Quinoid glycosides from Forsythia suspensa.

Phytochemical investigation on Forsythia suspensa (Thunb.) Vahl afforded 10 compounds, including quinoid glycosides, lignan glycosides, phenylethanoid glycoside and allylbenzene glycoside together with 13 known ones. Their structures were established based on extensive spectroscopic data analyses, including IR, UV, HRESIMS, 1D NMR and 2D NMR. Absolute configurations were determined by ECD calculation method and chemical degradation. In addition, all compounds were evaluated for their antiviral activity against influenza A (H1N1) virus and several were further evaluated against respiratory syncytial virus (RSV) in vitro. Among them, two previously known compounds showed significant activities against RSV with EC50 values of 3.43 and 6.72 µM.