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Structural Determination of Antioxidant and Anticancer Flavonoid Rutin in Solution through DFT Calculations of ¹H?NMR Chemical Shifts.

ABSTRACT: As the knowledge of the predominant molecular structure of antioxidant and anticancer flavonoid rutin in solution is very important for understanding the mechanism of action, a quantum chemical investigation of plausible rutin structures including solvent effects is of relevance. In this work, DFT calculations were performed to find possible minimum energy structures for the rutin molecule. ¹H?NMR chemical shift DFT calculations were carried out in DMSO solution using the polarizable continuum model (PCM) to simulate the solvent effect. Analysis of the experimental and theoretical ¹H?NMR chemical shift profiles offers a powerful fingerprint criterion to determine the predominant molecular structure in solution. Therefore, our aim is to find the best match between experimental (in DMSO-d) and theoretical (PCM-DMSO) ¹H?NMR spectrum profiles. Among 34 optimized structures located on the potential energy surface, we found that structure 32, with a B-ring deviated 30° from a planar configuration (geometry usually assumed for polyphenols), showed an almost perfect agreement with experimental the ¹H?NMR pattern when compared to the corresponding fully optimized planar geometry. This structure is also predicted as the global minimum based on room-temperature Gibbs free energy calculations in solution and, therefore, should be experimentally observed. This is new and valuable structural information regarding structure-activity relationship studies, and such information is hard to obtain by experimentalists without the aid of the X-ray diffraction technique.

SUBMITTER: De Souza LA

PROVIDER: S-EPMC6234759 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Structural Determination of Antioxidant and Anticancer Flavonoid Rutin in Solution through DFT Calculations of <sup>1</sup>H NMR Chemical Shifts.

De Souza Leonardo A LA Da Silva Haroldo C HC De Almeida Wagner B WB

ChemistryOpen 20181114 11

As the knowledge of the predominant molecular structure of antioxidant and anticancer flavonoid rutin in solution is very important for understanding the mechanism of action, a quantum chemical investigation of plausible rutin structures including solvent effects is of relevance. In this work, DFT calculations were performed to find possible minimum energy structures for the rutin molecule. <sup>1</sup>H NMR chemical shift DFT calculations were carried out in DMSO solution using the polarizable ...[more]

PMID: 30460171

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Project description:Detailed solvent and temperature effects on the experimental 1H-NMR chemical shifts of the natural products chrysophanol (1), emodin (2), and physcion (3) are reported for the investigation of hydrogen bonding, solvation and conformation effects in solution. Very small chemical shift of ???? < 0.3 ppm and temperature coefficients ???/??? ? 2.1 ppb/K were observed in DMSO-d6, acetone-d6 and CDCl3 for the C(1)-OH and C(8)-OH groups which demonstrate that they are involved in a strong intramolecular hydrogen bond. On the contrary, large chemical shift differences of 5.23 ppm at 298 K and ??/?? values in the range of -5.3 to -19.1 ppb/K between DMSO-d6 and CDCl3 were observed for the C(3)-OH group which demonstrate that the solvation state of the hydroxyl proton is a key factor in determining the value of the chemical shift. DFT calculated 1H-NMR chemical shifts, using various functionals and basis sets, the conductor-like polarizable continuum model, and discrete solute-solvent hydrogen bond interactions, were found to be in very good agreement with the experimental 1H-NMR chemical shifts even with computationally less demanding level of theory. The 1H-NMR chemical shifts of the OH groups which participate in intramolecular hydrogen bond are dependent on the conformational state of substituents and, thus, can be used as molecular sensors in conformational analysis. When the X-ray structures of chrysophanol (1), emodin (2), and physcion (3) were used as input geometries, the DFT-calculated 1H-NMR chemical shifts were shown to strongly deviate from the experimental chemical shifts and no functional dependence could be obtained. Comparison of the most important intramolecular data of the DFT calculated and the X-ray structures demonstrate significant differences for distances involving hydrogen atoms, most notably the intramolecular hydrogen bond O-H and C-H bond lengths which deviate by 0.152 t? 0.132 Å and 0.133 to 0.100 Å, respectively, in the two structural methods. Further differences were observed in the conformation of -OH, -CH3, and -OCH3 substituents.

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Structural Determination of Antioxidant and Anticancer Flavonoid Rutin in Solution through DFT Calculations of ¹H?NMR Chemical Shifts.

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Structural Determination of Antioxidant and Anticancer Flavonoid Rutin in Solution through DFT Calculations of <sup>1</sup>H NMR Chemical Shifts.

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Structural Determination of Antioxidant and Anticancer Flavonoid Rutin in Solution through DFT Calculations of 1H?NMR Chemical Shifts.

Publications

Structural Determination of Antioxidant and Anticancer Flavonoid Rutin in Solution through DFT Calculations of <sup>1</sup>H NMR Chemical Shifts.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

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Structural Determination of Antioxidant and Anticancer Flavonoid Rutin in Solution through DFT Calculations of ¹H?NMR Chemical Shifts.