Characterization of a novel polysaccharide with anti-colon cancer activity from Lactobacillus helveticus MB2-1

• LHEPS-1 could significantly inhibit the growth of human colon cancer Caco-2 cells.
• Structural feature of LHEPS-1 was elucidated by methylation, GC–MS and 1D/2D NMR.
• LHEPS-1 was a kind of moderate branching glucomannogalactan.
• A possible structure of LHEPS-1 was proposed.
• Anti-colon cancer activity was correlated with structure of LHEPS-1.

The present study aimed at investigating the potential anti-colon cancer activity of three purified exopolysaccharides fractions (LHEPS-1, LHEPS-2 and LHEPS-3) from the Lactobacillus helveticus MB2-1. The experimental evidence showed that LHEPS-1 significantly inhibited cell proliferation of human colon cancer Caco-2 cells in both time- and concentration-dependent manners. In contrast, no significant improvements of the inhibitory effects of LHEPS-2 and LHEPS-3 on Caco-2 cells were observed with increasing sample concentrations or prolonged incubation time. Furthermore, the structure of LHEPS-1 was elucidated using methylated analysis, gas chromatography–mass spectroscopy (GC–MS) and nuclear magnetic resonance spectroscopy (NMR), including one- and two-dimensional nuclear magnetic resonance (1D and 2D NMR). Results indicated that the LHEPS-1 consisted of a decasaccharide repeating unit with the following structure (n≈122)：Our results suggested that the LHEPS-1 produced by L. helveticus MB2-1 might be suitable for using as natural anti-colon cancer drugs and functional foods ingredients.

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