Structural analysis of metabolites in complex mixtures without column purification

April 12, 2016

Sophisticated multidimensional NMR pulse sequences and theoretical calculations used for structure verification

Using sophisticated multidimensional NMR pulse sequences, RIKEN CSRS has succeeded in analyzing the structure of and identifying secondary metabolites in Rhododendron japonicum extracts without column purifications.

Researchers uniformly labeled Rhododendron japonicum with Carbon-13, obtaining samples of biological small molecules (BSMs) with molecular complexity. They then used sophisticated multidimensional NMR pulse sequencing to estimate a framework of complex secondary metabolites, comparing theoretical values based on quantum chemical calculations against actual measurements from NMR spectrums to verify the predicted structures. Researchers were able to achieve the highest-ever observed resonance assignments of 386 carbon atoms and 380 hydrogen atoms. They also identified eight secondary metabolites, including terpenes and flavonoids, that were unlisted in any global NMR spectral databases.

As NMR experimental data measures physical quantity, the same measurements (resonance frequencies) can be replicated with any NMR machine. Accumulation of NMR spectral databases of metabolites provides valuable information for metabolism researchers in the world. Also, this research could open the way for onsite metabolite analysis for agriculture, forestry and fishery production sites with inexpensive, compact NMR devices that do not require column purifications.


Original article
Angewandte Chemie International Edition doi:10.1002/anie.201600334R1
T. Komatsu, R. Ohishi, A. Shino, J. Kikuchi,
"Structure and metabolic flow analysis of molecular complexity in 13C-labeled tree by 2D and 3D-NMR".

Jun Kikuchi
Team Leader
Environmental Metabolic Analysis Research Team