Analysis of essential trace elements in soils, amaranthus cruentus and amaranthus hypochondriacus grains, leaves and stems from selected parts of Kenya
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Kenya has been experiencing rising cases of diseases such as diabetes, tuberculosis, liver complications, HIV / AIDS among others. Management of these conditions can be enhanced by use of plant-based trace elements. There is a need therefore to investigate crops that can provide a cheap source of these essential immune boosting trace elements. Grain amaranth is grown in different parts of Kenya including Bureti, Mt Elgon, Bondo, Meru and Embu. However, little research has been reported on the levels of trace elements in the amaranth plants in Kenya. Therefore this study analysed the levels of zinc, copper, manganese, chromium and selenium in Amaranthus cruentus (L-) and Amaranthus hypochondriacus (L-) leaves, stems and grains obtained from Kenyatta University, Bureti, Mt Elgon, Bondo, Meru and Embu. The study also analyzed the levels of the same elements in the soils in the areas in which the plants were grown. The analysis was done by Atomic Absorption Spectroscopy (AAS). The data was analyzed by use of statistical program for social scientists (SPSS) computer software version 11.5. Analysis of variance was used to compare the levels of trace elements at different maturity stages and from different areas. The mean levels of the trace elements in mg/lOO g in the soils from Kenyatta University were: Zn (5.908), Cu (1.056), Mn (37.303), Cr (0.665), and Se (0.285). The soils from Bureti had the mean amounts of Zn, Cu, Mn, Cr and Se of21.160, 2.093,95.741, 1.240 and 0.150 mg/IOO g. The mean levels (mg/IOO g) contained in the soils from Mt Elgon were: Zn (6.960), Cu (1.134), Mn (52.567), Cr (1.059) and Se (0.305). The trace elements mean content (mg/IOO g) of A. cruentus leaves were Zn (5.040), Cu (1.261), Mn (26.603), Cr (0.467) and Se (0.033). The mean amount of Zn, Cu, Mn, Cr and Se present in A. hypochondriacus leaves were 5.495, 1.264, 24.340, 0.309 and 0.054 mg/IOO g respectively. The levels of Zn and Cr in the leaves of both species increased with the plants' maturity from 25 to 50 days and then declined from 50 to 75 days while those of Cu, Mn and Se decreased with the plants' ages. Significant differences (P<0.05) in the mean levels of all the trace elements in the leaves of both species were noted except Cu in A. cruentus. The A. cruentus stems had mean values of 4.148,0.924,6.089,0.245 and 0.018 mg/IOO g of Zn, Cu, Mn, Cr and Se respectively. The mean amounts (mg/IOO g) contained in A. hypochondriacus stems were: Zn (2.943), Cu (0.946), Mn (7.000), Cr (0.230) and Se (0.009). The levels of Zn and Cr in the stems of both species generally increased with the plants' ages upto 50 days and then decreased while those of Cu, Mri and Se declined with the plants' ages. Between the study areas, significant differences (P<0.05) in the mean amounts of trace elements were recorded in the two species except Cu and Zn in A. cruentus and A. hypochondriacus respectively. The mean contents (mg/IOO g) of the trace elements in A. cruentus grain were: Zn (5.686), Cu (0.967), Mn (5.642), Cr (0.475) and Se (0.015) while those recorded in A. hypochondriacus were: Zn (6.303), Cu (1.058), Mn (6.720), Cr (0.304) and Se (0.016). Comparison of the levels of trace elements in grains of both species between the study areas depicted significant differences (P<0.05). There was a positive correlation between levels of trace elements in soils and levels in Amaranthus. From the results, it can be concluded that the two grain amaranth species at different maturity stage in different geographical locations have varied levels of trace elements. The results from the study will be used to sensitize farmers and public on the use of A. cruentus and A. hypochondriacus for their health as sources of essential trace elements.