A new flavanone glycoside, onychin, in addition to a known alpha-indanone glycoside, wallichoside and a known diterpene, onychiol B, were isolated as cytotoxic principles from the aerial parts of Onychium japonicum. The structure of the new cytotoxic flavanoid was established as 5-hydroxy-7-rhamnosylglucosyloxyflavanone by spectroscopic methods.
