# Halophyte _Artemisia caerulescens_ L.: Metabolites from In Vitro Shoots and Wild Plants
## 2 Results and Discussion
### Phytochemical Investigation  
#### 2.3.1 Headspace Analysis  
The complete composition of the headspaces (HSs) emitted by both the different parts of the wild plant (leaves, young inflorescences, and ripe infloresances) and the in vitro shoots of _A. caerulescens_ are reported in Table 3. A total of 35 compounds were identified, representing 97.3-100% of the whole volatile organic compounds (VOCs). All the volatile emissions were characterized by the predominance of oxygenated monoterpenes, which resulted significantly higher in the HS of the in vitro culture (91.6%), followed by the ripe flowers (89.1%) \(>\) leaves (87.0%) \(>\) young inflorescences (70.2%). Among this class of compounds, thujones were the main constituent; in particular, \(\alpha\)-thujone was revealed in remarkable percentages in all the samples, ranging from 45.4% in the young inflorescences and 83.2% in the in vitro shoots, whose HS was characterized by only ten compounds. \(\beta\)-thujone was detected in good percentages as well: it was higher in the samples which presented lower percentages of the \(\alpha\)-isomer. The HS of young inflorescences exhibited the highest amount of this compound (11.2%), while the in vitro shoots had the lowest (7.6%). Monoterpene hydrocarbons were well-represented in the wild plant samples, whilst they were revealed in very low percentages (0.7%) in the volatilome of the in vitro culture. The young inflorescence HS presented the highest amount of this chemical class (27.2%), followed by the HSs of both the ripe infloresences (9.8%) and leaves (9.3%). Sabinene was the main monoterrene hydrocarbon component detected in these samples as it accounted for 5.2% of content in the leaves and 16.1% and 6.5% in the young and ripe flowering tops, respectively. As well-evidenced in Table 3, the in vitro culture showed a less complex chemical composition of the volatile emission as compared to that of the different parts of the mother plant, probably due to a higher production of the oxygenated monoterenes \(\alpha\)- and \(\beta\)-thujones, representing the 83.2% and 7.6% of the whole aroma composition, respectively. The higher percentage of thujones in the in vitro shoots was probably attributable to a metabolism strongly directed to their production, as [PERSON] et al. [PERSON] et al. (2019) reported a strong genetic regulation of the biosynthetic pathways involved in the volatile formation. To the best of our knowledge, this is the first study on the chemical composition of the spontaneous volatile emission of _A. caerulescens_, although the compositions of the HSs of other _Artemisia_ species have already been reported [PERSON] et al. (2019). The main VOCs identified in the analysed samples were aligned with _Artemisia umbelliformis_ subsp. _eriantha_, whose main compound was also \(\alpha\)-thujone, although it is usually present in lower amounts than the \(\beta\)-isomer [PERSON] et al. (2019). Conversely, the volatile profile of the analysed samples was very different from that of the _Artemisia argyi_ [PERSON]. studied by [PERSON] et al., who reported germacrene D (28.73%), \(\alpha\)-pinene (16.44%), limonene (12.22%), cyclofenchene (6.46%), and \(\alpha\)-phellandrene (4.06%) as the main components [PERSON] et al. (2019), and differing from that of _Artemisia spicigera_ [PERSON] [PERSON] and _Artemisia scoparia_ [PERSON]. et [PERSON], as reported by [PERSON] et al., characterized mainly by camphor (37.5%) and \(\beta\)-pinene (20.8%), respectively [PERSON] et al. (2019). Moreover, camphor, was also reported as a major component of _A. campestris_ L. (31.78%), which was also rich in 1,8-cineole (23.11%) and \(\alpha\)-thujone (16.82%) [PERSON] et al. (2019). The data of the volatile composition of the plant headspace (HSs) was subjected to multivariate statistical analysis with the use of the Hierarchical Cluster Analysis (HCA) and the Principal Component Analysis (PCA) methods. The dendrogram of the HCA, reported in Figure 2, showed two macro-clusters: the pink and green ones.