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.

Automated summary

By utilizing CGTase as a catalyst, rutin was polyglucosylated to enhance aqueous solubility, achieving high conversion yield under optimal conditions. The glucosylation reaction resulted in enhanced solubility and the yield of monoglucosylated product was increased with the treatment of amyloglucosidase STA1.