New Polymers from Natural Phenols Using Horseradish or Soybean Peroxidase

The flavonol quercetin, its glycoside rutin, the flavanol catechin, the isoflavone daidzein and 5,6,4′-trihydroxyisoflavone can be oxidatively polymerized via a radical polyrecombination mechanism catalyzed by horseradish or soybean peroxidase in a mixture of phosphate buffer (pH 7) and 1,4-dioxane. The average molecular weights of the polymers were found to be in the range 4 000–12 000 g/mol. Daidzein derivatives with a methoxy (formononetin) or nitro group or a hydrogen atom at C-4′ could not be polymerized under these conditions. These results and molecular modeling studies suggest that polymerization preferentially occurs via the electron-rich ring B of the isoflavonoids. The polymers were characterized by means of FT-IR and UV spectroscopy, and their redox behavior was analyzed using cyclic voltammetry.