Structural characterization, antioxidant and antimicrobial activity of water-soluble polysaccharides from bamboo (Phyllostachys pubescens Mazel) leaves

One water-soluble neutral polysaccharides (NPs), with an average molecular weight of 5.77 × 103 Da, was isolated from bamboo (Phyllostachys pubescens Mazel) leaves and the yield was 10.2% based on weight of raw material. Successively, two fractions (NPs-A and NPs-B) could be obtained after being eluted by DEAE-Sepharose. Structural analysis indicated that NPs was formed by 1,4-β-linked xylp backbone. Monosaccharide composition and methylation analysis suggested that glucose, arabinose, galactose and rhamnose constituted side chains with the molar ratio of 1.22:1.79:1.89:4.46 with the glycosidic linkages of →4)-Glc-(1→, →3,5)-Ara-(1→, →4)-Gla-(1→, →4)-Rha-(1 → and → 2,4)-Rha-(1→. Antioxidant assays demonstrated that NPs exhibited relatively high activity in a dose-dependent manner with the highest 85.9% DPPH and 99.78% ABTS free radical scavenging rate when the concentration was 4.0 and 3.0 mg/mL, respectively. Moreover, NPs exhibited obvious growth inhibitory against E. coli, S. aureus and B. subtilis when the NPs concentration was in range of 0.50-50.0 mg/mL. Therefore, we concluded that NPs from bamboo leaves could be used as a potential and natural bacteriostat and antioxidant.