New e:b-Friedo-Hopane Type Triterpenoids from Euphorbia peplus with Simiarendiol Possessing Significant Cytostatic Activity against HeLa Cells by Induction of Apoptosis and S/G2 Cell Cycle Arrest

Seven rare e:b-friedo-hopane-type triterpenoids including four new ( - ) and three known ( - ) ones with being first reported as a natural product, together with five other known triterpenoids ( - ), were isolated from the nonpolar fractions of the ethanolic extract of . Structural assignments for these compounds were based on spectroscopic analyses and quantum chemical computation method. The structural variations for the C-21 isopropyl group, including dehydrogenation ( and ) and hydroxylation at C-22 (simiarendiol, ), were the first cases among e:b-friedo-hopane-type triterpenoids. Simiarendiol ( ) bearing a 22-OH showed significant cytostatic activity against HeLa and A549 human tumor cell lines with IC values of 3.93 ± 0.10 and 7.90 ± 0.31 μM, respectively. The DAPI staining and flow cytometric analysis revealed that simiarendiol ( ) effectively induced cell apoptosis and arrested cell cycle at the S/G2 phases in a dose-dependent manner in HeLa cells.