Extraction and analysis of oxylipins from macroalgae illustrated on the example Gracilaria vermiculophylla

Oxylipins are natural products that are derived by oxidative transformations of unsaturated fatty acids. These metabolites are found in a wide range of organisms from the animal kingdom to plants and algae. They represent an important class of signaling molecules, mediating intra- and intercellular processes such as development, inflammation, and other stress responses. In addition, these metabolites directly function as chemical defense against grazers and pathogens. In the red alga Gracilaria vermiculophylla, oxylipin production is initiated by mechanical tissue disruption and can also be induced in intact algae in response to external stress signals. The defense metabolites mostly result from the lipase- and lipoxygenase-mediated conversion of phospho- and galactolipids. Oxylipins can vary greatly in their size, degree of unsaturation, oxidation state, and functional groups. But also isomers with only subtle chemical differences are found. A variety of methods have been developed for separation, detection, and identification of oxylipins. This chapter focuses on the analysis of oxylipins in macroalgae and covers all aspects from sample preparation (including protocols for the investigation of oxylipins in wounded and intact algal tissue), extraction, purification, and subsequent analysis using liquid chromatography coupled to a UV detector or a mass spectrometer. The protocols developed for G. vermiculophylla can be readily adapted to the investigation of other macroalgae