APPLICATION OF DFT B3LYP/GIAO AND B3LYP/CSGT METHODS FOR INTERPRETATION OF NMR SPECTRA OF FLAVONOIDS
 
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Pol. J. Food Nutr. Sci. 2003;53(Special issue 2s):157–162
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ABSTRACT
Accurate predictions of 1H (rms.±0.1 ppm) and 13C (rms.±2 ppm) NMR chemical shifts are achieved for several flavonoids belonging to flavanones, flavones and flavonols through empirical scaling of shieldings calculated from GIAO and CSGT theory by means of computationally inexpensive DFT B3LYP/6-31G**// B3LYP/6-31G** method. It was shown that the GIAO method better reproduces the experimental values of the chemical shifts for flavonoids studied than the CSGT method, especially for 1H NMR signals. It is demonstrated on the basis of the method proposed that the experimental NMR data recorded during kaempferol oxidation can be assigned to the compound with 3(2H)-benzofuranone moiety. The results indicate that the calculated NMR chemical shifts can find application in rapid and unequivocal identification of unknown bioactive low-mass compounds in food.
ISSN:1230-0322