2.6. Determination of DPP-IV inhibitory activity

The Dipeptidyl-peptidase 4 (DPP-IV) inhibitory activity was determined using a DPP-IV inhibitor screening kit (Sigma-Aldrich, Dorset, UK). Yogurt aqueous extracts (25 μl) were pipetted onto a black 96-well microplate containing the DPP-IV enzyme (50 μl). This was followed by the addition of 25 μl Enzymatic Reaction Mix, and the fluorescence (λ_ex = 360/λ_em = 460) was measured every minute on a plate fluorimeter (SpectraMax, GEMINI XS, Molecular Devices Ltd., Wokingham, UK) in kinetic mode at 37 °C for 15 min. The negative control contained 25 μl DPP-IV Assay Buffer instead of the extract. The enzyme inhibition was calculated as below: