Polyglucosylation of Rutin Catalyzed by Cyclodextrin Glucanotransferase from Geobacillus sp.: Optimization and Chemical Characterization of Products

Despite the presence of a rutinosyl group at 3-OH, the aqueous solubility of the flavonoid rutin is even lower than that of its aglycon quercetin. In this work, we describe a fast, simple, and easily scalable process for polyglucosylation of rutin to enhance aqueous solubility, catalyzed by a cyclodextrin glucanotransferase (CGTase). Several reaction parameters (source of enzyme, rutin/starch weight ratio, cosolvent, pH, and temperature) were assessed to optimize the transglucosylation yield. Under the best conditions (6 mg/mL rutin, 30 mg/mL soluble starch as glucosyl donor, 20% (v/v) acetonitrile, pH 9.2, 3.3 U/mL CGTase from Geobacillus sp., 60 degrees C), the total glucosides reached a maximum concentration of 6 mM (60% conversion yield). The glucosylated products were chemically characterized by MALDI-TOF mass spectrometry and 2D nuclear magnetic resonance. The glucosylation takes place with an alpha-configuration at the 4-OH position of the beta-Glc moiety. A series of maltooligosyl derivatives with 1-6 residues of glucose linked by a(1. 4) bonds was obtained. The yield of monoglucosylated product was increased 2-fold by treatment with amyloglucosidase STA1 from S. cerevisiae.