Sesquiterpenes from Carpesium faberi triggered ROS-induced apoptosis and protective autophagy in hepatocellular carcinoma cells

Ten previously undescribed sesquiterpenes, carpespenes A–J (1–10), and eight known compounds (11–18), were isolated from the whole plants of Carpesium faberi. Their structures were established by extensive analysis of HRESIMS, NMR, and ECD spectra. Carpespene A (1) is eudesmanolide-type sesquiterpene lactone with an open five membered ring involving C-2 and C-3. Furthermore, compound 1 showed significant cytotoxic effects against four cancer cell lines with IC50 values from 8.20 to 18.45 μM, compared with the positive controls cisplatin and doxorubicin. Mechanistically, compound 1 induced apoptosis in the HepG2 cells by triggering excessive ROS accumulation. The latter however induced cytoprotective autophagy, which impaired the cytotoxicity of compound 1. Simultaneous antophagy inhibition with compound 1 treatment augmented the cytotoxic effects of the latter on HepG2 cells. Our findings further establish the structural diversity and bioactivity of sesquiterpenes, and provide an experimental basis for targeting cytoprotective autophagy as a potential chemotherapeutic strategy.