Sesquiterpene Monomers and Dimers From the Flower of Inula japonica Thunb. With Selective Antiproliferation Against Breast Cancer Cells.

A total of 34 sesquiterpene derivates were obtained from the flower of Inula japonica Thunb. Compounds 2, 14-34 were identified as sesquiterpene monomers, whereas the other 12 isolates (1, 3-13) were characterized as sesquiterpene dimers. Among them, japonicone Z (1), a present undescribed sesquiterpene dimer, and another undescribed monomer, japonicol A (2), were discovered.