Oxygen heterocyclic Diels-Alder-Type sesquiterpenoid dimers from Vernonia anthelmintica

Eleven undescribed oxygen heterocyclic Diels-Alder-Type sesquiterpenoid dimers, vernodalidimer I–K and M-T, along with a known one, vernodalidimer B were isolated from the seeds of Vernonia anthelmintica . The structures of them were elucidated based on 1D, 2D-NMR experiments and HRESIMS. The absolute configurations of vernodalidimer I–K and M-T were determined by comparison of their experimental and calculated electronic circular dichroism spectra. Cytotoxicity of the isolates against HCT-15, PC-3, A549, and HeLa cell lines were tested. Vernodalidimer K and Q exhibited significant cytotoxic activity against HCT-15 cell line with IC 50 values of 9.8 ± 5.4 μM and 9.4 ± 1.3 μM, respectively. • Eleven undescribed sesquiterpenoid dimers were obtained from V. anthelmintica. • Structures were determined by extensive spectroscopic analyses. • Cytotoxicity of the isolates against HCT-15, PC-3, A549, and Hela cell lines were tested. • Vernodalidimer K and Q showed significant cytotoxic activity against HCT-15 cell line.