# Exploring the Biochemical Mechanism Beyond the Cytotoxic Activity of Sesquiterpene Lactones from Sicilian Accession of Laserpitium siler Subsp. siculum (Spreng.) Thell

## TL;DR

This study explores how new sesquiterpene lactones from a Sicilian plant kill breast cancer cells through oxidative stress and mitochondrial damage.

## Contribution

The study identifies novel sesquiterpene lactones from Laserpitium siler subsp. siculum and reveals their cytotoxic mechanism in triple-negative breast cancer cells.

## Key findings

- SL-1, a sesquiterpene lactone, showed the highest cytotoxicity against TNBC cells.
- SL-1 induced apoptosis via caspase-3 activation and PARP-1 cleavage.
- SL-1 caused mitochondrial dysfunction and oxidative stress in cancer cells.

## Abstract

Laserpitium siler subsp. siculum (Apiaceae) is a Mediterranean plant with a long history of traditional medicinal use. In this study, the chemical composition and anticancer potential of three novel (and one new to the genus) sesquiterpene lactones (SLs) isolated from its roots were investigated. The structural characterization, carried out through NMR and HPLC-MS analyses, identified unique guaianolide-type lactones. The biological activity of these compounds was evaluated in vitro using MDA-MB-231 cells, a triple-negative breast cancer (TNBC) cell line. Cell viability assays demonstrated that all SLs tested reduced TNBC cell viability in a dose- and time-dependent manner, with SL-1 exhibiting the highest cytotoxicity. Light microscopy analyses and acridine orange/ethidium bromide staining confirmed the induction of apoptotic cell death, further supported by Western blot analyses showing caspase-3 activation and PARP-1 cleavage. Additional experiments indicated that SL-1 induced oxidative stress, as evidenced by increased ROS production and upregulation of the levels of the antioxidant enzymes MnSOD and HO-1. Moreover, JC-1 staining and Western blot analyses revealed mitochondrial membrane depolarization as well as a significant reduction in VDAC-1 expression, suggesting mitochondrial dysfunction as a key event in the cytotoxic mechanism. These findings highlight L. siler subsp. siculum as a promising source of bioactive compounds with anticancer potential. The ability of its sesquiterpene lactones to induce oxidative stress and mitochondrial impairment provides new insights into their mode of action, supporting further research into their therapeutic applications for TNBC treatment.