Benign and straightforward synthesis of lignan-type dimers using crude peroxidase from red radish (Raphanus sativus var sativus)

Alkyl esters of hydroxycinnamic acids and vanillin derivatives were used as model compounds in the oxidative coupling reactions catalyzed by a crude enzymatic extract of Raphanus sativus var sativus (red radish). Six products were isolated and characterized: three alkyl esters of hydroxycinnamic acids dimers and three vanilloids dimers. Herein, we report the enzymatic extract of Raphanus sativus var. sativus showed peroxidase activity catalyzing the oxidative coupling of phenols. Vanilloid dimers were coupled in an ortho-ortho way as expected, while alkyl ester dimers were formed through 5-8 and 8-8 bonds via a radical mechanism prior to cyclization.

Keywords: new enzyme sources, radish peroxidase, enzymatic oxidative coupling, phenolic dimers.