Bioactive sesquiterpenoids and sesquiterpenoid glucosides from the flowers of Inula japonica.

Three new sesquiterpenoids (1-3) and two new sesquiterpenoid glucosides (4 &5), along with 24 known analogues (6-29), were obtained from the flowers of Inula japonica. Structures of the new compounds were determined by interpretation of spectroscopic data, and their absolute configurations were established via comparison of experimental with computed ECD curves. All the isolates were tested in an in vitro cytotoxic assay against human A549, MCF-7 and MDA-MB-231 cancer cell lines, and selective ones displayed significant activity close to the positive control adriamycin. The new molecules 1-5 were also evaluated for their nitric oxide (NO) release inhibitory effect in murine macrophage RAW264.7 cells, with compound 1 showing comparable activity (IC 16.2 ± 0.8 μM) to the positive control dexamethasome. A preliminary mechanistic study of the effect of 8 toward A549 cells revealed that it could arrest cell cycle at G/M phase and induce cell apoptosis in a dose-dependent manner.