Determination of α-glucosidase inhibitors from Scutellaria baicalensis using liquid chromatography with quadrupole time of flight tandem mass spectrometry coupled with centrifugal ultrafiltration

The present study aimed at identifying potential lead compounds for diabetes mellitus drug discovery. We developed a novel method involving centrifugal ultrafiltration separation subsequent liquid chromatography with quadrupole time of flight tandem mass spectrometry (LC-Q/TOF-MS/MS) determination to screen -glucosidase inhibitors in complex Scutellaria baicalensis Georgi (SBG) extract. By adding a second filter to the screening process, the level of non-specific binding of Compounds 1, 3, 10 and 11 was significantly decreased, and the level of non-specific binding of Compounds 5 and 15 also was reduced. As a result, five flavonoids identified as baicalein, baicalein, wogonin, chrysin, and oroxylin A, were rapidly found to interact with -glucosidase and possess potent anti--glucosidase activity in vitro. Specific binding of ligands to -glucosidase was demonstrated though the proposed method and the ligands could be ranked in order of affinity for -glucosidase, which were corresponded to the order of inhibitory activity in vitro. In conclusion, our results indicated that the developed method is a rapid and effective screening method for rat intestinal -glucosidase inhibitors from complex herbal medicines such as SBG.