Assessment of the structural characterization and anti-inflammatory activities of various parts of Astragalus (root, stem, leaf, flower) from a polysaccharide perspective

This study compares the synthesis mechanism, structural characteristics, and anti-neuroinflammatory activity of Astragalus polysaccharides (APS) from four parts of Astragalus membranaceus: root, stem, leaf, and flower. Ultrasonic-assisted extraction (UAE) was used to determine the optimal extraction conditions for APS: ultrasonic power of 291.76 watts, extraction time of 61.45 min, solid-liquid ratio of 1:27.88, and temperature of 60 °C, which significantly increased the APS yield. The highest APS content was found in the root (16.34 %), followed by the stem and leaf, with the flower containing the least. Transcriptomic and miRNA sequencing revealed significant differences in gene expression among tissues. Genes related to APS synthesis were most active in the root, while the stem, leaf, and flower exhibited distinct expression profiles related to secondary metabolite synthesis. Functional experiments demonstrated that APS from all parts inhibited LPS-induced inflammatory responses in BV2 microglial cells, reducing the production of NO, TNF-α, and IL-1β, with root-derived APS showing the strongest activity. Structural analyses further indicated notable differences in monosaccharide composition, molecular weight, and ultrastructure among APS from different parts. Root APS was predominantly composed of glucose (91.01 %) and had the lowest molecular weight. Flower APS had the highest molecular weight and was rich in galacturonic acid and galactose. Leaf APS contained rhamnose (22.76 %) and displayed unique structural features. These findings provide multi-dimensional insights into the tissue-specific regulatory mechanisms and bioactivity variations of APS, offering a theoretical foundation for the targeted development and utilization of Astragalus polysaccharides.