Cytotoxic activity of Nepeta rtanjensis Diklić & Milojević essential oil and its mode of action

Nepeta rtanjensis Diklić & Milojević (fam. Lamiaceae) is an endemic, critically endangered plant, protectedby the law in Serbia. Various biological activities have been ascribed to its major constituents, nepeta-lactones. In this study we describe for the first time cytotoxic activity of N. rtanjensis essential oil (EO),obtained from field cultivated plants, which was found to be especially rich in trans,cis-nepetalactone.MTT assays indicated that after 72 h of treatment the EO exhibited cytotoxic activity on investigatedcancer cell lines: HeLa, K562, A549, LS-174 and MDA-MB-231. Normal cell line (MRC-5) was the leastsensitive to the treatment and IC50value for this cell line was not reached within the tested range ofEO concentrations (up to 0.1 [1]L/mL). Analysis of morphological changes of treated cells confirmed thehigher sensitivity of tumor cells than normal cells to the tested EO. Application of N. rtanjensis EO resultedin the appearance of morphological changes in tested cancer cell lines characteristic for apoptotic celldeath, and induced perturbations of the cell cycle of HeLa cells. In addition, upregulation of Bax and p53,and downregulation of Bcl-2, and Skp2 genes, involved in apoptotic signalling cascades, confirmed anapoptosis-inducing effect of N. rtanjensis EO on HeLa cells. Presented results highlighted the potential ofN. rtanjensis EO in anticancer therapy.