Preparation And Structural Identification Of Mulberry Branch Bark Polysaccharides And Their Antioxidation In Vitro

In our experiments, the branch bark of lu mulberry (Morus multicaulis Perr.) cv HuSang 32 (100 g) was extracted in hot water. As a result, the crude polysaccharide (28.5 g) was obtained. It is showed that the productivity of the polysaccharide was 28.5%. By means of chromatography, spectroscopy, mass spectroscopy, nuclear magnetic resonance spectroscopy and other chemical researches, the composition and structure of mulberry branch bark polysaccharides (MBBP) were analyzed. The purified polysaccharides were obtained by anion-exchange DEAE52-cellulose chromatography and a Sephadex G-100 Gel filtration column; with two water soluble polysaccharides MBBP-1 and MBBP-2 (mass ratio is 2:1). Gas chromatography analysis suggested that MBBP-1 consisted of D-rhamnose, D-xylose, D-arabinose, D-mannose, D-glucose and D-galactose in the molar ratio of 4.53: 2.49: 4.38:4.67:17.85:5.88, respectively. For MBBP-2, D-rhamnose, D-xylose, D-arabinose, D-mannose, D-glucose, D-galactose and D-galacturonic acid which were in the molar ratio of 26.85:13.8:3.14:4.4:6.1:3.19:4.9 were determined by GC-MS. The molecular weight of MBBP-1 and MBBP-2 which were determined by gel permeation chromatography were 114.901 kDa and 124.785 kDa, respectively. The results of infrared spectra showed both Mulberry branch bark polysaccharides (MBBP-1 and MBBP-2) wereβ-D-pyranose; by analysis of periodate oxidation and Smith-degradation, of MBBP-1, (1â†'3) -linked glucose was made up of the main chain, while rhamnose, arabinose, xylose, mannose and galactose constituted the side chains or non-reducing terminal residue of main chain. Of MBBP-2, rhamnose, arabinose, xylose, glucose and galactose were made up of the main chain; (1â†'6)-linked rhamnose and (1â†'2)-linked arabinose were composed of the core of main chain; arabinose, mannose and galactose constituted the side chains or non-reducing terminal residue of the main chain. By measuring the total antioxidant capacity, reducing power, hydroxyl radical scavenging and DPPH free radical scavenging of the two water-soluble polysaccharides, all antioxidant activities of MBBP-2 were significantly stronger than those of MBBP-1.As far as the principal of reduction-oxidation (REDOX) reaction was concerned, it was probably mainly attributed to 8.2% uronic acid components of MBBP-2. What's more, the degree of branching of side chain, molecular weight, degree of polymerization and linkage of glycosyl bonds also probably determined the difference of antioxidative activities between MBBP-1and MBBP-2.