Selective hydrolysis by commercially available hesperidinase for isoquercitrin production

Isoquercitrin is a rare flavonol glycoside with various biological activities, and it is a primary synthetic precursor for enzymatically modified isoquercitrin (EMIQ), which was recently approved as a multiple food additive. The enzymatic method has a great potential to produce isoquercitrin from hydrolysis of rutin via selectively removing a terminal rhamnose. Commercially available hesperidinase was investigated and found that α-l-rhamnosidase achieves good catalytic capacity while β-d-glucosidase loses its activity at pH 7.0. The increased conversion of rutin to isoquercitrin was found by the addition of some metal ions (K+, Li+, Mg2+, Zn2+ and Al3+). Electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) were used to identify isoquercitrin from the transformed products. The enzymatic reaction conditions (temperature, substrate concentration, and reaction time) of isoquercitrin from rutin were optimized, and the apparent kinetic parameters Vm/Km at different temperatures were also measured. The results suggest that the commercially available hesperidinase can be applied into isoquercitrin production via highly selective hydrolysis.