Determination of Essential and Toxic Heavy Metals in Selected Leaves of Medicinal Plants Grown in Delo Mena District, Oromia Regional State South-Eastern Ethiopia

Abstract

Ethiopia is a home of diversity, having diverse plants as well as ethnic groups, each having different ways of utilization and manipulation of medicinal plants. More than 80% of the people are dependent on plants for their health service. Determination of essential and toxic heavy metals concentration in selected leaves of medicinal plants is very important to control their levels. The purpose of this study is to assess essential and toxic heavy metals concentration of the medicinal plants, in Ruta chalepensis, Rhamnus prinoides and Ocimum basilicum leaf samples in Delo Mena District, Oromia Regional State, South-Eastern Ethiopia. Nine leaf samples (three from each site) were collected and analyzed through different methods for analyzing some concentration of essential and toxic heavy metals, Fe, Cr, Cd, Zn, Pb and Ca. 1 g of oven-dried leaf sample was digested at optimum conditions using 3mL HNO3, 2mL of HClO4 at 150°C for 3hr. The optimized wet digestion procedure was evaluated using percent recovery and an acceptable percentage recovery obtained was in the range of 90.2±0.026 to 114.8±0.032 for the metals in leaf samples. The mean concentration of elements (mg/kg dry weight basis) ranges leaf samples were:385-649,4.7-7.5,0.3-0.85,34-44.5,10-13,374.5-438 for the metals Fe, C r , C d , Zn, Pb and Ca respectively. From the findings o f study, concentration of toxic metals was above the permissible level except that of cadmium in Ruta chalepensis leaf and lead in Rhamnus prinoides, while the concentrations of essential metals were below permissible level except iron and chromium in all samples. Due to above permissible level of toxic metals in these samples, the society should be educated on the problem associated with excessive usage and their dosage.