Two new cyclopentenones and a new furanone from Baeckea frutescens and their cytotoxicities.

Two new cyclopentenones, frutescencenones A (1) and B (2), and a new furanone derivative, frutescencenone C (3), together with two known cyclopentenones (4 and 5), were isolated from the leaves of Baeckea frutescens. Their structures were deduced by comprehensive spectroscopic analyses, including 1D and 2D NMR, and HREIMS data. Frutescencenone A (1) showed moderate growth inhibitory activity against human lung A549, pancreatic PSN-1, and breast MDA-MB-231 cancer cell lines, with IC50 values of 36.3μM, 38.2μM, and 29.3μM, respectively. In contrast, frutescencenone C (3) showed selective cytotoxic activity against PSN-1, with an IC50 value of 20.1μM.