Nuclear Magnetic Resonance as Analytical Tool for Crude Plant Extracts

Abstract

Authentication, quality control, and stability testing of crude plant extracts are generally achieved and well established through HPLC, HPTLC, and capillary GC, using specific detectors such as UV–vis, RI, and coupled systems (MS), which allow the qualitative and quantitative determination of the composition of the markers or active substances. The major disadvantages of these conventional methods lie in the time consuming for the development of simple and rapid chromatographic separation and for the preparation of samples before measurements. In addition, these techniques are not able to reveal unknown plant metabolites that can contribute to the biological activity. NMR spectroscopy is nondestructive, selective, and capable of simultaneous detection of a great number of constituents. The identification by NMR provides on both major and minor components, with no restrictions relating to volatility, polarity, or the presence of specific chromophores. Finally, the method can be applied without knowledge of the composition of the sample. NMR spectra contain information about the identity of the molecules in the extracts and are useful to quantify the constituents. NMR spectroscopy coupled with chemometric tools has been successfully applied to the characterization of various herbs and plant extracts for quality control, authentication, determining geographical origin, and detecting adulteration of herbal drugs and extracts. Keywords: plant extracts; 1D- and 2D-NMR analyses; DOSY NMR; quantitative NMR; NMR and multivariate statistics (or chemometrics); authentication; quality control and stability testing