Polysaccharide of caper (Capparis spinosa L.) Leaf: Extraction optimization, antioxidant potential and antimicrobial activity

•The Capparis spinosa leaves can be used as a potential, low-cost source of polysaccharide.•Box-Behnken design was applied to find out the optimum conditions.•Second order polynomial regression models were developed.•The real experiments demonstrated the validation of the proposed model by RSM.•Macromolecular characterizations of polysaccharides extract were determined.•Polysaccharides from Capparis spinosa leaves exhibited significant antioxidant activity.

Three-variable-three-level Box-Behnken design-response surface methodology (BBD-RSM) based on the single-factor experiments was used to optimize the extracting parameters of crude polysaccharides (CPSs) from the Capparis spinosa leaves (CSL) including extraction time (ETi, 60-120 min), extraction temperature (ETe, 60-80 °C), and the water/solid ratio (W/S, 6-16). The optimal process conditions in order to the highest yield (6.73%) of CSL-CPSs were 119.8 min ETi, 72.84 °C ETe, and 15.97:1W/S.Structure of polysaccharide extracted at the optimal operating point were identified by Fourier transform-infrared spectroscopy (FT-IR). CSL-CPSs (50-300 μg/L) revealed significantly scavenging activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH)and OH free-radicals in vitro. A much more antimicrobial activity using this polysaccharide against Gram-negative bacteria (Escherichia coli, Shigella dysenteriaeandSalmonella typhi) was found than Gram-positive bacteria (Bacillus panis and Staphylococcus aureus). CSL-CPSs can thus be used as anexcellent antioxidant and antimicrobial ingredient in food and medicinal preparations.