![]() Hu, Kaifeng Westler, William M Markley, John L Simultaneous quantification and identification of individual chemicals in metabolite mixtures by two-dimensional extrapolated time-zero (1)H-(13)C HSQC ( HSQC(0)). Overall, this effort demonstrates the power of the concerted use of these two NMR techniques for the structural elucidation of natural products containing labile hydroxy protons and a carbon framework that can be traced out via HSQC. This analytical approach is suitable for both the purified natural product proanthocyanidins and their commercial analogues. At the same time it is possible to acquire a fingerprint of the proanthocyanidin sample and evaluate its purity via the HSQC information. By integrating each of these regions in the (31)P NMR spectra, it is possible to identify the oxygenation patterns of the flavan-3-ol units. More specifically, rings A, B, and C of their flavan-3-ol units show well-defined and resolved absorbance regions in both the quantitative (31)P NMR and HSQC spectra. This approach has offered significant detailed information regarding the structure and purity of these complex and often elusive proanthocyanidins. The chemical composition of Acacia catechu, Schinopsis balansae, and Acacia mearnsii proanthocyanidins has been determined using a novel analytical approach that rests on the concerted use of quantitative (31)P NMR and two-dimensional heteronuclear NMR spectroscopy. This enables rapid quantification and integration over multiple signals without the need for complete resonance assignments and simplifies the integration of overlapping signals.ĭetailed Chemical Composition of Condensed Tannins via Quantitative (31)P NMR and HSQC Analyses: Acacia catechu, Schinopsis balansae, and Acacia mearnsii.Ĭrestini, Claudia Lange, Heiko Bianchetti, Giulia In this paper, we present a novel Quantitative, Equal Carbon HSQC (QEC- HSQC) experiment providing an equal response across different type of carbons regardless of the number of attached protons, in addition to an uniform response over a wide range of 1JCH couplings. This drawback can be solved by observing a different type of nuclei offering improved resolution or with multidimensional experiments, such as HSQC. While sensitive and simple to acquire, the low resolving power of 1D 1H NMR spectra can be a limiting factor when analyzing complex mixtures. Quantitative NMR has become increasingly useful and popular in recent years, with many new and emerging applications in metabolomics, quality control, reaction monitoring and other types of mixture analysis. Mäkelä, Valtteri Helminen, Jussi Kilpeläinen, Ilkka Heikkinen, Sami Quantitative, equal carbon response HSQC experiment, QEC- HSQC Copyright © 2015 John Wiley & Sons, Ltd. The resolution is enhanced by two orders of magnitudes without the usual complications due to spectral aliasing. The reconstructed spectra significantly facilitate both manual and automated spectral analyses and structure elucidation based on heteronuclear 2D experiments. We applied a new reconstruction method, RHUMBA (reconstruction of high-resolution using multiplet built on aliased spectra), to spectra obtained from the differential evolution for non-ambiguous aliasing- HSQC and the new AMNA (additional modulation for non-ambiguous aliasing)- HSQC experiments. Fortunately, this information is not completely lost and can be retrieved using methods in which chemical shifts are encoded in the aliased spectra and decoded after processing to reconstruct high-resolution (1) H-(13) C HSQC spectrum with full spectral width and a resolution similar to that of 1D spectra. Reducing the spectral window can significantly increase the resolution but at the cost of ambiguities in frequencies as a result of spectral aliasing. In conventional multidimensional NMR experiments, such as the (1) H-(13) C HSQC, the resolution in the indirect dimensions is typically 100 times lower as in 1D spectra because it is limited by the experimental time. Resolution enhancement is a long-sought goal in NMR spectroscopy. Reconstruction of full high-resolution HSQC using signal split in aliased spectra.įoroozandeh, Mohammadali Jeannerat, Damien ![]()
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