Abstract: A new fluorenone derivative, named chrysotoxone (3) was isolated from the ethanolic extract of the stems of Dendrobium chrysotoxum (Orchidaceae), along with three known compounds. The structure of the new fluorenone was elucidated as 2,5,8-trihydroxy-1,4-dimethoxy-9-fluorenone.

Key words: Dendrobium chrysotoxum, Orchidaceae, Fluorenone derivative, Chrysotoxone