Structural investigation of an antibacterial polysaccharide from Streptomyces virginia H03

The chemical structure of a polysaccharide from the broth of cultured Streptomyces virginia H03 was investigated. There might be 1-->2 and 1-->4 and no 1-->6 glycosidic linkages in the polysaccharide according to periodate oxidation and Smith degradation. Four fragments including 2,3,4,6-Me4-Man, 2,3,6-Me3-Gal, 2,4,6-Me3-Glc, and 3,6-Me2-Man were found in the methylated polysaccharide. Furthermore, the polysaccharide has a beta-Glc(1-->4)-alpha-Man(1-->4)-alpha-Gal(1-->3)-linked backbone and a branch at the C-2 position of (1-->2)-linked mannose residues as determined by the method of nuclear magnetic resonance (NMR) spectroscopy. The assumed structure of the polysaccharide is [formula see text]. Additionally, the polysaccharide has a wide antibiogram and was found to be most effective against Bacillus subtilis, Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli.