Heavy metal contents in samples of Hypericum and Thymus spec. collected from different mountain areas in Serbia

The beneficial effects of medicinal plants are well known from ancient times and consumption of different herbal extracts is recommended all over the world. Metallic elements are constitutive plant compounds with biological activity as essential or toxic agents in metabolism. Toxic effects of heavy metals on plants is very complex and can affect the content of pharmacologically active compounds in medicinal plants, and thereby, seriously impact the quality, safety and efficicacy of natural plant products. Therefore, among the other quality control analyses of the raw material of medicinal plants, determination of metals, especially toxic ones, is of special concern. The aim of this work was to determine contents of toxic metals like Cd and Pb in the herbs of Hypericum sp. and Thymus sp., collected during 2003, 2004, and 2005 from various localities of Serbian mountains: Golija, Zlatibor, and Rtanj. Cd and Pb contents in dried, homogenized and mineralized samples were determined by AAS (apparatus GBC 932AA).

In almost all investigated samples Cd levels are higher than the ones proposed by WHO (0.3mg Cd/kg dried plant materials). The contamination level of Pb can be classifed as normally low, because all samples contained less than 10mg/kg Pb (proposed by WHO). The content of Cd in Hypericum sp. were higher than in Thymus sp.

This work contributes to the investigations of toxic metals content in medicinal plants. Further investigations are needed in order to find out the correlation between metal pollution and content of pharmacologically active metabolites.