Isolation, Characterization, and Antiproliferative Activities of Eudesmanolide Derivatives from the Flowers of Inula japonica.

Inula japonica belongs to the family Asteraceae, and its flowers have been used as dietary supplements and health tea in China. The study aimed to identify the bioactive components with the antiproliferative property. Ten 1,10-seco-eudesmanolide derivatives, including four new compounds (1-4), were isolated from the flowers of I. japonica. Their structures were established on the basis of the interpretation of spectroscopic data and electronic circular dichroism (ECD) calculations. All of these isolates were evaluated for their antiproliferative activities against MCF-7 and MDA-MB-231 human breast cancer cells. Compound 4 possessed the most potent effects, with the IC50 values of 0.20 ± 0.04 and 6.22 ± 1.30 μM against MCF-7 and MDA-MB-231 cells, respectively. The present investigation indicated that eudesmanolide derivatives from the flowers of I. japonica, especially compound 4, might be used as potential antitumor chemotherapy agent candidates.