Glycosylation of anthocyanins by glycosyltransferases

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The semi-purified pigment and the pure cyanidin 3-glucoside (C3G) prepared in large quantities from purple corn pigment were examined the transglycosylation with various sugar substrates catalyzed by various sugar-related enzymes, resulting that cyclodextrin glucanotransferases (CGTases) best generated glycosylated C3G (Gly-C3Gs). Next, the transglycosylation of C3G was conducted with a commercial α-cyclodextrin powder Dexypearl K-100 as an optimum sugar substrate under a commercial CGTase Contizyme of as an optimum enzyme. It was ascertained that the optimum sugar concentration 100 g/100 mL, the optimum pH 4.0, the optimum pigment concentration 1g/100mL, and optimum reaction time 3 hours.Under the optimum reaction condition, the large-scale glycosylation gave many highly glycosylated and hydrophilic Gly-C3Gs. Of them, six major Gly-C3Gs (G1-G6) could be isolated through various column separation and purification. HPLC, UV-Vis, and ESI/TOFMS analyses of the isolated G1-G6 resulted that they were presumed the non-natural type polyglycosides sequentially glycosidated glucose chain with α-1,4 bond on 4-OH of C3G-3-glucosyl residue.Thus, we could obtain Gly-C3Gs expected by the large-scale reaction advanced in the same way as small-scale test, but each isolated glycoside was in very small amount. Therefore, conditional examination for yield up and evaluation for the stability and the functionality are future topics.