Polysaccharides from Inonotus obliquus employing subcritical water extraction: Extraction optimization, physiochemical properties and bioactivities analysis

As one of the main components in Inonotus obliquus, polysaccharides was potentially to be developed for the special physiochemical properties and bioactivity. However, the low extraction efficiency of Inonotus obliquus polysaccharides (IOP) significantly hindered the in-depth research and development. To achieve a higher extraction yield of IOP, subcritical water was selected and optimized by Box-Behnken Design (BBD) with a more reasonable yield investigation method in the present study. In addition, for the comparative analysis, the physiochemical properties and bioactivity of the subcritical water extracted polysaccharides (IOP-S), purified polysaccharides (IOP-P) and hot water extracted polysaccharides (IOP-W) were all investigated and analyzed. The results showed that the optimal extraction conditions were 200°C, 13.24 min and 30:1 (mL/g), which corresponded to a polysaccharide yield of 14.14±0.17 %. With simple purified process, the IOP-P with high purity (total sugar content of 87.55 %) was suitable for the further study. Compared to IOP-W, a wider molecular weight range (3.4–98 kDa) of polysaccharide was found in IOP-S, as well as higher sugar and polyphenol content, which might be the main reason for the well antioxidant and digestion enzyme inhibition activity. There were also various differences in the monosaccharide composition, micro-morphology and other physiochemical properties, which all suggested that the subcritical water could efficiently extract a special IOP for the fourthly study and development. In summary, the present study proved that subcritical water extraction could significantly improve the extraction efficiency of IOP, and the basic information in physiochemical properties and bioactivities of IOP would promote the development of IOP in the future.