New Sesquiterpene Coumarin From the Gum of <i>Ferula kokanica</i>

Ferula is a genus of flowering plants known for its edible and medicinal properties. The gum of the Ferula kokanica was selected for this study based on its traditional uses. From the gum of F. kokanica, an undescribed sesquiterpene coumarin was isolated, named kokanin A, along with 22 known compounds. Structure elucidation of the isolated compounds was carried out by one- and two-dimensional nuclear magnetic resonance and high-resolution-electrospray ionization-mass spectrometry data analysis. Using NOE correlation, the relative configurations of the isolated compounds were established. The absolute configurations of isolates were established by electronic circular dichroism calculation. Cytotoxicity and anti-vitiligo activity of the isolated compounds were tested. Gummosin demonstrated strong cytotoxicity against the HT-29 cell line with IC₅₀ values of 6.96 ± 0.38 µM. Colladonin, farnesiferol A, and feshurin provided greater relative melanin content than that of the positive control at 50 µM. The elemental composition of the gum of F. kokanica using the inductively coupled plasma mass spectrometry method allowed the determination of trace levels of As, Cd, Cu, Hg, Pb, Na, Mg, K, and Ca. The toxic elements were determined in the sample, and their content was found to be lower than the maximum acceptable concentration established by the World Health Organization. This study showed that some isolated compounds demonstrated significant anti-vitiligo activity and showed promise for future drug discovery. To our knowledge, this is the first report on the chemical composition and the bioactivities of the gum of F. kokanica.