Structural features and Properties of Dietary fiber.

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Carbohydrates of Gobo (edible burdock, Arctium lappa L.) and Yamagobo (Goboazami, Crisium dipsacolepis Matsum.) were compared using triturated, defatted samples. Fractionation of the carbohydrates, and sugar composition and sugar linkage composition analyses of the fractions suggested that their basic constituent polysaccharides are almost the same. Gobo and Yamagobo both contained fructan as a reserve polysaccharide. The cell walls of Gobo and Yamagobo consisted of pectic substances (rhamnogalacturonan with neutral sugars), hemicellulose (arabinan, xylan, galactan, arabinogalactan and xyloglucan) and cellulose in the ratio of 53.6 : 8.0 38.4 and of 55.8 : 7.2 : 37.0, respectively. Approximate ratio of fructan and cell-wall polysaccharides was 47 : 53 for Gobo and 66 : 34 for Yamagobo.An acidic xylan occurring in the hemicellulose II fraction (24 % potassium hydrcydroxide extract) of defatted Gobo (edible burdock, Arctium lappa L.) was isolated and characterized by methylation and fragmentation analyses. The results indicated that the acidic xylan had a linear backbone chain of beta-1,4-D- xylopyranosyl residues, about 8.3 % of which were substituted at the 2 position with 4-O-methyl-alpha-D-glucopyranosyluronic acid residues.