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Advanced NMR-Based Structural Investigation of Glucosinolates and Desulfoglucosinolates

Ibrahim, Nada, Allart-Simon, Ingrid, De Nicola, Gina R., Iori, Renato, Renault, Jean-Hugues, Rollin, Patrick, Nuzillard, Jean-Marc
Journal of natural products 2018 v.81 no.2 pp. 323-334
Brassicales, carbon, computer software, databases, glucosinolates, hydrophilicity, hydrophobicity, models, moieties, nuclear magnetic resonance spectroscopy, secondary metabolites, spectral analysis, stable isotopes
Glucosinolates (GLs) constitute a class of plant secondary metabolites that are characteristic of the order Brassicales. They each contain a common hydrophilic moiety connected to a mostly hydrophobic side chain whose constitution is the most frequent structural variant. Their transformations by myrosinases lead to intensively studied and highly reactive compounds of biological relevancy. In other respects, the enzymatic desulfation of GLs produces derivatives (DS-GLs) that are useful for GL analysis. A collection of 31 compounds, GLs and DS-GLs, representing 17 different side chains was established in order to report accurate descriptions of the molecules’ ¹H-, ¹³C-, and ¹⁵N-NMR parameters. The descriptions of the ¹H-NMR spectra were achieved using the PERCH software, which accurately analyzed the complex coupling patterns that arose from strongly coupled nuclei. The chemical shift assignments were supported by 2D COSY, HSQC, and HMBC spectra. The impact of desulfation and the influence of the nature of the side chains on the chemical shift values are discussed. The results of the spectroscopic analysis and the 3D chemical-structure models of the studied molecules were grouped in structure-and-data-format (SDF) files. The NMR parameters were also collected in a simple text file, a spreadsheet file, and a relational database.