Chemical composition, anti-inflammatory activity and cytotoxicity of Thymus zygis L. subsp. sylvestris (Hoffmanns. & Link) Cout. essential oil and its main compounds

Thymus L. is one of the most aromatic and medicinal plants used worldwide, mainly due to its essential oils. Several species of Thymus are currently used in herbal medicine for the prevention and treatment of various diseases, including disorders of the respiratory, gastrointestinal and nervous system. Moreover, they are widely used by their flavor as condiment and food preservatives, and a wide range of biological and therapeutic properties have been reported for this genus. The aim of the present research was to evaluate the anti-inflammatory activity of Thymus zygis L. subsp. sylvestris (Hoffmanns. & Link) Cout. oil and its major compounds and, of utmost importance, assess their safety profile in several mammalian cell types at concentrations presenting strong bioactivity. This oil is characterized by high percentage of two phenolic compounds (thymol 19.5% and carvacrol 16.3%) and their biochemical precursor ( p -cymene 22.0%). Interestingly, this is the first paper reporting high amounts of those phenols in the same sample of T. zygis subsp. sylvestris from Portugal. The anti-inflammatory potential was investigated in lipopolysaccharide (LPS)-triggered nitric oxide (NO) production by macrophages and microglia concomitantly treated with T. zygis subsp. sylvestris essential oil. Our results demonstrated a significant decrease of LPS-induced NO production at concentrations up to 0.32 and 0.16 μL/mL, respectively, without affecting cell viability. These results confirm the safety of T. zygis subsp. sylvestris oil and thus its suitability to be used as condiment and food preservative. Furthermore, the anti-inflammatory activity attributable to the essential oil supports further studies envisaging its putative use in pharmaceutical formulations for inhalation, topical application or oral administration.