Unequivocal glycyrrhizin isomer determination and comparative in vitro bioactivities of root extracts in four Glycyrrhiza species

Farag, Mohamed A.; Porzel, Andrea; Wessjohann, Ludger A.

NMR presents a powerful technology for isolates structural elucidation including conformational NMR experiments based on either 2D nuclear Overhauser enhancement spectroscopy (NOESY) or rotating frame Overhauser effect spectroscopy (ROESY) which provide information about couplings through space and consequently can allow for a configuration (and sometimes even conformation) assignments of isomers [15] . With an increasing interest in utilizing NMR for metabolic fingerprinting and phytomedicines QC analysis, it is now possible to record NMR spectra from crude plant extracts providing the valuable metabolite signature of a complex plant extract [16] . Unlike MS-based analyses, nuclear magnetic resonance (NMR) spectroscopy provides a large amount of information regarding molecular structure, and novel software innovations have facilitated the unequivocal identification of compounds within composite samples. However, NMR has a lower sensitivity compared to MS. Additionally, introducing another set of chemical shifts from the proton dimension as in ROESY spectra would also complicate the spectral processing using multivariate data analysis.