α -glucosidase enzyme (100 μL, 0.7 units/mL) was mixed with 10 μL methanol or samples and incubated at 37°C for 10 minutes in 96-well plate. After that 20 mM p-nitrophenyl- α -D-glucopyranoside in phosphate buffer saline (PBS) were added, mixed and incubated at 37°C for 15 minutes, and then 100 μL sodium carbonate were added to stop the reaction. Produced p-nitrophenyl was measured by microplate reader at the absorbance of 405 nm. Acarbose (1 mg/mL) was used as the positive control.