Screening of α-Glucosidase Inhibitors in Extracts of Polygonum bistorta Based on Spectrum-Effect Relationship

Bistortae Rhizoma is a traditional Chinese medicine, which is the dried rhizome of Polygonum bistorta (PB). It has anti-inflammatory, antibacterial, antioxidant, anti-diabetic effects and so on. Among them, there exists a limited number of studies investigating the anti-diabetic effect of PB, and the specific ingredients responsible for this effect remain unclear. To rapidly screen α-glucosidase inhibitors in extracts of PB, this study explored the relation between effective components and enzyme inhibitory activity based on component-effect analysis, revealing its key active component. After the suppressing effect of extracts of PB from different batches on α-glucosidase was tested, high performance liquid chromatography (HPLC) was employed to plot fingerprint of PB and evaluate the similarity of fingerprint. Combined with HPLC-Q-Orbitrap high-resolution mass spectrometry (HRMS)/MS qualitative analysis, the grey relational analysis and partial least squares regression analysis were performed to screen active components, and molecular docking was used for activity validation. The results indicated that the 11 batches of PB extracts can effectively inhibit α-glucosidase, with half-maximal inhibitory concentration (IC50) of 1.71-35.62 µg/mL, which had stronger inhibitory activity compared to the positive control acarbose (IC50 of 148.00 µg/mL). Among them, the PB07 batch of PB extract derived from Shandong province exerted the best inhibitory effect, with an IC50 of 1.71 µg/mL. The grey relational analysis and partial least squares regression analysis revealed that in the 11 batches of samples, 7 characteristic peaks had a relatively large correlation value with the inhibitory activity of PB on α-glucosidase, and the regression coefficient was positively correlated with inhibitory activity, indicating the importance of variables and high contribution. Through secondary mass spectrometry and database comparison, the 7 components were identified as 6-O-galloylglucose, L-tryptophan, (+)-gallocatechin-(4α→8)-(+)-catechin, deacetyl asperuloside, chlorogenic acid, catechin-5-O-glucoside, and digalloylglucose. It is noteworthy that the 7 components were all identified as α-glucosidase inhibitors in PB extract for the first time. Further molecular docking results showed that the binding energies of the 7 active components to α-glucosidase were all less than -6.0 kcal/mol, hinting significant inhibitory activity of α-glucosidase. Among them, the binding energy of catechin-5-O-glucoside was the lowest (-8.7 kcal/mol), which impacted enzyme active center mainly through hydrogen bonding. The results of this study provide research ideas for the development of hypoglycemic drugs using PB in the future.