Plant anticancer agents XXVII: Antileukemic and cytotoxic constituents of Dirca occidentalis (Thymelaeaceae)

Two antileukemic daphnane esters, Pimelea factor P2 (I) and the new compound dircin (II), were isolated from the twigs and flowers of Dirca occidentalis A. Gray (Thymelaeaceae). Three Lignans, (-)-medioresinol (III), (+)-syringaresinol (IV), and (-)-lariciresinol (V), as well as the coumarin daphnoretin (VI), were found to be additional cytotoxic constitents of this taxon.