## 3 Discussion
romana_ M) extracted with DVB/CAR/PDMS fiber were bicyclogermacrene, _trans_-caryophyllene, _trans_-\(\beta\)-farnesene, limonene and alloaromadendrene, while bicyclogermacrene, \(\beta\)-pinene, isocaryophyllene, _trans_-\(\beta\)-farnesene, germacrene D and \(\gamma\)-terpinene were dominant after the extraction with PDMS/DVB fiber. A different composition of EO was reported for _S. romana_ from Italy, where carvacrol, limonene and 1,8-cineole were reported as the dominant compounds isolated by hydrodistillation [19], while neither carvacrol and 1,8-cineole nor thymol, oct-1-en-3-ol and borneol, reported as the dominant compounds isolated by hydrodistillation from _S. romana_ subsp. _romana_ from Turkey [18], were detected in our samples of _S. romana_ from Croatia. For _S. romana_ M, the dominant compounds extracted with DVB/CAR/PDMS were benzyl alcohol, viridiflorol, ledene and limonene, while with PDMS/DVB these were viridiflorol, \(\beta\)-pinene, bicyclogermacrene and \(\gamma\)-terpinene. These results are not in accordance with the previously mentioned studies of _S. romana_ from Italy and Turkey. For other subspecies of _S. romana_, such as _S. romana_ subsp. _purpurrea_ from Greece, bicyclogermacrene, \(\beta\)-caryophyllene (=_trans_-caryophyllene or isocaryophyllene), \(\gamma\)-muurolene, \(\beta\)-pinene, (_E_)-\(\beta\)-farnesene (=_trans_-\(\beta\)-farnesene) and spathulenol were found as the major components obtained by hydrodistillation [21], while for the same subspecies from Montenegro, the major EOs constituents obtained by steam distillation were \(\gamma\)-elemene and spathulenol [27]. Moreover, the most abundant EO components obtained by hydrodistillation from the same subspecies, which was also collected in Montenegro, included bicyclogermacrene, germacrene D, (_E_)-caryophyllene and spathulenol [20]. According to the PCA analysis, even though it was present with more than 1% only in one of the analyzed samples, spathulenol appeared to be one of the compounds distinctive for _S. romana_. However, it was not found in _S. romana_ M, which was observed to contain much lower amounts of bicyclogermacrene, which were detected only using PDMS/DVB fiber. However, spathulenol may be an artifact, having in mind that bicyclogermacrene is easily converted to spathulenol at room temperature [39]. The compound may also be formed during the process of hydrodistillation, as seen in the comparison of EO composition and VOCs composition of _S. scardia_ samples prepared by other techniques of isolation such as solvent extraction and supercritical carbon dioxide extraction [40]. On the other hand, distinctive VOCs of _S. romana_ M such as viridiflorol (detected in higher amount using PDMS/DVB fiber) and ledene (detected only using DVB/CAR/PDMS fiber) may be the result of bicyclogermacrene hydration and/or rearrangement [41; 42]. According to [PERSON] et al. [43], who studied the volatile fractions of _in natura_, fresh, and dried _Caseraria sylvestris_ var. sylvestris_ Sw. and var. _lingua_ (Cambess.) Eichler leaves, viridiflorol is an artifact most likely formed from bicyclogermacrene, whose content increases during the drying process. As it can be seen from Table 4, the distinct sample of _S. romana_ from Morinje Bay (_S. romana_ M) was collected prior to other samples of the same species and, therefore, may have been more susceptible to transformations during processing and storage of plant material, having in mind that all collected samples were analyzed simultaneously. The sample from Morinje Bay also contained more other compounds (non-terpenes), which were mostly oxygenated compounds (alcohols, aldehydes and a carboxylic acid), indicating its possible oxidative degradation. Other compounds that were present and/or were more abundant in _S. romana_ populations other than _S. romana_ M, such as alloaromadendrene and aromadendrene, may also have been formed by isomerization from bicyclogermacrene [44] and could have produced spathulenol by further oxidation [43].