Abstract
The mushroom Inonotus obliquus has been widely used as a folk medicine in Russia, Poland and most of the Baltic countries. In this study, water-soluble and alkali-soluble crude polysaccharides (IOW and IOA) were isolated from I. obliquus, and the carbohydrate-rich fractions IOW-1 and IOA-1 were obtained respectively after deproteination and depigmentation. Their contents, such as neutral carbohydrate, uronic acid and protein, were measured. Their antioxidant properties against chemicals-induced reactive species (ROS) including 1,1′-Diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radical and superoxide anion radical, as well as their protective effects on H2O2-induced PC12 cell death were investigated. Results showed that I. obliquus polysaccharides can scavenge all ROS tested above in a dose-dependent manner. IOA and its product IOA-1 could rescue PC12 cell viability from 38.6% to 79.8% and 83.0% at a concentration of 20μg/mL. Similarly, IOW and its product IOW-1 at the same dose, can also increase cell viability to 84.9% and 88.6% respectively. The antioxidative activities of water-soluble and alkali-soluble polysaccharide constituents from I. obliquus might contribute to diverse medicinal and nutritional values of this mushroom.
Highlights
The mushroom Inonotus obliquus (I. obliquus), belonging to the Hymenochaetaceae family of Basidiomycetes, is a black parasitic fungus that grows on living trunks of the mature birch and is mainly found at latitudes of 45°N–50°N [1,2]
After deproteinization and depigmentation procedures, as expected, both IOW-1 and IOA-1 were predominantly composed of neutral carbohydrates (>50%)
The rigorous deproteinization process through the sevag method didn’t get rid of protein in IOW and IOA completely, implying that some proteins in IOW-1 and IOA-1 might be existed as polysaccharide-protein conjugates
Summary
The mushroom Inonotus obliquus (I. obliquus), belonging to the Hymenochaetaceae family of Basidiomycetes, is a black parasitic fungus that grows on living trunks of the mature birch and is mainly found at latitudes of 45°N–50°N [1,2]. Many polyphenolic compounds, triterpenoids [5], and steroids, such as lanosterol, inotodiol [6], trametenolic acids, and ergosterol peroxide [7] from this fungus have been identified and their biological activities, including hypoglycemic [1], hepato-protective [8] have been demonstrated. Polysaccharides are one of the main components of I. obliquus and they have been shown to exhibit many biological activities including anti-tumor [9], antioxidant, hypoglycemic and immune-stimulating effects [10,11]. In living organisms, prolonged elevated levels of ROS can cause intense oxidative stress, which is considered to play a very important role in the pathogenesis of several degenerative diseases [12] and pathological effects such as causing DNA damage, carcinogenesis and cellular degeneration related to aging [13]. Natural antioxidants, for example, fucoidan [16], chitosan [17], tea polysaccharide [18], Lycium barbarum polysaccharide [19], which can scavenge ROS in vitro and in vivo attract more attention
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