Cytotoxic xanthanolide sesquiterpenes from the fruits of Xanthium italicum Moretti.

One previously undescribed xanthanolide sesquiterpene dimer pungiolide P (1), possessing an unprecedented scaffold with a 5/7/5/7/5 ring system skeleton and its intermediate pungiolide Q (2), ten xanthanolide sesquiterpenes (3-12), two eudesmene sesquiterpene derivatives (13-14), one phenylpropionic acid derivative (15), together with eleven known compounds (16-26) were obtained from the fruits of Xanthium italicum Moretti. A possible biosynthetic pathway for pungiolide P (1) was also proposed, which was supported by its bio-synthetic intermediate (2). Compounds 1, 4-5, 18-21, and 25 exhibited cytotoxic activity against a variety of human cancer cell lines. Furthermore, compounds 1, 4-5, could cause blockage of the cell cycle in the G2/M phase and induce apoptosis in H460 cells. Notably, pungiolide P (1) exhibited significantly superior cytotoxicity compared to previously reported compounds, providing valuable insights for natural anti-tumor sources.