Ultrasound–microwave synergistic extraction enhances bioactivities of Phyllanthus emblica L. polysaccharides through structure–function modulation

Phyllanthus emblica L. is a traditional medicinal and edible plant, and its primary bioactive constituents are polysaccharides. In this study, the Ultrasonic-Microwave synergistic extraction method (UMSE) was used to extract polysaccharides from Phyllanthus emblica L. (PEP) under optimized conditions: microwave power of 370 W, ultrasonic power of 340 W, a solid–liquid ratio of 1:6.5 (w/v), and a time of 25 min, resulting in an extraction yield of 8.05 % ± 0.12 %. After purification using DEAE-52 cellulose and Sephadex G-100, three polysaccharide fractions exhibiting distinct differences in molecular weight named PEP-A, PEP-B, and PEP-C were obtained. Structural characterization demonstrated that UMSE influenced the monosaccharide composition, spectral properties, surface morphology, and thermal stability of the polysaccharides, revealing the regulatory effect of extraction methods on structure. Bioactivity assays indicated that all three polysaccharides exhibited concentration-dependent scavenging activity against DPPH, ABTS, and hydroxyl radicals. They also stimulated the proliferation and phagocytic activity of RAW 264.7 macrophages and increased production of NO, ROS, TNF-α, IL-1β, IL-6, and IL-10. In summary, UMSE not only enhanced extraction efficiency but also improved the antioxidant and immunomodulatory activities of the polysaccharides by changing their structural characteristics, underscoring the close correlation between extraction method, structure, and bioactivity. This study provides a theoretical basis for the application of PEP as functional food ingredients and laid a foundation for their use in health-promoting products and nutraceuticals.