4-Methylumbelliferyl oleate is a fluorescent substrate for lipases (Ex/Em=320/450 nm), which can be cleaved by lipase and can be used to measure pancreatic inhibitory activity.

Pancreatic lipase inhibitory activity was assessed by employing 4-Methylumbelliferyl (4-MU) oleate as the substrate. The assay mixture contained 0.1 mM 4-MU oleate (50 µL), McIlvaine buffer (20 µL of 0.1 M citrate-Na2HPO4, pH 7.4), and the test sample (5 µL). This was followed by the addition of porcine pancreatic lipase (25 µL), adjusting the total volume to 0.1 mL. Post incubation at 37℃ for 10 minutes, lipase-catalyzed liberation of 4-MU was quantified using fluorescence multi-detection reader at excitation and emission wavelengths of 320 nm and 450 nm, respectively [1].