## 2 Results
### HS-SPME/GC-MS Analysis
#### 2.1.2 PDMS/DVB Fiber  
V VOCs of the same four populations of _Sideritis romana_ and two populations of _S. montana_ were extracted by HS-SPME, using also PDMS/DVB fiber and their composition was analyzed by GC-MS. In total, 56 VOCs were identified, accounting for 89.35-97.09% of the total VOCs content (Table 2). As with DVB/CAR/PDMS fiber, the VOCs compo \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Compound**} & \multirow{2}{*}{**CD 1**} & \multirow{2}{*}{**RI 2**} & S. _romana_ & S. _romana_ & S. _romana_ & S. _romana_ & S. _montana_ & S. _montana_ \\  & & & & **K** & **B** & **M** & **P** & **J** & **M** \\ \hline
55 & Germacrene D & C26 & 1484 & 1.50 & 0.06 & - & - & 23.23 & 17.04 \\
56 & trans-\(\beta\)-Ionone & & 1489 & 0.31 & 0.18 & 0.37 & 0.22 & - & - \\
57 & \(\beta\)-Cadinene & C27 & 1494 & 2.19 & 1.68 & - & 1.24 & 0.98 & 1.47 \\
58 & Ledene & C28 & 1497 & - & - & 8.20 & - & 2.27 & - \\
59 & Bicyclogermacrene & C29 & 1498 & 23.04 & 20.48 & - & 15.16 & 4.19 & 11.76 \\
60 & \(\alpha\)-Muurolene & C30 & 1502 & 0.61 & 0.18 & - & - & 1.78 & 2.93 \\
61 & \(\gamma\)-Cadinene & C31 & 1517 & 0.58 & - & - & - & 3.33 & 3.37 \\
62 & \(\delta\)-Cadinene & C32 & 1527 & 1.84 & 0.15 & - & - & 7.57 & 8.85 \\
63 & Dihydroactinidiolide & & 1532 & 0.41 & 0.41 & 0.60 & 0.33 & 0.11 & 0.35 \\
64 & Cadina-1,4-diene & C33 & 1536 & 0.20 & - & - & - & 0.94 & 1.24 \\
65 & \(\alpha\)-Cadinene & C34 & 1541 & 0.24 & - & - & - & 1.41 & 1.70 \\
66 & \(\alpha\)-Calacore & C35 & 1547 & 0.47 & 0.04 & - & - & 1.05 & 1.36 \\
67 & Spathulenol & C36 & 1580 & 0.58 & 1.30 & - & 0.52 & 0.15 & 0.47 \\
68 & Viridiflorol & C37 & 1595 & 0.42 & 0.36 & 10.29 & 0.20 & 0.08 & 0.21 \\
69 & \(\alpha\)-Cadinol & & 1658 & 0.34 & - & - & - & - & - \\ \hline  & Total identified [\%] & & & 86.18 & 90.29 & 88.87 & 89.60 & 89.28 & 86.38 \\ \hline \end{tabular}  
* CD: Compound designation of the major components (average percentages \(\geq\) 1.0% in at least one of the samples), which were included in the principal component analysis. 2 RI: Retention index determined relative to a homologous series of \(n\)-alkanes (C\({}_{9}\)–C\({}_{25}\)) on a HP-5 MS column; 3 Tentatively identified.  
\end{table} 
Table 1: \(Cont.\)  
Figure 1: Average relative percentages of different classes of headspace volatile organic compounds obtained from various populations of _S. romana_ and _S. montana_ using DVB/CAR/PDMS fiber. sitions of investigated populations of both species were characterized by sesquiterpene hydrocarbons, followed by monoterpene hydrocarbons, except for that of _S. romana_ M, in which monoterpene hydrocarbons and oxygenated sesquiterpenes were more abundant than sesquiterpene hydrocarbons. Moreover, other compounds were more abundant in this population than in other investigated samples (Figure 2). By applying PDMS/DVB fiber, more sesquiterpene hydrocarbons, and less oxygenated monoterpenes and other compounds were extracted than with the application of DVB/CAR/PDMS fiber. The main individual compounds that were identified for _S. romana_ were bicyclogermacrene (10.21-57.50%), \(\beta\)-pinene (6.78-13.26%), isocaryophyllene (5.17-7.10%) (except _S. romana_ M), _trans_-\(\beta\)-farnesene (3.55-7.71%), germacrene D (1.22-12.18%), \(\gamma\)-terpinene (0.11-8.96%), limonene (1.97-3.86%) and \(\alpha\)-pinene (2.09-3.91%). For _S. romana_ M, the main individual compounds were viridiflorl (24.19%), \(\beta\)-pinene (13.26%), bicyclogermacrene (10.21%), \(\gamma\)-terpinene (8.96%) and _trans_-caryophyllene (6.35%). In _S. montana_, the main individual compounds were germacrene D (51.08-53.63%), bicyclogermacrene (9.54-18.03%), _trans_-caryophyllene (6.65-15.49%), limonene (2.91-3.74%) and _trans_-\(\beta\)-farnesene (2.17-4.02%) (Table 2).