Ultrasound-assisted extraction optimization of Ganoderma sinense polysaccharides and comparative structural analysis across six Ganoderma species

This study optimized ultrasound-assisted extraction (UAE) of Ganoderma sinense polysaccharides using response surface methodology with a Box-Behnken design. Optimal conditions (47–52 °C, solid–liquid ratio 1:35–1:40, ultrasound time 45–55 min) improved extraction yield at relatively low temperatures compared to conventional hot water extraction (80–100 °C). Comparative analysis of six Ganoderma species ( G. sinense, G. lucidum, G. applanatum, G. resinaceum, G. cochlear, and G. hainanesis ) revealed substantial interspecies variations in yields (3.86 %–12.15 %), total sugar contents (11.24 %–42.88 %), and molecular weights (1.76 kDa–1.44 × 10 5  kDa). Monosaccharide profiles were dominated by glucose and galactose (>70 %), with species-specific distribution. FT-IR spectroscopy revealed species-specific functional group variations, while methylation analysis of G. lucidum polysaccharides identified primarily (1 → 3)- and (1 → 4)-linked β-glucans with complex branching. Ethanol-precipitated fractions showed structural differentiation: GL-40 was rich in (1 → 6)-linked galactans, GL-60 had a balanced linkage profile, and GL-80 was enriched in branched (1 → 3,6)-β-glucans. These findings offer insights into Ganoderma polysaccharide diversity and structure–function relationships, supporting quality control and development of standardized functional foods.