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Application of qNMR. Part 3:Quantification of quercetin in Tartary buckwheat


NMR spectroscopy can count the number of atoms in molecules, and so purity of the sample  can be quantitatively determined from the ratio of signal intensities of a standard material  and a target material. Quantitative NMR (qNMR) has wide applicability because it does not  require a target matrial of known purity as standard. This application note introduces an  example of qNMR analysis for quercetin, a functional component of Tartary buckwheat.

Target material:Quercetin

Tartary buckwheat, containing functional flavonoid rutin as a main component, gets attention as a healthy food. Rutin, however, is not detected in Tartary buckwheat noodle because of coexisting rutin-degrading enzyme. Instead, another flavonoid quercetin is detected.

Fig. 1 qNMR spectrum of Tartary buckwheat  (Spectrometer: JNM-ECA600)
Fig. 1 qNMR spectrum of Tartary buckwheat  (Spectrometer: JNM-ECA600)

Purpose: Purity of quercetin in extraction liquid  of Tartary buckwheat is quantitatively determined  by HPLC and qNMR.

Fig. 2 qNMR spectra of commercial reagents of rutin and  quercetin and Tartary buckwheat extract.
Fig. 2 qNMR spectra of commercial reagents of rutin and  quercetin and Tartary buckwheat extract.

Table  Measurement conditions
Parameter of JNM-ECA600
Observed nucleus 1H
Observed range -5ppm~15ppm
Data points 32K
Digital filter ON(8 times)
Recycle delay 60s
Flip angle 90°
Scans 8 scan
Temperature 25℃
Spinning OFF

The NMR signals of 6, 8, 5’, 6’-protons for Tartary buckwheat may be attributed to rutin and other  flavonoid glycosides, and so the signal of 2-proton is used for analysis.


  • Purity of quercetin in Tartary buckwheat  was determined by qNMR.
  • Purity determined by LC almost agrees  with that by qNMR.

Though qNMR is a useful analysis when a  target sample of known purity is not avail-  able, its sensitivity is lower than chromatog-  raphy. However, the combination of these  may lead to quantitative analysis with high  reliability.

図3 韃靼そば中のクエルセチン定量分析結果比較
Fig. 3  Purities of quercetin in Tartary buckwheat
* Corrected with the purity determined by qNMR.


N.Sugimoto, A.Tada, T. Suematsu et al. , Jpn.J.Food Chem.Safety, 17(3),179-184


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