Essential Oils of Foeniculum vulgare subsp. piperitum and Their in Vitro Anti‐Arthritic Potential

Wild Foeniculum vulgare subsp. piperitum (C.Presl) Bég. flowers, fruits and leaves were extracted with steam distillation and obtained essential oils (EOs) were characterized using GC/MS. The study was designed to verify the potential effectiveness of fennel EOs in the treatment of inflammation and arthritis. Since tissue proteins denaturation is a major cause of arthritic diseases, fennel EOs and their main constituents were evaluated for their ability to inhibit the heat‐induced proteins degradation using bovine serum albumin as a protein model. Moreover, the in vitro inhibitory effects of the three EOs on the pro‐inflammatory mediator nitric oxide (NO) production were verified in LPS‐stimulated RAW 264.7 cells. Estragole (28.81–33.40 %), anethole (24.16–27.40 %), fenchone (9.76–18.48 %), α‐phellandrene (1.63–8.37 %) and limonene (5.54–6.05 %) were the major constituents. All the EOs showed a concentration‐dependent biological activity, being the flower EO the most effective in inhibiting NO production (IC50=232.2±11.3 μg/mL). The leaf EO showed a very good bovine serum albumin (BSA) anti‐denaturation activity (IC50=95.9±2.4 μg/mL). Moreover, four components were proved to be effective in protecting protein from heat‐induced degradation, being α‐phellandrene the most active compound (IC50=73.2±1.9 μg/mL).