A Comparative Study on the Structural Properties of Polysaccharides From Nitraria sibirica Fruits With Different Extraction Methods and Their Antioxidant and Prebiotic Activities

In this paper, the physicochemical, structural properties, antioxidant, and prebiotic activities of polysaccharides obtained from Nitraria sibirica pall fruit with different extraction methods were investigated and compared. Structural features were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, x-ray diffraction, Congo red staining, thermogravimetric analysis, periodate oxidation, and Smith degradation analysis. Results showed that extraction methods had a remarkable impact on the chemical compositions and structural properties of the polysaccharides. Ultrasound or enzyme-assisted extraction significantly increased the yield and functionality of Nitraria sibirica polysaccharides (NSPs), yielding the highest amount of 14.11% ± 1.23% and exhibiting the strongest DPPH/•OH scavenging ability with IC₅₀ values of 0.209/0.138 mg/mL. At the same time, pectinase released the highest neutral sugar of 61.24% ± 1.39%. All NSPs are rhamnose-rich heteropolysaccharides with distinct Mw and surface morphology, and the extraction method did not alter monosaccharide types, but affected their molar ratio. Crucially, each NSP selectively stimulated probiotic growth (Bifidobacterium adolescentis, Lactobacillus bulgaricus, Enterococcus faecalis), confirming the NSP's prebiotic potential. The biological activity correlates with uronic acid level, molecular weight, and surface porosity, rather than any single factor. These results could provide a theoretical and technical foundation for selecting the appropriate extraction method for Nitraria sibirica polysaccharides, thereby enabling their applications in the pharmaceutical, cosmetic, and food industries.