1
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Eltemur D, Robatscher P, Oberhuber M, Ceccon A. Improved Detection and Quantification of Cyclopropane Fatty Acids via Homonuclear Decoupling Double Irradiation NMR Methods. ACS OMEGA 2023; 8:41835-41843. [PMID: 37970028 PMCID: PMC10634279 DOI: 10.1021/acsomega.3c06538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 10/03/2023] [Indexed: 11/17/2023]
Abstract
Over the years, NMR spectroscopy has become a powerful analytical tool for the identification and quantification of a variety of natural compounds in a broad range of food matrices. Furthermore, NMR can be useful for characterizing food matrices in terms of quality and authenticity, also allowing for the identification of counterfeits. Although NMR requires minimal sample preparation, this technique suffers from low intrinsic sensitivity relative to complementary techniques; thus, the detection of adulterants or markers for authenticity at low concentrations remains challenging. Here, we present a strategy to overcome this limitation by the introduction of a simple band-selective homonuclear decoupling sequence that consists of double irradiation on 1H during NMR signal acquisition. The utility of the proposed method is tested on dihydrosterculic acid (DHSA), one of the cyclopropane fatty acids (CPFAs) shown to be a powerful molecular marker for authentication of milk products. A quantitative description of how the proposed NMR scheme allows sensitivity enhancement yet accurate quantification of DHSA is provided.
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Affiliation(s)
- Dilek Eltemur
- Laimburg
Research Centre, Laimburg
6 - Pfatten (Vadena), Auer (Ora), BZ 39040, Italy
- Faculty
of Agricultural, Environmental and Food Sciences, Free University of Bozen-Bolzano, Piazza Università 5, Bozen-Bolzano 39100, Italy
| | - Peter Robatscher
- Laimburg
Research Centre, Laimburg
6 - Pfatten (Vadena), Auer (Ora), BZ 39040, Italy
| | - Michael Oberhuber
- Laimburg
Research Centre, Laimburg
6 - Pfatten (Vadena), Auer (Ora), BZ 39040, Italy
| | - Alberto Ceccon
- Laimburg
Research Centre, Laimburg
6 - Pfatten (Vadena), Auer (Ora), BZ 39040, Italy
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2
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Bahadoor A, Watt S, Rajotte I, Bates J. Tautomerization and Isomerization in Quantitative NMR: A Case Study with 4-Deoxynivalenol (DON). JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2022; 70:2733-2740. [PMID: 35171597 DOI: 10.1021/acs.jafc.1c08053] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The regulated mycotoxin 4-deoxynivalenol (DON) has a heterocyclic structure that is readily amenable to tautomerization and conformational isomerization in solution. An analysis of DON in solution by NMR revealed the presence of hemiacetal tautomer(s) and putative conformational isomers, which maintain the intact enone functional group. The extent and type of tautomerization/isomerization vary according to the NMR solvent used and produce different signal patterns in the NMR spectra. Thus, the same proton produces multiple signals depending on which isomer/tautomer it belongs to. To maintain the accuracy of quantitative NMR (qNMR) measurements, it was essential to conclusively identify all signals belonging to the same proton to avoid underestimating its integral value. A strategy to overcome the complications of DON tautomerization and isomerization in solution during qNMR is reported. Of all proton atoms on the DON carbo-skeleton, H-10 produced clearly defined signals centered at 6.6 ppm for suspected conformational isomers and at 5.5 ppm for hemiacetal tautomers. To determine the purity of DON by quantitative proton NMR, the collective integrals of all isomeric and tautomeric signals belonging to H-10 provided the most accurate value. The purity of DON obtained with this protocol is highly accurate and suitable for the value assignment of certified reference materials (CRMs).
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Affiliation(s)
- Adilah Bahadoor
- National Research Council, Metrology, Ottawa, Ontario K1A 0R6, Canada
| | - Sarah Watt
- National Research Council, Metrology, Ottawa, Ontario K1A 0R6, Canada
| | - Isabelle Rajotte
- National Research Council, Metrology, Ottawa, Ontario K1A 0R6, Canada
| | - Jennifer Bates
- National Research Council, Metrology, Ottawa, Ontario K1A 0R6, Canada
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3
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Charlier C, Cox N, Prud'homme S, Geffard A, Nuzillard JM, Luy B, Lippens G. Virtual decoupling to break the simplification versus resolution trade-off in nuclear magnetic resonance of complex metabolic mixtures. MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2021; 2:619-627. [PMID: 37905230 PMCID: PMC10539796 DOI: 10.5194/mr-2-619-2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 07/19/2021] [Indexed: 11/01/2023]
Abstract
The heteronuclear single quantum correlation (HSQC) experiment developed by Bodenhausen and Ruben (1980) in the early days of modern nuclear magnetic resonance (NMR) is without a doubt one of the most widely used experiments, with applications in almost every aspect of NMR including metabolomics. Acquiring this experiment, however, always implies a trade-off: simplification versus resolution. Here, we present a method that artificially lifts this barrier and demonstrate its application towards metabolite identification in a complex mixture. Based on the measurement of clean in-phase and clean anti-phase (CLIP/CLAP) HSQC spectra (Enthart et al., 2008), we construct a virtually decoupled HSQC (vd-HSQC) spectrum that maintains the highest possible resolution in the proton dimension. Combining this vd-HSQC spectrum with a J -resolved spectrum (Pell and Keeler, 2007) provides useful information for the one-dimensional proton spectrum assignment and for the identification of metabolites in Dreissena polymorpha (Prud'homme et al., 2020).
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Affiliation(s)
- Cyril Charlier
- Toulouse Biotechnology Institute (TBI), Université de Toulouse,
CNRS, INRAE, INSA, Toulouse, France
| | - Neil Cox
- Toulouse Biotechnology Institute (TBI), Université de Toulouse,
CNRS, INRAE, INSA, Toulouse, France
| | - Sophie Martine Prud'homme
- Université de Reims Champagne-Ardenne (URCA), UMR-I 02 SEBIO
(Stress Environnementaux et Biosurveillance des milieux aquatiques), Moulin
de la Housse, Reims, France
- present address: Université de Lorraine, CNRS, LIEC, 57000, Metz, France
| | - Alain Geffard
- Université de Reims Champagne-Ardenne (URCA), UMR-I 02 SEBIO
(Stress Environnementaux et Biosurveillance des milieux aquatiques), Moulin
de la Housse, Reims, France
| | - Jean-Marc Nuzillard
- Université de Reims Champagne Ardenne, CNRS, ICMR UMR 7312, 51097 Reims, France
| | - Burkhard Luy
- Institute for Biological Interfaces 4 – Magnetic Resonance,
Karlsruhe Institute of Technology (KIT), Herrmann-von-Helmholtz-Platz 1,
76344 Eggenstein-Leopoldshafen, Germany
| | - Guy Lippens
- Toulouse Biotechnology Institute (TBI), Université de Toulouse,
CNRS, INRAE, INSA, Toulouse, France
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