Determination and Comparison of γ-Aminobutyric Acid (GABA) Content in Pu-erh and Other Types of Chinese Tea

Abstract

Two previous studies have reported that pu-erh tea contains a high level of γ-aminobutyric acid (GABA), which is the major inhibitory neurotransmitter in the central nervous system and has several physiological functions. However, two other researchers have demonstrated that the GABA content of several pu-erh teas was low. Due to the high value and health benefits of GABA, analysis of mass-produced pu-erh tea is necessary to determine whether it is actually enriched with GABA. A high-performance liquid chromatography (HPLC) method was developed for the determination of GABA in tea, the results of which were verified by amino acid analysis using an Amino Acid Analyzer (AAA). A total of 114 samples of various types of Chinese tea, including 62 pu-erh teas, 13 green teas, 8 oolong teas, 8 black teas, 3 white teas, 4 GABA teas, and 16 process samples from two industrial fermentations of pu-erh tea (including the raw material and the first to seventh turnings), were analyzed using HPLC. Statistical analysis demonstrated that the GABA content in pu-erh tea was significantly lower than that in other types of tea (p < 0.05) and that the GABA content decreased during industrial fermentation of pu-erh tea (p < 0.05). This mass analysis and comparison suggested GABA was not a major bioactive constituent and resolved the disagreement GABA content in pu-erh tea. In addition, the GABA content in white tea was found to be significantly higher than that in the other types of tea (p < 0.05), leading to the possibility of producing GABA-enriched white tea.

Metabolic Changes during the Pu‐erh Tea Pile‐Fermentation Revealed by a Liquid Chromatography Tandem Mass‐Spectrometry‐Based Metabolomics Approach

“…It is still unclear that how the compounds change during the pile fermentation of pu‐erh tea. Furthermore, there are still some inconsistent results among different reported papers (Zhao and others ). For example, some previous reports about the content of GABA in pu‐erh tea were controversial, even with differing obtained by the same research group in different studies (Zhao and others ).…”

“…Species of bacteria and fungi strains, which can alter the composition and contents of the active compounds of pu‐erh tea, contribute to the good taste of pu‐erh tea (Chen and others ). For example, effect of short‐term fermentation with Streptomyces bacillaris or S. cinereus can enhance the content of statin and γ‐aminobutyric acid (GABA) (Jeng and others ; Zhao and others ).…”

L-theanine, unique amino acid of tea, and its metabolism, health effects, and safety

“…In some studies, it was found out that white tea, which is not being subjected to fermentation and oxidation processes, has higher levels of L-Theanine compared to the other types of tea (Alcazar et al, 2007;Zhao et al, 2011). In some studies, it was found out that green tea, which is not being subjected to fermentation process, had similar levels of L-Theanine with half fermented oolong tea and fermented black tea (Alcazar et al, 2007;Ying et al, 2005).…”

Determination of Gamma-aminobutyric Acid (GABA) Content in Grains and Cruciferous Vegetable Seeds

“…Recoveries ranged from 100.0 to 110.5% with the DAD and 98.8 to 111.2% with the FLD detector, which established the accuracy of the method. Zhao et al (2011) extracted GABA from tea in hot water (85°C) for 2 hours. In this study, we observed that extraction of GABA with hot water did not work.…”

“…GABA content for germination of grains experiments has been tested primarily by using HPLC on a reversed phase column, C-8 or C18 after pre-column online derivatization with o-phthaldialdehyde (OPA) (Hayat et al, 2015;Ding et al, 2018a) or with addition of dansyl chloride to the sample (Ding et al, 2018b) and detection by an ultraviolet visible (UV-Vis) detector. Zhao et al (2011) analyzed GABA in Chinese teas with HPLC-FLD using OPA for pre-column online derivatization. Ding et al (2016) tested GABA in ungerminated and germinated dehulled rice under normoxic and hypoxic conditions by GC-MS using bismethylsilane trifluoracetamide (BSTFA) to derivatize samples.…”