Structurally intriguing diterpenoids from Euphorbia wallichii Hook. f. with potential antioxidant activity.

Chemical investigation of Euphorbia wallichii Hook. f. led to the isolation of four undescribed rearranged diterpenoids, euphwanoids I-IV (1-4), and six unreported tigliane diterpenoids walliglianes A-F (5-10). Euphwanoids I-III (1-3) possess a rare 6/6/7/3 ring scaffold, euphwanoid IV (4) is the first spiro[tricyclo[5.4.0.02,4]undecane-8,1'-cyclopentane] skeleton to be found in the tigliane family. The structures of compounds 1-10 were established by utilizing spectroscopic data analysis, experimental electronic circular dichroism measurements, 13C NMR calculations, and single-crystal X-ray diffraction. In the preliminary bioassay, compounds 3, 4, and 7 were found to protect BV-2 cells against H2O2-induced cell injury in a dose-dependent manner by the CCK8 assay.