The aim of this paper was to determine the content of the essential microelements (Fe, Mn, Zn, Cu and Co) in the following medicinal plant species: Hypericum perforatum L., Acillea millefolium L., Linum usitatissimum L., Melissa officinalis L. and Calendulla officinalis L. The samples were collected from the wild habitats, plantations and retail trade, during the growing season 1999. The obtained results indicate that the content of analyzed microelements was mostly within their normal range in a plant tissue. Deficiency or toxicity symptoms were not recorded in neither of the investigated specimens. Therefore, the essential micronutrients content in the soils and plants does not represent the limiting factor for medicinal plants growth in our agro ecological climate. According to Fe content, Calendulla officinalis L. and especially Melissa officinalis L. might be considered for use in human and animal supply with this element.

Key words: micronutrients, content, Hypericum perforatum L., Acillea millefolium L., Linum usitatissimum L., Melissa officinalis L., Calendulla officinalis L.

Microelements are natural components of plant tissue. Some of them (Fe, Mn, Cu, Zn) are necessary for plant growth and significant for physiological and biochemical processes in human and animal organisms. Determination of microelements content in medicinal plants is of importance for several reasons: 1. Comprehension of natural microelements content in particular plant species; 2. Discovering of elevating concentrations, which are likely to cause toxic effects in the food chain and 3. Distinguishing of particular species that could be used for human supply with microelements through teas or other phytopreparations.

Micronutrient content of medicinal plants grown in our agro ecological climate has been obtained for Thymus vulgaris L., Chamomilla recutita (L.) Rauch., Mentha piperita L. and Salvia officinalis L. (Stevanović et al., 1997, Maksimović et al., 1998 a, b, Maksimović et al., 1999). This research represents further contribution to that matter. The aim was to determine microelements content in the following medicinal plants: Hypericum perforatum L., Achillea milefolium L., Calendulla officinalis L., Linum usitatissimum L. and Melissa officinalis L.

Plant material

The following medicinal plant species were investigated: Hypericum perforatum L. - herb, Achillea milefolium L. - herb, Calendulla officinalis L. - flos, Linum usitatissimum L. - semen and Melissa officinalis L. - herb.

The specimens were collected during the vegetation season 1999 in Serbia and Republic of Srpska: in the wild at 25 different sites, from cultivated production at 7 different sites and from retail trade, covering 4 pharmacies.

Analytical methods

The heavy metal content (Cr, Pb, Ni, Cd) 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.

Iron: The Fe content shows great variations between the different plant species and their origins, which is in agreement with the results of other authors (Chizzola and Franz, 1996). Lini semen had the lowest content, probably due to low Fe mobilization in the seeds, while appears that Calendula flos and especially Melissae herb could be of great importance in human and animal supply with this microelement. Although only two samples of Melisae herb were included in this screening, obtained results underlined this species as a potential hyper accumulator of Fe, which is to be confirmed in a future research.

Manganese: The Mn content was within its optimum levels for plant material in Hypericum perforatum L., Achillea milefolium L. and Melissa officinalis L. However, its content in greater number of Calendulla officinalis L. and Linum usitatissimum L. samples was close to the deficiency limit (15-25 mg/kg). This difference between investigated species may be explained by the different distribution of microelements in the analyzed plant organs. Namely, the first group is composed of herbal drugs, while flowers and seed are utilized organs (in pharmacology) of Calendulla officinalis L. and Linum usitatissimum L., respectively.

Zinc: The obtained values of Zn content in all investigated species correspond to the values recorded by other authors (Chizzola and Franz, 1996). There were little variations of its content between different species, as well as within the same species from different growing sites. Recently, there is a great concern about Zn pollution (by mine activities, smelting and refining), although it is among the essential microelements. On the basis of the results obtained, it can be concluded that significant number of growing areas, covered by this screening, my be considered as unpolluted.

Copper: Most of the obtained values are within range of Cu normal content in a plant tissue. The highest values (15 - 27 mg/kg) are recorded in Milefolii herba samples. These specimens were collected from the wild, mainly from mountain soils, which were characterized with low pH (4.00 to 5.10 in nKCl). In such conditions hydrolysis and dissolution of Cu²⁺ - forms are intensified (Cavallaro and McBride, 1978), what could be an explanation for the higher Cu uptake by yarrow.

Cobalt: Content of Co was generally much higher then optimum levels (0.02-1.0 mg/kg, Kabata-Pendias and Pendias, 1992), but lower then critical concentrations when toxicity symptoms are likely to occur (15-50 mg/kg). Its average content in Calendulae flos was 2.0 mg/kg, while Melisae herba contained even 4.0 mg/kg. Previous results (Stevanović et al., 1997, Maksimović et al., 1998 a, b, Maksimović et al., 1999) have also indicated that medicinal plants grown in our climate contain substantial Co amounts. Synergetic behavior between Fe and Co uptakes has been noticed.

The obtained micronutrients content in the investigated medicinal plants was mostly within their normal range in a plant tissue. Deficiency or toxicity symptoms were recorded in neither of the investigated specimens. Therefore, the essential micronutrients content in the soils and plants does not represent the limiting factor for medicinal plants growth in our agro ecological climate.

According to the obtained Fe content, Calendulla officinalis L. and especially Melissa officinalis L. might be considered for use in human and animal supply with this element.

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