Retusone A, a Guaiane-Type Sesquiterpene Dimer from and Its Inhibitory Effects on Histone Acetyltransferase HBO1 Expression.

Retusone A (), a new sesquiterpene dimer consisting of two guaiane-type sesquiterpenoids, and oleodaphnal () were isolated from heartwood of (Thymelaeaceae). The planar structure of was elucidated on the basis of HRESIMS and NMR spectroscopic data, and the relative stereochemistry was established by X-ray diffraction analysis. The absolute configuration of was determined by electronic circular dichroism. Compound suppressed luciferase reporter gene expression driven by the HBO1 (histone acetyltransferase binding to ORC1) gene promoter in human breast cancer MCF7 cells. Compound also decreased the expression of endogenous HBO1 mRNA and protein, and inhibited proliferation of the cells. These results suggest that retusone A (), which has a unique dimeric sesquiterpenoid structure with inhibitory activity against HBO1 expression, may contribute to the development of a novel therapeutic candidate for the treatment of breast cancer.