The volatile compounds in AG essential oil samples (seeds, flowers, leaves and stems) were extracted by HS-SPME, followed by desorption and analysis with GC-MS. The volatile compounds in AG oil samples were also extracted by using HD method. The extracted compounds are tabulated in Table 1. Figs. S1-4 (a&b), showed the GC chromatograms of AG essential oils of seeds, flowers, leaves and stems extracted by HS-SPME and HD methods. The typical total ion chromatograms (TIC) of the seeds, flowers, leaves, and stems essential oils obtained by HS-SPME and HD were shown in Fig. 1 and indicated the differences in the volatiles composition between the two methods. The chemical analysis results obtained by HD and HS-SPME methods from AG seeds, flowers, leaves and stems are presented in Table 1 (were present in amount more than 0.05%) in which compounds are listed in order of their elution on the column HP-5 MS. Retention indices (RI) calculated by GC capillary columns and obtained from literature were also listed in the tables.
In the AG essential oil of seed, forty volatile compounds were identified by HS-SPME method (Table 1 & Fig. S1a): monoterpenes (65.1%) and miscellaneous classes (33.8%). The most abundant compounds were dill apiole (33.3%), limonene (30.8%), carvone (17.7%), trans-dihydrocarvone (12.2%) and cis-dihydrocarvone (3.0%). The minor compounds were verbenene (0.4%), p-cymenene (0.2%), dihydrocarveol (0.2%), myristicine (0.2%) and elemicin (0.2%). The HS-SPME analysis of AG essential oil of seeds led to identifying five major and five minor volatile components accounting for about 98.2% of the total identified components. HD analysis of AG seeds oil led to identification of twenty-five components accounting for 99.6% of the total GC peak area. The main components from the seeds oil were carvone (30.8%), limonene (25.4%), dill apiole (20.9%) and trans-dihydrocarvone (15.4%). The minor compounds were α-phellandrene (0.5%), dihydrocarveol isomer II (0.5%), p-cymenene (0.2%), dihydrocarveol isomer I (0.2%), carveol (0.2%) and myristicine (0.2%), Table 1 & Fig. S1b. The dominant compounds in the AG essential oil of the seeds in both extraction methods were dill apiole, limonene, carvone, trans-dihydrocarvone, whereas carvone, limonene and camphor were reported earlier as the major constituents isolated from AG essential oil seed by using column chromatography (CC) and identified by NMR and GC-MS analysis1.
Moreover, the headspace oil extract of the flowers was rich in regard to oxygenated monoterpenes and monoterpene hydrocarbons (24.2% and 12.3%, respectively), whereas the hydrodistilled oil extract contained mainly monoterpene hydrocarbons (59.7%) and oxygenated monoterpenes (11.8%). dill apiole (46.9%), carvone (22.6%), dill ether (8.5%), cis-dihydrocarvone (3.1%), limonene (3.0%), α-Phellandrene (2.9%), trans-dihydrocarvone (1.4%), myristicine (1.3%), and sedanolide (1.2%) were reported as the main compounds among the sixty constituents identified in the HS-SPME extract, representing 96.6% of the total components detected. The minor compounds in the AG essential oil flowers extract by using HS-SPME method were p-cymenene (0.6%), camphor (0.5%), neo-phytadiene (0.5%) neo-iso-dihydrocarveol (0.4%), 2-nonanone (0.3%), α- pinene (0.2%), iso-dihydrocarveol (0.2%), (E)-anethol (0.2%) and (E)-ethyl cinnamate (0.2%) as shown in Table 1 & Fig. S2a.
From the other hand, in the flowers of AG essential oil, thirty-seven components were identified, representing 99.1% by HD method. The major components in the hydrodistilled oil from the flowers were α-phellandrene (34.6%), dill apiole (20.0%), limonene (14.7%), carvone (11.3%), dill ether (5.7%), β-phellandrene (4.2%), p-cymenene (1.5%), α- pinene (1.4%), trans-dihydrocarvone (1.4%) and myristicine (1.4%) (Table 1 & Fig. S2b). Both AG extraction methods for flowers oil revealed to the dominant compounds were dill apiole, carvone, dill ether, limonene, trans-dihydrocarvone and myristicine.
As indicated in Table 1 & Fig. S3a, sixty-six components representing 83.1% of the total content were identified in the AG essential oil leaves by HS-SPME method included 40.9% monoterpenes and 10.2% sesquiterpenes. Sixteen of them were found over 1.0% peak area, while rest of constituents were in concentrations less than 1.0% peak area, Fig. 1. The major constituents of the leaves of AG essential oil by using HS-SPME extraction method were as follows; dill apiole (16.0%), carvone (14.1%), dill ether (7.3%), α-phellandrene (6.1%), neo-phytadiene (6.1%), limonene (4.9%), camphor (3.7%), cis-dihydrocarvone (2.7%), E-anethol (2.1%), β-phellandrene (1.4%), p-Cymene (1.2%), E-ethyl cinnamate (1.2%), dimethyltetrahydrobenzofuranone (1.0%), linalool (1.0%) and bornyl acetate (1.0%). The minor compounds which were found in the range of 0.2–0.9 % peak area by HS-SPME method and represented about 10.4% were; E-β-caryophyllene (0.9%), myristicin (0.9%), cis-davanone (0.9%), 2-nonanone (0.8%), trans-dihydrocarvone (0.7%), E-nerolidol (0.7%), carvacrol (0.6%), cis-sabinene hydrate (0.5%), α-pinene (0.4%), Z-ethyl cinnamate (0.4%), myrcene (0.3%), γ-terpinene (0.3%), E-β-farnesene (0.3%), germacrene D (0.3%), β-selinene (0.3%), elemicin (0.3%), α-thujene (0.2%), α-terpinene (0.2%), artemisia ketone (0.2%), terpinolene (0.2%), cumin aldehyde (0.2%), fenchyl acetate (0.2%), carvotanacetone (0.2%), E-methyl cinnamate (0.2%) and δ-cadinene (0.2%).
In contrast, hydrodistillation analysis of the leaves essential oil of AG led to the identification of thirty-nine components accounting for 97.5% of the total GC peak area, as indicated in Table 1 & Fig. S3b. Monoterpene as major class of the oil were extracted by HD extraction method by 82.5% with constituents like α-phellandrene (61.4%), dill ether (9.2%), β-phellandrene (8.0%), limonene (4.7%), p-cymene (2.9%), α-Pinene (2.5%), dill apiole (2.6%) and E-anethol (2.3%). minor constituents were in the range of 0.2–0.9 % peak area with myrcene (0.8%), α-thujene (0.4%), carvone (0.4%), germacrene D (0.3%), sabinene (0.2%), β-pinene (0.2%) and terpinolene (0.2%).
Furthermore, forty-eight and thirty-three components were extracted from the stem of AG essential oils by HS-SPME and HD method, respectively (Table 1 & Figs. S4a,b). α-Phellandrene, limonene, dill ether and dill apiole were the major compounds of stem oils; their percentages were 1.1%, 6.3%, 4.1% and 31.9% in HS-SPME and 58.9%, 4.5%, 10.3% and 1.5% in HD, respectively (Fig. 1). Whereas, myristicine (0.9%), carvacrol (0.7%), sedanolide (0.7%), p-cymene (0.6%), camphor (0.6%), neo-iso-dihydrocarveol (0.5%), 2-undecanone (0.5%), ethyl palmitate (0.5%), artemisia ketone (0.4%), E-nerolidol (0.4%), 5-methyl-3-heptanone (0.3%), linalool (0.3%), iso-dihydrocarveol (0.3%) and E-β-caryophyllene (0.3%), were the minor constituents found in the range of 0.3–0.9 % peak area by HS-SPME method, while α-thujene (0.4%) was the only compound which found in this range by HD extraction method. Structures of major constituents present in the essential oils of AG seeds, flower, leaves and stems are illustrated Fig. 2.