Synthesis, Inhibitory Effects on Nitric Oxide and Structure-Activity Relationships of a Glycosphingolipid from the Marine Sponge Aplysinella rhax and Its Analogues

The novel glycosphingolipid, b-D-GalNAcp(1®4)[a-D-Fucp(1®3)]-b-D-GlcNAcp(1®)Cer (A), isolated from the marine sponge Aplysinella rhax has a unique structure, with D-fucose and N-acetyl-D-galactosamine moieties attached to a reducing-end N-acetyl-D-glucosamine through an a1®3 and b1®4 linkage, respectively. We synthesized glycolipid 1 and some non-natural di- and trisaccharide analogues 2-6 containing a D-fucose residue. Among these compounds, the natural type showed the most potent nitric oxide (NO) production inhibitory activity against LPS-induced J774.1 cells. Our results indicate that both the presence of a D-Fuca1-3GlcNAc-linkage and the ceramide aglycon portion are crucial for optimal NO inhibition.