Comparison of Essential Oil Constituents of Scirpus Littoralis Schrad . and Scirpus Wardianus J . R . Drumm . from Iran

The essential oils obtained by hydrodistillation of aerial part of S. littoralis and S. wardianus grown in Iran were analyzed by GC/MS. Twenty seven components of S. littoralis and S. wardianus representing 85.5% and 86% of the oils were identified respectively. The major components in both oils were cyperene and cyperotundone, representing 18.7% and 14.8% in S. litoralis and 24.1% and 11.1%, in S. wardianus. Both oils were richer in sesquiterpene hydrocarbon and oxygenated sesquiterpene.


Introduction
The plant genus scirpus consists of a large number of aquatic, grass-like species in the family cyperceae and grows in wetlands and moist soil.Scirpus species are often planted to inhibit soil erosion and provide habitat for other wildlife 1 .They have been extensively used in constructed wetlands for wastewater treatment because they can efficiently remove nutrients and pathogens from effluent [2][3][4][5][6][7] .Also, some species of Scirpus may have a relatively low ability to take up heavy metals, for example, S. robustus that efficiently removes selenium (Se) from contaminated water demonstrating potential for Se phytoremediation by wetlands 8,9 .On the other hand, it has been reported that the rhizomes of S. yagara Ohwi, as a commonly used traditional Chinese medicine (TCM), have the therapeutic functions of promoting blood circulation, removing stagnation, relieving pain, etc.It has been used solely or as an important ingredient in some traditional prescriptions for the treatment of hyperemesis gravidarum, postpartum abdominal pain, dyspepsia and amenorrhea 10 .Two species of this genus, which grow wild in the east and southern east of Iran, are Scirpus littoralis Schrad.and Scirpus wardianus J. R. Drummond 11,12 .To date, no information on the chemical composition of the essential oil of S. littoralis and S. wardianus Iran origin is available.So we decided to examine this oil.

Experimental
The aerial parts of the S. littoralis species were collected between Zabol and Takht adalat around Hamun Lake in Province of Sistan va Balutchestan, Iran, in April 2007 at the flowering stage and S. wardianus from around Hirmand River, Province of Sistan va Balutchestan, Iran, in June 2007.Voucher specimens have been deposited at the herbarium of Research Institute of Forests and Rangelands (TARI).

Hydrodistillation
The aerial parts of the plant after grinding had been submitted to hydrodistillation with a Clevenger type apparatus according to the standard procedure described in the European Pharmacopoeia 13 .The essential oil had been co-distilled with water for 3 h, collected, dried under anhydrous sodium sulfate and stored at 4 ºC until used.The yield of the oil was 1.5% and 1.2% (v/w), based on dry plant weight.

Gas chromatography-mass spectrometry
The essential oils were analyzed by gas chromatography coupled to mass spectrometry (GC-MS) (Hewlett-Packard computerized system comprising a 6890 gas chromatograph coupled to a 5973 mass spectrometer) using a capillary column, Hp-5Ms (5% phenylmethyl siloxane) (30 m × 0.25 mm, film thickness 0.25 µm).Oven temperature was programmed 60 ºC for 20 min, and then increased to 220 ºC at a rate of 4 ºC/min, finally holding at 220 ºC for 20 min.Helium was used as carrier gas at a flow rate of 1 ml/min.The ionization energy was 70 eV with a scan time of 1 s and mass range of 40-300 amu.Retention indices for all the compounds were determined according to the Kovats method using n-alkanes as standards.The identification of the oil components was accomplished by comparison of their GC retention indices as well as their mass spectra with corresponding data of authentic compounds or of components of reference oils 14,15 .Relative percentage was calculated from TIC by the computer.

Results and Discussion
Data obtained from qualitative and quantitative determination of the oil samples are shown in Table 1.Twenty seven components were identified in the oil of S. littoralis which represented 85.5% of the total composition of the oil.Cyperene (18.7%) was the dominant constituent.The second major compound was cyperotundone (14.8%).Also, the oil had significant amounts of isorotundene (8.2%), β-selinene (5.6%), isocyperol (5.3%) and β-pinene (4.5%).