Pancreatic lipase inhibitory constituents from Fructus Psoraleae.

Pancreatic lipase (PL), a crucial enzyme in the digestive system of mammals, has been proven as a therapeutic target to prevent and treat obesity. The purpose of this study is to evaluate and characterize the PL inhibition activities of the major constituents from Fructus Psoraleae (FP), one of the most frequently used Chinese herbs with lipid-lowering activity. To this end, a total of eleven major constituents isolated from Fructus Psoraleae have been obtained and their inhibition potentials against PL have been assayed by a fluorescence-based assay. Among all tested compounds, isobavachalcone, bavachalcone and corylifol A displayed strong inhibition on PL (IC50 < 10 µmol·L-1). Inhibition kinetic analyses demonstrated that isobavachalcone, bavachalcone and corylifol A acted as mixed inhibitors against PL-mediated 4-methylumbelliferyl oleate (4-MUO) hydrolysis, with the Ki values of 1.61, 3.77 and 10.16 µmol·L-1, respectively. Furthermore, docking simulations indicated that two chalcones (isobavachalcone and bavachalcone) could interact with the key residues located in the catalytic cavity of PL via hydrogen binding and hydrophobic interactions. Collectively, these finding provided solid evidence to support that Fructus Psoraleae contained bioactive compounds with lipid-lowering effects via targeting PL, and also suggested that the chalcones in Fructus Psoraleae could be used as ideal leading compounds to develop novel PL inhibitors.

Inhibition of pancreatic lipase by the constituents in St. John's Wort: In vitro and in silico investigations.

Herbal medicines are frequently used for the prevention and treatment of obesity and obesity-related disorders. Our preliminary screening showed that St. John's Wort (SJW) displayed potent inhibition on pancreatic lipase (PL), a key hydrolase responsible for lipid digestion and absorption in mammals. Herein, the inhibition potentials and inhibitory mechanism of SJW extract and its major constituents on PL were fully investigated by a set of in vitro and in silico studies. The results clearly demonstrated that the naphthodianthrones, biflavones and most of flavonoids in SJW displayed strong to moderate inhibition on PL. Among all tested natural compounds, two naphthodianthrones (hypericin and pseudohypericin) and one biflavone (I3,II8-biapigenin) isolated from SJW exhibited potent PL inhibition activity, with the IC50 values of <1 µM. Inhibition kinetics analyses showed that hypericin, pseudohypericin and I3,II8-biapigenin inhibited PL via a mixed manner, while molecular dynamics simulations revealed that three newly identified PL inhibitors could bind on PL at both the catalytic cavity and the interface between colipase and the C-terminal domain of PL. Collectively, our findings suggested that part of major constituents in SJW displayed potent PL inhibition activities, which could be used as lead compounds for the development of novel PL inhibitors.