A new labdane diterpene compound in Forsythia suspensa (Thunb.) Vahl

The chemical constituents of the fruits of Forsythia suspensa (Thunb.) Vahl were investigated by using chromatographic techniques (silica gel, MCI, and sephadex LH-20 gel column chromatography, etc). Fourteen compounds were isolated from the 95% ethanol extract of F. suspensa, and their structures were identified by HR-ESI-MS, NMR, and calculated electronic circular dichroism (ECD) methods. The compounds included labdane diterpenes (1-6), clerodane diterpene (7), norlabdane diterpene (8), norclerodane diterpene (9), oleanane triterpenoid (10), ursane triterpenoids (11, 12), lupane triterpenoids (13, 14). Among them, compound 1 was a new compound and compounds 3-9, 11, and 12 were obtained from this plant for the first time. The inhibitory effect of these compounds on lipopolysaccharide-induced nitric oxide production in mouse macrophage RAW 264.7 cells also was evaluated. Unfortunately, none of these compounds exhibited significant inhibitory activity.