Structures of new cyclic diarylheptanoids and inhibitors of nitric oxide production from Japanese folk medicine Acer nikoense.

Three new cyclic diarylheptanoids, acerosides B1 and B2 and aceroketoside, were isolated together with 20 known compounds from a Japanese folk medicine, the stem bark of Acer nikoense. The absolute stereostructures of the new compounds were determined on the basis of chemical and physicochemical evidence. In addition, the principal diarylheptanoid constituents were found to exhibit inhibitory activity on nitric oxide production in lipopolysaccharide-activated macrophages.