Extraction optimization, purification, characterization, and hypolipidemic activities of polysaccharide from pumpkin

Polysaccharides derived from pumpkin have garnered increasing interest due to their diverse biological activities. In this study, pumpkin polysaccharides were extracted using an ultrasound-assisted extraction method, optimized via response surface methodology. The optimal extraction conditions were identified as follows: a solid-liquid ratio of 1:60 (g/mL), an extraction time of 1.9 h, an extraction temperature of 62 °C, and an ultrasonic power of 286 W. Under these conditions, the total carbohydrate content in pumpkin polysaccharides reached 71.14 ± 1.53 %, closely aligning with the predicted value. Post extraction, the polysaccharides were purified using DEAE Sepharose Fast Flow and Sephadex G-100 columns, resulting in a pure fraction termed PPS3. Structural analysis revealed that PPS3, with a molecular mass of 5.96 × 10 4  Da, consisted of mannose, glucosamine hydrochloride, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, and arabinose in a molar ratio of 0.005:0.004:0.041:0.013:0.545:0.004:0.241:0.147, respectively. The backbone primarily contained →4)-α-D-GalpA-6-OMe-(1→ residue with several branched chains. Functionally, PPS3 demonstrated potent in vitro hypolipidemic activities. These findings elucidated the structural characteristics of pumpkin polysaccharides and suggested their potential as natural hypolipidemic agents.