyroid hormone and thyrocalcitonin. Growing, pregnant and especially lactating humans and animals require liberal amounts of calcium (Soetan et al., 2010). Phosphorus (P) is located in every cell of the body. It functions as a constituent of bones, teeth, adenosine triphosphate (ATP), phosphorylated metabolic intermediates and nucleic acids. Practically, every form of energy exchange inside living cells involve the forming or breaking of high-energy bonds that link oxides of phosphorus to carbon or to carbon-nitrogen compounds (Soetan et al., 2010; Murray et al., 2000). Potassium (K) is the principal cation in intracellular fluid and functions in acid-base balance, regulation of osmotic pressure, conduction of nerve impulse, muscle contraction particularly the cardiac muscle, cell membrane function and Na+/K+-ATPase. Plant products contain many times as much potassium as sodium. Sources include vegetables, fruits, nuts (Soetan et al., 2010). Magnesium (Mg) is an active component of several enzyme systems in which thymine pyrophosphate is a cofactor. Approximately one-third to one-half of dietary magnesium is absorbed into the body (Murray et al., 2000). Iron (Fe) functions as haemoglobin in the transport of oxygen. In cellular respiration, it functions as essential component of enzymes involved in biological oxidation. Brain is quite sensitive to dietary iron depletion and uses a host of mechanisms to regulate iron flux homostatically (Batra and Seth, 2002). For example, excessive accumulation of iron in human tissues causes haemosiderosis (Akpabio et al., 2012; Murray et al., 2000). Sources of iron include red meat, spleen, heart, liver, kidney, fish, egg yolk, nuts, legumes, molasses, iron cooking ware, dark green leafy vegetables. Aluminum (Al) is the third most abundant element in the earth’s crust. Increased aluminum exposure has the potential to cause a number of health problems such as anemia and other blood disorders, colic, fatigue, dental caries, dementia dialactica, kidney and liver dysfunctions, neuromuscular disorders, osteomalacia and Parkinson’s disease (Lokeshappa et al., 2012). Thus, due to the multiple roles of metals and their importance in human’s diet, the main objective of the present work is to evaluate the metal and nutrient composition of commonly consumed leafy vegetables sold in marketplaces of Libreville.


Collection of samples, sample preparation and treatment:

This study was conducted in Libreville, capital of Gabon (9°25’ east longitude and 0°27’ north latitude). The climate is equatorial type. The annual rainfall varies from 1,600 to 1,800 mm. Average temperatures oscillate between 25 and 28°C with minima (18°C) in July and maxima (35°C) in April. Three types of leafy vegetables were randomly purchased in seven markets of Libreville, which were the markets of Okala, Nkembo, Owendo, PK8, Akébé, NzengAyong and Mont-Bouet. The leafy vegetables bought were amaranth (Amaranthus cruentus), roselle (Hibiscus sabdariffa) and cassava (Manihot esculenta). The vegetables were brought to the laboratory where they were washed with distilled water to remove dust particles. Then, after separating the leaves from the other parts of plants with a knife. these latter were air-dried, then oven-dried at 70?C. Dried leaves samples were ground into a fine powder using a mill of IKA A10 type, thereafter stored in polyethylene bags kept at room temperature. 500 mg of plant samples were digested at 150°C for 1 hour in a microwave mineralizer, using a mixture of nitric acid, hydrogen peroxide and ultra-pure water with a volume proportion ratio of 2:1:1 (Nardi et al., 2009). Each mineralization product was filtered through a 0.45-μM filter (PTFE, from Millipore, Massachusetts, USA) and the metal concentrations determined by the ICPAES method (Activa M model, JobinYvon, France). Daily intake of metals (DIM): The estimated daily intake (DIM) of Al, Ca, Mg, Fe, K and P through vegetable consumption was calculated as: DIM=[M]×K×I where [M] is the heavy metal concentration in the plant (mg/kg), K is the conversion factor used to convert fresh part consumed plant weight to dry weight, estimated as 0.085, and I is the daily intake of consumed plant, estimated as 0.255 kg/day per adult. Target hazard quotient (THQ): The health risks to local inhabitants from consumption of vegetables were assessed based on the THQ, which is the ratio of a determined dose of a pollutant to a reference dose level. As a rule, the greater the value of the THQ is above unity, the greater the level of concern is high. The method of estimating risk using the THQ is based on the equation THQ = [(EFr × ED × FI × MC) / (RfD × BW × AT)] × 0.001 where EFr is exposure frequency (365 days/year), ED is exposure duration (60 years for adults), FI is food ingestion, MC is the metal concentration in the food (mg/kg fresh weight), RfD is the oral reference dose (mg/kg/day), BW is the average body weight for an adult (60 kg) and AT is the average exposure time for non carcinogenic effects (365 days/year ×number of exposure years, assuming 60 years in this study). The RfD is an estimation of the daily exposure for people that is unlikely to pose an appreciable risk of adverse health effects during a lifetime and was based on value of 0.14 mg/kg/day for Al. Statistical analysis: The significance of differences between the means of metals in leaves, the edible part of plants, was evaluated by Tukey’s test (P<0.05). Statistical analyses were performed with the software XLSTAT, Version 2010 (Addinsoft, Paris, France).


The accumulation of metals in vegetables depends on cultivated soil, irrigated water and atmospheric conditions. In this study a non-essential metal, aluminum, and some essential metals such as Ca, Fe, K, Mg and P were assessed by ICP-AES in mg/kg on dry weight basis (Table-1). The mean and range of daily intake of nutrients from vegetables for adults are presented in Table-2. There was no significant difference between concentrations of Al in roselle, amaranth and cassava leaves. The lowest concentration of Al was found in cassava sample of PK8 market (11 mg/kg) and the highest concentration in amaranth of Akebe’s market (173 mg/kg). The uptake of Ca was significantly different in three leafy vegetables. The concentration of Ca decreased in the order: amaranth > roselle > cassava. The lowest Ca concentration was in cassava of Mt-Bouet (5897 mg/kg) and the highest Ca concentration was in amaranth of Nzeng Ayong (24911 mg/kg). The lowest concentration was observed in cassava of Okala (135 mg/kg) and the highest concentration in amaranth of Owendo (1220 mg/kg). The mean daily intake of Ca of the leafy vegetables studied varied between 13% and 56% of the recommended dietary allowances (RDA), which confirms that consumption of leafy vegetables is of utmost of importance since horticultural crops may be secondary source of calcium in comparison to dairy products but, taken as a whole, fruits and vegetables account for almost 10% of the calcium in the food supply. The dark green leafy vegetables are potential calcium sources because of their absorbable calcium content (Titchenal and Dobbs, 2007). There was no significant difference in Fe uptake in leafy vegetables. Its concentration varied between 135 mg/kg (cassava of Mt-Bouet) and 1220 mg/kg (amaranth of Owendo market). The estimated daily intake of Fe from consumption of the leafy vegetables studied ranged between 4 to 36 mg/day. The recommended dietary allowance (RDA) of Fe is 10-18 mg/day for an adult (Dimirezen and Uruc, 2006). This value was lower than those found for the roselle bought in Okala market (146%) and amaranth of Owendo market (199%). The uptake of K, Mg and P was significantly higher in amaranth than in the other vegetables. Thus, the highest concentrations were found in amaranth of Nkembo (9728 mg/kg), amaranth of NzengAyong (7146 mg/kg) and amaranth of Nkembo (1277 mg/kg) for K, Mg and P, respectively. The lowest concentrations were found in roselle of Mt-Bouet (1531 mg/kg), roselle of Owendo (1470 mg/kg) and cassava of Mt-Bouet (186 mg/kg) for K, Mg and P, respectively. The daily intake of P and K from leafy vegetables studied is the lowest. It is always less than 6% of the RDA. Vicente et al. (2009) indicated that fruit and vegetable contribution to the total phosphorus in the US food supply was an average of 9.5%. But Potassium is the most abundant individual mineral element in vegetables. It normally varies between 600 and 6000 mg/kg of fresh tissue. Leafy green vegetables are known such as potassium-rich vegetables. The daily intake of Mg varied between 43 mg/kg and 210 mg/kg, 10% and 50% of RDA. People who eat of good quantities of green leafy vegetables, nuts, and whole grain breads and cereals ensures a sufficient intake of magnesium and are found to have higher magnesium densities than high-fat users, who consume significantly more servings of meat and higher levels of discretionary fat (Sigman-Grant et al., 2003). Generally, magnesium levels are significantly higher in vegetables than in fruits, but nuts are good sources of this nutrient.




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One article from every issue is selected for the ‘Best Article Award’. Authors of selected ‘Best Article’ are rewarded with a certificate. IJCRR Editorial Board members select one ‘Best Article’ from the published issue based on originality, novelty, social usefulness of the work. The corresponding author of selected ‘Best Article Award’ is communicated and information of award is displayed on IJCRR’s website. Drop a mail to for more details.

Women Researcher Award:

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Best Article Award

A Study by Juna Byun et al. entitled "Study on Difference in Coronavirus-19 Related Anxiety between Face-to-face and Non-face-to-face Classes among University Students in South Korea" is awarded Best Article for Vol 12 issue 16
A Study by Sudha Ramachandra & Vinay Chavan entitled "Enhanced-Hybrid-Age Layered Population Structure (E-Hybrid-ALPS): A Genetic Algorithm with Adaptive Crossover for Molecular Docking Studies of Drug Discovery Process" is awarded Best article for Vol 12 issue 15
A Study by Varsha M. Shindhe et al. entitled "A Study on Effect of Smokeless Tobacco on Pulmonary Function Tests in Class IV Workers of USM-KLE (Universiti Sains Malaysia-Karnataka Lingayat Education Society) International Medical Programme, Belagavi" is awarded Best article of Vol 12 issue 14, July 2020
A study by Amruta Choudhary et al. entitled "Family Planning Knowledge, Attitude and Practice Among Women of Reproductive Age from Rural Area of Central India" is awarded Best Article for special issue "Modern Therapeutics Applications"
A study by Raunak Das entitled "Study of Cardiovascular Dysfunctions in Interstitial Lung Diseas epatients by Correlating the Levels of Serum NT PRO BNP and Microalbuminuria (Biomarkers of Cardiovascular Dysfunction) with Echocardiographic, Bronchoscopic and HighResolution Computed Tomography Findings of These ILD Patients" is awarded Best Article of Vol 12 issue 13 
A Study by Kannamani Ramasamy et al. entitled "COVID-19 Situation at Chennai City – Forecasting for the Better Pandemic Management" is awarded best article for  Vol 12 issue 12
A Study by Muhammet Lutfi SELCUK and Fatma COLAKOGLU entitled "Distinction of Gray and White Matter for Some Histological Staining Methods in New Zealand Rabbit's Brain" is awarded best article for  Vol 12 issue 11
A Study by Anamul Haq et al. entitled "Etiology of Abnormal Uterine Bleeding in Adolescents – Emphasis Upon Polycystic Ovarian Syndrome" is awarded best article for  Vol 12 issue 10
A Study by Arpita M. et al entitled "Estimation of Reference Interval of Serum Progesterone During Three Trimesters of Normal Pregnancy in a Tertiary Care Hospital of Kolkata" is awarded best article for  Vol 12 issue 09
A Study by Ilona Gracie De Souza & Pavan Kumar G. entitled "Effect of Releasing Myofascial Chain in Patients with Patellofemoral Pain Syndrome - A Randomized Clinical Trial" is awarded best article for  Vol 12 issue 08
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A Study by K. Krupashree et. al. entitled "Protective Effects of Picrorhizakurroa Against Fumonisin B1 Induced Hepatotoxicity in Mice" is awarded best article for issue Vol 10 issue 20
A study by Mithun K.P. et al "Larvicidal Activity of Crude Solanum Nigrum Leaf and Berries Extract Against Dengue Vector-Aedesaegypti" is awarded Best Article for Vol 10 issue 14 of IJCRR
A study by Asha Menon "Women in Child Care and Early Education: Truly Nontraditional Work" is awarded Best Article for Vol 10 issue 13
A study by Deep J. M. "Prevalence of Molar-Incisor Hypomineralization in 7-13 Years Old Children of Biratnagar, Nepal: A Cross Sectional Study" is awarded Best Article for Vol 10 issue 11 of IJCRR
A review by Chitra et al to analyse relation between Obesity and Type 2 diabetes is awarded 'Best Article' for Vol 10 issue 10 by IJCRR. 
A study by Karanpreet et al "Pregnancy Induced Hypertension: A Study on Its Multisystem Involvement" is given Best Paper Award for Vol 10 issue 09
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Awardees of COVID-19 Research

Woman Researcher Award

A Study by Neha Garg et al. entitled "Optimization of the Response to nCOVID-19 Pandemic in Pregnant Women – An Urgent Appeal in Indian Scenario" published in Vol 12 issue 09

A Study by Sana Parveen and Shraddha Jain entitled "Pathophysiologic Enigma of COVID-19 Pandemic with Clinical Correlates" published in Vol 12 issue 13

A Study by Rashmi Jain et al. entitled "Current Consensus Review Article on Drugs and Biologics against nCOVID-19 – A Systematic Review" published in Vol 12 issue 09

Emerging Researcher Award

A Study by Madhan Jeyaraman et al. entitled "Vitamin-D: An Immune Shield Against nCOVID-19" published in Vol 12 issue 09

Study by Dheeraj Kumar Chopra et al. entitled "Lipid-Based Solid Dispersions of Azilsartan Medoxomil with Improved Oral Bioavailability: In Vitro and In Vivo Evaluation" published in Vol 12 issue 19

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