Isolation and characterization of diterpene glycosides from Siegesbeckia pubescens.

Five new diterpenoid glycosides, siegesides A-E (1-5), along with the known compound darutoside (6) were isolated and characterized from the ethanol extract of Siegesbeckia pubescens. The structural elucidation of the isolates was accomplished by extensive HRESIMS and NMR analysis. Compounds 1 and 2 are epimers of 6. All isolates were evaluated for their inhibition on the migration of MB-MDA-231 breast cancer cells induced by the chemokine epithelial growth factor, and compound 2 showed superior inhibitory activities in comparison with the positive control drug with IC50 value of 0.27μM.