Optimized enzymatic synthesis of digestive resistant anomalous isoquercitrin glucosides using amylosucrase and response surface methodology
2021
Rha, Chan-Su | Park, Cheon-Seok | Kim, Dae-Ok
Diverse flavonoid glycosides are present in the plant kingdom. Advanced technologies have been utilized to synthesize glycosyl flavonoids which exhibit good physicochemical characteristics. Previously, novel isoquercitrin (IQ) mono-, di-, and tri-glucosides (IQ-G1′, IQ-G2′, and IQ-G3′; atypical IQ-Gs (IQ-Gₐₚ)) were synthesized through the reaction of amylosucrase. Here, the regio-selective transglycosylation yields were predicted using response surface methodology for three variables (glucose donor (sucrose; 100–1500 mM), glucose acceptor (IQ; 100–400 µM), and pH (5.0–8.8)) using 1 unit/mL of enzyme at 45 °C; then, the optima were verified according to the experimental responses. Acidity (pH 5.0) was a major contributor for IQ-G1′ production (> 50%), and high sucrose concentration (1500 mM) limited IQ-G3′ production (< 15%). Low sucrose concentration (100 mM) at pH 7.0 promoted higher glycosyl IQ production (> 30%). Time-course production of IQ-Gₐₚ showed an exponential growth with different rates. IQ-Gₐₚ was stable under the simulated intestinal conditions compared with typical IQ-Gs. Digestive stable IQ-Gₐₚ can be effectively synthesized by modulating reaction conditions; thereby, atypical glycosyl products may contribute to the elucidation of nutraceutical potential of flavonoid glycosides. KEY POINTS: •Predictions of RSM were validated for the regio-selective IQ-Gₐₚ production. • Time course changes of IQ-Gₐₚ indicate non-processive glycosylation of DGAS. • IQ-Gₐₚ exceed typical IQ-G in digestive stability at simulated intestinal condition.
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