Application of qNMR. Part 3:Quantification of quercetin in 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

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.

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.

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.

Reference

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