Structural Analysis of Oxidized Cerebrosides from the Extract of Deep-Sea Sponge sp.: Occurrence of Amide-Linked Allylically Oxygenated Fatty Acids.

The structural elucidation of primary and secondary peroxidation products, formed from complex lipids, is a challenge in lipid analysis. In the present study, rare minor oxidized cerebrosides, isolated from the extract of a far eastern deep-sea glass sponge, sp., were analyzed as constituents of a multi-component RP-HPLC (high-performance liquid chromatography on reversed-phase column) fraction using NMR (nuclear magnetic resonance) spectroscopy, mass spectrometry, GC (gas chromatography), and chemical transformations (including hydrogenation or derivatization with dimethyl disulfide before hydrolysis). Eighteen previously unknown β-D-glucopyranosyl-(1→1)-ceramides (-, -, -, -, -, -) were shown to contain phytosphingosine-type backbones (2,3,4,11)-2-aminoeicos-11-ene-1,3,4-triol (in ), (2,3,4,13)-2-aminoeicos-13-ene-1,3,4-triol (in ), and (13*,14*)-2-amino-13,14-methylene-eicosane-1,3,4-triol (in ). These backbones were -acylated with straight-chain monoenoic (2)-2-hydroxy acids that had allylic hydroperoxy/hydroxy/keto groups on C-17 in the 15-23:1 chain (-), C-16 in the 17-23:1 (-) and 14-22:1 (-) chains, and C-15 in the 16-22:1 chain (-). Utilizing complementary instrumental and chemical methods allowed for the first detailed structural analysis of a complex mixture of glycosphingolipids, containing allylically oxygenated monoenoic acyl chains.