Determination of the natural deuterium distribution of fatty acids by application of ²H 2D-NMR in liquid crystals: fundamentals, advances, around and beyond

ABSTRACT

Based on pioneering work reported in the 1980s by Martin and co-workers, experimental investigation of the site-specific, natural (²H/¹H) isotope fractionation in bioproducts by natural abundance deuterium 1D-NMR (NAD 1D-NMR) spectroscopy is the method of choice to understand the enzymatic mechanisms leading to their synthesis or transformation, but also to determine their geographical or botanical origins. This approach, known as ²H-SNIF-NMR^TM method, is also an effective tool in the fight against the counterfeiting of molecules of economical interests. However, the use of achiral isotropic solvents has two significant disadvantages that reduce accessible isotopic information: a rate of overlap of signals generally too high for complex analytes and the absence of spectral discrimination of enantiotopic directions in prochiral compounds. Both drawbacks can be overcome by replacing liquid solvents with chiral liquid crystals (CLCs). In this review, we overview the theoretical basis and the analytical advantages of anisotropic NAD (ANAD) 2D-NMR using polypeptide-based, lyotropic CLCs as enantiodiscriminating ordered NMR solvents. We discuss how and why ANAD 2D-NMR can provide a robust alternative to the conventional method of determining isotopic ratios (²H/¹H)_i, particularly when applied to long-chain fatty acids or homogeneous triglycerides. Various applicative aspects are presented.

Graphical abstract

KEYWORDS:

• Deuterium
• natural abundance
• SNIF-NMR
• 2D-NMR
• isotope fractionation
• chiral liquid crystal
• fatty acid
• triglyceride

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was supported by the Centre National de la Recherche Scientifique: [Grant Number recurrent funding].