Trace elements in commonly used medicinal plants from Varna region, Bulgaria

In this study, we assessed the concentrations of some trace and toxic elements (Cd, Pb, Zn, Cu, Ni, Cr, Fe, and Mn) in traditionally used wild medicinal plants: chamomile (Matricaria chamomilla), white yarrow (Achillea millefolium), linden (Tilia sp.), and elder (Sambucus nigra L.) collected from urban and rural region near Varna, Bulgaria. Concentrations of examined elements were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) after sample mineralization. The samples were digested with concentrated nitric acid in a microwave system. Mean element levels in medicinal herbs were established in decreasing order as follows: Fe > Mn > Zn ≈ Cu > Pb > Ni > Cr > Cd. The content of toxic elements in medicinal herbs was found significantly higher in areas with intensive traffic compared with a suburban area. Instead discrimination between metal content in rural and urban samples was confirmed by PCA. Concentrations of toxic elements Cd and Pb in all plant species from the rural region were found in the range from not detected to 0.08 and 0.796 ng/kg, respectively and were below the permissible limit of the WHO.