Six new diterpenoids from the resins of Populus euphratica and their anti-inflammatory activities.

Six new diterpenoids, identified as two abietane derivatives, euphraticanoids J and K (1 and 2), two pimarane derivatives, euphraticanoids L and M (3 and 4), and two 9,10-seco-abietane derivatives, euphraticanoids N and O (5 and 6) were isolated from Populus euphratica resins. Their structures including absolute configurations were characterized using spectroscopic, quantum chemical NMR, and ECD calculation methods. The anti-inflammatory activity of the compounds was tested and the results revealed that compounds 4 and 6 inhibited the production of iNOS and COX-2 in a dose-dependent manner in lipopolysaccharide (LPS)-induced RAW 264.7 cells.