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231224s2015 xx |||||o 00| ||eng c |
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|a 10.1002/mrc.4269
|2 doi
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|a pubmed24n0837.xml
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|a (DE-627)NLM251080080
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|a (NLM)26195084
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|a DE-627
|b ger
|c DE-627
|e rakwb
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|a eng
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|a Stark, Timo D
|e verfasserin
|4 aut
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|a A new NMR approach for structure determination of thermally unstable biflavanones and application to phytochemicals from Garcinia buchananii
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|c 2015
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|a Text
|b txt
|2 rdacontent
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|a ƒaComputermedien
|b c
|2 rdamedia
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|a ƒa Online-Ressource
|b cr
|2 rdacarrier
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|a Date Completed 15.04.2016
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|a Date Revised 19.09.2015
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|a published: Print-Electronic
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|a Citation Status MEDLINE
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|a Copyright © 2015 John Wiley & Sons, Ltd.
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|a Previous activity-guided phytochemical studies on Garcinia buchananii stem bark, which is traditionally used in Africa to treat various gastrointestinal and metabolic illnesses, revealed xanthones, polyisoprenylated benzophenones, flavanone-C-glycosides, biflavonoids, and/or biflavanones as bioactive key molecules. Unequivocal structure elucidation of biflavonoids and biflavanones by means of NMR spectroscopy is often complicated by the hindered rotation of the monomers around the C-C axis (atropisomerism), resulting in a high spectral complexity. In order to facilitate an unrestricted rotation, NMR spectra are usually recorded at elevated temperatures, commonly over 80 °C, which effects in a single set of resonance signals. However, under these conditions, one of the target compounds of this investigation, (2R,3S,2″R,3″R)-manniflavanone (1), undergoes degradation. Therefore, we demonstrated in the present study that the 1,1-ADEQUATE could be successfully used as a powerful alternative approach to confirm the C-C connectivities in 1, avoiding detrimental conditions. However, a moderate increase in temperature up to 50 °C was sufficient to deliver sharp signals in the proton NMR experiment of (2R,3S,2″R,3″R)-isomanniflavanone (2) and (2″R,3″R)-preussianone (3). In addition, two new compounds could be isolated, namely (2R,3S,2″R,3″R)-GB-2 7″-O-β-D-glucopyranoside (4) and (2R,3S,2″R,3″R)-manniflavanone-7″-O-β-D-glucopyranoside (5), and whose structures were elucidated by spectroscopic analysis including 1D and 2D NMR and mass spectrometry methods. The absolute configurations were determined by a combination of NMR and electronic circular dichroism (ECD) spectroscopy. The aforementioned compounds exhibited high anti-oxidative capacity in the H2O2 scavenging, hydrophilic Trolox equivalent antioxidant capacity (H-TEAC) and hydrophilic oxygen radical absorbance capacity (H-ORAC) assays
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|a Journal Article
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|a 1,1-ADEQUATE
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|a 13C
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|a 1H
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|a GB2 7″-O-β-d-glucopyranoside
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|a NMR
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|a biflavanone glucosides
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|a biflavanones
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|a manniflavanone
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|a manniflavanone-7″-O-β-d-glucopyranoside
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|a variable temperature NMR
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|a Flavanones
|2 NLM
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|a Flavones
|2 NLM
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|a Phytochemicals
|2 NLM
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|a Plant Extracts
|2 NLM
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|a manniflavanone
|2 NLM
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1 |
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|a Lösch, Sofie
|e verfasserin
|4 aut
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|a Salger, Mathias
|e verfasserin
|4 aut
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|a Balemba, Onesmo B
|e verfasserin
|4 aut
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|a Wakamatsu, Junichiro
|e verfasserin
|4 aut
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|a Frank, Oliver
|e verfasserin
|4 aut
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|a Hofmann, Thomas
|e verfasserin
|4 aut
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| 773 |
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|i Enthalten in
|t Magnetic resonance in chemistry : MRC
|d 1985
|g 53(2015), 10 vom: 21. Okt., Seite 813-20
|w (DE-627)NLM098179667
|x 1097-458X
|7 nnns
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| 773 |
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|g volume:53
|g year:2015
|g number:10
|g day:21
|g month:10
|g pages:813-20
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|u http://dx.doi.org/10.1002/mrc.4269
|3 Volltext
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