The polysaccharides from blackened jujube with ultrasonic assistance extraction: Optimization of extraction conditions, antioxidant activity and structural analysis

Jujube is a widely grown agricultural product. In order to avoid the waste of resources and improve the added value of the blackened jujube, the blackened jujube was processed under certain temperature and humidity conditions. At present, there are relatively few researches on polysaccharides of blackened jujube. The selection of extraction method is very important for the study and utilization of plant polysaccharides. Ultrasonic assisted extraction technology has been widely used in polysaccharide extraction for its advantages of environmental protection, economy and high extraction rate. In order to fully tap the utilization potential of polysaccharides from blackened jujube, the ultrasonic assisted extraction technology of polysaccharides from blackened jujube was optimized. Based on the optimal conditions obtained by response surface analysis, the extraction rate of polysaccharide was as high as 12.75 ± 0.05%. The IC₅₀ values of hydroxyl radical, DPPH radical and superoxide anion were 2.604 mg/mL, 0.754 mg/mL and 8.069 mg/mL, respectively. The blackened jujube polysaccharide (BJP) was mainly composed of rhamnose (Rha), arabinose (Ara), galactose (Gal) and galacturonic acid (Gal-UA), with a molecular weight of 1.42 × 10⁶ Da, and the surface was a dense network structure with voids. The results showed that ultrasound-assisted extraction could extract polysaccharides more economically and efficiently. In this study, the polysaccharide extracted from blackened jujube has natural antioxidant effect, which may be related to the high content of galacturonic acid in polysaccharide and the molecular chain structure of polysaccharide can be destroyed by ultrasonic wave. As a kind of natural antioxidant, blackened jujube polysaccharide has important application value in functional products in food and medicine industries.