A new NMR approach for structure determination of thermally unstable biflavanones and application to phytochemicals from Garcinia buchananii
Copyright © 2015 John Wiley & Sons, Ltd.
| Veröffentlicht in: | Magnetic resonance in chemistry : MRC. - 1985. - 53(2015), 10 vom: 21. Okt., Seite 813-20 |
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| Weitere Verfasser: | , , , , , |
| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2015
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| Zugriff auf das übergeordnete Werk: | Magnetic resonance in chemistry : MRC |
| Schlagworte: | Journal Article 1,1-ADEQUATE 13C 1H GB2 7″-O-β-d-glucopyranoside NMR biflavanone glucosides biflavanones manniflavanone manniflavanone-7″-O-β-d-glucopyranoside mehr... |
| Zusammenfassung: | Copyright © 2015 John Wiley & Sons, Ltd. 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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| Beschreibung: | Date Completed 15.04.2016 Date Revised 19.09.2015 published: Print-Electronic Citation Status MEDLINE |
| ISSN: | 1097-458X |
| DOI: | 10.1002/mrc.4269 |