Acute Toxicity Evaluation and Compositional Analysis of a Polysaccharide from the Medicinal Mushroom Inonotus obliquus

A water-soluble polysaccharide (IOPS) was isolated from the Inonotus obliquus (Fr.) Pilat, which was a medicinal mushroom with many health-benefiting functions. The chemical composition and acute toxicity of IOPS was investigated in order to determine the possibility of using them for human consumption. Chemical analysis of IOPS showed that it was a nonstarch protein bounded acidic polysaccharide. The protein, neutral sugar, uronic acid contents of the polysaccharide IOPS were 42.50%, 18.50% and 6.10%, respectively. The neutral sugars of IOPS were composed of Rha (D-rhamnose), Xyl (D-xylan), Gal (D-galactose) and Glc (D-glucose). The contents of thirteen mineral elements in IOPS were measured by inductivity coupled plasma-optical emission spectrometry (ICP-OES). Results showed that the concentrations of the elements in IOPS were much higher than that of Inonotus obliquus powder. IOPS, when orally administrated to mice at the single dose of 5000 mg/kg body weight, was found no toxicity to the liver, kidney, heart, thymus or spleen of the mice and none of the mice died throughout the period of the experiment. Based on the study, IOPS could be classified either as a very low toxicity substance, i.e. GHS Category 5 (globally harmonized system) or unclassified when orally administrated to mice and it might be a candidate of dietary supplements.