Cytotoxic sesquiterpene alkaloids isolated from Nuphar pumila (Timm) de Candolle.

Five undescribed nupharidines, namely amidonupumones A-C (1-3), amidonupumol A (4), and dinupharolutine (7), along with twelve known analogues (5, 6, 8-17) were isolated from Nuphar pumila. Their structures were elucidated by extensive spectroscopic data, ECD, NMR calculations, and X-ray diffraction. Among them, compounds 1-4 represent the first alkaloids containing an amide structure isolated from N. pumila. In vitro bioassays revealed that compounds 7 and 11 exhibited broad-spectrum cytotoxic activity at a concentration of 40 μM.