Daphnane-type diterpenoids from Euphorbia fischeriana Steud and their cytotoxic activities.

Two new daphnane-type diterpenoids fischerianin A (1) and fischerianin B (2), as well as two known ones langduin A (3) and langduin A6 (4), were isolated from the extracts of Euphorbia fischeriana Steud dry roots. Their structures including the absolute stereochemistry were determined by various spectroscopic methods and comparing their experimental and calculated CD spectra. 1 and 2 harbor a ketal group and a 9,13-oxide bridge in their C ring which is rare in daphnane-type diterpenoids. In cytotoxic assays, moderately inhibitory activities of 1-4 against human cancer cell lines (human malignant melanoma cell line, A375; human liver carcinoma cell line, HepG2; human promyelocytic leukemia cell line, HL-60; human Caucasian chronic myelogenous leukemia cell line, K562; human cervix epithelioid carcinoma cell line, HeLa) were observed, with IC50 values ranging from 5.31 to 21.46 μM.