Abietane Diterpenoids With Potent Cytotoxic Activities From the Resins of Populus euphratica

A new abietane norditerpenoid, 5-(6-isopropyl-2-methylnaphthalen-1-yl)pentan-2-one (1), with a rare 4,5-seco-19-norabietane skeleton possessing a rearranged angular methyl group at C-5, 2 new naturally occurring compounds, 19-norabieta-4,6,8,11,13-penttaen-3-one (2) and 14-hydroxy-7-oxo ester (3), along with 10 known analogs (4？13) were isolated from the resins of Populus euphratica. The new structures were elucidated by spectroscopic analysis (one-/two-dimensional nuclear magnetic resonance and high-reolution electrospray ionization mass spectrometry). Biological evaluation showed that compounds 1 and 2 display low cytotoxicity against normal cells and appreciable cytotoxicity in cancer cells, with 2 to be more sensitive in HepG2 cells with a half-maximal inhibitory concentration value of 27.0 μM