Abstract
The growing use of herbal medicines worldwide requires ensuring their quality, safety,
and efficiency to consumers and patients. Quality controls of vegetal extracts are
usually undertaken according to pharmacopeial monographs. Analyses may range from
simple chemical experiments to more sophisticated but more accurate methods. Nowadays,
metabolomic analyses allow a fast characterization of complex mixtures. In the field,
besides mass spectrometry (MS), nuclear magnetic resonance spectroscopy (NMR) has
gained importance in the direct identification of natural products in complex herbal
extracts. For a decade, automated dereplication processes based on 13C-NMR have been emerging to efficiently identify known major compounds in mixtures.
Though less sensitive than MS, 13C-NMR has the advantage of being appropriate to discriminate stereoisomers. Since
NMR spectrometers nowadays provide useful datasets in a reasonable time frame, we
have recently made
available MixONat, a software that processes 13C as well as distortionless enhancement by polarization transfer (DEPT)-135 and -90
data, allowing carbon multiplicity (i.e., CH3, CH2, CH, and C) filtering as a critical step. MixONat requires experimental or predicted
chemical shifts (δ
C) databases and displays interactive results that can be refined based on the userʼs
phytochemical knowledge. The present article provides step-by-step instructions to
use MixONat starting from database creation with freely available and/or marketed
δ
C datasets. Then, for training purposes, the reader is led through a 30 – 60 min procedure
consisting of the 13C-NMR based dereplication of a peppermint essential oil.
Key words
database - essential oils - Lamiaceae -
Mentha piperita
- MixONat -
13C-NMR-based dereplication