The potential of LC-NMR in phytochemical analysis

The coupling of high performance liquid chromatography with nuclear magneti c resonance spectroscopy (LC-NMR) is one of the most powerful methods for t he separation and structural elucidation of unknown compounds in mixtures. The recent progress in pulse field gradients and solvent suppression, the i mprovement in probe technology, and the construction of high held magnets h ave given a new stimulus to this technique, which has emerged since the mid 1990s as a very efficient method for the on-line identification of organic molecules. LC-NMR thus represents a potentially interesting complementary technique to LC-UV-MS in phytochemical analysis for the detailed on-line st ructural analysis of natural products. Recent applications have fully demon strated the usefulness of this technique. A brief review of the application s of LC-NMR in natural product chemistry is presented in this paper, and a summary of the basic principles and modes of operation of LC-NMR is provide d. Selected examples of LC-NMR analyses of plant metabolites in crude extra cts or in enriched fractions are outlined and used to illustrate the differ ent strategies for employing the technique. The practical possibilities and limitations of LC-MMR in its application to the analysis of crude plant ex tracts are discussed by means of several examples. Analytical strategies in volving LC multi-coupled (hyphenated) techniques for the chemical screening and dereplication of crude plant extracts are presented. An analysis of th e future development of the technique with respect to its application in ph otochemical analysis is also given. Copyright (C) 2001 John Wiley & Sons, L td.