Oxidative coupling of natural phenol derivatives catalyzed by laccases

Laccases (benzenediol:oxygen oxidoreductases; EC 1.10.3.2) are multicopper enzymes that catalyze the one-electron oxidation of a wide variety of substrates, i. e. phenols and aromatic amines, with the concomitant reduction of molecular oxygen to water. Recent reports describe the use of laccases for the oxidation of different classes of organic compounds using suitable “mediators”. Conversely, literature data on the laccase-mediated oxidation of complex natural compounds are quite scant. For instance, 30 years ago a laccase from Polyporus versicolor was used for the oxidation of steroid hormones (i. e. beta-estradiol) in emulsion of water and organic solvents to give a mixture of isomeric dimers.In the frame of our general interest in the biocatalyzed formation of carbon-carbon bonds, we are studying the performances of laccases in the oxidative coupling of natural compounds in water solution or in the presence of organic cosolvents. In this report we will present the results obtained using the laccases from Myceliophtora thermophyla and from Trametes versicolor for the oxidation of the phenolic derivatives beta-estradiol, resveratrol and catechin.