An immobilization enzyme for screening lipase inhibitors from Tibetan medicines

With the increasing demand for lipase inhibitors and new drugs used in the clinical treatment of obesity, it is of great significance to screen lipase inhibitors from traditional Chinese medicines (TCMs) via capillary electrophoresis. In this work, Fe₃O₄@TiO₂ nanoparticles was fabricated by solvothermal method and employed as an improved magnetic support to immobilize lipase through electrostatic interaction. By the method of transmission electron microscopy, fourier transform infrared spectroscopy and X-ray diffraction, the magnetic nanoparticles were characterized. The immobilized enzyme possessed advantages of a wider range for pH and temperature endurance, better storage stability and reusability. The kinetics performances of the immobilized lipase were studied. When p-Nitrophenyl palmitate (pNPP) was used as enzyme substrate, the Michaelis-Menten constant was calculated to be 2.51 mM and its inhibition constant for Orlistat was ascertained to be 13.41 μM. Ultimately, the established method was applied to lipase inhibitors screening from 6 Tibetan medicines with lipase inhibitory activity and Oxytropis falcate Bunge was screened out for its supreme lipase inhibitory activity. 11 compounds in the Oxytropis falcate Bunge were further screened, five compounds exhibited similar inhibitory activity to Orlistat, and one compound (kaempferol) presented better inhibitory activity than Orlistat, which is the most commonly used drugs to treat obesity in clinic. This work not only developed a method for new anti-obesity drugs discovery, but also provided inspiration for exploring new medicinal value of the TCMs.