Optimization of Ultrasonic-Assisted Extraction, Structural Characterization, and Bioactivities of Polysaccharides...

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.