Cytotoxic ent-kauranoids from Isodon leucophyllus.

Two new compounds, baiyecrystals D and E (1, 2), together with eight known analogues, xerophilusin B (4), macrocalin B (5), oridonin (6), rosthorin A (7), lasiocarpanin (8), rabdoternin A (9) and phyllostachysin A (10) and B (11), were isolated from the aerial parts of Isodon leucophyllus. The structures of 1 and 2 and 4-11 were elucidated on the basis of spectroscopic methods, especially the 2D NMR spectral analysis. Compounds 2, 6-8 and 10 were evaluated for their antineoplastic activities in vitro. Among them, lasiocarpanin (8) showed significant inhibitory activities against K562 and Bcap37 cells, with the IC50 values of 0.13 and 1.26 microg mL(-1), respectively, which were lower than those of the positive control.