Analysis of α-amylase inhibitor from corni fructus by coupling magnetic cross-linked enzyme aggregates of α-amylase with HPLC–MS

•The MCLEAs of α-amylase was first utilized in screening of α-amylase inhibitors.•The MCLEAs of α-amylase showed good reusability in the screening experiment.•The α-amylase inhibitor in corni fructus was screened as querciturone.

As a carrier-free immobilization strategy, magnetic cross-linked enzyme aggregates (MCLEAs) showed improved enzyme activity, stability and magnetic response. In this study, MCLEAs of α-amylase (MCLEAs–amylase) was prepared under optimized conditions and characterized with scanning electron microscope and vibrating sample magnetometer. The prepared MCLEAs–amylase showed an amorphous structure and the saturation magnetization was 33.5 emu/g, which was sufficient for magnetic separation. Then MCLEAs–amylase coupled with high performance liquid chromatography–mass spectrometry (HPLC–MS) was utilized to screen and identify α-amylase inhibitors from ethyl acetate extract of corni fructus. The experiment conditions were optimized. At the optimum conditions (incubation time: 10 min, pH: 7.0 and temperature: 20 °C), querciturone was successfully screened and identified with weak non-specific binding. The screening result was verified by inhibition assays and the IC50 value of querciturone was 22.5 μg/mL. This method provided a rapid way to screen active compounds from natural products.