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

Abstract

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 α-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 α-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 α-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 α-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 α-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 (C_d = 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.

Keywords: Flavonoids; LC-MS; Network pharmacology; Radix scutellariae; Ultrafiltration; α-Glucosidase inhibitors.

Fig. 1

Chemical structures of the potential α-glucosidase inhibitors from flavonoids of Radix Scutellariae extract

Fig. 2

Compound-target-pathway (CTP) network of the potential α-glucosidase inhibitors from RS. The network consists of 13 red nodes (potential α-glucosidase inhibitors), 117 yellow nodes (target proteins), 86 green nodes (pathways), and 877 connections. The larger circles denote key nodes with the most connections. Node information is listed in Additional file 4. Gray lines represent connections

Fig. 3

a Degree distribution of the CTP network. k represents degree values, and that P(k) indicates degree distribution. b Degree values (k) of all nodes in the CTP network, ranked in a descending order

Fig. 4

Protein-protein interaction (PPI) weighted network for the ligands of α-glucosidase inhibitors from RS and targets of T2D, containing 104 nodes and 228 connections. The yellow nodes are the targets of potential α-glucosidase inhibitors from RS, and that blue nodes represent therapeutic targets of T2D

Fig. 5

a Average strength s(k) as a function of degree k in logarithmic coordinates. The data points are fitted to a straight line, showing the relation s(k) ∼ k^β.b Node strengths of the PPI network sorted in descending order. c Disparity Y(k) in the edge weight decays as a function of k. The data points are well approximated by the curve Y(k) = 1/k

Fig. 6

Three-dimensional diagram of degree centrality (C_d), betweenness centrality (C_b) and closeness centrality (C_c) for the nodes in PPI network

Fig. 7

Core subnetwork for the potential α-glucosidase inhibitors and type 2 diabetes mellitus, consisted of 29 nodes and 47 connections. The yellow nodes are the targets of potential α-glucosidase inhibitors from RS, and that blue nodes indicate therapeutic targets of T2D. Red and green nodes represent the related α-glucosidase inhibitors and pathways, respectively

Fig. 8

Critical pathways of the potential α-glucosidase inhibitors from RS. a Type 2 diabetes mellitus pathway. b PPAR signaling pathway. The yellow nodes are the targets of potential α-glucosidase inhibitors from RS, blue nodes indicate therapeutic targets of T2D, and that pink nodes denote targets belonged to both the two groups. Red nodes represent the related α-glucosidase inhibitors