Essential trace element levels in sesuvium portulacastrum, soil and water along kwale county coastline and community utilization of the plant
Gathii, Lucy Waigwe
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Many underutilized indigenous foods contain high levels of essential trace elements some of which have immunological effect, and play important roles in many metabolic and enzymatic functions in man. Such elements include zinc, vanadium, selenium, chromium and iodine among others. If sustainably exploited, they would cost-effectively promote good health and thus reduce the medical bills. There is need therefore to analyze for these essential trace elements in foods, and especially the indigenous vegetables which have not been fully exploited. These would not only serve as nutrient source but also as a source of food for food security. This study therefore aimed at assessing the level of utilization of an indigenous marine halophytic vegetable Sesuvium portulacastrum (L) L. locally known as „Mboga ya Pwani‟ that grows along the Kenyan Kwale Coastline and analyze the content of selected essential trace elements in it. The level of utilization was assessed through a questionnaire distributed among the local communities of Vanga, Funzi and Wasini regions along the coastline. The leaves and stems of the vegetable, and water and soil supporting its growth were sampled from the same regions and analyzed for vanadium, zinc, chromium and selenium using Atomic Absorption Spectroscopy (AAS), and iodine by iodimetric titration. The data collected was statistically analyzed using analysis of variance (ANOVA). The results showed Wasini region to have the highest utilization at 83.3%, followed by Funzi with 26.7% and finally Vanga with 13.3%. The major specific use as food ranged from 10.0% to 73.3%, and the minor use as medicine from 3.3% to 10.0% across the regions. vi The Atomic Absorption Spectroscopy method was validated using the Energy Dispersive X-ray Fluorescence method. The results showed the soil to contain the highest mean levels of the metals, followed by stems, leaves and water. Zinc was the most abundant with levels ranging from 0.72±0.01 to 21.26±0.85 μg/g, followed by vanadium from 2.44±0.05 to 11.03±0.24 μg/g, chromium 0.29±0.00 to 7.16±0.22 μg/g and selenium from 0.23±0.01 to 1.37±0.07 μg/g respectively. Iodine was relatively abundant in all the samples, ranging from 9.55±0.38 μg/g in the leaves to 14.59±0.43 μg/g in the stems. Zinc, vanadium and iodine levels were relatively high in all the samples. A positive r-correlation was observed between the level of all elements in the plant and the soil, while only iodine and zinc in the soil showed significant but negative correlation to their levels in the water. The results of present study suggest that the communities should be sensitized to the existence and nutritional value of the plant, and thus enhance utilization. The results will also provide a database for further research on the plant and will be availed to relevant stakeholders for appropriate action.