Comparative chemical analysis of volatile compounds ofEchinops ilicifoliususing hydrodistillation and headspace solid-phase microextraction and the antibacterial activities of its essential oil

The volatile compounds from various parts ofEchinops ilicifolius(Compositae) such as flowers, leaves and roots obtained by hydrodistillation (HD) and headspace solid-phase microextraction (HS-SPME) methods were subsequently analysed by GC and GC/MS and compared. Thirty-seven and 20 components of the flower ofE. ilicifoliuswere characterized, representing 99.7% and 100.0% of the total compositions using the HD and HS-SPME methods, respectively. The major constituents of the hydrodistilled oil were identified as linalool (58.6%), geraniol (17.4%),n-dodecane (10.9%) and nerol (5.4%), whereas HS-SPME extract was rich inn-octane (34.0%),n-decane (25.1%),p-cymene (11.1%),γ-terpinene (5.3%) and 1,8-cineole (5.1%).n-Hexadecanoic acid (32.3%), linalool (16.4%) and geraniol (8.3%) were the main components among 43 constituents identified in hydrodistilled extract of the leaf, representing 99.5% of the total components detected, whereas 16 compounds representing 99.9% of the HS-SPME method were identified, among whichn-decane (32.6%),p-cymene (14.0%),n-octane (10.3%), limonene (9.2%),γ-terpinene (9.1%), 1,8-cineole (7.9%) andα-pinene (5.9%) were the major ones. Among 23 components comprising 91.2% of the total hydrodistilled oil detected,n-decane (23.1%),n-dodecane (14.5%), silphiperfol-4,7(14)-diene (11.1%), selin-11-en-4-a-ol (9.5%),n-hexadecanoic acid (7.8%) andn-tetradecane (5.3%) were the main constituents in the root ofE. ilicifolius, whereas 1,8-cineole (29.0%),n-decane (12.6%),n-octane (12.6%), camphor (12.0%),p-cymene (9.6%) andγ-terpinene (5.9%) were the main components among the 20 constituents characterized in HS-SPME extract, representing 99.9% of the total components detected. The antibacterial activity of the flower, leaf and root oils ofE. ilicifoliusagainst six Gram-positive and Gram-negative bacteria was determined using the MIC method. The growth inhibitory zone (mm) was also measured.