3D superposition and 2D comparison of curcumin and piceatannol. Comparison of curcumin and piceatannol structures by three-dimensional (3D) and two-dimensional (2D) superposition. A, The lead structure curcumin (blue) was aligned in a 3D superposition with the structure of piceatannol (green) obtained in the database. B, 2D similarities of curcumin and piceatannol are demonstrated. Both structures contain two aromatic rings and a large number of H-bond-acceptors. Using this information the Tanimoto-coefficient shown in Table 1 was calculated.