GC, GC–MS, and NMR spectroscopy integrated analyses and in vitro antibacterial, anticholinesterase, anti-tyrosinase, and anti-5-lipoxygenase potential of Inula viscosa root fractionated essential oil

The aim of this study was to characterize the chemical composition of the roots essential oil from Inula viscosa (L.) through its fractionation during extraction, and to evaluate the antibacterial, anticholinesterase, anti-tyrosinase and anti-5-lipoxygenase activities of the isolated oil (REO) and its fractions (R1–R10). The REO and its fractions (R1–R10) were isolated by hydrodistillation of the fresh roots in a Clevenger type apparatus. Fifty-three constitu- ents were identified by GC-FID and GC–MS analyses. The REO was characterized by a high proportion of oxygen- ated monoterpenes (50.5%), followed by oxygenated sesquiterpenes (37.5%) and sesquiterpene hydrocarbons (7.6%). The major constituents of the REO and all the fractions were (Z)-neryl isovalerate (17.5–29.8%), 1,10- di-epi-cubenol (19.1–27.2%) and 2,5-dimethoxy-p-cymene (5.9–17.7%). The antibacterial activity of REO and its fractions (R1–R10) was tested by using the micro dilution methods against two Gram-positive and four Gram-negative bacteria. The REO and its fractions (R1–R10) showed a strong inhibition of Enterococcus faecalis (MIC = 20.0 μg/mL) and Staphylococcus aureus (MIC = 20.0 μg/mL). Results showed that the fraction R8 exerted the highest anti-tyrosinase activity, with 88.4% of inhibition at 50 μg/mL, and R1 exhibited a significant 5- lipoxygenase inhibitory effect (IC50 = 21.15 ± 0.12 μg/mL).