Five novel triterpenoid saponins from Hovenia dulcis and their Nrf2 inhibitory activities

Five novel triterpenoid saponins, hovenidulciosides C−G (1–5), and one known saponin hovenidulcioside A1 (6) were isolated from the seeds of Hovenia dulcis Thunb. The structures of 1–5 were determined through spectroscopic methods such as HR-ESI-MS, 2D-NMR (1H–1H COSY, HSQC, HMBC, ROESY and TOCSY), UV and IR and chemical methods. There were amino acetylated substituent in the sugar resident of hovenidulciosides F−G, which were firstly reported from this genus. Compound 1 supressed ARE-luciferase activity in MDA-MB-231 cells and inhibited the Nrf2 protein levels in A549 cells.