Verbascum nigrum: Cytotoxicity Evaluation in A431 Epidermoid Carcinoma Cells and Untargeted LC-HR-MS/MS Metabolite Profiling.

The crude methanolic extract obtained from Verbascum nigrum aerial parts (VNE) and its six fractions (VNF1-VNF6) were initially screened regarding their effects on the viability of immortalized HaCaT keratinocytes and A431 epidermoid carcinoma cells (MTT assay, 24 h). None of the tested samples affected the viability of HaCaT cells in a concentration range of 25-150 µg/mL. VNE and VNF4 exhibited significant cytotoxic effects in A431 cells, with IC50 values of 81.92 and 12.27 µg/mL, respectively; the selectivity index was higher than 10 for VNF4. The untargeted LC/HR-MS/MS metabolite profiling led to the tentative annotation of a total number of 23 compounds. Of these, VNE comprised mainly iridoid glycosides (harpagoside, laterioside, acylated aucubin derivatives), whereas VNF4 showed a high abundance of triterpene saponin glycosides (ilwensisaponins A and C, songarosaponins A and B), constituents known for their selective cytotoxic potential.