Chemical Composition and Antibacterial Activity of Essential Oils from Ferula L. Species against Methicillin-Resistant Staphylococcus aureus

Essential oils (EOs) were obtained by hydrodistillation of various parts of Ferula ovina (Boiss.) Boiss., Ferula iliensis Krasn. ex. Korovin, and Ferula akitschkensis B. Fedtsch. ex Koso-Pol., collected in the flowering/budding and fruiting stages. Eight samples of EOs isolated from F. ovina and four samples from F. akitsckensis were analyzed by gas chromatography-mass spectrometry (GC-MS). The major constituents of F. ovina EOs were alpha-pinene (6.9-47.8%), beta-pinene (1.5-7.1%), sabinene (0.1-20.5%), beta-phellandrene (0-6.5%), trans-verbenol (0.9-7.4%), eremophilene (3.1-12%), and 6Z-2,5,5,10-tetramethyl-undeca-2,6,9-trien-8-one (0-13.7%). The major constituents of F. akitsckensis EOs were alpha-pinene (0-46.2%), beta-pinene (0-47.9%), sabinene (0-28.3%), eremophilene (0-10.6), beta-caryophyllene (0-7.5%), himachalen-7-ol (0-28.2%), and an himachalol derivative (0-8.3%). Samples of EOs from F. ovina, F. iliensis, and F. akitsckensis were evaluated for antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) pulse-field gel electrophoresis type USA300 (LAC). EOs from F. ovina exhibited the highest antibacterial activity compared to samples from other Ferula spp., with the most potent EOs being isolated from roots at the flowering and fruiting stages and stems at the fruiting stage (IC50 values of 19.1, 20.9, and 22.9 mu g/mL, respectively). Although EOs demonstrated concentration-dependent inhibition of MRSA growth, analysis of the major constituents (alpha-pinene, beta-pinene, and sabinene) showed that they had low activity, suggesting that other components were likely responsible for the observed bioactivity of the unfractionated EOs. Indeed, correlation of the GC-MS data with antibacterial activity suggested that the putative components responsible for antibacterial activity were, either individually or in combination, eremophilene and trans-verbenol. Overall, these results suggest that the EOs from F. ovina could have potential for use as alternative remedies for the treatment of infectious diseases caused by MRSA.