Six undescribed and six known bisbenzylisoquinoline alkaloids were isolated from the embryo of seeds. Their structures were fully characterized by a combination of H, C NMR, 2D NMR, and HRESIMS analyses, as well as ECD computational calculations. The antiadipogenic activity of 11 alkaloids was observed in a dose-responsive manner, leading to the suppression of lipid accumulation in 3T3-L1 cells. Luciferase assay and Western blot analysis showed that the active alkaloids downregulated peroxisome proliferator-activated receptor gamma (, a key antiadipogenic receptor) expression in 3T3-L1 cells. Analysis of the structure-activity relationship unveiled that a 1,1' configuration in bisbenzylisoquinoline alkaloids led to a notable enhancement in antiadipogenic activity. The resistance level against lipid accumulation highlighted a consistent pattern with the suppressive effect on the expression. These activity results indicate that alkaloids from the embryo of seeds have a potential of antiobesity effects through downregulation.