A simple and portable method for β-Glucosidase activity assay and its inhibitor screening based on a personal glucose meter.

In this study, a simple and portable enzyme activity assay and inhibitor screening method was developed based on β-Glucosidase-mediated cascade reaction in a personal glucose meter (PGM). The inhibition of castanospermine (β-Glucosidase inhibitor) on β-Glucosidase leads to reducing the yields of glucose and saligenin produced by the catalysis hydrolysis of D (-)-Salicin. The ferricyanide (K3 [Fe(CN)6]) can be reduced by the products of glucose and saligenin to form ferrocyanide ([K4[Fe(CN)6]) in the glucose strips, and thereby get the electron to generate PGM detectable signals. This strategy can realize the direct determination of glucose and saligenin using PGM as simple as measuring the glucose in blood. Under the optimum experimental conditions, quantitative detection of β-Glucosidase in crude almond sample was achieved within the ranges of 1.0-9.0 U/mL with the limit of detection of 0.45 U/mL. The recoveries of β-Glucosidase spiked with two different concentrations (3.0 and 6.0 U/mL) in the crude bitter almond extracts were determined as 96.2% and 84.3%, respectively. Furthermore, gallic acid, protocatechualdehyde, cryptochlorogenic acid, epigallocatechin, epicatechin and vanillic acid exhibited good inhibitory effect (all higher than 40%) on β-Glucosidase. In addition, tea polyphenol extracts of raw Pu-erh and Fuding white tea had good inhibition potency and the % of inhibition were (29.0 ± 3.5)% and (21.1 ± 2.2)% on β-Glucosidase, respectively. Finally, molecular docking study indicated that hydrogen bonding plays an important role in the interaction between the compounds and β-Glucosidase. The enzyme activity assay and inhibitor screening method developed in present study using PGM based on β-Glucosidase-mediated cascade reaction would be of value for expanding the application of PGM in non-glucose target analysis.