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Oxylipins are oxygenated derivatives of polyunsaturated fatty acids (PUFAs) that act as chemical mediators in many ecological and physiological processes in marine and freshwater diatoms. The occurrence and distribution of these molecules are relatively widespread within the lineage with considerable species-specific differences due to the variability of both the fatty acids recognized as substrates and the enzymatic transformations. The present review provides a general introduction to recent studies on diatom oxylipins and describes an analytical method for the detection and assessment of these elusive molecules in laboratory and field samples. This methodology is based on selective enrichment of the oxylipin fraction by solvent extraction, followed by parallel acquisition of full-scan UV and tandem mass spectra on reverse phase liquid chromatography (LC) peaks. The analytical procedure enables identification of potential genetic differences, enzymatic regulation, and ecophysiological conditions that result in different oxylipin signatures, thus providing an effective tool for probing the functional relevance of this class of lipids in plankton communities. Examples of oxylipin measurements in field samples are also provided as a demonstration of the analytical potential of the methodology.

The structure of the O-specific polysaccharide from the lipopolysaccharide fraction of the phytopathogenic bacterium Xanthomonas fragariae, the causal agent of the angular leaf spot of strawberry, is described. On the basis of the spectroscopic data, chemical analyses and degradation methods, a structure is suggested.

Two novel triterpenoids, aplysiols A ( 5 ) and B ( 6 ), have been isolated, together with structurally related known metabolites, from a South China Sea collection of the anaspidean mollusc Aplysia dactylomela . The structures of 5 and 6 were determined mainly by spectroscopic NMR techniques. The absolute stereochemistry of compound 5 was deduced by Mosher's method as well as by biogenetical consideration, whereas the absolute stereochemistry of compound 6 was established also using an integrated NMR-QM (Quantum Mechanical) approach, based on the combination of 13 C NMR chemical shifts and 2,3 J C–H coupling constant DFT (density functional theory) calculations.

The absolute stereochemistry of amphilectene metabolites from Cribochalina sp. has been revised by a detailed NMR spectroscopic study of the mosher ester derivatives of a related alcohol. The relative stereochemistry of the previously described amphilectenes has been reinvestigated and reassigned on the basis of the X-ray structural analysis carried out on one of them. The structure of a new amphilectene metabolite, which is an isothiocyanato analogue, is also presented.