α-Glucosidase Inhibitory Assay

The α-glucosidase inhibitory activity was performed using the protocol previously described [27]. Briefly, 50 μL sample solution (2 mg HI lyophilized extract/mL), 50 μL glutathione (0.5 mg/mL), 50 μL of 10 mM PNPG (*p*-nitrophenyl-β-d-glucuronide) solution, and 50 μL α-glucosidase solution in PB (pH 6.8) were mixed in a 96-wells microplate and incubated at 37 ◦C for 15 min. Similarly, the blank was prepared by adding a sample solution to all reaction reagents without the enzyme (α-glucosidase) solution. The reaction was finally stopped by adding 50 μL of 0.2 M sodium carbonate. The absorbance for sample and blank were read at 400 nm and then the absorbance of blank was subtracted from the absorbance of the sample.
