Marine natural products

This review covers the literature published in 2019 for marine natural products (MNPs), with 719 citations (701 for the period January to December 2019) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1490 in 440 papers for 2019), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Methods used to study marine fungi and their chemical diversity have also been discussed.

Structural Analysis of Oxidized Cerebrosides from the Extract of Deep-Sea Sponge Aulosaccus 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, Aulosaccus 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 (1a-a//, 1b-b//, 2a-a//, 2b-b//, 3c-c//, 3d-d//) were shown to contain phytosphingosine-type backbones (2S,3S,4R,11Z)-2-aminoeicos-11-ene-1,3,4-triol (in 1), (2S,3S,4R,13Z)-2-aminoeicos-13-ene-1,3,4-triol (in 2), and (13S*,14R*)-2-amino-13,14-methylene-eicosane-1,3,4-triol (in 3). These backbones were N-acylated with straight-chain monoenoic (2R)-2-hydroxy acids that had allylic hydroperoxy/hydroxy/keto groups on C-17/ in the 15/E-23:1 chain (a-a//), C-16/ in the 17/E-23:1 (b-b//) and 14/E-22:1 (c-c//) chains, and C-15/ in the 16/E-22:1 chain (d-d//). 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.