Ficus carica polysaccharide extraction via ultrasound-assisted technique: Structure characterization, antioxidant, hypoglycemic and immunomodulatory activities

In this research, the ultrasound-assisted extraction (UAE) conditions of the water-soluble polysaccharide (FCPS) from Ficus carica fruits were optimized using the response surface methodology. The optimal FCPS yield was 7.97 % achieved by conducting ultrasound-assisted extraction four times at a solid-liquid ratio of 1:20 (g/mL) and an ultrasound temperature of 70 °C. Then, the structure, antioxidant properties, hypoglycemic effects, and immunomodulatory activities of FCPS were evaluated. FCPS was characterized as irregular, rough-surfaced, flaky materials consisting of pyran-type polysaccharides with α- and β-glycosidic linkages, and composed of multiple monosaccharides and only one homogeneous concentrated polysaccharide component (FCPS1) with a molecular weight of 4.224 × 104 Da. The results suggested FCPS exhibited remarkable antioxidant activity in vitro, as evidenced by improved cell viability and reduced the reactive oxygen species (ROS) levels. Meanwhile, FCPS effectively improved liver-related insulin resistance by promoting glucose consumption in hepatocytes and activated the immune response through activation of murine bone marrow-derived dendritic cells (DCs) and upregulation of interleukin 6 (IL6) and interleukin 12 (IL-12) expression. The findings demonstrate the efficacy of the UAE technique in isolating FCPS with biological functionality and FCPS could potentially serve as a beneficial organic antioxidant source and functional food, carrying important implications for future studies.