Structures and allelopathic effects of Nuphar alkaloids: Nupharolutine and 6,6'-dihydroxythiobinupharidine

Two of the major Nuphar alkaloids, nupharolutine and 6,6'-dihydroxythiobinupharidine, were isolated from the aquatic perennial herb Nuphar lutea (L.) Sibth. & Sm., yellow water lily. In a lettuce seedling bioassay of the two pure compounds, the former was inactive and the latter was highly inhibitory of radicle elongation at concentrations greater than 2 ppm. Structures and stereochemistry of the two compounds were confirmed by DEPT, H-1-H-1 COSY, H-1-C-13 COSY, and H-1-H-1 NOESY experiments.