## 2 Results and Discussion
### Headspace and Volatile Oil Composition of P. pavonica
**} & \multirow{2}{*}{**Compound**} & \multirow{2}{*}{**RI**} & \multicolumn{3}{c}{**Area Percentages (\%)**} \\ \cline{4-5}  & & & **HS-SPME** & **HS-SPME** \\  & & & **(PDMS/DVB) \(\pm\) SD** & **(DVB/CAR/PDMS) \(\pm\) SD** & **HD \(\pm\) SD** \\ \hline
1 & Dimethyl sulfide [5] & 523 & 18.27 \(\pm\) 1.46 & 26.37 \(\pm\) 2.10 & - \\
2 & _P_-Xylene [5] & 869 & - & - & 0.06 \(\pm\) 0.01 \\
3 & Benzaldehyde [5] & 970 & 2.48 \(\pm\) 0.07 & 0.33 \(\pm\) 0.02 & - \\
4 & 6-Methylhept-5-en-2-one & 990 & 0.87 \(\pm\) 0.01 & - & - \\
5 & Octanal [5] & 1005 & 9.63 \(\pm\) 0.91 & 7.98 \(\pm\) 0.20 & - \\
6 & 1,8-Cineo [5] & 1038 & 2.43 \(\pm\) 0.05 & 0.87 \(\pm\) 0.04 & - \\
7 & 2-Ethylexan-1-ol & 1039 & & 0.87 \(\pm\) 0.03 & - \\
8 & 2,2,6-Trimethylcyclohexanone [5] & 1041 & 0.68 \(\pm\) 0.02 & 0.55 \(\pm\) 0.01 & - \\
9 & Octanal-1-ol [5] & 1079 & 37.73 \(\pm\) 2.80 & 38.60 \(\pm\) 2.71 & - \\
10 & \(\alpha\)-Cumyl alcohol & 1092 & - & 1.171 \(\pm\) 0.05 & - \\
11 & Dictyopetrene A & 1119 & 1.27 \(\pm\) 0.02 & 0.87 \(\pm\) 0.03 & - \\
12 & Dictyopetrene D [FOOTNOTE:]Footnote : \(\alpha\)-Cumyl alcohol[ENDFOOTNOTE] & 1157 & 1.15 \(\pm\) 0.05 & - & - \\
13 & Berkheyraduelene [13] & 1387 & - & - & 0.18 \(\pm\) 0.01 \\
14 & _B_-Yangene & 1421 & - & - & 0.10 \(\pm\) 0.00 \\
15 & _trans_-\(\alpha\)-Bergamotene & 1439 & - & - & 0.05 \(\pm\) 0.01 \\
16 & epi-gantaleene & 1449 & - & - & 0.16 \(\pm\) 0.03 \\
17 & _a_-Humulene & 1455 & - & - & 0.05 \(\pm\) 0.01 \\
18 & (E)-\(\beta\)-Farnesene [5] & 1460 & 7.92 \(\pm\) 0.85 & 6.28 \(\pm\) 0.99 & 0.03 \(\pm\) 0.01 \\
19 & \(\beta\)-Santialeene & 1462 & - & - & 0.04 \(\pm\) 0.01 \\
20 & (_E_)-\(\beta\)-Guaine & 1487 & - & - & 0.24 \(\pm\) 0.02 \\
21 & epi-Bicyclosequiphellandrene & 1496 & - & - &epi-\(\beta\)-santalene, \(\alpha\)-humulene, \(\beta\)-santalene, (\(E\))-\(\beta\)-guaiene, \(\beta\)-bisabolene, and (\(E\))-\(\alpha\)-bisabolene. These sesquiterpenes as well as pachydictol A and isopachydictol A were for the first time found in _P. pavonica_. In comparison with previous papers on VOCs, from this alga, only partial similarity is observed. Namely, the major compound of SDE isolate [22] was bis-2-ethylhexyl phtalate (40.22%), while in the current research, disobutyl phthalate was found as a minor constituent. Fatty esters such as methyl eicosa-5,8,11,14-tetraenoate, methyl eicosa-5,8,11,14,17-tetraenoate and diterpene phytol were found previously in this alga [22] as well in the current research. The presence of free fatty acids was also reported [22]. Sesquiterpene compounds \(\beta\)-cubebene, germacrene D and santalol were previously detected in _P. pavonica_ SDE isolate [22], but not in the present research where several other sesquiterpenes were found (Table 2). _P. pavonica_ toluene extract subjected to 4-h SDE [17] provided esters benzyl acetate and benzyl formate as the major compounds. Besides the esters of benzoic acid, significant concentrations of their biogenic precursors benzaldehyde and benzyl alcohol were found, but they were not identified in the isolated oil. Therefore, the assumption that these compounds can serve as biomarkers for these algae [17] is questionable. In addition, low concentrations of the common marine algal terpene dihydroactinidiolide and C\({}_{13}\)-norisoprenoid \(\beta\)-ionone were found previously, and in the obtained oil, diterpenes isopachydictol A and pachydictol A as well as C\({}_{13}\)-norisoprenoid 3-oxo-\(\alpha\)-ionol were present.