Two new ent-atisanes from the root of Euphorbia fischeriana Steud.

Two new ent-atisanes ent-1β,3β,16β,17-tetrahydroxyatisane (1), ent-1β,3α,16β,17-tetrahydroxyatisane (2) together with 11 known diterpenes were isolated from the anti-tumour activity fraction of Euphorbia fischeriana Steud. The compounds were identified by detailed spectroscopic analysis, including extensive 2D-NMR experiments. X-ray analysis was applied to determine the structure of compound 2. All 13 compounds were screened for cytotoxicity in vitro against human tumour MCF-7, HepG-2 and SGC-7901 cell lines. Compounds 1 and 2 showed the inhibitory effects against MCF-7 with IC₅₀ levels of 23.21 and 15.42 μM; simultaneously, compounds 4, 6, 8 and 11 also had definite inhibitory effect against different cell lines.