Toxic and some essential metals in medicinal plants used in herbal medicines: A case study in Pakistan

The levels of some heavy metals in eight different medicinal plant samples along with soils were collected from two different locations from salt range of Punjab, Pakistan in order to evaluate those vital metals involved in human health implications. These plant species were: Dodonaea viscosa, Withania somnifera, Solanum nigrum, Calotropis gigantea, Mentha spicata, Paganum hermala, Cannabis sativa, Adhatoda vasica, especially those used in the treatment of diseases and their long term usage. The evaluated metals were cadmium (Cd), Nickel (Ni), Chromium (Cr) and lead (Pb). Atomic absorption spectrophotometry (wet digestion) was used for the analyses, and content of metals per sample was expressed as mg/kg. The analysis of variance revealed that there were significant effects of site variation on medicinal species in Ni and Cr contents while the opposite were observed in case of Pb and Cd at location I. The Ni concentrations found in medicinal plants varied significantly while Pb, Cd and Cr were evident as non significant at location II. There was positive non significant correlation of Pb and Cr among soil and plant while negative non significant for Ni and Cd at both locations. The findings suggest that the use of these plant species for the management of diseases will not cause heavy metal toxicity and may be beneficial to the users in cases of micronutrient deficiency, as these metals were found to be present in readily bioavailable form.