13C CP MAS NMR and GIAO-CHF/DFT calculations of flavonoids: Morin, kaempferol, tricin, genistein, formononetin and 3,7-dihydroxyflavone
✍ Scribed by Agnieszka Zielińska; Katarzyna Paradowska; Jacek Jakowski; Iwona Wawer
- Publisher
- Elsevier Science
- Year
- 2008
- Tongue
- English
- Weight
- 292 KB
- Volume
- 873
- Category
- Article
- ISSN
- 0022-2860
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✦ Synopsis
13 C CP MAS NMR spectra of the flavonoids: morin, kaempferol, 3,7-dihydroxyflavone, tricin and isoflavones: genistein and formononetin were recorded to characterize solid-state conformations. Intramolecular hydrogen bonds forming five-, six-and seven-membered rings are present in the two morin molecules in the crystals -their 13 C resonances have been assigned with the aid of the calculated shielding constants. Linear relationships between the calculated shielding constants r DFT (ppm) and chemical shifts (d CPMAS , ppm) were obtained for all studied compounds. Higher correlation coefficients suggest that the conformation with ''clockwise'' orientation of both OH groups is more probable in the solid 3,7-dihydroxyflavone, whereas in the solid formononetin the OH and OCH 3 substituents are directed ''anticlockwise''. The barrier to the rotation of phenyl ring B decreases in the order: morin (2 0 -OH, 3-OH) > kaempferol (3-OH) > tricin.