Optimized Extraction of Medicinal Mushroom Polysaccharides and Their Protective Effects Against 5-Fluorouracil-Induced Gastrointestinal Mucositis

Background: Ganoderma lucidum is a medicinal mushroom widely recognized for its high content of bioactive polysaccharides, particularly β-glucans with immunomodulatory properties. This study aimed to optimize polysaccharide extraction conditions to maximize yield and glucan content, and to evaluate the biological activity of the obtained fractions in an experimental model of intestinal mucositis. Methods: Polysaccharides were extracted using a combination of hot-water extraction and ethanol precipitation, optimized by response surface methodology. Optimal conditions (121 °C for 120 min followed by 90% ethanol precipitation) yielded a crude polysaccharide fraction (Poli-GL). A subsequent freeze–thaw process generated a soluble fraction (S-Poli-GL). Structural and compositional characterization was performed using enzymatic assays, monosaccharide profiling, and NMR spectroscopy. The biological effects of Poli-GL and S-Poli-GL were evaluated in a 5-fluorouracil-induced intestinal mucositis model following oral administration at doses of 30, 100, and 300 mg/kg. Results: The optimized extraction protocol enabled efficient recovery of polysaccharides enriched in glucans. S-Poli-GL exhibited a high total glucan content, including 43.3% β-glucans and 3.45% α-glucans, along with minor amounts of galactose and mannose. Structural analysis confirmed the predominance of branched β-(1→3),(1→6)-D-glucans. While Poli-GL did not prevent mucositis development, S-Poli-GL significantly reduced the disease activity index and attenuated intestinal inflammation, indicating enhanced biological activity associated with the soluble glucan-rich fraction. Conclusions: Optimization of extraction and fractionation improves the functional properties of G. lucidum polysaccharides. The soluble glucan-enriched fraction (S-Poli-GL) demonstrated significant protective effects in intestinal mucositis, supporting its potential as a therapeutic candidate and warranting further investigation for clinical application.