1. Introduction

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Oral consumption of metal-contaminated vegetables is of public concern because these bioaccumulated metals could create complicated health problems in the consumers (Khan et al. 2008). According to Ghous et al. (2015), Momordica charantia is a common fruity vegetable besides being used as a traditional medicine in South Asia. It is under the Family: Cucurbitaceae and commonly known as “bitter gourd”. It is an annual and climber plant (Savsatli et al., 2016). Besides being a traditional medicinal plant, it is also a cultural plant. It can adapt well in many ecological conditions (Savsatli and Seyis, 2014), including many tropical and subtropical countries.

The bitter gourd is a potential source of enrichment of phenolic compounds (Islam et al., 2011; Gupta et al., 2011). Therefore, it has pharmacological values for many diseases. The fruits of bitter gourd contain laxative, antibilious, emetic and stomachic effects (Arya et al., 2011). Verma (2015) reported that all parts of the bitter gourd are beneficial for human and there is a distribution of elemental concentrations in different parts of the plant while Kosanovicet al. (2009) stated that bitter gourd is an important source of essential Ca, Mg, Mn, Cu and Zn.

The objectives of this study were to 1) assess the concentrations of Fe, Cu, Ni, Pb, and Zn in bitter gourd M. charantia from three farming areas of Peninsular Malaysia, and 2) assess the human health risks of the above five metals in the collected bitter gourds.

2. Materials And Methods

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Bitter gourds M. charantia were collected between May and December 2016 from Kg Ara Kuda (Penang), Kuala Ketil (Kedah) and Sg. Rengat, Jerantut (Pahang) of Peninsular Malaysia (Table 1).

The samples were kept in clean polyethene bags and transported to the laboratory for further analyses. The identification of the bitter gourd was done based on Chin and Yap (1999), and Prohens and Nuez (2008a, 2008b). In the laboratory, the samples were washed with distilled water to remove soil particles. Later, they were cut into small pieces using a clean knife and were dried in an oven at 60°C for 72 hours days until a constant dry weight.

For determination of heavy metals, all filtered samples were analysed by using a flame atomic absorption spectrophotometer (AAS) model Thermo Scientific iCE 3000 series for Cu, Fe, Ni, Pb, and Zn. All data obtained from the AAS were presented in mg/kg dry weight basis.

For quality assurance and quality control, all the glassware used in this study were acid-washed to avoid external ontamination. Two certified reference materials (CRM) were used to check for the analytical procedures of the present method. The CRMs analysed were Lagarosiphon major N.60 and Peach Leaves (NIST 1547). The recoveries for the CRM Lagarosiphon major N.60 were 97.4, 120.2, 119% for Zn, Cu and Pb, respectively, while CRM Peach Leaves (NIST 1547) were 97.0 and 117% for Ni and Fe, respectively (Table 2).

For the human health risk assessment, the basis in dry weight was converted into wet weight by using a conversion factor of 0.061. The assessment included estimated daily intake (EDI) and target hazard quotient (THQ) values, as shown in the following formulas:

In this study, a non-carcinogenic risk assessment method was based on THQ, a ratio between the estimated dose of contaminant and the oral reference dose (RfD), below which there will not be any appreciable risk. The THQ was determined with a formula described by USEPA (2000):

3. Results And Discussion

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3.1. Concentrations of Fe, Cu, Ni, Pb, and Zn
The metal concentrations (mg/kg dry weight) in the bitter gourd collected from three farms are given in Table 1. The ranges of metal concentrations (mg/kg dry weight (wet weight)) from the three sites were 8.00-16.1 (0.49-0.98) for Cu, 46.0-118 (2.81-7.18) for Fe, 0.18-1.99(0.01-0.12) for Ni, 0.79-1.46 (0.05-0.09) for Pb and 17.2-46.8 (1.05-2.85) for Zn.

Table 1

Based on M. charantia collected from reclaimed tidal flat soils of Pearl River Estuary (China), Li et al. (2012) reported the Cu and Zn levels (mg/kg wet weight) were 0.71 and 1.46, respectively. Khan et al. (2013) reported the metal concentrations (mg/kg wet weight) M. charantia from Swat District, northern Pakistan as 0.05 for Cu, 0.06 for Ni and 0.09 for Zn. Based on M. charantia grown around effluent sites of District Sargodha (Pakistan), Bibi et al. (2014) showed that the concentrations (mg/kg dry weight) of Ni, Cu and Zn in bitter gourds at both sites were 4.78-5.6 for Ni, 20.2-22.7 for Cu, and 52.3-61.8 for Zn. Therefore, the intake of M. charantia was not safe for consumption in the sampling area.

Table 2

3.2. Health Risk Assessments
The values of EDI and THQ of the five heavy metals in bitter gourd for adults and children are shown in Tables 3 and 4, respectively. All the THQ values for Fe, Cu, Ni, Pb, and Zn in both adults and children were found below 1.00. This indicates that there is no non-carcinogenic risk of Cu, Fe, Ni, Pb, and Zn via the consumption of the bitter gourd from the three farms. In general, the THQ values of heavy metals in children are higher than those in adults.

Zhang et al. (2017) reported that THQ values heavy metals were greater than one for adolescents in Kunming City (China), indicating non-carcinogenic risk of heavy metals to the adolescents. Islam et al. (2016) reported that THQs for Cu and Zn were below 1based on vegetables in Bogra District. This indicated that consumers would not experience significant health hazards of metals via ingestion of the vegetable. Khan et al. (2017) reported the concentrations of Mo, As, Mn, Ni and Zn were higher than the maximum permissible limits in the bitter gourd irrigated with domestic wastewater. Unni et al. (1992) studied the effect of Pb on germination, growth, chlorophyll a, b and total chlorophyll contents in M. charantia in a hydroponic system. They found that chlorophyll content is useful in vivo indicator of heavy metal toxicity for calculating the upper critical tissue concentrations. Ghous et al. (2015) determined the levels of antioxidant, metal chelating and antiglycation activities of aqueous extracts of M. charantia fruit flesh and fruit pulp fractions.

Table 3    Table 4

4. Conclusion

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Based on the THQ values for Cu, Fe, Ni, Pb, and Zn in both adult and children, there were no non-carcinogenic risks of the five metals through the consumption of bitter gourds from the three farms. However, there is a need for regular monitoring of heavy metals in order to check for possible contamination of bitter gourd.

5. Acknowledgement

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The authors wish to acknowledge the partial financial support provided through the Fundamental Research Grant Scheme (FRGS), No. Project: 02-10-10-954FR and vote no.: 5524953, by Ministry of Higher Education, Malaysia.

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