Cytotoxic tigliane diterpenoids from Euphorbia neorubella

Two new tigliane diterpenes, named eupneonoids A (1) and B (2), together with four known analogues (3–6) were isolated from the whole plant of Euphorbia neorubella Bruyns. Their structures were deduced based on the detailed spectroscopic analysis. All the isolates displayed cytotoxic effects against A549 human tumor cell lines with IC₅₀ values ranging from 1.318 to 7.042 μM.