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

In this study, the extraction, purification and metabolic enzyme inhibition potential of <i>Selaginella doederleinii</i> were investigated. In order to extract the total biflavonoids from <i>S. doederleinii</i> (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 <i>S. doederleinii</i> 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.