Abstract The wood of Alnus japonica has been shown to contain a number of biarylheptanoids as well as other phenolics, including secoisolariciresinol diferulate. The co-occurrence of cyclized biarylheptanoids with their corresponding acyclic biarylheptanoids has been demonstrated and this fact may have biosynthetic significance. The possible chemotaxonomic importance of biarylheptanoids in members