A systematic analysis of natural α-glucosidase inhibitors from flavonoids of Radix scutellariae using ultrafiltration UPLC-TripleTOF-MS/MS and network pharmacology

Background: Flavonoids from plant medicines are supposed to be viable alternatives for the treatment of type 2 diabetes (T2D) as less toxicity and side effects. Radix scutellariae (RS) is a widely used traditional medicine in Asia. It has shown great potential in the research of T2D. However, the pharmacological actions remain obscured due to the complex chemical nature of plant medicines. Methods: In the present study, a systematic method combining ultrafiltration UPLC-TripleTOF-MS/MS and network pharmacology was developed to screen a-glucosidase inhibitors from flavonoids of RS, and explore the underlying mechanism for the treatment of T2D. Results: The n-butanol part of ethanol extract from RS showed a strong alpha-glucosidase inhibition activity (90.55%, IC50 0.551 mg/mL) against positive control acarbose (90.59%, IC50 1.079 mg/mL). A total of 32 kinds of flavonoids were identified from the extract, and their ESI-MS/MS behaviors were elucidated. Thirteen compounds were screened as alpha-glucosidase inhibitors, including viscidulin III, 2',3,5,6',7-pentahydroxyflavanone, and so on. A compound-target-pathway (CTP) network was constructed by integrating these alpha-glucosidase inhibitors, target proteins, and related pathways. This network exhibited an uneven distribution and approximate scale-free property. Chrysin (k = 87), 5,8,2'-trihydroxy-7-methoxyflavone (k = 21) and wogonin (k = 20) were selected as the main active constituents with much higher degree values. A protein-protein interaction (PPI) weighted network was built for target proteins of these a-glucosidase inhibitors and drug targets of T2D. PPARG (C-d = 0.165, C-b = 0.232, C-c = 0.401), ACACB (C-d = 0.155, C-b = 0.184, C-c = 0.318), NFKB1 (Cd = 0.233, C-b = 0.161, C-c = 0.431), and PGH2 (C-d = 0.194, C-b = 0.157, C-c = 0.427) exhibited as key targets with the highest scores of centrality indices. Furthermore, a core subnetwork was extracted from the CTP and PPI weighted network. Type II diabetes mellitus (hsa04930) and PPAR signaling pathway (hsa03320) were confirmed as the critical pathways. Conclusions: These results improved current understanding of natural flavonoids on the treatment of T2D. The combination of ultrafiltration UPLC-TripleTOF-MS/MS and network pharmacology provides a novel strategy for the research of plant medicines and complex diseases.