4.2.2. Essential Oil Extraction

The oil extraction was obtained from 1 kg of fresh whole C. siliqua pods (with seeds) via hydrodistillation over 3 h using a Clevenger-type apparatus [85]. The essential oils from CSE and CSH were then diluted with 2 mL of n-hexane and filtered through anhydrous sodium sulfate to remove water traces. The resulting essential oils were stored at 4 °C. The oil content was estimated in mL/100 g (dry weight of the plant material).

GC–MS analysis of the isolated essential oils was performed on a Shimadzu GC-2030 Nexis gas chromatograph (Shimadzu Corporation, Kyoto, Japan) coupled with a Shimadzu GCMS-QP 2020 NX mass-selective Quadrupole Mass Spectrometer as detector with the appropriate data system. The GC was equipped with a Grob-type split-splitless injector; the fused silica capillary column (Mega-5 HT with 0.25 μm film thickness, 30 m × 0.25 mm i.d.) was directly coupled to the ion source. Helium was used as a carrier gas with a back pressure of 0.8 Atm. The injector temperature was 250 °C and the oven temperature program started at 50 °C for 5 min and then increased at a rate of 5 °C/min up to 150 °C, retained at this temperature for 10 min and increased again at a rate of 5 °C/min up to 280 °C, where it remained for 20 min. The scanning range was 30–700 m/z. A GS-MS detection electron ionization system was used with ionization energy of 70 eV.

The quantification of the components was based on the total number of fragments (total ion count) of the metabolites, as detected by the mass spectrometer. The identification of the chemical components was carried out based on the retention time of each component (Rt) compared with that of commercially available compounds by analyzing their mass spectra through the use of the NIST21, NIST107, and PMW_TOX2 mass spectra libraries [86] as well as through a comparison with the literature data [87]. A calculation of retention indices was performed in accordance with the work of Van den Dool and Kratz [88], in comparison to the retention times of standard hydrocarbons (C8–C40). When necessary, co-injection with standard compounds was also carried out.