| Phellinus linteus is a rare medicinal fungus that is parasitic on the trunks of poplar, birch and oak trees. It is considered as a titbit in Chinese Traditional Medicine. Recent research has shown that materials extracted from P. linteus fruit bodies have antitumor activity, anti-hepatic fibrosis function, and immunomodulatory properties. The active component has been identified as polysaccharides present in the fruit body. Studies on the optimal extraction process and the activities of the polysaccharides from P. linteus fruit body have significant meaning and practical value to further exploit this rare medicinal fungus and develop new medicine and functional food.There are rare reports about extracting polysaccharides, and most of them were about water extraction. This showed that the history of the research on P. linteus polysaccharides (PLP) was short and imperfect.The ethanol-alkali water extraction was first used to extract PLP in this study. The study was given to find the optimal extraction process of PLP by ethanol-alkali water. The polysaccharides were tested by infrared spectrum, which certified that the groups of the polysaccharides extracted by ethanol-alkali water were as same as those of the polysaccharides extracted by water or alkali water.Factors related to the extraction efficacy were studied by single factor test and orthogonal test. The optimum extraction conditions were as follows: temperature 100°C, time 4 h, solvent sample ratio 30:1 mL/g, pH 10, and ethanol concentration 5%. The yields of PLP extracted by water, alkali water (pH 10), and ethanol-alkali water (pH 10, ethanol concentration 5%) with the other conditions same were 4.74%, 5.29%, and 5.66%, respectively, which indicated that ethanol-alkali water extraction method was simple, cost-effective and reproducible method with the highest yield of PLP. Dissolvent of ethanol and alkali coupled with modern supersonic and supercritical fluid extraction procedure are the basement for developing a kind of high quality and effective way to extract PLP.The PLPs extracted by three different solvents have a concordant clearance effect on O2-·,·OH, respectively, and an anti-oxygen capability according to vitro bioactivity experiment. The polysaccharides with MW 50~100 kD have the highest clearance (17.5%) on O2-·. The clearance on·OH increased significantly in the concentration range of 0.167~0.835 mg/mL of PLPs. The PLPs extracted by three different solvents have a concordant inhibition effect on E. coli,S. cerevisiae, respectively, according to vitro bioactivity experiment. The inhibiting rate on E. coli,S. cerevisiae increased in the concentration range of 0.1~0.8 mg/mL of PLPs.The reasons of high yield of PLP have been investigated according to cell morphology observation and comparisons of the extraction efficacies of the major component of the cell wall. As the optical microscopic photos (×400) of cell wall residues of P. linteus fruit body powder extracted by three different solvents shown, the cells extracted by ethanol-alkali water arranged loosely, and the cells were fragmentized, indicated that the effect of cell wall-cracking after pretreated by ethanol-alkali water was the best. As the Scanning electron microscopic photos (×1000) of cell wall residues of P. linteus fruit body powder extracted by three different solvents shown, the cells extracted by ethanol-alkali water arranged loosely, became bent, and the diameter of the cells got small. Acid-soluble and alkali-soluble glucan yields from the cell wall residues pretreated by ethanol-alkali water were 0.044% and 0.064%, respectively, both more than those from the cell wall residues pretreated by water and alkali water, indicated that ethanol-alkali water decreased the stability of proteins in the inner layer which play the role of junction points between the glucans, and made the cell wall cracked. Due to the cell wall cracking effect of alkali on dissolving mannans and the effect of ethanol on decreasing protein stability, the yield of PLP was increased. The ethanol-alkali water extraction method coupled with other modern extractction techniques can be applied to the extraction and investigation of the active components from medicinal plants.
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