Anti-inflammatory and antibacterial evaluation of Thymus sipyleus Boiss. subsp. sipyleus var. sipyleus essential oil against rhinosinusitis pathogens.

Thymus sipyleus Boiss. subsp. sipyleus var. sipyleus of the Lamiaceae, locally known as thyme scented lemon, which is an endemic taxon collected from Sivas in Anatolia, was investigated in this study due to its folk medicine use against rhinosinusitis. The aromatic characteristics of the plant material gave the idea for the detailed evaluation of the volatiles and essential oil thereof. Consequently, the oil was obtained by Clevenger type hydrodistillation followed by gas chromatography-flame ionization detector (GC-FID) and gas chromatography/mass spectrometry (GC/MS) analyses for phytochemical characterization. To confirm the folk medicinal use against sinusitis, in vitro antimicrobial activities of the essential oil was evaluated by agar diffusion, microdilution and vapour diffusion methods against selected rhinosinusitis associated strains such as Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), S. epidermidis, Streptococcus pyogenes, S. pneumoniae, Pseudomonas aeruginosa, Haemophilus influenzae and Moraxella catarrhalis. Additionally, the in vitro anti-inflammatory activity was evaluated by 5-lipoxygenase (5-LOX) inhibitory effect of the essential oil spectrophotometrically. Furthermore, the composition of the volatiles of the vapour phase of the oil was determined by headspace-solid phase microextraction (HS-SPME-GC/MS) after 15 min and 24 h in accordance with antimicrobial vapour diffusion method conditions, respectively. According to the analytical results, the main component was determined as thymol (66.2%). Whereas in the HS-SPME method p-cymene (26.1%) and γ-terpinene (26%) were identified as the main volatile components within the 15. min., and thymol (75.3%) after 24 h, respectively. The antibacterial activity against rhinosinusitis pathogens varied between 160 and 1250 μg/mL minimum inhibitory concentrations, with the best inhibitory effects observed against the S. aureus, S. pyogenes and M. catarrhalis. The anti-inflammatory activity of the oil was determined as 12.1 ± 1.8% in 100 μg/mL. The results showed the in vitro antimicrobial and anti-inflammatory potential of the oil also in vapour phase against sinusitis supporting the traditional use.