Isoquercitrin production from rutin catalyzed by naringinase under ultrasound irradiation

Isoquercitrin, a rare flavonol glycoside with wide biological activities and key synthetic intermediate for the production of enzymatically modified isoquercitrin (EMIQ), was conducted by naringinase-catalyzed conversion of rutin under ultrasound irradiation. The maximum yields were obtained to 98.35 ± 3.13% and 95.20 ± 2.52% under conventional heating and ultrasound irradiation, respectively. The optimal results under ultrasound irradiation were obtained under the following conditions: rutin concentration 0.8 g/L, naringinase concentration 3000 U/L, reaction temperature 40 °C for 20 min, which was more economical than that with conventional heating. The reaction time was reduced from 60 min to 20 min, and the apparent kinetic parameter (V_m/K_m) was increased 3.72-fold. The lower activity energy E_a under ultrasonic irradiation was 0.7-fold of that in an incubator reactor, which could easily initiate the enzymatic reaction. The association saturation constant K_a was 1.98-fold higher than that with conventional heating, showed a better affinity between rutin and naringinase detected by surface plasmon resonance (SPR) analysis. These results suggest that ultrasound irradiation can accelerate the enzymatic synthesis of isoquercitrin from rutin.