NMR, RP-HPLC-PDA-ESI-MSn, and RP-HPLC-FD Characterization of Green and Oolong Teas (Camellia sinensis L.)

Anatoly P Sobolev,Simone Circi,Cinzia Ingallina,Maria Daglia,Arianna Di Lorenzo,Cristina Santarcangelo,Luisa Mannina

doi:10.3390/molecules26175125

Abstract

Untargeted (NMR) and targeted (RP-HPLC-PDA-ESI-MSn, RP-HPLC-FD) analytical methodologies were used to determine the bioactive components of 19 tea samples, characterized by different production processes (common tea and GABA tea), degrees of fermentation (green and oolong teas), and harvesting season (autumn and spring). The combination of NMR data and a multivariate statistical approach led to a statistical model able to discriminate between GABA and non-GABA teas and green and oolong teas. Targeted analyses showed that green and GABA green teas had similar polyphenol and caffeine contents, but the GABA level was higher in GABA green teas than in regular green tea samples. GABA oolong teas showed lower contents of polyphenols, caffeine, and amino acids, and a higher content of GABA, in comparison with non-GABA oolong teas. In conclusion, the results of this study suggest that the healthy properties of teas, especially GABA teas, have to be evaluated via comprehensive metabolic profiling rather than only the GABA content.

Highlights

The chemical composition of tea has been extensively studied, leading to the identification of many phytochemicals responsible for its healthy properties [1,2,3,4,5]
The 1 H spectra (Figure 1) of the analyzed teas were assigned according to the literature [22], with the presence of theanine at 1.118 ppm, threonine/lactate (THR/LAT) at 1.348 ppm, alanine (ALA) at 1.498 ppm, quinic acid (QA) at 1.888 ppm, gamma aminobutyric acid (GABA) at 2.314 ppm, epicatechin gallate (ECG) at 5.057 ppm, 2-O-arabinopyranosyl-myo-inositol (ARBMI) at 5.207 ppm, α-glucose at 5.255 ppm, sucrose at 5.427 ppm, GCG/GC at 6.563 ppm, EGCG at 6.597 ppm, EGC at 6.631 ppm, gallic acid (GA)
Non-GABA teas, whereas PC2 was mostly responsible for discriminating oolong from green teas

Summary

Introduction

The chemical composition of tea has been extensively studied, leading to the identification of many phytochemicals responsible for its healthy properties [1,2,3,4,5]. These bioactive compounds can be subdivided into polyphenolic components and non-polyphenolic compounds. During the oxidation process, flavan-3-ols undergo oxidation and polymerization reactions, catalyzed by polyphenol oxidase and peroxidase, leading to the formation of theaflavins (TFs) and thearubigins (TRs), the most representative compounds of oolong and black teas, respectively [6,8].

Methods

Results

Conclusion