A new alkaloid with cytotoxic activity from Fritillaria thunbergii Miq

A new alkaloid named zhebeisine (1), together with four known compounds, eduardine (2), zhebeirine (3), isoverticine (4), and verticine (5), was isolated from the bulbs of Fritillaria thunbergii Miq. The structure of the new compound was elucidated on the basis of extensive spectroscopic methods and the in vitro biological activities of it were evaluated as well. Compound 1 features a veratramine skeleton with a rare 6/6/5/6/6/6 fused-ring system, representing the first reported veratramine-type alkaloid with a new oxazinane ring (ring-F) in Fritillaria genus. The cytotoxic activities study revealed that compound 1 inhibited the cell proliferation of HT29 and DLD1 (IC₅₀ values of 25.1 and 48.8 µM, respectively) and also induced apoptosis of the above-mentioned two cancer cell lines.[Formula: see text].