Diterpenoids from the roots of Euphorbia ebracteolata and their inhibitory effects on human carboxylesterase 2.

A chemical investigation of the roots of Euphorbia ebracteolata identified eighteen diterpenoids and glycosides. On the basis of spectroscopic data, they were determined to be ent-kauranes, ent-atisanes, tigliane derivatives, ingenane, and ent-abietanes, among which were eleven previously undescribed diterpenoids. The inhibitory effects of the isolated compounds against human carboxylesterase 2 (hCE-2) were evaluated in vitro, which revealed moderate inhibitory effects with IC50 values < 50 µM. Next, the inhibitory kinetics were evaluated for the putative hCE-2 inhibitor 4ß,9α,16,20-tetrahydroxy-14(13 → 12)-abeo-12αH-1,6-tigliadiene-3,13-dione (IC50 3.88 µM), and results indicated competitive inhibition with Ki 4.94 µM. Additionally, none of the diterpenoids showed cytotoxic effects against five human tumor cell lines as determined by MTT assays.