Purification and characterization of a glucan from Bacillus Calmette Guerin and the antitumor activity of its sulfated derivative

•A water-soluble glucan (BCG-PASW) was separated from polysaccharide nucleic acid fraction of Bacillus Calmette Guerin.•Structural features of BCG-PASW were investigated.•Antitumor activities in vitro of BCG-PASW and its sulfated polysaccharides were studied and compared.•The combined action of sulfated content might influence their antitumor activities. A water-soluble glucan, BCG-PASW, with a molecular weight of 2.10×104Da, was separated from polysaccharide nucleic acid fraction of Bacillus Calmette Guerin (BCG-PSN) using DEAE-52 cellulose and Sephadex G-200 chromatography. Based on gas chromatography–mass spectrometry (GC–MS), fourier transform infrared (FT-IR) spectra, 1D and 2D nuclear magnetic resonance (NMR) spectroscopy techniques (COSY, HSQC and HMBC), BCG-PASW was found to be an α-d-glucan composed of α-d-(1→4)-linked glucopyranosyl residues, with branches at O-6 consisting of non-reducing terminal α-d-Glcp approximately every eight residues. In vitro antitumor activity by MTS method, its sulfated derivative with a substitution degree of 0.59, could inhibite C666-1 nasopharyngeal carcinoma cells growth significantly. The results indicated that the sulfate content play a decisive role in the bioactivities of the polysaccharides.