Enzymatic Synthesis and Characterization of PolyQuercetin

Quercetin is a flavonol found in fruits, onions and wine. Recently, quercetin has been extensively investigated for its antioxidant behavior in food such as poultry and fish. While quercetin has been shown to be a good stabilizer for several oils, the thermal stability and solubility at neutral and slightly alkaline conditions continue to be an area of huge concern. However, increasing the stability and the antioxidant potency of this flavonol would be beneficial to the food industry. We utilized horseradish peroxidase, a phytochemical enzyme, to polymerize quercetin in biocompatible water/ethanol mixtures. This unique, one pot procedure has provided a method to synthesize polyquercetin under mild conditions. The final polymer is soluble in a water/ethanol mixture. Preliminary data were presented in the Material Research Society fall meeting in Boston on December 3, 2008. However, in this article, enzymatically synthesized polyquercetin has also been characterized by a variety of techniques. Using UV-Vis FTIR, GPC, NMR and TGA we have deduced certain aspects of the structure. Structural elucidation was further refined by results from molecular modeling. Density functional theory calculations predict that the UV-Vis spectra of polyquercetin can show high conjugation relative to those of quercetin monomer. This was confirmed by the experimental results. This novel thermally stable polymer, synthesized using Green Chemistry principles, can be used as a potent antioxidant in the highly regulated food industry.