The aim of this research was to evaluate the content of: Cr, Pb, Ni, Cd and Hg in the following medicinal species, which are known as heavy metal "accumulators": Hypericum perforatum L., Acillea millefolium L., Linum usitatissimum L. and Calendula officinalis L. The samples were collected from the wild habitats, plantations and retail trade. The obtained results shown that the content of the potentially toxic trace elements in most of the investigated medicinal plant specimens was far below the recommended values. Higher content of Ni and Cd, found in Hyperici herba and Milefoli herba, confirms the genetic characteristic of these species to accumulate heavy metals and is being under the great influence of the soil properties. It has been concluded that a determination of heavy metals content in medicinal plants must become standard criterion for evaluation of their quality. Also, an appropriate choice of growing sites could greatly reduce the problem of heavy metal accumulation in medicinal plants.

Key words: trace elements, content, Hyperici herba, Milefolii herba, Calendulae flos, Lini semen.

The content of potentially toxic trace elements (heavy metals) in medicinal plants has recently been used as an additional criterion for evaluation of raw material quality (Schilcher, 1994). Since medicinal plants originate from quite different growing areas, significant differences regarding heavy metals content can be expected. Diversity of species and genotype variations within the species may also play an important role for heavy metals accumulation (Hasselbach, 1992, cit. Röhricht et al., 1997). The following medicinal plant species show tendencies for heavy metals accumulation: Hypericum perforatum L., Acillea millefolium L., Linum usitatissimum L., Calendula officinalis L., Chamomilla recitita (L.) Raush.

In order to estimate the contamination of medicinal plants with potentially toxic trace elements, guide or recommended values have been legislatively established and regulated. Based on the particular element and plant species recommended values on d.m. bases (Schilcher, 1994) are:

• 5.0 mg/kg of lead (Pb)

• 0.2 mg/kg of cadmium (Cd) for nonacumulating species, 0.3 mg Cd/kg for Achillea milefolium L. and Linii semen, 0.5 Cd mg/kg for Hypericum perforatum L.

• 0.1 mg/kg of mercury (Hg).

1. Plant material: Specimens were collected in the wild, from the plantations and from the retail trade, as listed in tab. 1.

2. Localities: (growing areas in Serbia and republic of Srpska): Pancevo (1, 1a, 1b, 1c)*, Deliblatska pescara (2), Padej (3), Koceljeva M.B. (4), Titel (5), Tara (6), Petrovac na Mlavi (7), Ribnik (8), Laktasi (9, 9a), Kladovo (10, 10a, 10b,), Petrovo Selo (11), Rudnik (12, 12a, 12b), Mali Zvornik (13), Lozovik (14), Vranje (15), Sremska Kamenica (16), Backi Petrovac (17), Lijevce - Polje (18).
* Numbers in parentheses represent laboratory number of locality

3. Analytics: The heavy metal content (Cr, Pb, Ni, Cod) in dried (80°C) and ground plant material was determined by flame AAS, after the digestion in mixture of acids: HNO₃+HClO₄, including H₂O_2. Mercury content was determined (after the digestion) by hydride generation AAS, after the oxidation to Hg²⁺, with HNO₃ and 5 % K₂Cr₂0₇.

The contents of Cr and Pb were, in most samples, for all investigated plant species within the recommended values. For Cr exception was found in only one sample of Achillea millefolium - herba, while Pb concentration exceeded limits in two samples of Achillea millefolium - herba and in three samples of Calendula officinalis - flos. These growing sites are mostly located on Rudnik Mountain or are being under influence of delluvial processes from that area.

Ni is considered to be a highly mobile element within a plant. During vegetation growth it is found to accumulate mainly in leaves, but a considerable amounts could be mobilized in seeds (McGrath, 1995). For these reasons content of Ni is equal or higher then recommended limits in greater number of the investigated samples. This is particularly relating to the obtained higher Ni content in Achillea millefolium - herba which appeared to be connected with acidic soil reaction (Alloway, 1995).

Cadmium is rather mobile element in a soil and as so can easily be taken up by plants (Fiedler and Rösler, 1987). Among medicinal plants, Hypericum perforatum L. has pronounced ability to accumulate Cd (Schneider and Marquard, 1995). In agreement with that, Cd content, which exceeded recommended values have been found in great number of analyzed samples of Hyperium perforatum - herba, as well as in Achilea millefolium - herba samples, both from wild growing habitats and retail trade. The higher content of Cd relates to plants grown on acidic soils and/or on Rudnik mountain soils.

The content of the potentially toxic trace elements in most of the investigated medicinal plant specimens was far below the recommended values.

Higher content of some elements (Ni, Cd), found in Hypericum perforatum - herba and Achillea millefolium - herba confirms the genetic characteristic of these species to accumulate heavy metals and is being under a great influence of the soil properties.

Determination of heavy metal content in medicinal plants must become standard criterion for an evaluation of their quality.

An appropriate choice of growing sites could greatly reduce the problem of heavy metal accumulation in medicinal plants.

1. Alloway B.J. (1995): Heavy Metals in Soils. Blackie Academic & Professional, London.

2. Fiedler H.J., Rösler H.J. (1987): Spurenelemente in der Umwelt. VEB Gustav Fisher, Jena.

3. McGrath S.P. (1995): Chromium and Nickel. In: Alloway B.J. (Ed.) Heavy Metals in Soils. Blackie Academic & Professional, London, 152-179.

4. Röhricht Ch., Mänicke S., Grunet M. (1997): Der Anbau von Kamille Chamomila recutita (L.) Raushert. in Sachsen. Z. Arzn. Gew. Pfl. 2, 135-146.

5. Schilcher H. (1994): Zur Frage der Schadstoffe in Arznei-und Gewürzpflanzen sowie deren Zubereitungen. Übersicht und aktuelle rechtliche Bewrtung von Rückständen. Herba Germanica 2, 11-18.