Environmental context The application of metabolomics from an environmental perspective depends on the analytical ability to discriminate minute changes in the organism resulting from exposure. In this study, 1-D and 2-D Nuclear Magnetic Resonance (NMR) experiments were examined to characterise the earthworm’s metabolic response to an organochlorine pesticide. 2-D NMR showed considerable improvement in discriminating exposed worms from controls and in identifying the metabolites responsible. This study demonstrates the potential of 2-D NMR in understanding subtle biochemical responses resulting from environmental exposure. Abstract Nuclear Magnetic Resonance (NMR) based metabolomics is a powerful approach to monitoring an organism’s metabolic response to environmental exposure. However, the discrimination between exposed and control groups, depends largely on the NMR technique chosen. Here, three 1-D NMR and three 2-D NMR techniques were investigated for their ability to discriminate between control earthworms (Eisenia fetida) and those exposed to a sub-lethal concentration of a commonly occurring organochlorine pesticide, endosulfan. Partial least-squares discriminant analysis found 1H–13C Heteronuclear Single Quantum Coherence (HSQC) spectroscopy to have the highest discrimination with a MANOVA value (degree of separation) three orders lower than any of the 1-D and 2-D NMR techniques. HSQC spectroscopy identified alanine, leucine, lysine, glutamate, glucose and maltose as the major metabolites of exposure to endosulfan, more than all the other techniques combined. HSQC spectroscopy in combination with a shorter 1-D experiment may prove to be an effective tool for the discrimination and identification of significant metabolites in organisms under environmental stress.
Recent Advances in Computational Methods for Nuclear Magnetic Resonance Data Processing