Occurrence of Melibiose-containing Glycosphingolipids in a Sample of a Sponge-coral Association (Desmapsamma anchorata/Carijoa riisei).

In our research on biologically active compounds from Vietnamese marine invertebrates, rare melibiose-containing glycosphingolipids were found in a sample of a sponge-coral association (Desmapsamma anchorata/Carijoa riisei). Melibiosylceramides were analyzed as constituents of some multi-component RP-HPLC fractions, and the structures of fourteen new (1b, 3b, 4a - c, 6a - c, 8b, 9a, 9b, 10b, 11a, 11b) and five known (2b, 5a - c, 7b) natural compounds were elucidated using NMR, mass spectrometry, optical rotation, and chemical transformations. These α-D-Galp-(1→6)-β-D-Glcp-(1↔1)-ceramides (presumably sponge-derived compounds) were shown to contain phytosphingosine-type n-t17:0 (1), 6E-n-t17:1 (2), i-t17:0 (3), n-t18:0 (4), 6E-n-t18:1 (5), i-t18:0 (6), 6E-i-t18:1 (7), i-t19:0 (8), 6E-i-t19:1 (9), ai-t19:0 (10), and 6E-ai-t19:1 (11) backbones N-acylated with saturated straight-chain (2R)-2-hydroxy C21 (a), C22 (b), and C23 (c) acids. Characteristic trends in the fragmentations of the terminal parts of tetraacetylated normal-chain and iso- and anteiso- branched sphingoid bases were observed using GC-MS. The total sum of melibiosylceramides and compound 5b caused a reduction in colony formation of human melanoma cells.