DETERMINATION OF THE STRUCTURE OF THE EXOPOLYSACCHARIDE PRODUCED BY LACTOBACILLUS-SAKE-0-1

The exopolysaccharide produced by Lactobacillus sake 0-1 in a semi-defined medium was found to have an average molecular mass of 6 X 10(6) Da and a composition of D-glucose, L-rhamnose, and sn-glycerol 3-phosphate (3:2:1). The polysaccharide is partially O-acetylated. By means of partial acid hydrolysis, O-deacetylation, deglycerophosphorylation, methylation analysis, and 1D/2D NMR (H-1, C-13, and P-31) studies the polysaccharide was shown to be composed of repeating units with the following structure: [GRAPHICS] tetra-O-acetyl-2-epi-streptozotocin (the acetylated alpha-mannosamine epimer of streptozotocin). Administration of 50 mg/kg/day X 5 to leukemia L1210-bearing DBA/2Ha mice resulted in 5/5 35-day survivors. Neutralization of 1,3,3,6-tetra-O-acetyl-2-amino-2-deoxy-alpha-D-mannopyranose oxalate under aqueous conditions led to 2-acetamido-1,4,6-tri-O-acetyl-2-deoxy-alpha-D-mannopyranose, the oxidation of which gave 2-acetamido-4,6-di-O-acetyl-1,5-anhydro-2-deoxy-D-erythro-hex-1-en-3-ulose. This agent demonstrated an IC50 of 25 mu M with a murine L1210 cell culture. Administration of 100 mg/kg/day X 5 resulted in 42% ILS in DBA/2 mice with ip L1210 leukemia. Several other nonacetylated derivatives were also prepared by direct N-acylation, producing, for example, fluorescently tagged N-dansylmannosamine.