Metabolite profiling

In the November Nature Biotechnology Fiehn et al. offer an alternative to the profiling of messenger RNA and protein levels. They use gas chromatography coupled to mass spectrometry (GC/MS) to assay the relative levels of 326 small compounds from a plant leaf extract (Nat Biotech 2000, 18:1157-1161). A simple methanol extraction is followed by derivitization to increase metabolite stability and volatility. Approximately half of the chromatographed compounds can be identified based on retention times and mass spectra; these results can be viewed on the accompanying website. Biological variability (of approximately 40%) is in clear excess of variability inherent to the method (about 8%). Principal component analysis allows metabolite profiles from plants of a particular genetic background or with a particular mutation to be clustered. Mutation of a single gene causes many changes, most of them unexplained. Metabolite profiles may be useful to address public concerns about the safety of genetically modified food.