A colorimetric method for α-glucosidase activity assay and its inhibitor screening based on aggregation of gold nanoparticles induced by specific recognition between phenylenediboronic acid and 4-aminophenyl-α-D-glucopyranoside

A colorimetric method has been established for α-glucosidase activity assay and its inhibitor screening. The method is based on the specific recognition between 1, 4-phenylenediboronic acid (PDBA) and 4-aminophenyl-α-D-glucopyranoside (pAPG), which may induce aggregation of pAPG-functionalized gold nanoparticles (AuNPs) to achieve color change of the test solution. Because pAPG is the substrate of α-glucosidase, the aggregation of AuNPs will be influenced by α-glucosidase since there is no coordination reactivity between PDBA and 4-aminobenzene, the hydrolyzed product of pAPG catalyzed by the enzyme. Therefore, a simple and easily-operated colorimetric method for the assay of α-glucosidase activity can be developed. Under the optimized experimental conditions, the ratios of absorbance at a wavelength of 650 nm to that at 520 nm vary linearly with the α-glucosidase activity within a range from 0.05 to 1.1 U/mL with a lowest detection limit of 0.004 U/mL. Moreover, using the proposed method, the inhibition effect of gallic acid and quercetin on α-glucosidase activity can be tested with IC₅₀ values of 1.16 mM and 1.82 μM, respectively. Thus, the method has a great potential not only for the detection of α-glucosidase activity, but also for the screening of its inhibitors.