Objective To investigate the chemical constituents from the inflorescences of Inula japonica and their in vitro anti-hepatocellular carcinoma activity. Methods The compounds were isolated and purified by multiple chromatographic techniques.. Their structures were identified by HRESIMS, NMR, IR, UV spectroscopic methods, and the absolute configurations of new compounds were determined by calculated NMR and ECD. The inhibitory effects of the compounds on the proliferation of HepG2 cells were evaluated by MTT assay and colony formation assay. Results Six sesquiterpenoid dimers were isolated from the ethyl acetate fraction of the 90% ethanol extract of I. japonica, among which compounds 1 (inujaponolide T) and 3 (inujaponolide U) were identified as new compounds. The bioactivity screening results showed that compounds 1—6exhibited potent cytotoxicity against HepG2 cells, with IC₅₀ values ranging from 2.61 to 13.94 μmol/L. Furthermore, compounds 1 and 3 inhibited the cell viability and reduced the colony formation of HepG2 cells in a dose-dependent manner. Conclusion Compounds 1 and 3 are new sesquiterpenoid dimers with anti-hepatocellular carcinoma activity, and may serve as potential antitumor lead compounds for further in-depth investigation.

Inula Thunb.  /  Inula japonica Thunb.  /  sesquiterpenoid dimers  /  inujaponolides T  /  inujaponolides U  /  anti-hepatocellular carcinoma activity