Pancreatic lipase digests dietary fats by hydrolysis, which is a key enzyme for lipid absorption. Therefore, reduction of fat absorption by the inhibition of pancreatic lipase is suggested to be a therapeutic strategy for obesity. We previously reported coumarins and secoiridoids of Fraxinus rhynchophylla as inhibitory constituents on adipocyte differentiation. Further investigation on F. rhynchophylla led to the isolation of lignan derivatives such as lignans (1 - 10), sesquilignans (11 - 14) and coumarinolignans (15 - 17). Among them, coumarinolignans and sesquilignans were first reported from Fraxinus species. Among the constituents isolated, sesquilignans showed the significant inhibition on pancreatic lipase, whereas lignans and coumarinolignans exerted weak effects.