Optimization of extraction, structural modification, and bioactivity of polysaccharides from <i>Euphorbia trigona</i> Mill. and their derivatives

The optimal hot water extraction process for a polysaccharide from <i>Euphorbia trigona</i> Mill. was established using single-factor and orthogonal experiments, yielding the best conditions of a 1:30 (g/mL) solid-to-liquid ratio at 90 °C for 3.5 h, with a polysaccharide yield of 5.89%. Sulfated (ETM-S) and phosphorylated (ETM-P) derivatives were successfully prepared, with degree of substitution of 0.32 and 0.48, respectively. Structural analysis confirmed the polysaccharides were acidic with complex monosaccharide compositions. Bioactivity assessments revealed that both modifications markedly improved functional properties. ETM-P exhibited significantly enhanced antioxidant activity, with IC₅₀ values of 2.16, 1.57, and 1.79 mg/mL against DPPH, ·OH, and O₂·^-, respectively. Sulfation boosted inhibitory effects on α-amylase and α-glucosidase, suggesting hypoglycemic potential, and also increased pancreatic lipase inhibition, indicating a synergistic role in regulating glucose and lipid metabolism. Furthermore, ETM-S showed the strongest <i>in vitro</i> cytotoxicity against HepG2 cells, achieving an inhibition rate of 45.00% at 800 μg/mL, outperforming ETM-P (33.37% at 400 μg/mL) and the native polysaccharide (27.92% at 800 μg/mL). Both modified polysaccharides promoted RAW264.7 macrophage proliferation, enhanced phagocytosis, and stimulated NO release, demonstrating immunomodulatory capacity. In summary, chemical modification, especially sulfation, effectively enhances the bioactivities of polysaccharides, showing promise for regulating glycolipid metabolism and immune modulation.