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Quantum chemical and nuclear magnetic resonance spectral studies on molecular properties and electronic structure of berberine and berberrubine
Author(s) -
Tripathi A. N.,
Chauhan Lata,
Thankachan P. P.,
Barthwal Ritu
Publication year - 2007
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2019
Subject(s) - chemistry , chemical shift , berberine , molecule , carbon 13 nmr , proton nmr , density functional theory , computational chemistry , proton , spectral line , nuclear magnetic resonance , stereochemistry , organic chemistry , physics , quantum mechanics , astronomy
The structural and electronic properties of berberine and berberrubine have been studied extensively using density functional theory (DFT) employing B3LYP exchange correlation. The geometries of these molecules have been fully optimized at the B3LYP/6‐311G** level. The chemical shift of 1 H and 13 C resonances in NMR spectra of these molecules have been calculated using the gauge invariant atomic model (GIAO) method as implemented in Gaussian 98. One‐ and two‐dimensional HSQC ( 1 H 13 C), HMBC ( 1 H 13 C) and ROESY ( 1 H 1 H) spectra were recorded at 500 MHz for the berberine molecule in D 2 O solution. All proton and carbon resonances were unambiguously assigned, and inter‐proton distances obtained from ten observed NOE contacts. A restrained molecular dynamics (RMD) approach was used to get the optimized solution structure of berberine. The structure of berberine and berberrubine molecules was also obtained using the ROESY data available in literature. Comparison of the calculated NMR chemical shifts with the experimental values revealed that DFT methods produce very good results for both proton and carbon chemical shifts. The importance of the basis sets to the calculated NMR parameters is discussed. It has been found that calculated structure and chemical shifts in the gas phase predicted with B3LYP/6‐311G** are in very good agreement with the present experimental data and the measured values reported earlier. Copyright © 2007 John Wiley & Sons, Ltd.