α-Glucosidase inhibition assay

α-Glucosidase inhibition assay was carried out using previously reported method (Ma et al. 2015). In brief, CBD stock solution was prepared in DMSO (10 mg/mL) and diluted to desired concentrations with phosphate buffer (0.1 M, pH 6.8). A mixture of test sample (10 μL), phosphate buffer (80 μL), and yeast α-glucosidase (0.5 U/mL; 10 μL) was incubated in a 96-well plate at room temperature for 10 min followed by adding pNPG (1 M; 100 μL) to each well. The reaction mixtures were incubated at room temperature for 30 min before the absorbance was recorded at wavelength of 405 nm with a micro-plate reader (SpectraMax M2, Molecular Devices Corp., operated by SoftmaxPro v.4.6 software, Sunnyvale, CA, USA). α-Glucosidase inhibitory activity was expressed as inhibition% as compared to the control group. Each sample was tested three times, each in three replicates (n = 3), and data were shown as mean ± standard deviation (S.D). Statistical analysis was performed using GraphPad Prism 7 (GraphPad Software; La Jolla, CA, USA) using one-way analysis. A p-value that less than 0.001 (***) or 0.0001 (****) was considered as a statistical significance between the control group and the experimental groups.