Four lathyrane diterpenoids from the seeds of Euphorbia lathyris

Four new diterpenoids, including three secolathyrane diterpenoids (1–3) and one lathyrane diterpenoid (4), together with seven known diterpenoids, were obtained in the shelled seeds of Euphorbia lathyris. In particular, 1–3 possess a rare split ring structure, and currently only one compound with the same skeleton has been identified in E. lathyris. Compound 4 furnishes an unprecedented oxygen bridge structure. The structures were identified using various spectral techniques, including NMR, HR-ESI-MS, single-crystal X-ray diffraction and calculated electronic circular dichroism (ECD). The biosynthetic pathway of 1–4 was inferred. Furthermore, the cytotoxic activities of all compounds (1−11) were measured on three human tumor cells. New compounds 2 and 3 showed moderate cytotoxic activities against U937 cells with IC50 values of 22.18 and 25.41 μM, respectively.