## 2 Results and Discussion
### Essential Oils  
The results of the chemical composition of the essential oils of sea fennel isolated by the two distillation methods are summarized in Table 1, while the corresponding chromatograms are shown in Figure 1. The constituents of EO were identified and quantified by gas chromatography coupled with mass spectrometry (GC-MS) (Table 1, Figure 1). As can be seen from the results, 15 detected compounds differed in their occurrence in the EO samples obtained by HD and MHD. Similar to our previous reports ([PERSON] _et al._, 2016; [PERSON] _et al._, 2016), as well as other reports on Croatian sea fennel (2016), the dominant components were non-polar monoterpene compounds, of which limonene (51.4-53.1%) and sabinene (25.2-27.8%) were found in the highest amounts. In the MHD sample, both compounds were detected in higher amounts. Of the other non-oxygenated compounds, only the content of \(p\)-cymene was highest in the MHD sample (1.84% in HD and 2.53% in MHD, respectively), while all other compounds were detected in lower amounts in EO obtained by MHD. A particularly significant decrease was observed for the content of \(\alpha\)-pinene (from 4.26 to 2.33%), (\(E\))-\(\beta\)-ocimene (from 4.04 to 2.96%), \(\beta\)-pinene (from 1.77 to 1.14%), and \(\alpha\)-terpinene (from 1.12 to 0.72%). The yield of oxygenated monoterpenes was significantly lower in both samples, 1.90% in HD EO and 2.09% in MHD EO, with only four compounds from this chemical group detected, namely, (\(Z\))-sabinene hydrate, linalool, (\(E\))-\(p\)-mentha-2,8-dien-1-ol, and terpinen-4-ol. Of them, terpinen-4-ol (1.3-1.76%) was found in the highest amount. In Croatian sea fennel, non-oxygenated compounds dominated, accounting for about \begin{table}
\begin{tabular}{c l c c c c c c} \hline \hline
**No.** & **Component** & **Rt** & **LRI** & **Literature LRI** & **HD (\%)** & **MHD (\%)** & **Mode of Identification** \\ \hline
1. & a-thujene & 5.989 & 926 & 924 & 0.69 \(\pm\) 0.13 & 0.50 \(\pm\) 0.09 & GC, MS \\
2 & a-pinene & 6.195 & 932 & 932 & 4.26 \(\pm\) 0.84 & 2.33 \(\pm\) 0.44 & GC, MS \\
3. & camphene & 6.608 & 946 & 946 & tr & nd & GC, MS \\
4. & sabinene & 7.410 & 972 & 969 & 25.24 \(\pm\) 2.64 & 27.81 \(\pm\) 4.30 & GC, MS \\
5. & \(\beta\)-pinene & 7.986 & 991 & 974 & 1.77 \(\pm\) 0.43 & 1.14 \(\pm\) 0.26 & GC, MS \\
6. & a-terpinene & 8.897 & 1016 & 1014 & 1.12 \(\pm\) 0.05 & 0.72 \(\pm\) 0.09 & GC, MS \\
7. & \(p\)-cymene & 9.175 & 1023 & 1020 & 1.84 \(\pm\) 0.65 & 2.53 \(\pm\) 0.09 & GC, MS \\
8. & limonene & 9.337 & 1027 & 1024 & 51.38 \(\pm\) 4.42 & 53.05 \(\pm\) 5.20 & GC, MS \\
9. & (\(E\))-\(\beta\)-ocimene & 9.698 & 1037 & 1044 & 4.04 \(\pm\) 0.59 & 2.96 \(\pm\) 0.38 & GC, MS \\
10. & \(\gamma\)-terpinene & 10.506 & 1057 & 1054 & 7.12 \(\pm\) 0.73 & 6.54 \(\pm\) 0.43 & GC, MS \\
11. & (\(Z\))-sabinene hydrate & 10.820 & 1065 & 1065 & 0.14 \(\pm\) 0.13 & 0.41 \(\pm\) 0.06 & GC, MS \\
12. & terpinenlee & 11.689 & 1088 & 1086 & 0.38 \(\pm\) 0.08 & 0.15 \(\pm\) 0.03 & GC, MS \\
13. & linalool & 12.073 & 1097 & 1095 & nd & 0.38 \(\pm\) 0.06 & GC, MS \\
14. & (\(E\))-\(p\)-mentha-2,8-dien-1-ol & 13.024 & 1120 & - & tr & nd & GC, MS \\
15. & terpinen-4-ol & 15.438 & 1177 & 1174 & 1.76 \(\pm\) 0.04 & 1.30 \(\pm\) 0.31 & GC, MS \\ \hline \multicolumn{2}{l}{_Total identified (\%):_} & & & & _99.82_ & _99.74_ & \\ \hline \multicolumn{2}{l}{_Total non-oxygenated compounds_} & & & & _97.92_ & _97.73_ & \\ \multicolumn{2}{l}{_Total oxygenated compounds_} & & & & _1.90_ & _2.09_ & \\ \hline \hline \end{tabular}  
\(\mathrm{Rt}\)—Retention time, LRI—Linear Retention Index, tr—traces (<0.10%), nd—not detected.  
\end{table} 
Table 1: Chemical composition of sea fennel essential oils isolated by hydro-distillation (HD) and microwave-assisted hydro-distillation (MHD), analysed by gas chromatography coupled with mass spectrometry (GC-MS). 91% of the total EO compounds (for both hydrodistillation methods), thus no significant differences in oil profiles were expected due to this specific chemical profile.