Determination of the levels of selected metals in seeds, flowers and fruits of medicinal plants used for tapeworm treatment in Ethiopia

The level of accumulation of selected essential and non-essential metals, namely; Ca, Cu, Fe, Zn, Mn, Cd, Pb, and Cr have been investigated in the seeds, fruits, and flowers of some medicinal plants utilized for tapeworm treatment in Ethiopia and their respective soil samples. These include seed of Cucurbita maxima (Duba), fruit of Embelia abyssinica (Ankoko), flowers of Hagenia abyssinica (Kosso), and fruits of Rosa abyssinica (Kega) and their respective soil samples. A wet digestion procedure with a mixture of conc. HNO3 and HClO4 for the plant samples and a mixture of conc. HNO3, HCl, and H2O2 for soil samples were used to solubilize the metals. Ca (1280–12,670 mg kg−1) was the predominant metal followed by Fe (104–420 mg kg−1), and Zn (18–185 mg kg−1) in all the plant materials except for Hagenia abyssinica flower from Hirna in which Mn (16–42 mg kg−1) followed by Fe. Among the non-essential toxic metals, Pb was not detected in Cucurbita maxima of Boji, Gedo and Hirna origins and in Rosa abyssinica of Hirna site. Similarly, Cr was not detected in Rosa abyssinica fruits of Boji and Gedo sites. The sampled soils were found to be between strongly acidic to weakly basic (pH: 4.7–7.1). In the soil samples, Ca (8528–18,900 mg kg−1) was the most abundant metal followed by Fe (417–912 mg kg−1), Zn (155–588 mg kg−1), Mn (54–220 mg kg−1), Cr (21–105. mg kg−1), Cu (11–58 mg kg−1), Pb (13–32 mg kg−1) and Cd (2.8–4.8 mg kg−1). The levels of most of the metals determined in the medicinal plants and the respective soil samples are in good agreement with those reported in the literature and the standards set for the soil by various legislative authorities.