Sulfated O-polysaccharide with anticancer activity from the marine bacterium Poseidonocella sedimentorum KMM 9023T

•Structure of sulfated OPS of P. sedimentorum was established.•Carbohydrate polymer of a new, previously unknown structure has been found.•OPS contains 3-deoxy-9-O-methyl-d-glycero-d-galacto-non-2-ulosonic acid.•OPS contains 3-O-acetyl-2-O-sulfate-d-glucuronic acid.•O-deacylated LPS inhibits a colony formation of human cancer cells. The sulfated polysaccharides are of study interest due to their high structural diversity and broad spectrum of biological activity including antitumor properties. In this paper, we report on the structural analysis of sulfated O-specific polysaccharide (OPS) and in vitro anticancer activity of O-deacylated lipopolysaccharide (DPS) of the marine-derived bacterium Poseidonocella sedimentorum KMM 9023T achieved by a multidisciplinary approach (chemical analysis, NMR, MS, and bioassay). The OPS is shown to include two rare monosaccharide derivatives: 3-deoxy-9-O-methyl-d-glycero-d-galacto-non-2-ulosonic acid (Kdn9Me) and 3-O-acetyl-2-O-sulfate-d-glucuronic acid (D-GlcA2S3Ac). The structure of polysaccharide moiety of a previously unknown carbohydrate-containing biopolymer is established: →4)-α-Kdnp9Me-(2→4)-α-d-GlcpA2S3Ac-(1→. From a biological point of view, we demonstrate that DPS of the P. sedimentorum KMM 9023T has no cytotoxicity and inhibits colony formation of human HT-29, MCF-7 and SK-MEL-5 cells in a dose-dependent manner. The investigated polysaccharide is the second glycan isolated from the bacteria of the genus Poseidonocella: previously we studied the OPS of P. pacifica KMM 9010T (Kokoulin et al., 2017). Both polysaccharides are sulfated and contain rare residues of ulosonic acids. Thus, obtained findings provide a new knowledge about kinds and antitumor properties of sulfated polysaccharides and can be a starting point for further investigations of mechanisms of anticancer action of carbohydrate-containing biopolymers from marine Gram-negative bacteria.