Anti-inflammatory and anti-viral labdane diterpenoids from the fruits of Forsythia suspensa

Eight labdane diterpenoids, including two new labdane diterpenoids, named forsyshiyanins A-B (2-3), along with six known ones (1, 4-8), were isolated from the fruits of Forsythia suspensa. The new structures including their absolute configurations were elucidated by extensive spectroscopic analyses, X-ray diffraction and computational calculation. In vitro, eight labdane diterpenoids showed anti-inflammatory activities, with the inhibition rates of release of β-glucuronidase from polymorphonuclear leukocytes of rats being in the range 46.8-51.0% at concentrations of 10 µM, as well as anti-viral activities against influenza A (H1N1) virus and respiratory syncytial virus (RSV), with the IC₅₀ values in the range 18.4-26.2 μM and EC₅₀ values in the range 10.5-14.4 μM, respectively.