Analytical contribution of deuterium 2D‐NMR in oriented media to 2H/1H isotopic characterization: the case of vanillin. (20th February 2018)

• Record Type: Journal Article
• Authors: Texier–Bonniot, Tristan; Berdagué, Philippe; Robins, Richard J.; Remaud, Gérald; Lesot, Philippe
• Is Part Of: Flavour and fragrance journal. Volume 33:Number 3(2018:May)
• Page Start: 217
• Page End: 229
• Publication Date: 2018-02-20
• Subjects: (bio)synthetic pathway -- 2H NMR -- isotope ratio -- liquid crystals -- vanillin (4‐hydroxy‐3‐methoxybenzaldehyde); Flavor -- Periodicals; Odors -- Periodicals; Smell -- Periodicals; 668.54
• DOI: 10.1002/ffj.3441
• Languages: English
• ISSNs: 0882-5734

Abstract

Abstract: The evaluation of intramolecular 2 H or 13 C isotopic composition of vanillin by liquid‐state nuclear magnetic resonance (NMR) is an illustrative example of the analytical challenges associated with molecular authenticity/traceability investigations in food products, and the determination/understanding of metabolic/synthetic pathways. Although isotopic ratio monitoring by 13 C NMR (irm‐ 13 C NMR) provides a valuable new source of isotopic information, the analysis of position‐specific ( 2 H/ 1 H) isotopic fractionation of vanillin remains incomplete because of the overlap of two aromatic 2 H resonances, and the impossibility of separating these fortuitous isochronous nuclei by isotropic NMR. Exploiting the analytical potential of 2 H 2D‐NMR in media containing polypeptide‐based liquid crystals, we show that all aromatic monodeuterated isotopomers can be spectrally discriminated on the basis of 2 H residual quadrupolar couplings, ΔνQ ( 2 H), thus enabling the determination of their relative proportions for the first time. After discussing the multiple relevant cofactors leading to the best discrimination and optimization of experimental conditions for reliable quantitative measurements by anisotropic 2D‐NMR, a comparative analysis of six vanillin samples from diverse origins is reported. How the 2 H distribution might relate to the biosynthesis of vanillin is discussed. Abstract : An analytical solution involving deuterium 2D‐NMR experiments in liquid crystals is proposed to spectrally discriminate between all 2 H aromatic sites of vanillin, thus to give access to their associated ( 2 H/ 1 H) isotope ratios for the first time.