Cassaine diterpenoids from the seeds of Erythrophleum fordii and their cytotoxic activities.

Six new cassaine diterpenoids (1, 3-7), along with three known ones (2, 8-9) were isolated from the seeds of Erythrophleum fordii. Their structures were elucidated by extensive spectroscopic methods and acid hydrolysis. Compound 2 was tested to be the most potent one and showed more sensitive activities on MCF-7 and A549 cancer cells with IC50 values of 3.66 ± 1.20 and 2.87 ± 0.46 μM, respectively. Furthermore, compound 2 reduced the number of cell colonies significantly in a dose-dependent manner in the colony formation assay and triggered apoptosis of MCF-7 cell.