Ultrasound-assisted extraction of total saponins from Ardisia mamillata Hance and their effects on the gut microbiota of mice fed a higher-fat and -sugar diet.

Ardisia mamillata Hance is a traditional Chinese medicinal plant rich in saponins and shows considerable potential for application in functional foods. However, systematic investigations into efficient extraction strategies and the biological activities of its constituents remain limited. To address this gap, the present study optimized an extraction process for total saponins from Ardisia mamillata Hance and evaluated their regulatory effects on gut microbiota dysbiosis induced by a high-fat, high-sugar diet in mice. Ultrasound-assisted extraction (UAE), combined with a Box-Behnken response surface design, was employed to optimize extraction parameters. The optimal conditions were determined to be an ethanol concentration of 71% (v/v), an ultrasonic time of 31 min, an ultrasonic temperature of 61 °C, and a solid-liquid ratio of 1:32 (g/mL). Under these conditions, the yield of total saponins reached (27.52 ± 0.16) mg/g, demonstrating superior extraction efficiency compared with conventional ethanol heating methods. In a diet-induced mouse model, administration of total saponins from Ardisia mamillata Hance partially inhibited body weight gain and alleviated excessive adipose accumulation, hepatocellular injury, and lipid metabolism disorders associated with the high-fat, high-sugar diet. Furthermore, the saponins contributed to the restoration of intestinal homeostasis by increasing the relative abundance of Muribaculaceae and Alloprevotella, enhancing short-chain fatty acid (SCFA) production, reducing the abundance of Lachnospiraceae_NK4A136 and Lactobacillus, and modulating the Firmicutes/Bacteroidetes (F/B) ratio. Overall, this study not only establishes an efficient extraction protocol for total saponins from Ardisia mamillata Hance but also highlights their potential to mitigate metabolic disorders through modulation of the "gut microbiota-SCFAs" axis. These findings provide a scientific foundation for the development of Ardisia mamillata Hance as a functional food ingredient or a promising prebiotic candidate.