Nuclear deuterium exchange in methoxybenzenes and methylated flavonoids

Kolar, G.F.

doi:10.1002/jlcr.2590070404

Cited by 7 publications

(6 citation statements)

References 11 publications

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“…When measured at 90°C, the signal of H-6, and H-8 at d 5.91 of the spectrum of a DMSO-d 6 solution of naringenin kept overnight after addition of D 2 O, revealed the exchange with the deuterium of the solvent. The H/D exchange phenomenon has also been reported by Kolar (1971). The signals of H-6 and H-8 of some methylated and methoxylated flavonoid-like compounds dissolved in a solution of dioxane:D 2 O (3:1) exchanged with the deuterium of the solvent after heating at 95°C prolonged for 16 h. According to the author the exchange reaction is a typical electrophilic aromatic substitution reaction being promoted by the Pyrex glass of the NMR tube.…”

Section: Resultsmentioning

confidence: 86%

Identification of natural epimeric flavanone glycosides by NMR spectroscopy

et al. 2009

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Section: Resultsmentioning

confidence: 86%

Identification of natural epimeric flavanone glycosides by NMR spectroscopy

et al. 2009

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“…Experiments performed with petunidin 3- O -β-glucopyranoside ( 2 ) dissolved in pure CD 3 OD, in CF 3 CO 2 D/CD 3 OD (5:95, v/v), and in CF 3 CO 2 D/CD 3 OD (15:85, v/v) showed similar H → D exchange rates for both H-6 and H-8 (Tables and ). Kolar examined H → D exchange reactions for H-6 and H-8 of some methylated flavanols in D 2 O/dioxane (3:1) solutions after heating the samples for 16 h at 95 °C in Pyrex glasses. He concluded that the observed exchange reactions, following first-order kinetics, were typical electrophilic aromatic substitution reactions being catalyzed by acid.…”

Section: Discussionmentioning

confidence: 99%

“…Using mass spectrometry applied to various flavonoids under chemical ionization conditions, the aromatic hydrogens of flavonoids may undergo exchange with deuterium . This type of H → D exchange has also been observed in catechin/epicatechin 3′,4′,5,7-tetramethyl ethers, formed after cleavage of a methylated condensed procyanidin in D 2 O–dioxane , in 3′,4′,5,7-tetramethoxyflavan when a solution of this compound in 3:1 D 2 O–dioxane is heated at 95 °C for 16 h in Pyrex glass , and during labeling of isoflavone phytoestrogens .…”

Section: Introductionmentioning

confidence: 91%

Reactivity of Anthocyanins and Pyranoanthocyanins. Studies on Aromatic Hydrogen–Deuterium Exchange Reactions in Methanol

Jordheim

Fossen

Songstad

et al. 2007

J. Agric. Food Chem.

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Reactivity studies involving anthocyanin structures and their equilibrium forms will lead to better understanding of the properties of these antioxidants. Hydrogen-deuterium (H --> D) exchange reactions at various sites of the 3-glucosides of delphinidin (1), petunidin (2), malvidin (3), and the corresponding 3-glucosides of carboxypyranodelphinidin (4), carboxypyranopetunidin (5), carboxypyranomalvidin (6), and the flavonol quercetin 3-O-(6-alpha-rhamnopyranosyl-beta-glucopyranoside)(7) have been examined at room temperature in pure CD 3OD and in CD 3OD acidified with CF 3CO 2D. The H --> D exchange rate constants of H-6 and H-8 of 2 determined from (1)H NMR integration data were found to be independent upon pigment concentration (up to 4 x 10 (-2) M) and trifluoroactic acid concentration (0-15%, v/v), respectively. This suggest that these reactions follow first-order kinetics and unexpectedly to be independent of the acid concentration. H-6 and H-8 of the flavylium cation A-rings of 1- 3, and in the corresponding hydrogens of the hemiketal forms, exchanged with half-lives of approximately 100 h ( 1) and approximately 50 h ( 2 and 3), respectively. The pyranoanthocyanins (4-6) experienced no H --> D exchange for the analogous hydrogens, but H --> D exchange of H-beta (H-4)(t 1/2 approximately 25 h) for these compounds was observed. Only H-8 underwent significant H --> D exchange in 7. It is concluded that a stabilization of the sigma-complexes, assumed to be the intermediates in the reactions, takes place for the common anthocyanins (1-3) contrary to the pyranoanthocyanins (4-6).

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“…Although less rapid than hydroxyl or carboxyl hydrogen exchange, the exchange of these aromatic hydrogen atoms, via keto-enol tautomerism, was a fairly fast process and as shown in Figure 3 , and was complete in 12 h at pH 7.4. The phenomena of H/D exchange have previously been reported in response to heating samples containing flavonoid metabolites [ 45 , 46 ] and also in related anthocyanin molecules in acidified methanolic or aqueous solutions [ 47 ]. For the operation of the high throughput screen, varying degrees of exchange of the catechin H-6 and H-8 hydrogens, have potential to give false positive results in multivariate analyses of large sets of spectra.…”

Section: Resultsmentioning

confidence: 99%

An Efficient High Throughput Metabotyping Platform for Screening of Biomass Willows

2014

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Future improvement of woody biomass crops such as willow and poplar relies on our ability to select for metabolic traits that sequester more atmospheric carbon into biomass, or into useful products to replace petrochemical streams. We describe the development of metabotyping screens for willow, using combined 1D 1H-NMR-MS. A protocol was developed to overcome 1D 1H-NMR spectral alignment problems caused by variable pH and peak broadening arising from high organic acid levels and metal cations. The outcome was a robust method to allow direct statistical comparison of profiles arising from source (leaf) and sink (stem) tissues allowing data to be normalised to a constant weight of the soluble metabolome. We also describe the analysis of two willow biomass varieties, demonstrating how fingerprints from 1D 1H-NMR-MS vary from the top to the bottom of the plant. Automated extraction of quantitative data of 56 primary and secondary metabolites from 1D 1H-NMR spectra was realised by the construction and application of a Salix metabolite spectral library using the Chenomx software suite. The optimised metabotyping screen in conjunction with automated quantitation will enable high-throughput screening of genetic collections. It also provides genotype and tissue specific data for future modelling of carbon flow in metabolic networks.

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Nuclear deuterium exchange in methoxybenzenes and methylated flavonoids

Abstract: SUMMARYThe isolation of 6,8-d~-catechinlepicatechin 5,7,3',4'-tetramethyI ether

Cited by 7 publications

References 11 publications

Identification of natural epimeric flavanone glycosides by NMR spectroscopy

Identification of natural epimeric flavanone glycosides by NMR spectroscopy

Reactivity of Anthocyanins and Pyranoanthocyanins. Studies on Aromatic Hydrogen–Deuterium Exchange Reactions in Methanol

An Efficient High Throughput Metabotyping Platform for Screening of Biomass Willows

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