Laccase-catalyzed dimerization of ferulic acid amplifies antioxidant activity

Enzymatic modification can be used to enhance the bioactive properties of phenolic compounds. The present study employed laccase from Trametes pubescens to catalyze the modification of ferulic acid in a monophasic or biphasic system, as a way of enhancing its antioxidant capacity. Two dimeric products (m/z 385.1) were purified and characterized as the β-5 and β–β dimers. In the monophasic system, the β-5 dimer was preferentially formed in dioxane while the β–β dimer formation was enriched in ethanol as co-solvent. In the biphasic system, formation of the dimers increased as the concentration of ethyl acetate was increased from 80% to 95%. The β-5 dimer showed higher antioxidant capacity than the substrate as demonstrated by standard antioxidant assays (DPPH and TEAC). These results demonstrate that alteration of reaction conditions influences the laccase-mediated oxidation of ferulic acid to form dimers with higher antioxidant capacity than the substrate.