Cytotoxic polycyclic polyprenylated acylphloroglucinols from Hypericum attenuatum.

Six new polycyclic polyprenylated acylphloroglucinols, attenuatumiones A-F (1-6), together with twelve known analogs (7-18) were isolated from the whole plant of Hypericum attenuatum. Their structures were elucidated by spectroscopic methods, and the absolute configuration of C-13 in attenuatumione C (3) was deduced via the circular dichroism datum of the in situ formed [Rh2(OCOCF3)4] complexes. All isolates were evaluated for the cytotoxic activities on three human cancer cell lines. Compound 3 showed moderate cytotoxic activities with IC50 values of 10.12 and 10.56 μM against SMMC7721 and U2OS, respectively.