Two new types of polyhydroxylated alkaloids, broussonetines and radicamines, which have an aliphatic or an aromatic moiety, were isolated from Broussonetia kazinoki (Moraceae) and Lobelia chinensis (Campanulaceae), respectively, as glycosidase inhibitors. Feeding experiments using [1-13C] glucose and 13C-NMR spectroscopic studies showed that broussonetines are biosynthesized through routes similar to those of sphingosine and phytosphingosine.