Occurrence of Melibiose‐Containing Glycosphingolipids in a Sample of a Sponge‐Coral Association (Desmapsamma anchorata/Carijoa riisei)

Abstract

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 14 new (1b, 3b, 4a–4c, 6a–6c, 8b, 9a, 9b, 10b, 11a, 11b) and five known (2b, 5a–5c, 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.

Phytoceramides from the Marine Sponge Monanchora clathrata: Structural Analysis and Cytoprotective Effects

“…The 1 H-NMR spectra of these compounds also showed signals of the methyl groups of major iso -methyl-branched ( δ H 0.86, d , J = 6.6 Hz), minor anteiso -methyl-branched ( δ H 0.84, d , J = 6.2 Hz; δ H 0.855, t , J = 7.2 Hz), and minor normal -chain ( δ H 0.88, t , J = 7.0 Hz) forms. The mass spectra of the acetates of sphingoid bases were also used for distinguishing between their terminal structures because the differences in the relative abundances of [M − AcOH − CH 3 ] + and [M − AcOH − CH 2 CH 3 ] + ions reflected the position of methyl branching in iso - and anteiso - forms [ 21 ]. In the mass spectrum of tetraacetylated i -t19:0, the gap of 28 amu between the peaks at m/z 396 [M − AcOH − CH(CH 3 ) 2 ] + and 424 [M − AcOH − CH 3 ] + reflected cleavage on either side of the carbon, bearing a methyl group (–CH 2 –CH 2 -/-CH(CH 3 )-/-CH 3 ).…”

“… * The data are given according to the results of the GC-MS analyses of tetracetylated sphingoid bases. The structures of sphingoid bases were identified using also the GC-MS data (fragmentations and retention times) of tetraacetylated sphingoid bases, previously obtained by the authors in the study of melibiosylceramides [ 21 ]. ** RRT, relative retention time; RRT = 1.00 for tetraacetylated n -t18:0.…”