Evaluation of extraction methods for use with NMR-based metabolomics in the marine polychaete ragworm, Hediste diversicolor

The sediment-dwelling polychaete, Hediste diversicolor, is commonly found in Northern temperate estuaries. Its limited mobility and tolerance to polluted conditions makes it a good candidate for biological monitoring. Moreover, its importance in the functioning of the sediment ecosystem has caused it to be described as a keystone species. Here we present the development of analytical methodology that will enable the use of H. diversicolor in environmental metabolomics studies for the biomonitoring of estuarine ecosystems. Polar and non-polar extraction solvents have been used to solubilise a wide range of metabolites. Extraction solvents assessed include: aqueous phosphate buffer solution, methanol:chloroform:water (1:1:0.9), methanol:water (1:1 and 2:1) and chloroform. The metabolites were analysed using 1-dimensional (1D) ¹H nuclear magnetic resonance (NMR) spectroscopy. Using the methanol:water (1:1) method, previous freezing to aid cell rupture did not result in an enhanced extraction. Removal of methanol with a speed vacuum resulted in reduction in yield. Methanol:water (1:1) and chloroform extractions proved to be the most appropriate techniques based on the sample yield and repeatability. NMR-based metabolomics in the ragworm can now be used to understand the ecophysiology of this important estuarine organism and has applications in biomonitoring, biomarker development and ecotoxicological studies.