Journal of the Korean Magnetic Resonance Society (한국자기공명학회논문지)

Korean Magnetic Resonance Society (한국자기공명학회)
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Quantitative analysis of metabolites in Korean green tea using NMR

  • Choi, Kwang-Ho (Department of Chemistry and RINS, Gyeongsang National University) ;
  • Lee, Joon-Hwa (Department of Chemistry and RINS, Gyeongsang National University)
  • Received : 2018.12.07
  • Accepted : 2018.12.16
  • Published : 2018.12.20
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Abstract

The plucking season of green tea leaves is one of the important parameters that decide their metabolic quality. Here, we performed the identification and quantity analysis of the metabolites of the green tea using NMR spectroscopy. We assigned the $^1H$ resonances for sixteen metabolites. This analysis found that four metabolites, gallic acid, quinic acid, theobromine and ECG, exhibited clear discrimination of green teas by the three different grades, Ujeon, Sejak and Jungjak. Our results suggest that these four metabolites could be used for diagnostics for quality control of green tea.

Keywords

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Figure 1. Resonance assignments of amino acids. (upper) 1D 1H and (lower) 2D TOCSY spectra.

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Figure 2. Quantification of (A) Alanine, (B) Caffeine, (C) ECG, (D) EGCG, (E) Fumaric acid, (F) GABA, (G) gallic acid, (H) quinic acid, (I) theanine, (J) theobromine and (K) theogallin identified from extracts of Hadong green tea. Symbol X indicates average value and two horizontal bars indicate the standard deviation from the average value.

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Figure 3. Resonance assignment of theanine. (upper) 1D 1H and (lower) 2D TOCSY spectra. The chemical structure of theanine is shown in upper right.

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Figure 4. Resonance assignment of GABA. (upper) 1D 1H and (lower) 2D TOCSY spectra. The chemical structure of GABA is shown in upper right.

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Figure 5. Resonance assignment of fumaric acid, theobromine, caffeine and gallic acid. (upper) chemical structures and (lower) 1D 1H NMR spectra of fumaric acid, theobromine, caffeine and gallic acid.

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Figure 6. Resonance assignment of quinic acid. (upper) 1D 1H and (lower) 2D TOCSY spectra. The chemical structure of quinic acid is shown in upper right.

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Figure 7. Resonance assignment of theogallin. (upper) 1D 1H and (lower) 2D TOCSY spectra. The chemical structure of theogallin is shown in upper right.

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Figure 8. Resonance assignment of catechin. (upper) chemical structures and (lower) 1D 1H NMR spectra of EC, EGC, ECG and EGCG.

Table 1. 1H chemical shifts of compounds of green tea (Ujeon grade).

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