4.7.3. Determination of Pancreatic Lipase Inhibition by Basil Extracts Using a Spectrophotometric Assay

The inhibitory potential of basil extracts on pancreatic lipase activity was determined by a colorimetric assay as previously described [68], but with a minor modification to adapt it to 96 well-plates. Porcine pancreatic lipase type II (Sigma Aldrich, L3126-25G) was suspended in Tris-HCl buffer (2.5 mmol, pH 7,4 with 2,5 mmol NaCl) at a concentration of 200 units/mL. p-Nitrophenyl palmitate (PNPP), a PL substrate, was dissolved in Tris-Na deoxycholate buffer (50 mM Tris-HCl pH 8, 5 mM Na deoxycholate) to a final concentration of 320 µM. Each tested extract was preincubated with PL for at least 10 min at 37 °C before adding the substrate mixture to begin the reaction, which was also maintained at 37 °C. By comparing the lipase activity of PL with and without the extract, the percentage of PL’s residual activity was calculated for each extract. Orlistat, a well-known PL inhibitor, served as the positive control. The solvent’s final concentration was fixed and did not increase beyond 5% [69].