## 2 Results and Discussion
### C. erythraea Essential Oil Composition  
A total of 89 compounds were identified in the essential oil of _C. erythraea_ Rafn (Table 2). In comparison with the sole previous report on this oil from Serbia [10], the overall number of identified compounds seems moderate, but it should be emphasized that the previously published oil composition predominated (_ca._ 50%) with the compounds in traces (<0.05%). This research was focused on detailed determination of non-trace compounds of the oil including the results of the oil fractionation to non-polar and polar fractions. Total essential oil contained a low abundance of oxygenated monoterpenes, the major ones being menthol (7.0%), linalool (3.0%), borneol (1.4%) and methone (2.5%). Menthol and menthone were not found in Serbian oil (only traces of isomenthol were detected) as well as \(\beta\)-thujone (0.8%). Borneol (1.4%) and camphor (1.5%) were identified in Croatian oil, while only traces were reported in Serbian oil. Monoterpene phenols thymol (2.6%) and carvacrol (6.1%) were interesting features also reported among the major constituents in Serbian oil (thymol 7.9% and carvacrol 4.2%). Although these phenols were present in the oil, they were not identified in the headspace. On the contrary, their biosynthetic precursors \(\gamma\)-terpinene and _p_-cymene were found in the headspace, but not in the oil. Neophytadiene (10.1%) was major compound of Serbian oil, while in this research it amounted to 1.4%. Neophytadiene is presumably a chlorophyll metabolite [15]. Chlorophyll chlorin rings can be constructed from several different side chains, usually including the long diterpene alcohol phytol \begin{table}
\begin{tabular}{l l c c c c} \hline \hline
**No.** & **Compound** & **RI** & **RI** & **Peak area (\%)** \\
**87** & **Dihydroedulan II** & / & 1514 & 0.3 & - & - \\
**88** & **Dihydroedulan I** & / & 1544 & 0.5 & - & - \\
**89** & **Cuminal** & / & 1815 & 0.2 & - & 0.3 \\  & & Total identified (\%) & 89.4 & 94.1 & 91.1 \\ \hline \hline \end{tabular}  
* RI = retention indices on HP-5 MS and HP-FFAP columns; **C*
* = total essential oil; **D*
* = non-polar fraction of the oil; **E*
* = polar fraction of the oil; **- = compound not found; / = compound not identified on the column;
* - correct isomer not identified.  
\end{table} 
Table 2: _Cont._(found in the oil at 1.9%). Isophytol (0.3% in the oil) is a phytol isomer and isomerisation of isophytol to phytol in plant leaf waxes is reported [16]. Oxidation of the phytol moiety of chlorophyll could lead, among others, to the methylated long chain fatty acid ketone hexahydroxfanesyl acetone (6,10,14-trimethylpentadecan-2-one, phytone) that was found in the oil at 4.0%. The fourth major compound of Serbian oil was hexadecanoic acid (4.9%), while Croatian oil contained 5.7%, followed by linoleic acid (3.9%) and tetradecanoic acid (1.5%). High-molecular aliphatic hydrocarbons were present, particularly tricosane (6.8%). Their abundance was higher in comparison with Serbian oil. Sesquiterpenes were also found with minor percentages; the major ones were Caryophyllene oxide (0.9%) and \(\delta\)-cadinene (0.8%). As was expected, high-molecular compounds of the essential oil were not identified in the headspace due to low volatility. Silicagel microcolumn fractionation enabled a more detailed analysis by the oil separation into non-polar and polar compounds. As was expected from total oil composition, the fraction of non-polar compounds (Figure 1a) dominated by higher aliphatic hydrocarbons such as tricosane (25.7%), heneciosane (8.7%), nonadecane (4.6%) and others. However, the pentane fraction revealed the presence of low-molecular aliphatic hydrocarbons (overlapped in total oil), and nonane (8.6%) was the major one. In addition, alk-1-enes were only found in this fraction, including hexadec-1-ene (1.7%), octadec-1-ene (2.6%) and tetradec-1-ene (0.5%) as well as eicos-3-ene (2.3%). According to their chain length and positions of double bonds they are derived from corresponding fatty acids [17].