13C NMR-based dereplication of natural products: New opportunities for reducing isolation efforts

Natural product screening programs for drug discovery remain limited by equipment, labor and time investments required to isolate and structurally elucidate biologically active metabolites from natural resources. Attempts are currently being made to develop efficient dereplication methods with multidisciplinary analytical, computer and data mining tools. Recent NMR technical improvements enable today the fast acquisition of ¹³C NMR spectra, opening up new perspective to address the chemical profiling of natural extracts.

Here are presented two ways of understanding the ¹³C NMR spectral profiles of natural metabolite mixtures, both exploiting the advantages of low ¹³C NMR signal overlaps due to individualized resonance per carbon position and large spectral width. The first method aims to identify the major compounds and thus the main classes of metabolites in a crude extract from a single ¹³C NMR analysis without any isolation procedure. Its principle is to calculate a score resulting from a database searching method where predicted ¹³C NMR chemical shift values of known natural metabolites are compared to experimental ¹³C NMR signals of the crude mixture. The second method involves an up-stream liquid-liquid fractionation step, which is more appropriate if further detailed chemical analysis or identification of the active substances of the initial mixture is required. In this case all ¹³C NMR spectra of the generated fraction series are processed together and the collected data are submitted to hierarchical clustering analysis for pattern recognition [1]. Strong signal correlations caused by the same structure within adjacent fractions are visualized as clusters and assigned to a molecular structure using again a natural metabolite database.

Through different concrete examples of plant and marine extracts, we will demonstrate that ¹³C NMR-based dereplication processes offer promising perspectives to accelerate the identification of natural products in mixtures.

Acknowledgements: The authors thank the company Soliance-Givaudan, the CNRS, and the Ministry of Higher Education and Research for financial support. The EU-program FEDER for the PlAneT CPER project is also gratefully acknowledged.

Keywords: Natural product dereplication, ¹³C NMR, metabolomics.

References:

[1] Hubert J, Nuzillard JM, Purson S, Hamzaoui M, Borie N, Reynaud R, Renault JH. Identification of natural metabolites in mixture: a pattern recognition strategy based on ¹³C NMR. Anal Chem 2014; 86: 2955 – 2962