2.8 Assay for DPP-4 inhibition
96 microwell plates were used to performe the DPPIV assay. Pre-incubation solution 50 ml contained in Tris-HCl buffer (35 ml) and DPP-IV (15 ml) at various dilution and different concentration of extract and standard (6.25 – 100 mg/ml) were incubated. The prepared sample was re-incubated at room temperature (37°C) for 15 min, followed by addition of substrate (gly-propnitroanilide).The reaction mixture was re-incubated at 37°C for 30 min and the absorbance was estimated by using the microplate readers (Lamont and Drucker, 2008).