Japanese grape (Hovenia dulcis) polysaccharides: New insight into extraction, characterization, rheological...

In this study, accelerated solvent extraction (ASE) technology was applied to extract Hovenia dulcis polysaccharides (HDPs). The polysaccharide yields, physicochemical properties, rheological properties, antioxidant activities, and hypoglycemic effects were compared between ASE-HDPs and hot water extracted polysaccharides (HWE-HDPs). The maximum ASE-HDPs yield was obtained using a response surface method (RSM) with optimized ASE conditions comprising 2 cycles at 130 °C for 23 min. The maximum ASE-HDPs yield of 8.62 ± 0.29% is significantly higher than the maximum HWE-HDP yield of 6.89 ± 0.21%. The chemical compositions, molecular weight (Mw) distributions, rheological properties, antioxidant activities, and hypoglycemic effects of polysaccharides varied with each extraction method, while the primary structure remained the same. Both HDPs exhibited typical shear thinning behavior and non-Newtonian properties. The storage modulus (G') and loss modulus (G″) of the HDPs solutions were enhanced with increasing oscillation frequency, and displayed gelatinous behavior (G' > G″). ASE-HDPs displayed better antioxidant activities in DPPH and ABTS, as well as superior reducing power and hydroxyl and superoxide anion scavenging ability, whereas HWE-HDPs exhibited higher Fe²⁺ chelating activity. The in vitro experiments indicated that HDPs have a decidedly hypoglycemic effect.