Characterization of an antiproliferative exopolysaccharide (LHEPS-2) from Lactobacillus helveticus MB2-1

•LHEPS-2 exhibited strong inhibitory activity against gastric cancer BGC-823 cells.•Structure of LHEPS-2 from L. helveticus MB2-1 was investigated.•Methylation and 1D/2D NMR were used to elucidate the structural feature of LHEPS-2.•LHEPS-2 was found to contain a galactomannan backbone with a glucomannan side chain.•A possible structure of LHEPS-2 was proposed.

In this study, we reported that three purified exopolysaccharides fractions (LHEPS-1, LHEPS-2 and LHEPS-3) and crude LHEPS from the Lactobacillus helveticus MB2-1 inhibited the proliferation potential of human gastric cancer BGC-823 cells. We found that all the LHEPS fractions and crude LHEPS exerted concentration and time dependent inhibitory activities in vitro on BGC-823 cells. LHEPS-2 exhibited higher antiproliferative activity against BGC-823 cells in vitro than LHEPS-1, LHEPS-3 and crude LHEPS. With the consideration of the outstanding antiproliferative effect of LHEPS-2 on BGC-823 cells, more fine structural characterization of LHEPS-2 was further identified. The structure of LHEPS-2 was elucidated by methylated analysis, GC–MS, 1H NMR and 13C NMR spectroscopy, together with two-dimensional (2D) COSY, TOCSY, HSQC, HMBC and NOESY spectroscopy. Results showed that the LHEPS-2 was consisted of the following repeating units:Figure optionsDownload full-size imageDownload as PowerPoint slide