No / Croton membranaceus is used by herbalists and traditional healers in Ghana for the management of various cancers, especially prostate cancers. A methanolic extract of the roots showed cytotoxic activities against two cancer cell lines, and bioassay-guided fractionation of this extract revealed that the cytotoxic activity resided mostly in the ethyl acetate fraction. Six compounds were isolated from this fraction, including a new furano-clerodane diterpenoid (1), for which the trivial name crotomembranafuran is suggested. This compound exhibited an IC50 value of 4.1 microgram/mL (10.6 microM) against human prostate (PC-3) cells, providing some support for the traditional use of C. membranaceus in the treatment of cancers