Lignans from the fruits of Forsythia suspensa.

Bioactivity-guided fractionation of the methanol extract of the fruits of Forsythia suspensa Vahl has led to the isolation of two new monoepoxylignans, forsythialan A (1) and B (2), together with a known tetrahydrofurofuran lignan, phillyrin (3). The structures of compounds 1 and 2 were elucidated by spectroscopic methods. The antioxidant activities of these lignans have been assessed by evaluating their protective effects against peroxynitrite-induced oxidative stress. The compounds 1 and 2 showed protective effects against renal epithelial cell injury by 3-morpholinosydnonimine (SIN-1), a peroxynitrite generator. The relatively stronger antioxidant activities of compounds 1 and 2 may be associated with the presence of aromatic hydroxy function.