Flavone C-glycosides from the flowers of Trollius chinensis and their anti-complementary activity

Phytochemical investigation of ethanol extract from the flowers of Trollius chinensis Bunge resulted in the isolation of two new flavone C-glycosides (12), along with 10 known compounds (312). The structures of the new compounds were established as 6?-(3-hydroxy-3-methylglutaroyl)-2-O--d-galactopyranosyl orientin (1) and 6?-(3-hydroxy-3-methylglutaroyl)-2-O--d-galactopyranosyl vitexin (2) on the basis of various spectroscopic analysis (including different 1D and 2D NMR spectroscopies, high-resolution electrospray ionization mass spectrometry) and chemical evidences. Bioassay showed that eight flavonoids inhibited complement activation on the classic pathway in vitro, with their IC50 values ranging from 0.88 to 4.02mM, which may contribute to the applications of the herb in treatment of acute respiratory distress syndrome, etc.