Antidiabetic and Antigout Properties of the Ultrasound-Assisted Extraction of Total Biflavonoids from Selaginella doederleinii Revealed by In Vitro and In Silico Studies

Abstract

In this study, the extraction, purification and metabolic enzyme inhibition potential of Selaginella doederleinii were investigated. In order to extract the total biflavonoids from S. doederleinii (SDTBs), the optimum extraction process was obtained by optimizing the ultrasonic extraction parameters using response-surface methodology. This resulted in a total biflavonoid content of 22.26 ± 0.35 mg/g. Purification of the S. doederleinii extract was carried out using octadecylsilane (ODS), and the transfer rate of the SDTBs was 82.12 ± 3.48% under the optimum purification conditions. We determined the effect of the SDTBs on α-glucosidase (AG), α-amylase and xanthine oxidase (XOD) and found that the SDTBs had an extremely potent inhibitory effect on AG, with an IC₅₀ value of 57.46 μg/mL, which was much lower than that of the positive control. Meanwhile, they also showed significant inhibition of XOD and α-amylase, with IC₅₀ values of 289.67 μg/mL and 50.85 μg/mL, respectively. In addition, molecular docking studies were carried out to understand the nature of the action of the biflavonoids on AG and XOD. The results showed that robustaflavone had the lowest binding energy to AG (-11.33 kcal/mol) and XOD (-10.21 kcal/mol), while, on the other hand, amentoflavone showed a good binding affinity to AG (-10.40 kcal/mol) and XOD (-9.962 kcal/mol). Moreover, molecular dynamics simulations verified the above results.

Keywords: Selaginella doederleinii; bioflavonoids; enzyme inhibition; molecular docking.

Figure 1

Chromatograms of samples (a) and mixed standards (b) (1 for Amentoflavone (AMF), 2 for Robustaflavone (ROF), 3 for Hinokiflavone (HIF), 4 for Heveaflavone (HEF)).

Figure 2

Three-dimensional structures of the proteins (represented by a cartoon model) α-glucosidase (A) and XOD (B); three-dimensional structures of small-molecule ligands allopurinol (C), AMF (D), acarbose (E) and ROF (F).

Figure 3

Effects of extraction time (A), extraction power (B), extraction concentration (C), extraction temperature (D) and liquid-solid ratio (E) on the total biflavonoids from Selaginella doederleinii.

Figure 4

Response surface plots and contour plots show the effect of (A) extraction time and ultrasonic power, (B) extraction time and ethanol concentration, and (C) ultrasonic power and ethanol concentration on response of the total biflavonoids from Selaginella doederleinii.

Figure 5

Transfer rates of different fillers (A); Transfer rates of biflavonoids in Selaginella doederleinii under different elution conditions (methanol concentration (B), elution flow rate (C), sample concentration (D)).

Figure 6

Enzyme activity results ((A) for α-glucosidase, (B) for α-amylase, (C) for xanthine oxidase (XOD)).

Figure 7

Two-dimensional plots of the binding details of α-glucosidase protein and the small molecules acarbose (A), AMF (B) and ROF (C), and 2D plots of the binding details of XOD protein and the small molecules allopurinol (D), AMF (E) and ROF (F). Dashed lines indicate hydrogen bonds and red eyelashes indicate hydrophobic interaction amino acids.

Figure 8

Global view (left) of the binding of α-glucosidase protein and the small molecules acarbose (A), AMF (B) and ROF (C), and 3D view of the binding details of the optimal structure (right). Proteins are represented as cartoons and small molecules as stick models; red dashed lines indicate hydrogen bonds, blue dashed lines indicate π–π interactions, yellow dashed lines indicate van der Waals/hydrophobic interactions and pink dashed lines indicate ion–π interactions.

Figure 9

Global view (left) of the binding of the XOD proteins and the small molecules allopurinol (A), AMF (B) and ROF (C) as well as 3D view of the binding details of the optimal structures (right). Proteins are represented as cartoons and small molecules as stick models; red dashed lines indicate hydrogen bonding, blue dashed lines indicate π–π interactions and yellow dashed lines indicate van der Waals/hydrophobic interactions.

Figure 10

AG MD results: (A) RMSD; (B) RMSF; (C) Rg; (D) H-bonds.

Figure 11

XOD MD results: (A) RMSD; (B) RMSF; (C) Rg; (D) H-bonds.