Structural characteristics and antioxidant activity of a low-molecular-weight jujube polysaccharide by ultrasound assisted metal-free Fenton reaction

This study used an ultrasonically accelerated metal-free Fenton (H₂O₂-V_c system) reaction to promote water-extracted degrading polysaccharides from <i>Ziziphus Jujuba cv. Muzao</i> (DZMP). A novel jujube polysaccharide (DPZMP3) was obtained by degradation using DEAE-Sepharose Fast Flow and Sephacryl S-100 column chromatography. Methylation analysis, HPGPC, ion chromatography, FT-IR, and NMR spectroscopies were used to clarify the chemical structures of DPZMP3. Monosaccharide compositional analysis of DPZMP3 revealed the presence of Rha, Ara, Gal, and GalA at a molar ratio of 1.00:1.49:1.60:7.68, and the HPGPC data demonstrated the average <i>Mw</i> of 34.3 kDa. Based on the structural and linkage research using NMR spectroscopy and GC-MS, it was determined that DPZMP3 was a homogalacturonan pectic polysaccharide with a (1 → 4)-Gal<i>p</i> branch at C-6 and a small amount of Ara<i>f</i> and Rha<i>p</i> residues. The ultrasonic-aided Fenton treatment did not significantly alter the structure of DPZMP3. It may also be useful for DZMP and enhancing their antioxidant activity <i>in vitro</i>. The current study's findings could pave the way for the food sector to use jujube polysaccharides obtained by degradation as a functional food component.