Eudesmane-guaiane sesquiterpenoid dimers from Aucklandia costus trigger paraptosis-like cell death via ROS accumulation and MAPK hyperactivation

Three novel sesquiterpenoid heterodimers, designated as auckcostusolides A–C (1–3), were isolated from Aucklandia costus leaves. The structures of compounds 1–3 were elucidated through comprehensive spectroscopic analysis, with their absolute configurations established using a combination of X-ray single-crystal diffraction and electronic circular dichroism (ECD) calculations. Notably, compounds 1 and 2, despite sharing identical planar structures derived from two identical sesquiterpenoids, exhibited opposite configurations at C-11 and C-8′. This configurational difference can be attributed to distinct Diels−Alder cycloaddition processes between the sesquiterpenoid monomers. Additionally, the cytotoxic effects of compounds 1–3 were evaluated against colorectal cancer HCT116 cells, fibrosarcoma HT1080 cells, and hepatocellular carcinoma HepG2 cells. Compounds 1–3 induced cell death was characterized by endoplasmic reticulum (ER) swelling and cytoplasmic vacuolization, typical morphological changes associated with paraptosis. Mechanistic studies revealed that compounds 1 and 3 triggered paraptosis-like cell death through the accumulation of reactive oxygen species (ROS), activation of ER stress, and stimulation of the MAPK signaling pathway.