Terpenoids Induce Cell Cycle Arrest and Apoptosis from the Stems of Celastrus kusanoi Associated with Reactive Oxygen Species

Bioguided fractionation of the CHCl(3) extracts obtained from Celastrus kusanoi stems led to isolation of two new terpenoids, 3 beta-hydroxy-11,14-oxo-abieta-8,12-diene (1) and 3 beta-trans-(3,4-dihydroxycinnamoyloxy)-11 alpha-methoxy-12-ursene (2), and four known compounds characterized by spectroscopic methods. Compounds 1 and 2 and known triterpenoid erythrodiol (3) exhibited cytotoxic activity against bladder cancer cells (NTUB1) with IC(50) values of 58.2 +/- 2.3, 160.1 +/- 60.9, and 18.3 +/- 0.5 mu M, respectively. Exposure of NTUB1 to 3 (5 and 10 mu M) for 24 h significantly increased the level of production of reactive oxygen species (ROS). Flow cytometric analysis showed that treatment of NTUB1 with 3 led to the cell cycle arrest at G0/G1 accompanied by an increase in the extent of apoptotic cell death after 24 h. These data suggest that the presentation of G1 phase arrest and apoptosis in 3-treated NTUB1 for 24 h was mediated through an increased amount of ROS in cells exposed to 3.