Isolation and identification of phase I metabolites of phillyrin in rats.

Abstract Phillyrin was one of the main chemical constituents of the fruit of Forsythia suspensa (Thunb.) Vahl. It showed various bioactivities including antioxidant and anti-inflammatory activities. However, the metabolism of phillyrin remained unknown. This report described the isolation and identification of phase I metabolites of phillyrin in rats. Nine metabolites including six new ones were isolated by various column chromatographies and high-performance liquid chromatography. Their structures were elucidated by extensive spectroscopic analysis. The antiviral activities of phillyrin and the metabolites were evaluated against influenza A (H3N2) virus. Among them, one metabolite M8 showed moderate activity with the IC 50 value of 26.39 μM, and three metabolites ( M2 , M3 , M9 ) showed weak antiviral activities at the concentration of 100 μM. Based on the structures of the metabolites, possible metabolic pathways of phillyrin in rats were also proposed.