Chemical Composition and Antioxidant Activity of Essential Oils and Hexane Extract of Onopordum arenarium from Tunisia.

In the present study, volatile oils from Onopordum arenarium fresh flowers and stems were obtained by hydrodistillation and the non-polar aerial part hexane extract was prepared using a Soxhlet apparatus. The constituents of different organs were identified for the first time by gas chromatography equipped with flame ionization detector and gas chromatography coupled to mass spectrometry. A total of 29 and 25 compounds were identified constituting over 91.6 and 89.2% of the whole constituents from flower and stem volatile oils, respectively. Both organs were constituted mainly of long-chain hydrocarbons (23.3-36.4%) followed by oxygenated long-chain hydrocarbons (31.5-33.8%) and oxygenated monoterpenes (14.4-6.6%). The major identified compound was palmitic acid [25.5% in O. arenarium flower essential oil (EO) and 28.7% in the stem EO]. Eighteen compounds representing 80.7% of the whole constituents were identified in the n-hexane extract, which was characterized by high amounts of triterpenoids (39.6%) and dominated by lupeol acetate (19.2%) and β-amyrin acetate (10.1%). Moreover, all extracts were evaluated for antioxidant potential using 1,1-diphenyl-2-picrylhydrazyl radical assay. The obtained results demonstrated that the EOs and the hexane extract could be a new source of natural potentially bioactive molecules.