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

  • Summary

NM100008

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.

Quercetin
Quercetin
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.

Conclusion

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

Reference

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

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