摘要
The functions of polysaccharides are governed by their structures, making sample purity essential for robust structure-activity studies. Polygalacturonic acid (PGA) is widely used as a reference hydrocolloid in bioactivity and materials science research. However, commercial PGA is frequently contaminated with co-purifying polysaccharides, which complicates structure-activity relationship studies. This study identifies a prevalent impurity in commercial PGA and reveals its previously unrecognized, dual role in governing both immunostimulatory activity and hydrogel properties. Using chromatographic methods combined with enzymatic strategies, we isolated two distinct impurities and further purified PGA (pPGA). The impurities were determined to be a free β-1,4-galactan (Galactan) and a rhamnogalacturonan I decorated with β-1,4-galactan side chains (RGI) by structural analyses via MS, NMR, methylation and oligosaccharide profiling. Among them, only the RGI—which naturally carries galactan side chains—triggered a significant immune response in RAW264.7 cells, activating MAPK signaling and increasing levels of NO, IL-6, IL-1β, and TNF-α In contrast, neither the pPGA nor the other impurity, Galactan, showed any immunostimulatory activity. Critically, this bioactive RGI was also essential for material properties. Its removal from commercial PGA markedly weakened the Ca 2+ -crosslinked gels, leading to reductions in both storage (G′) and loss (G″) moduli and resulting in a fragile microstructure. In contrast, the removal of the Galactan did not significantly affect the properties of the hydrogel. Our findings demonstrate that a co-purifying RGI, not PGA itself, is the decisive factor for key biological and physical functionalities attributed to commercial PGA. This finding emphasizes the importance of using structurally defined polysaccharides standards for accurate mechanistic research and controlled biomaterial design.
危险品化学品经营许可证（带存储）