2.6.2. α-Glucosidase Inhibition Assay

The inhibition assay with the α-glucosidase was carried out as a previously described protocol [17]. Briefly, the 1 U mL⁻¹ α-glucosidase (EC3.2.1.20) and 3 mM p-nitrophenyl-α-D-glucopyranoside (pNP-α-G) were dissolved in PBS, except samples and acarbose were prepared using the method described as α-amylase inhibition assay. The incubated system contained 50 μL of samples and 100 μL of the α-glucosidase solution was added to a 96-well plate at 37 °C for 10 min. Then, 50 μL of the substrate pNP-α-G was added to start the reaction at 37 °C. After 10 min, 100 μL of 1 M Na₂CO₃ solution was added to inactivate α-glucosidase and halt the generation of substrates, and the absorbance was read at 405 nm with the micro-plate reader (SpectraMax 190, Molecular Devices Co., Sunnyvale, CA, USA). The percentage of inhibition and the values of IC₅₀ of samples were calculated by the same equation as α-amylase inhibition assay.