Spectroscopic analysis of heavy metals distribution in selected traditional medicinal plants and soil in Raya Azebo district, Northern Ethiopia

Abstract

The use of traditional medicine is increasing dramatically worldwide. In Ethiopia, people largely depend on the use of  traditional medicinal plants as herbal remedies. However, the effectiveness of medicinal plants is affected by the  presence of heavy metals. Thus, this study aimed to evaluate the distribution of heavy metals in selected medicinal plant  roots and the soils in which they were grown. A total of five root and soil samples in triplicate were used for  analysis. A wet digestion procedure involving the use of a mixture of strong acids was used for the analysis of plant and  soil samples. Based on the results, the concentrations of Zn (21.82mg/kg) and Fe (7.78mg/kg) were higher in Solanum  incanum and Carissa spinarum plant samples, respectively, than in the other plants. The concentrations of Mn, Cu, and  Pb ranged from 1.70 ˗ 4.22mg/kg, 1.34 ˗ 3.43mg/kg, and 0.14 ˗ 0.34 mg/kg, respectively, but Cd was detected only in  Carissa spinarum (0.15 mg/kg) and in Solanum incunm (0.21mg/kg). Regarding the contents of the metals in the soil  samples, Zn (15.45 ˗ 44.3 mg/kg) is the most dominant metal, followed by Mn (9.54 - 23.07mg/kg), Fe (7.58 ˗ 12.68 mg/kg),  Cu (3.16 - 12.55 mg/kg), and Pb (0.14 - 2.85 mg/kg) whereas Cd was detected only in Boyegararsa soil (0.21 mg/kg) and  Warabaye (0.65 mg/kg) soil samples. The results indicated that the contents of the metals studied did not exceed the  permissible limit for medicinal plants set by WHO/FAO. Further studies should be carried out on the bioavailability of  toxic heavy metals in traditional herbal medicines.