Cent. Eur. J. Biol.• 6(4) • 2011 • 616-623 DOI: 10.2478/s11535-011-0013-0 Central European Journal of Biology Trace elements in aerial parts and rhizosphere of Thymus pannonicus All. Research Article Jelena Arsenijević1,*, Slavica Ražić2, Zoran Maksimović1, Svetlana Đogo2 1Department of Pharmacognosy, School of Pharmacy, University of Belgrade, 11221 Belgrade, Serbia 2Department of Analytical Chemistry, School of Pharmacy, University of Belgrade, 11221 Belgrade, Serbia Received 22 November 2010; Accepted 14 January 2011 Abstract: This paper brings out the results of the study on the levels of selected trace elements (Cu, Fe, Mn, Zn and Cr) in aerial parts of Thymus pannonicus All. (Lamiaceae) and rhizosphere soil from twelve locations in Serbia. Prior to assays by flame and flameless atomic absorption spectrometry, samples were subjected to microwave-assisted acid digestion. Real and potential acidity of soil samples were also measured. Obtained results for soil samples, although slightly higher for some elements (Cu: 12.38–45.18 mg/kg; Fe: 22102–46193 mg/kg; Mn: 776.95–4901.27 mg/kg; Zn: 62.27–214.02 mg/kg; Cr: 48.86–69.13 mg/kg), were found to fit into biogeochemical background. Element contents in plant samples differed depending on collecting site (Cu: 5.26–14.07 mg/kg; Fe: 25.92–1454.07 mg/kg; Mn: 89.29–278.25 mg/kg; Zn: 1.81–10.64 mg/kg; Cr: 1.11–3.51 mg/kg), which can be partly explainable by different nutrient availability influenced by soil acidity. Zinc levels in T. pannonicus were below expected and seem to be strongly influenced by plant physiological properties. Keywords: Thymus pannonicus • Trace elements • Rhizosphere soil • Plant tissues • AAS © Versita Sp. z o.o. plant tissues. Bearing in mind that plants are an essential 1. Introduction part of regular diet, questions of their safety for human Soil is the main source for both organic and inorganic health have frequently arisen [2,3]. On the other hand, plant nutrients. Depending on plant species and soil holding a focus on two environmental compartments type, there is a variety of different chemical environments (both soil and plant tissues), a close insight on the influencing biological availability, absorption, distribution elemental composition could be reached, which can and accumulation of each element in many ways. prove itself significant in highlighting its influence on Seventeen elements are considered to be essential for biosynthetic pathways and production of secondary plants: C, H , O, N, K, Ca, Mg, P, S, B, Cl, Cu, Fe, Mn, metabolites, e.g. essential oils [4]. Both approaches Mo, Ni and Zn. These elements are involved in various justify the objectives of this work. processes of primary and secondary plant metabolism. The genus Thymus comprises more than 200 With respect to concentration levels in plant tissues, they species native for Europe, Asia, North Africa and the are classified as major, minor and trace elements. Beside Canary Islands. Apart from T. vulgaris L., T. zygis Loefl. a common knowledge, essentiality of certain elements ex L. and T. serpyllum L., which are recognized in a is not proven yet, but some beneficial effects on plant majority of the world’s pharmacopoeias as biological growth have been noticed (e.g. the effects of Cr) [1]. sources of official herbal drugs, the other representatives Elemental pattern in medicinal herbs and soils could of this genus are widely used in traditional medicine, or be discussed in a few different ways. Growing on a as culinary herbs and ornamentals [5]. To the best of soil rich in potentially toxic heavy elements can lead to our knowledge, several authors have reported values accumulation of higher amounts of these elements in for a number of major, minor, and trace elements in * E-mail: [email protected] 616 Unauthenticated Download Date | 7/31/19 4:38 PM J. Arsenijević et al. aerial parts of Thymus species so far [6-10], but only a Lack of reliable data for elemental content and patterns few have investigated levels and relationships between in T. pannonicus tissues and soil where it was grown, adds metal concentrations in soil and herb [11-13]. to the overall importance of conducted research. Hungarian or Eurasian thyme (Thymus pannonicus All., Lamiaceae) is an herbaceous perennial plant growing wild in the Pannonian plain and surrounding areas. The area 2. Experimental Procedures of distribution of T. pannonicus in Serbia includes eastern and southeastern parts of the country, as well as the whole All chemicals were of analytical grade. In preparation of all Vojvodina province [14]. In eastern Serbia, on Mts. Stol, solutions, double distilled water was used. Stock solutions Ozren and Rtanj, Hungarian thyme grows on the soils of Cu, Mn, Zn, Fe and Cr salts (1 g/l) were purchased derived from underlying limestone [15]. Citral T. pannonicus from Merck (Darmstadt, Germany). Working solutions chemotype from Mt. Vršačke planine in Vojvodina were produced by suitable dilution of corresponding stock province, grows on acidic soils derived on albite-muscovite solution with 2.5% nitric acid (HNO3). Nitric acid (65%, v/v) schist and granite gneiss. In this region, Hungarian was provided by Merck and solution of H2O2 (30%, v/v) thyme is traditionally used for treatment of respiratory and KCl from Zorka Pharma Šabac (Serbia). and gastrointestinal complaints, as well as a flavoring Aerial parts of plants and rhizosphere soils were agent because of its lemon-like scent [16]. Hungarian collected during the flowering period from Mts. Rtanj thymol/p-cymen T. pannonicus chemotype, as Pluhar et al. and Ozren, two locations on Mt. Stol (near the city of reported recently, can develop on variety of soil substrates Bor) and eight locations on the Mt. Vršačke planine in and tolerate a wide soil pH range as well [17]. 2008 (Table 1). For each location three representative No. Location Description Coordinates Bedrock [15] N 45° 07’ 37.7’’ 1 Mt. Vršačke planine Mountain lodge E 21° 20’ 31.9’’ Amygdaloidal and Augen gneiss H 357 m N 45° 07’ 11.7’’ 2 Mt. Vršačke planine Path E 21° 19’ 47.1’’ Amygdaloidal and Augen gneiss H 293 m N 45° 07’ 06.4’’ 3 Mt. Vršačke planine Hill side road E 21° 19’ 47.9’’ Amygdaloidal and Augen gneiss H 271 m N 45° 06’ 59.1’’ 4 Mt. Vršačke planine – Kapela Meadow E 21° 19’ 43.2’’ Amygdaloidal and Augen gneiss H 249 m N 45° 07’ 18.5’’ 5 Mt. Vršačke planine – Đakov vrh Meadow E 21° 21’ 10.0’’ Amygdaloidal and Augen gneiss H 418 m N 45° 06’ 34.6’’ 6 Mt. Vršačke planine – Mesić village Meadow E 21° 24’ 26.6’’ Claystone H 202 m N 45° 05’ 36.3’’ 7 Mt. Vršačke planine – Fizeš stream Meadow E 21° 27’ 36.2’’ Albite-muscovite schist H 139 m N 45° 05’ 31.3’’ 8 Mt. Vršačke planine – Sočica village Meadow (pasture) E 21° 27’ 23.5’’ Albite-muscovite schist H 191 m N 44° 10’ 15,8’’ 9 Mt. Stol Meadow E 21° 07’ 25,2’’ Limestone H 878 m N 44° 10’ 33,7’’ 10 Mt. Stol Hillside E 22° 07’ 50,0’’ Limestone H 1081 m N 43° 35’ 28,8’’ 11 Mt. Ozren Hill side road E 21° 53’ 15,8’’ Limestone H 954 m N 43° 43’ 34,4’’ 12 Mt. Rtanj – Vrmdža village Hill side road E 21° 50’ 45,6’’ Limestone H 651 m Table 1. Description of sampling locations. 617 Unauthenticated Download Date | 7/31/19 4:38 PM Trace elements in aerial parts and rhizosphere of Thymus pannonicus All. samples of both plants and soils were collected and [19]. Wavelengths and method detection limits used analyzed. The soil was sampled from the root zone, in for measuring both in FAAS and GF-AAS are given in a depth of approximately 5–15 cm. The identification of Table 2. plant material was confirmed by Ivan Šoštarić from the Acidity of soil samples was determined in both KCl Department of Botany, Faculty of Agriculture, Belgrade solution (potential acidity) and aqueous suspensions based on voucher specimens deposited there. Both (real acidity). To 10.00 g of soil samples, 25.00 ml of plant and soil samples were air-dried and grounded 1 M KCl or 25.00 ml of redistilled water were added. before subsequent procedures. Suspensions were stirred occasionally, and acidity Acidity was measured using a PHM240 pH meter measured after 30 min. (Radiometer). For microwave-assisted acid digestion of Prior to elemental analysis, plant and soil samples plants and soil samples, a close-vessel high-pressure were subjected to microwave-assisted acid digestion, microwave digesters CEM MDS-2000 model was used. according to the procedure performed by Ražić The determination of Cu, Zn, Mn, and Fe was et al. [19]. Each sample (about 0.5 g dry weight) was performed with a Perkin–Elmer Model 5000 atomic digested with 2 ml H2O2 (30%, v/v) and 7 ml HNO3 in a absorption spectrophotometer under optimized microwave oven. After filtration, the obtained solutions measurement conditions using suitable hollow cathode were transferred into 25 ml volumetric flasks and diluted lamps. Signals were measured with background to the volume with redistilled water. One blank sample, correction (deuterium lamp) at the optimal flame (A–Ac) containing the same amounts of acid and oxidant, was height [18]. processed along with each set of analyzed samples. The determination of Cr was performed by using Accuracy of the methods applied for determination a Perkin–Elmer Model 5000 atomic absorption of Cu, Zn, Cr, Mn and Fe, after microwave-assisted acid spectrophotometer with a graphite furnace HGA 400 digestion of plants and soil samples, was checked by Automatic Burner Control, with pyrolytic graphite tubes analysis of SRMs: NIST SRM 1547 - Peach Leaves according to the temeperature program, with optimal and NIST SRM 2711 - Montana II Soil (Table 3).