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Four new polycyclic diterpenoids euphoranes A − D (1–4), together with 12 known terpenoids (5–16) were isolated from the whole plants of Euphorbia dracunculoides. Compound 2 represents the first example of aromatic 15,16,17-trinorabietane diterpenoid in Euphorbia species, and euphorane C (3) is an unusual 17-norabietane diterpenoid. The absolute configurations of 1, 2, and 4 were determined by single crystal X-ray diffraction, while that of 3 was established with the aid of ECD and 1D NMR quantum chemical calculation. Moreover, the absolute stereochemistry of 11 was demonstrated for the first time by crystallographic data. Compounds 1–16 were screened for antiproliferative activities against five human cancer cell lines, and 3 showed significant cytotoxicity against the human leukemia K562 cells with IC50 value of 3.59 μM. Preliminary mechanistic investigation revealed that 3 could induce cell cycle arrest at G0/G1 phase and apoptosis in K562 cells.

Six new tigliane diterpenoids, euphkanoids A − F (1–6), along with 12 known diterpenoids (7–18) were isolated from the roots of Euphorbia kansuensis, a traditional Chinese medicinal plant. Their structures were elucidated by spectroscopic analysis, ECD calculation and chemical methods. Compounds 1–3 represent the unusual examples of tigliane diterpenoids with a conjugated olefinic aldehyde moiety. 1–18 and two hydrolyzed analogues (1c and 4a) were screened for the inhibitory effects on nitric oxide (NO) production induced by lipopolysaccharide (LPS) in RAW264.7 cells. The results showed that 1–3 and 6 markedly inhibited NO production with IC50 values in the range of 4.8–11.3 μM, which were more active than the positive control quercetin (IC50 = 12.3 μM).