Isolation, Structure Elucidition, and Immunosuppressive Activity of Diterpenoids from Ligularia fischeri

Six new ( 1 – 3 and 6 – 8 ) and seven known diterpenoids were isolated from the whole plant of Ligularia fischeri . Compound 1 is a new 15,16-dinorerythroxylane-type diterpenoid possessing a C 18 skeleton, and 2 is the first example of a 6/6/6/6/5/5-fused hexacyclic ent -kaurane diterpenoid with 19,20-olide and 11,16-epoxy moieties. The structures of the new compounds were elucidated by spectroscopic analysis and chemical methods. The absolute configurations of 1 and 7 were determined by single-crystal X-ray diffraction. Compounds 1 – 13 were evaluated for their immunosuppressive activity, and 4, 7, and 13 showed moderate inhibitory activities against human B lymphoblast HMy2.CIR cells with IC 50 values of 56.3 ± 2.2, 13.3 ± 0.8, and 31.4 ± 0.9 μM, respectively.