Proton nuclear magnetic resonance studies of monoacylated anthocyanins from the wild carrot: Part 1. Inter- and intra-molecular interactions in solution
✍ Scribed by Elena G. Gakh; Donald K. Dougall; David C. Baker
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 142 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0958-0344
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✦ Synopsis
Inter-and intra-molecular interactions of five anthocyanins (one non-acylated and four acylated with either sinapic acid or 4-methylated sinapic acid) obtained from cell culture of the wild carrot (Daucus carota ssp. carota) have been studied by one-and two-dimensional proton nuclear magnetic resonance (NMR) spectroscopy. Temperature and concentration dependencies of proton chemical shifts show that self-association of non-acylated anthocyanins depends upon the number and position of the sugar units. It was found for the first time that there were non-acylated anthocyanins that were not protected by self-association. Both intra-and inter-molecular interactions were found in the acylated anthocyanins under study. These compounds form strong intra-molecular -complexes between the sinapoyl group and the anthocyanidin nucleus, the double bond of sinapic acid being involved as well as its aromatic ring. Upon increasing the concentration of the anthocyanins or lowering the temperature of the NMR sample, the -complexes form multinuclear complexes as shown by the resultant negative nuclear Overhauser effect (NOE) values. Spin diffusion was observed in the acylated anthocyanins for temperatures below Ϫ 40°C. It was also concluded that, because anthocyanins fall in the range of medium-size molecules with NOEs of small magnitude, and because they readily form complexes, two-dimensional NOE experiments are more reliable for structural elucidation of the anthocyanins than are one-dimensional steadystate NOE experiments.