Efficient screening of pancreatic lipase inhibitors from Rheum palmatum by affinity ultrafiltration-high-performance liquid chromatography combined with high-resolution inhibition profiling.

Introduction: Pancreatic lipase is one of the most important key targets in the treatment of obesity. Inhibition of pancreatic lipase can effectively reduce lipid absorption and treat obesity and other related metabolic disorders.

Objectives: The goal of this study is the efficient screening of pancreatic lipase inhibitors in the root and rhizome of Rheum palmatum using affinity ultrafiltration-high-performance liquid chromatography (AUF-HPLC) combined with high-resolution inhibition profiling (HRIP).

Methods: Potential pancreatic lipase ligands and pancreatic lipase inhibitors in ethyl acetate fraction of R. palmatum were screened using AUF-HPLC and HRIP, respectively. All screened compounds were identified by HPLC- quadrupole time-of-flight (Q-TOF)/MS. Eight compounds were screened out by both AUF-HPLC and HRIP, and six compounds were screened out by either AUF-HPLC or HRIP alone. The pancreatic lipase inhibitory activities of all screened compounds were verified by enzyme inhibition assay and molecular docking.

Results: Five new potent pancreatic lipase inhibitors were discovered, namely procyanidin B5 3,3'-di-O-gallate (IC = 0.06 ± 0.01 μM), 1,6-di-O-galloyl-2-O-cinnamoyl-β-D-glucoside (IC = 12.83 ± 0.67 μM), 1-O-(1,3,5-trihydroxy)phenyl-2-O-galloyl-6-O-cinnamoyl-β-D-glucoside (IC = 17.84 ± 1.33 μM), 1,2-di-O-galloyl-6-O-cinnamoyl-β-D-glucoside (IC = 18.39 ± 1.52 μM), and 4-(4'-hydroxyphenyl)-2-butanone-4'-O-β-D-(2"-O-galloyl-6"-O-cinnamoyl)-glucoside (IC = 2.91 ± 0.40 μM). It was found that procyanidin B5 3,3'-di-O-gallate showed higher pancreatic lipase inhibitory activity than the positive control orlistat (IC = 0.12 ± 0.02 μM).

Conclusion: The combination of affinity ultrafiltration-high-performance liquid chromatography (AUF-HPLC) and high-resolution inhibition profiling (HRIP) could reduce the risk of false-negative screening and missed screening and could achieve more efficient screening of bioactive compounds in complex natural products.