## 2 Results  
### Chemical Composition of Essential Oils  
This paper identifies, in detail, the chemical constituents of EOs extracted from fresh and dried _S. persica_ L. roots. The hydro-distillation of fresh and dried roots of _S. persica_ L. produced light yellow oils in yields of 0.2% and 0.03%, _w/w_, respectively. The comparison of the oil yield of fresh and dried roots of _S. persica_ L. in the present study revealed that fresh roots contained about a seven times higher oil yield than those of the dried roots. GC-MS and GC-FID housing a nonpolar column HP-5 MS (Agilent Technologies, Santa Clara, CA, USA) were used to determine the phytochemical constituents of these oils. A total of four components were detected from both oils. Based on mass fragmentation pattern, retention time, and calculated linear retention index values, three components from each essential oil were identified, which account for 99.7% and 98.8% of the total oils of fresh and dried _S. persica_ L. roots, respectively. The identified chemical constituents from fresh and dried roots of _S. persica_ L. and their relative quantity (%) are detailed in Table 1 according to their order of elution through the HP-5 MS column. Moreover, a GC-FID chromatogram of fresh and dried of _S. persica_ L. roots EOs is given in Figures 1 and 2, respectively.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**No.** & **Compound** & **MF** & **MW** & **RT (min)** & **LRI\({}_{\text{Lit}}\)** & **LRI\({}_{\text{Exp}}\)a** & **MF-1** & **MD-1** \\
2 & Benzaldehyde & C\({}_{7}\)H\({}_{6}\)O & 106 & 11.9 & 952 & 958 & 0.5 & 4.7 \\
2 & Benzyl nitrile & C\({}_{8}\)H\({}_{7}\)N & 117 & 18.8 & - & 1140 & 13.4 & 26.0 \\
3 & Unknown & - & - & 26.2 & - & 1355 & 0.2 & 0.6 \\
4 & Benzyl Isothiocyanate & C\({}_{8}\)H\({}_{7}\)NS & 149 & 26.8 & - & 1373 & 85.8 & 68.1 \\ \hline  & **Total** & & & & & **99.7** & **98.8** \\
**identified** & & & & & & **99.7** & **98.8** \\ \hline  & **Oil Yield** & & & & & **0.2** & **0.03** \\ \hline \hline \end{tabular}  
* MF, MW and RT denote molecular formula, molecular weight and retention time, respectively; LRI\({}_{\text{Lit}}\) = Linear retention index from the literature ([PERSON], 2007); LRI\({}^{\text{R}}\) = Computed LRI with reference to _n_-alkanes mixture (C8–C31) on HP-5 MS; MF-1 = essential oil of _S. persica_ L. fresh roots; MD-1 = essential oil of _S. persica_ L. dried roots.  
\end{table}
Table 1: Chemical constituents identified from the fresh and dried roots essential oils of _S. persica_ L.  
Figure 1: GC-FID chromatogram of EO constituents of the fresh _S. persica_ L. roots on HP-5 MS column.  
The main volatile components identified from the fresh and dried roots of _S. persica_ L. were: benzyl isothicyanate (LRI 1373, 85.8% and 68.1%); benzyl nitrile (LRI 1140, 13.4% and 26.0%) and benzaldehyde (LRI 958, 0.5% and 4.7%), respectively (Figure 3). From Table 1, it is clearly evident that the chemical components of the fresh and dried roots of _S. persica_ L. were almost identical. However, the content of each constituent differed significantly in both oils. For instance, the content of benzyl isothirate, the most abundant compound of _S. persica_ L. oils, was found to be about 18% less in the essential oil of dried _S. persica_ L. roots. On the contrary, it was noticed that the contents of other constituents, such as benzaldehyde and benzyl nitrile were 4%-13% higher in the essential oils of dried _S. persica_ L. roots. Thus, this study reveals that drying of _S. persica_ L. roots at room temperature has prominent effects on the quantitative composition of _S. persica_ L. roots essential oils.  
Figure 2: GC-FID chromatogram of EO constituents of the dried _S. persica_ L. roots on HP-5 MS column.