Optimization extraction of polysaccharide from Tunisian Zizyphus lotus fruit by response surface methodology: Composition and antioxidant activity

• Water soluble polysaccharides were extracted from Z. lotus fruit.
• Box–Behnken design of RSM methodology was used for optimization of polysaccharides extraction conditions.
• Macromolecular characterization and monosaccharide composition of polysaccharides extract were determined.
• Polysaccharides from Z. lotus fruit (pulp and peel) exhibited significant antioxidant activity.

Response surface methodology using a Box-Behnken design was employed to optimize extraction temperature, extraction time and ratio of water to material to obtain a maximum polysaccharide yield with high uronic acid content and antioxidant property from edible Zizyphus lotus fruit. The optimal conditions were: extraction time of 3 h 15 min, extraction temperature of 91.2 °C and water to solid ratio of 39 mL/g. Under these conditions, the experimental extraction yield, uronic acid content and 2,2-diphenyl-1-picrylhydrazyl scavenging ability (IC50) were 18.88%, 41.89 and 0.518 mg/mL, respectively. Chemical analysis revealed that the extract was composed of 97.92% carbohydrate of which 41.89% is uronic acid. The extracted polysaccharides, with an average molecular weight of 2720 kDa, are composed of arabinose, rhamnose, glucose, fructose, galactose and xylose. Moreover, the polysaccharides exhibited a significant reducing power and anti-lipid peroxidation activities.