Oxidation of ferulic acid by laccase: identification of the products and inhibitory effects of some dipeptides.

The laccase activity, in the presence of ferulic acid as substrate, was tested with high performance liquid chromatography (HPLC). The two products initially formed were identified by HPLC-mass spectrometry and HPLC-diode array as trans-5-[(E)-2-carboxyvinyl]-2-(4-hydroxy-3-methoxy-phenyl)-7-methoxy-2,3-dihydrobenzofuran-3-carboxylic acid and (Z)-beta-{4-[(E)-2-carboxyvinyl]-2-methoxyphenoxy}-4-hydroxy-3-methoxy cinnamic acid. The inhibitory effects of some dipeptides due to the formation of copper complexes have also been reported. The results obtained confirm that the inhibitory effects on laccase activity are strongly related to the structure of the dipeptides and confirm the important role of copper(II) in the reaction mechanism.