Optimization of Ultrasonic-Assisted Extraction, Structural Characterization, and Bioactivities of Polysaccharides from Nitraria tangutorum Bobr.

Nitraria tangutorum Bobr. fruits are rich in bioactive polysaccharides (QBC) with high nutritional and developmental potential. This study optimized the ultrasonic-assisted extraction QBC via RSM, determining the optimal parameters to be 45 min, 59 °C, 19:1 mL/g, and 50% (150 W eq.), yielding 15.13%. Structurally, QBC exhibited a Mw of 1.997 × 105, Mw/Mn of 3.727, Rz of 15.6, and a monosaccharide molar ratio of rhamnose:arabinose:mannose:glucose:galactose = 1:1.12:1.66:7.3:1.86. In this study, the effects of QBC on oxidative stress markers and pro-inflammatory cytokines were evaluated via in vivo experiments. The results demonstrated that QBC significantly improved the thymic index and restored immune function. Specifically, QBC upregulated the expression of pro-inflammatory cytokines such as IL-6, TNF-α, and IFN-γ. The analysis of α/β diversity via 16S rRNA sequencing revealed that the CTX group induced a reduction in microbial richness, a more dispersed community structure, and increased intergroup dissimilarities. KEGG functional prediction indicated that polysaccharides regulated the ‘Infectious disease: parasitic’ and ‘Nitrotoluene degradation’ pathways, potentially by exerting their effects through metabolite-mediated immune regulation.