New Polyhydroxysteroid Glycosides with Antioxidant Activity from the Far Eastern Sea Star Ceramaster patagonicus

Four new glycosides of polyhydroxysteroids, ceramasterosides A, B, D, and E (<b>1</b>-<b>4</b>), and two previously known compounds, ceramasteroside C₁ (<b>5</b>) and attenuatoside B-I (<b>6</b>), were isolated from an extract of a deep-sea sea star species, the orange cookie star <i>Ceramaster patagonicus</i>. The structures of <b>1</b>-<b>4</b> were elucidated by the extensive NMR and ESIMS methods. Steroid monoglycosides <b>1</b> and <b>2</b> had a common 3β,6α,8,15β,16β-pentahydroxysteroid nucleus and a C-29 oxidized stigmastane side chain and differed from each other only in monosaccharide residues. Ceramasteroside A (<b>1</b>) contained 3-<i>O</i>-methyl-4-<i>O</i>-sulfated β-D-xylopyranose, while ceramasteroside B (<b>2</b>) had 3-<i>O</i>-methyl-4-<i>O</i>-sulfated β-D-glucopyranose, recorded from starfish-derived steroid glycosides for the first time. Their biological activity was studied using a model of lipopolysaccharide-induced (LPS) inflammation in a SIM-A9 murine microglial cell line. During the LPS-induced activation of microglial cells, <b>1</b>, <b>3</b>, and <b>5</b>, at a non-toxic concentration of 1 µM, showed the highest efficiency in reducing the production of intracellular NO, while <b>4</b> proved to be most efficient in reducing the extracellular nitrite production. All the test compounds reduced the LPS-induced malondialdehyde (MDA) production. The in vitro experiments have demonstrated, for the first time, the antioxidant activity of the compounds under study.