Phenolic profiles and screening of potential α-glucosidase inhibitors from Polygonum aviculare L. leaves using ultra-filtration combined with HPLC-ESI-qTOF-MS/MS and molecular docking analysis

Abstract Polygonum aviculare L. leaves (PALs), as an important medicinal crop product, have been reported to have a strong α-glucosidase inhibitory effect. However, it is unclear which exact active compositions are primary responsible for the beneficial effects. This study showed that PALs extracted with 70 % ethanol as solvent had significantly higher total phenolic/flavonoid contents and α-glucosidase inhibitory activity than PALs extracted with other solvents. The PALs ethanol extracts showed excellent α-glucosidase inhibitory activity (IC50 = 21.42 ± 1.37 μg/mL), which was significantly higher than that of anti-diabetes drug acarbose (IC50 = 176.79 ± 1.72 μg/mL). The phenolic compositions of the PALs extracts were identified by high performance liquid chromatography and quadrupole-time-of-flight-mass spectrometry (HPLC-ESI-qTOF-MS/MS) method. In order to discriminate the specific α-glucosidase inhibitors from the PALs extract, an combined strategy integrating affinity ultrafiltration and HPLC-ESI-qTOF-MS/MS was developed. Seven potential α-glucosidase inhibitors with high affinity ability including orientin, myricitrin, hyperoside, isoquercitrin, o-coumaric acid, polydatin and quercetin from PALs extract were screened. The α-glucosidase inhibitory activity assay confirmed that myricitrin (IC50 = 8.65 ± 1.48 μg/mL), quercetin (IC50 = 15.17 ± 3.25 μg/mL), and polydatin (IC50 = 35.15 ± 3.25 μg/mL) were primarily responsible for the α-glucosidase inhibitory activity of the PALs extract. Then, structure-activity relationships of these potential inhibitors were also discussed. More importantly, the possible inhibitory mechanisms of the identified inhibitors toward α-glucosidase were further clarified by molecular docking analysis. In conclusion, the proposed method can be used to effectively recognize the potential α-glucosidase inhibitors from complex extracts system in natural products.