Structural Studies of Curcuminoids. I. The Crystal Structure of Curcumin.

Abstract

The crystal and molecular structure of the food additive 1,7-bis(4-hydroxy-3-methoxyphenyl)1,6-heptadien-3,5-dione (curcumin) has been determined at 121 K by X-ray crystallographic methods using 3368 reflections observed by counter methods. The crystals are monoclinic, space group P2/n with unit cell dimensions a=20.028(3) Å, b=7.073(1) Å, c=12.609(2) Å, β=94.94(1)°. The structure was refined to a conventional R-factor of 0.055. Estimated standard deviations are 3 x 10-3 Å and 0.2° in interatomic distances and angles when hydrogen atoms are not involved.