Essential oils yield and heavy metals content of some aromatic medicinal plants grown in Ash-Shoubak Region, South of Jordan.
The use of aromatic medicinal herbs to relieve and treat many human diseases has been increased in Jordan and around the world because of their mild features and low side effects. [1,2]. At present, there are many aromatic medicinal herbs widely cultivated and consumed in Jordan. Among these herbs, Thymus vulgaris L. (common thyme), Thymus serpyllum L. (wild thyme), and Salvia officinallis L. (sage) which are the most popular aromatic medicinal herbs used for medical purposes or maintaining good health [1,3,4].
T. vulgaris and T. serpyllum are aromatic producing high quality of essential oil required by the pharmaceutical, food and cosmetic industry [5-8] The pharmacological activities of this medicinal plant are antispasmodic, expectorant, antiseptic, antimicrobial, and antioxidant activity [9-11]. S.officinalis (Sage) is a herb considered mainly for its content of essential oil, it has been credited with a long list of medicinal uses: e.g. spasmolytic, antiseptic, astringent, antioxidant and antimicrobial [12-15]. Also, it is largely used as an infusion where polar compounds play a central role . In Jordan, there are twenty species of Salvia cultivated or grow wildly [4,16] used to improve the taste of tea and included in many phytopreparations, for the treatment of inflammations, catarrhs, mouth and throat gargling [15,17].
Medicinal herbs can be easily contaminated with heavy metals from the environment (soil, water, or air) during growth and the manufacturing processes when the ready-made products are produced . Additional sources of heavy metal contamination are rainfall, atmospheric dust, plant protective agents, and fertilizers [19-21]. The level of essential elements in plants is conditional, the content being affected by the geochemical characteristics of the soil and by the ability of plants to selectively accumulate some of these elements [22-23].
Considering the complexity of these aromatic medicinal herbs and their inherent biological variation, it becomes necessary to evaluate their safety, efficacy and quality . While many investigations of the quality values of aromatic medicinal plants grown in Jordan are being reported in the current literature [15,17,22] less emphasis has been made on the metal content of herbal products. As well as T. vulgaris L. T. serpyllum L. and S. officinallis L. have various applications in ethno pharmacology. It is important to have a good quality control to protect consumers from contamination . Therefore, the aim of the present study was to carry out a comparative evaluation of essential oils yield and heavy metals content in Thymus vulgaris L., Thymus serpyllum L. and salvia officinallis L. grown in Ash-Shoubak, south environmental region in Jordan.
Materials and methods
Aerial parts of wild T.srpyllum, cultivated T.vulgaris and S.officinalis have been collected at vegetation during may, June and July 2008 respectively, from experimental area of the Ash-Shoubak University Collage, in Ash-shoubak region (30[degrees] 32N ,35[degrees] 33 E) in the southern altitudes of Jordan, 1365 m above the sea level. Ambient temperature is 4.11-19.9C[degrees] and seasonal means of rainfall is about 294.2mm/year. The collected plant materials were dried in draughty place at about 20[degrees]C, all specimens were identified on the basis of macroscopic characteristics by comparison with authentic sample and a voucher specimens were deposited by the Herbarium of Ash-Shoubak University College. The dried material of studied plants were separately crushed and mild in to small pieces and sieved through (0,5mm) mesh sieve.
Determination of Essential Oil
Essential oils contents of particular specimens of studied plants were extracted separately by the hydrodistillation method utilizing Clevenger-type apparatus similar to European Pharmacopoeia (EP) (22), using 50 gr of the dried mild and sieved plant (0,5mm), 500 ml of water in 1000 ml round -bottomed flask. The distillation time was 2 h at a rate of 2-3 [min.sup.-1]. The values reported are the mean of at least 3 distillations . There were three replications for each specimen; all the results obtained were statistically analyzed.
Determination of heavy metals content in medicinal plant samples
Heavy metals content of particular collected samples were analyzed using Atomic Absorption. Flame Emission Spectrophotometer Model (Shimadzu, Japan) AA-6200 . The plant samples were oven dried at 70[degrees]C for 24 hours until the dry weight was constant. The dried samples were then ground and passed through a 0.2 mm plastic sieve. Then, 0.5g of plant sample was wet digested with an Ultra-pure nitric acid (HN[O.sub.3] (10-15ml) in a polyethylene test tube using a heating block digestion unit at 120 C[degrees]. The final solution was filtered into a 25 ml or 50 ml volumetric flask through a 45-[micro]m filter paper and diluted to the mark with ultra-pure water. Ultra-pure water was used for all dilutions and sample preparation.
Results and discussion
Means of essential oil contents in the studied aerial parts of T.vulgaris L., T.serpyllum L. and S.officinalis L. are presented in table (1). The essential oil contents in T.vulgaris L., T.serpyllum, and S.officnalis were 4.0, 2.5, and 1.90 respectively. The results showed that T. vulgaris L. and T.serpyllum contain higher volumes of essential oil than S.officnalis. However, The yields were found to satisfy the requirements of Pharmacopeias such as European Pharmacopoeia (EP), which requires a yield of oil should be [greater than or equal to] 1.2, 0.3, and 1.0% v/w for T. vulgaris , T.serpyllum, and S.officnalis respectively . On the other hand, the results of previous studies [7,8] revealed a wide variation in essential oil contents in T.vulgaris cultivated in other neighboring places located in the south and middle regions of Jordan. However, Ash-shoubak region yielded higher than these cultivated in other places located in the south of Jordan such as in Maan 2.00[+ or -]0.00% and in Al-Tafelieh 2.30[+ or -] 0.002%(8),or in Mshaqar (middle region of Jordan), 1.6% , but less than these cultivated in the north region of country ,where T.vulgaris cultivated in Jeresh and Ajlune yielded 5.4[+ or -]0.12 and 5.2[+ or -] 0.09%, respectively . However T.vulgaris cultivated in Ash-shoubak region yielded higher than those cultivated in other regions of the world, where in Egypt, Iran, Brazil, Iraq, and Turkey yielded 1.07, 1.45, 0.56, 1.67 and 1.6%, respectively) [24-28]. The higher volumes of essential oil in T.vulgaris was observed with a lower content in T.serpyllum. However, the results showed that, T.serpyllum grown in Ash-shoubak region yielded higher volumes of essential oil than these investigated from other regions of the world, where in Estonia, the yield of essential oil was ranged between 0.6-4.4 ml/kg, while in Russia, Latvia and Armenia was ranged between 1.9 and 8.2 ml/kg, . This variation of essential oil yielded from a particular species of thyme plant could be explained by the effect of harvesting season [25,26], geographical environment and other agronomical factors [8,30-32].
The essential oils content in S.officnalis was 1.90%. This result is in agreement with others who reported that S.officnalis cultivated in other locations from the middle region of Jordan; Hfashiet Al Dbajbe and Al Fesalia, yielded essential oil ranged from 1.18 to 2.13% . However, this variation in essential oil yield of S.officnalis cultivated in Ash-shoubak region in south and other regions of Jordan could be ascribed according to climate variations among regions , growth region [7,8,24] and cultivation practices such as spacing , irrigation regimen (25), and harvesting time [26,32].
The results of heavy metal concentrations (ppm) in T.vulgaris, T.serpyllum, and S.officnalis grown in Ash-shoubak region are presented in table (2). In all investigated medicinal herbs, Cadmium (Cd) and Chromium (Cr) were not detectable. The un detectable concentration of Cd and Cr in all investigated herbs may be due to a low soil content of Cd in suburbanized areas in Jordan or due to cultivation these herbs in locations free off industrial activities such as steel and glass industries that have been shown to be a source of chromium pollution (33,34). However, high Cd content was detected in urban areas in Jordan  near the road and their level increased with increasing traffic densities . On the other hand, Cd was not detectable in T.vulgaris cultivated in other regions of Jordan  and had not yet determined in S.officnalis cultivated in the middle region of Jordan . Comparing Ash-shoubak region to other locations of the world, it was obtained that the studied species grown in that locations are contaminated with Cd and Cr [36,3739].
The average concentrations of Pb in T.vulgaris, and T.serpyllum, were 32.03 and 1.26, respectively. The concentration of Pb in T.vulgaris cultivated in Ash-shoubak region was higher than that detected in wild T.serpyllum at the same region and exceeded the level (< 10 ppm) recommended by WHO . However, it was lower than that detected in the north regions . On the other hand, Pb was not detectable in S.officinalis cultivated in Ash-shoubak region while, it was characterized by higher level of these trace elements in the middle region . The contamination of studied T.vulgaris by Pb, could be clarified according to location of cultivation area of these species, especially it was known that motor vehicles are the leading factor in Pb contamination [15,18,21,33-38] while, in wild T.serpyllum grown in natural habitat Pb was low and below the toxic level . On the other hand, the variation in Pb content in studied plants may be due the type of soil, species of plant, the availability of plant to absorb the metal and accumulate it [38-40].
The average content of Ni was 23.85 ppm in T.vulgaris and not detectable in wild grown T.serpyllum. In S.officinalis, it was within normal range (0.47 ppm) since the toxic level ranges from 10 to 100 ppm. Also, the Copper (Cu) contents in all studied plants were within normal level (2-20 ppm). The detected level of Cu was ranged from 10.4 ppm in T.serpyllum to 13.23 ppm in T.vulgaris, while it decreased to 7.66 ppm in S.officinalis. This variation of Cu content in the studied samples, could be due to genetic differences between plant species , or different plant selectivity for heavy metals . These results are in agreement with the results of others who found that the contents of Cu in some medicinal plants in the same family such as salvia officinalis, Mentha piperita, Melissa officinalis, Ocimum basilicum, and Origanum vulgaris were varying from 5.92 to 14.79 mg/kg . On the other hand, the concentration of Cu detected in S. officinalis cultivated in Ash-shoubak is less than that detected in the middle of Jordan, where it was varied from 61 to 70 mg/kg , and less than cultivated in other regions of the world. [37,38]. This indicates the effect of anthropogenic activities and heavy traffic activities by which the Cu metal may accumulate in the soil [33,43].
As well as Cu is one of important constituent of many enzymes essential for living organisms, Also Zn has the same role and considered an important factor in the biosynthesis of enzymes and some proteins. [18,44,45]. The concentration of Zn in plant may vary between 30-150 ppm, but usually it is 2050 ppm. In the investigated plant materials the highest concentration was found in S.officinalis, while the lowest was detected in T.serpyllum. These results indicated that S.officinalis cultivated in Ash-Shouback south environment is rich with Zn content compared with the middle growth area in Jordan (114.19 vs. 22-29 ppm) .The concentrations of Manganese (Mn) were found to be closely relative to each other in T.serpyllum, and T.vulgaris. They were 14.7 and, 15.52 ppm, respectively, where the highest concentration (44.0ppm) was found in S. officinalis. However, the concentration of Mn in S. officinalis was lower than that detected in S. officinalis cultivated in middle of Jordan which was ranged from 92 mg/kg to 108 mg/kg . The high content of Mn could be ascribed as a cultivation of plant in industrial and residential sites rich of Mn and Ni ,due to their using as fuel additives just like Pb  since the critical threshold for Mn deficiency in plants is <10 ppm, it is obvious that studied plants were sufficiently provided with Mn.
Ferrous (Fe) concentration in dry plant material typically reaches 1000 ppm or more . In the studied herbs, Fe content was in the following order T.vulgaris <T.serpyllum < S. officinalis. The highest content of Fe was been detected in S.officinalis (756.17 ppm), while the lowest was detected in T. vulgaris (142.3ppm). The variation in Fe content in Salvia species and thymus species may be due to plant availability of the essential micronutrients and plant uptake of micronutrients which vary and depend on genetic differences between plant species [20,41]. On the contrary, a low Fe content ranged from 122 mg/kg to 184 mg /kg was found in S.officinalis grown in the middle region of Jordan (near highway between Amman and Sahab) . These differences in Fe contents could be ascribed to a well-supplied soil in Ash-shoubak south region, and according to the neighborhood location the cement factory in the south of Jordan .
Cobalt (Co) concentration in T.serpyllum was within the optimum range 0.02-1.0 mg/kg in the plant . It was 0.40 ppm and not detectable in T.vulgaris and S.officinalis. In 303 samples, which represent 20 different types of spices and medicinal plants that were collected from areas of exportation in Egypt, Co was not detectable . Also in infusion of S.officinalis consumed in Turkey these metal was not detected .The presence of Co in T.serpyllum and its absence in other studied herbs could be ascribed that cobalt distribution in plants is entirely species-dependent. The uptake is controlled by different mechanisms in different species. Physical conditions like salinity, temperature, pH of the medium, and presence of other metals influence the process of uptake and accumulation of Co in medicinal plant .
The essential oils yields in Thymus vulgaris L., Thymus serpyllum L. and Salvia officinallis L. grown in Ash-shoubak region were found to satisfy the requirement of European pharmacopoeia.
The contents of heavy metals in Ash-Shouback south environment are variable and mainly affected by plant species. Thymus vulgaris is rich in Pb content, Thymus serpyllum and Salvia officinallis are more safely and rich sources of Fe. Further studies of heavy metals concentrations in medicinal plants grown in Jordan environment are recommended.
The author express his thanks to the deanship of scientific research and Al-Balqa"Applied University for their financial support and advice, and to agricultural engineer Sanaa Al-shqerat for technical assistant.
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Mohammad Sanad Abu-Darwish
Ash-Shoubak University College, Al-Balqa Applied University, Al Salt 19117, Jordan
Mohammad Sanad Abu-Darwish, Department of Basic and Applied Sciences, Al-Shouback University College, Al-Balqa" Applied University, Jordan Work
TeleFax: 00962 03 2164035
Table 1: Mean [+ or -] SD of essential oil Yields (%) extracted from Thymus Vulgaris L, Tymus serpyllum L., and Saliva officinalis L. collected from Ash-shouback region-south of Jordan. Plant Species Essential Oil (%) Moisture (%) Thymus Vulgaris L * 4.0 [+ or -] 0.007 6.00 [+ or -] 0.020 Thymus serpyllum L 2.5 [+ or -] 0.008 6.60 [+ or -] 0.010 Saliva officinalis L. 1.9 [+ or -] 0.002 9.40 [+ or -] 0.012 * Results of T. vulgaris were delivered from previous paper for the same author . Table 2: Concentration of heavy metals (ppm) in Thymus Vulgaris L, Tymns serpyllum L. and Saliva officinalis L. collected from Ash-shouback south region, Jordan. Plant species Cd Cr Thymus vulgaris * ND ND Thymus serpyllum ND ND Saliva officinalis ND ND Detection limit [micro]g/L 0.002 0.004 Plant species Pb Ni Thymus vulgaris * 32.03 [+ or -] 0.04 23.85 [+ or -] 0.03 Thymus serpyllum 1.26 [+ or -] 0.01 ND Saliva officinalis ND 0.47 [+ or -] 0.23 Detection limit [micro]g/L 0.050 0.070 Plant species Cu Mn Thymus vulgaris * 13.23 [+ or -] 0.13 15.52 [+ or -] 0.16 Thymus serpyllum 10.40 [+ or -] 0.150 14.7 [+ or -] 0.06 Saliva officinalis 7.66 [+ or -] 0.77 44.0 [+ or -] 0.46 Detection limit [micro]g/L 0.014 0.028 Plant species Zn Fe Thymus vulgaris * 16.18 [+ or -] 0.24 141.3 [+ or -] 0.67 Thymus serpyllum 15.80 [+ or -] 0.02 142.00 [+ or -] 0.879 Saliva officinalis 114.91 [+ or -] 0.36 756.17 [+ or -] 5.82 Detection limit [micro]g/L 0.150 0.06 Plant species Co Thymus vulgaris * ND Thymus serpyllum 0.40 [+ or -] 0.003 Saliva officinalis ND Detection limit [micro]g/L 0.011 * Results of Cd, Cr, Pb, Ni, Cu, Mn, Zn, contents in T. vulgaris were delivered for Comparison from a previous paper for the same author .
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|Title Annotation:||Original Article|
|Author:||Abu-Darwish, Mohammad Sanad|
|Publication:||Advances in Environmental Biology|
|Date:||Sep 1, 2009|
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