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Structural Characterization and Anticancer Activity of Cell-Bound Exopolysaccharide from Lactobacillus helveticus MB2-1

Li, Wei, Xia, Xiudong, Tang, Weizhi, Ji, Juan, Rui, Xin, Chen, Xiaohong, Jiang, Mei, Zhou, Jianzhong, Zhang, Qiuqin, Dong, Mingsheng
Journal of agricultural and food chemistry 2015 v.63 no.13 pp. 3454-3463
Lactobacillus helveticus, anion exchange, antineoplastic activity, arabinose, atomic force microscopy, exopolysaccharides, galactose, gel chromatography, glucose, in vitro studies, mannose, methylation, molecular weight, neoplasm cells, neoplasms, nuclear magnetic resonance spectroscopy, rhamnose, scanning electron microscopy, ultrasonics
A novel cell-bound exopolysaccharide (c-EPS) was isolated from Lactobacillus helveticus MB2-1 by ultrasonic extraction, anion exchange, and gel filtration chromatography before being structurally characterized. The c-EPS is a heteropolysaccharide with an average molecular weight of 1.83 × 105 Da and is composed of glucose, mannose, galactose, rhamnose, and arabinose at a molar ratio of 3.12:1.01:1.00:0.18:0.16. Methylation analysis and nuclear magnetic resonance analysis revealed that the c-EPS is a linear glucomannogalactan containing repeating units of →6)-β-d-Manp-(1 → 3)-β-d-Glcp-(1 → 3)-β-d-Glcp-(1 → 3)-β-d-Glcp-(1 → 4)-α-d-Galp-(1→ and trace amounts of Rhap-(1→ and (1 → 4)-Arap residues. Complex formation with Congo red demonstrated a triple-strand helical conformation for the c-EPS. Scanning electron microscopy of the c-EPS revealed many regular feather-like structural units. Topographical examination of c-EPS by atomic force microscopy revealed that the c-EPS formed rounded-to-spherical lumps with different sizes and chain formations. Furthermore, preliminary in vitro tests revealed that c-EPS significantly inhibited the proliferation of HepG-2, BGC-823, and especially HT-29 cancer cells.