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.