Chemical composition, antimicrobial, antiradical and anticholinesterase activity of the essential oil of Pulicaria stephanocarpa from Soqotra

The chemical composition of the hydrodistilled leaf essential oil from Pulicaria stephanocarpa Balf. Fil was determined by GC-MS analysis, and its antimicrobial, antioxidant and anticholinesterase (AChE) activities were evaluated. Eighty-three compounds were identified representing 97.2% of the total oil. (E)-Caryophyllene 13.4%, (E)-nerolidol 8.5%, caryophyllene oxide 8.5%, alpha-cadinol 8.2% spathulenol 6.8% and tau-cadinol 4.7%, were the main components. Antimicrobial activity of the oil, evaluated using the disc diffusion and broth dilution methods, demonstrated the highest susceptibility on Gram-positive bacteria and Candida albicans. The free radical scavenging ability of the oil was assessed by the DPPH assay to show antiradical activity with IC50 of 330 microg/mL. Moreover, the oil revealed an AChE inhibitory activity of 47% at a concentration of 200 microg/mL using Ellman's method.