Conformational behaviour of biologically active ferulic acid derivatives

The conformational behaviour of several biologically relevant hydroxycinnamic systems - ferulic acid and its methyl, ethyl, propyl and butyl esters - was studied by quantum mechanical calculations, at the DFT level. A full geometry optimisation was carried out, as well as a Fourier analysis of the main internal rotations within these molecules. The geometrical preferences of these compounds result from a balance between the stabilising resonance and hydrogen bonding effects and the destabilising non-bonding repulsions, the most stable conformers displaying an s-cis conformation and hydroxyl/methoxyl substituent groups coplanar to the aromatic ring. The results thus obtained allow a better understanding of the well recognised in vitro and in vivo antioxidant and growth-inhibiting properties of this type of phenolic systems. (C) 2009 Published by Elsevier B.V.