Potassium chloride-assisted heat treatment enhances the de-glycosylation efficiency and xanthine oxidase inhibitory activity of Sophora japonica L. flavonoids

Salt-assisted heat treatment is considered an effective way to enhance the bioactivities of flavonoids in Flos Sophorae Immaturus tea (FSIt). Herein, sodium chloride (NaCl)- and potassium chloride (KCl)-assisted heat treatment was employed to process FSIt, the components, xanthine oxidase (XO) inhibitory activity, and degradation or conversion kinetics of FSIt flavonoids were recorded. Results showed that KCl-assisted heat treatment significantly increased the XO inhibition rate of FSIt from 28.05 % to 69.50 %. The de-glycosylation of flavonoids was the crucial reason for enhancing XO inhibitory activity. Notably, KCl exhibited a better catalytic effect on the de-glycosylation reaction than NaCl. Meanwhile, conversion kinetics showed that the generation rate of quercetin, kaempferol, and isorhamnetin reached the maximum at 180, 160, 160 °C, respectively. Furthermore, the established artificial neural network model could accurately predict the changes of FSIt flavonoids during salt-assisted heat treatment. Thus, KCl can be used as a valuable food processing adjuvant to enhance the bioactivities of food materials.