2Faculty of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: +7 (495) 932-5846; E-mail: firstname.lastname@example.org
3State Research Institute of Chemistry and Technology of Organoelement Compounds, 105118 Moscow, Russia; fax: +7 (495) 913-2536; E-mail: email@example.com
* To whom correspondence should be addressed.
Received July 14, 2014; Revision received September 10, 2014
Dihydroquercetin (or taxifolin) is one of the most famous flavonoids and is abundant in Siberian larch (Larix sibirica). The oxidative polymerization of dihydroquercetin (DHQ) using bilirubin oxidase as a biocatalyst was investigated and some physicochemical properties of the products were studied. DHQ oligomers (oligoDHQ) with molecular mass of 2800 and polydispersity of 8.6 were obtained by enzymatic reaction under optimal conditions. The oligomers appeared to be soluble in dimethylsulfoxide, dimethylformamide, and methanol. UV-visible spectra of oligoDHQ in dimethylsulfoxide indicated the presence of highly conjugated bonds. The synthesized oligoDHQ was also characterized by FTIR and 1H and 13C NMR spectroscopy. Comparison of NMR spectra of oligoDHQ with DHQ monomer and the parent flavonoids revealed irregular structure of a polymer formed via the enzymatic oxidation of DHQ followed by nonselective radical polymerization. As compared with the monomer, oligoDHQ demonstrated higher thermal stability and high antioxidant activity.
KEY WORDS: dihydroquercetin, enzymatic polymerization, bilirubin oxidase, oligomers, 1H and 13C NMR spectra