Ultrasound-assisted extraction, purification, structural characterization, and hypoglycemic activities of a polysaccharide from Momordica charantia L.

Polysaccharides from Momordica charantia L. (MCP) have attracted interest for their diverse biological activities. This study investigated the ultrasound-assisted extraction of MCP, optimizing conditions using response surface methodology. The optimal extraction parameters were a material-liquid ratio of 1:4 (g/mL), a temperature of 74 °C, an extraction time of 2.4 h, and an ultrasonic power of 296 W, resulting in a total carbohydrate content of 40.22 ± 1.69 %, closely matching theoretical predictions. Following extraction, MCP was purified using DEAE Sepharose Fast Flow anion exchange and Sephadex G-100 dextran gel chromatography, isolating a pure polysaccharide fraction, MCPS-3. Structural analysis revealed that MCPS-3, with a molecular mass of 93.796 kDa, consisted of rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, and arabinose in molar ratios of 10.66:3.66:258.0:1.0:51.0:9.338. Methylation and NMR analyses suggested that MCPS-3 was a complex polysaccharide, predominantly homogalacturonan domains with rhamnogalacturonan I side chains. In functional assays, MCPS-3 demonstrated inhibition of α-amylase and α-glucosidase activities. Additionally, in insulin-resistant HepG2 cells, MCPS-3 improved glucose consumption, increased glycogen content, and enhanced the activities of hexokinase and pyruvate kinase. These findings provided insights into the structural properties of MCPS-3 and underscored its potential as a natural compound with significant hypoglycemic activity.