Abstract

Twelve new diterpenoids, isoresbins A–L ( 1 – 12 ), together with twenty-eight known ones, were isolated from the aerial parts of Isodon oresbius . Their diverse structures included 6,7-seco- ent -kaurane, 7,20-epoxy- ent -kaurane, 6,7:8,15-diseco- ent -kaurane, and abietanes skeletons, which were elucidated by spectroscopic data interpretation, single-crystal X-ray diffraction, and quantum chemical calculation. Isoresbins A ( 1 ) and B ( 2 ) possessed a new rearranged 15(8 → 11)- abeo -6,7-seco- ent -kaurane skeleton. 1 and 5 promoted lysosomal function, which was evaluated by LysoTracker Red staining and DQ-ovalbumin dequenching assay. 1 showed cytotoxicity against six human tumor cell lines with IC 50 values in 2.07–4.04 μM range. Moreover, 1 induced damage of mitochondrial membrane potential, G2/M cell cycle arrest and apoptosis in SW480 cells.