Immobilized α-glucosidase using polydopamine-coated magnetic nanoparticles for targeted screening of an active component from Toona sinensis

Toona sinensis is a traditional vegetable with rich nutrition and wide biological activity. In our previous study, an active composition against α-amylase was screened from T. sinensis by ligand fishing. To investigate the effect of T. sinensis on other targets of antidiabetes, in this work, α-glucosidase was immobilized on polydopamine-coated magnetic nanoparticles to further screen the compounds against α-glucosidase by ligand fishing. The enzyme activity test showed that the 70% ethanol extract of T. sinensis (crude sample) had weak α-glucosidase inhibitory activity, but after extraction with different solvents, the ethyl acetate extract showed the highest α-glucosidase inhibitory activity. After immobilization of α-glucosidase on polydopamine (PDA)-coated magnetic nanoparticles, the properties of the enzyme were characterized and determined, and then quercetin-3-O-α-L-rhamnopyranoside was screened by ligand fishing and isolated by high-speed counter-current chromatography using the two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (1:5:1:5, v/v). The results of enzymes assay showed that the screened compound (IC50 value of 374.94 ± 4.35 μg/mL) possessed moderate α-glucosidase inhibitory activity. The presented results not only proved that ligand fishing based on polydopamine-coated magnetic α-glucosidase was an effective method for the rapid discovery of natural active substances, but also further strengthened the evidence of antidiabetic effect of T. sinensis.