Tea Chemistry

As a contribution towards a better understanding of phenolic variation in the genus Cyclopia (honeybush tea), a collection of 82 samples from 15 of the 23 known species was analysed using liquid-chromatography–high resolution mass spectrometry (UPLC-HRMS) in electrospray ionization (ESI) negative mode. Mangiferin and isomangiferin were found to be the main compounds detected in most samples, with the exception of C. bowiena and C. buxifolia where none of these compounds were detected. These xanthones were found to be absent from the seeds and also illustrated consistent differences between species and provenances. Results for contemporary samples agreed closely with those based on analysis of a collection of ca. 30-year-old samples. The use of multivariate tools allowed for graphical visualizations of the patterns of variation as well as the levels of the main phenolic compounds. Exclusion of mangiferin and citric acid from the data was found to give better visual separation between species. The use of UPLC-HRMS generated a large dataset that allowed for comparisons between species, provenances and plant parts (leaves, pods, flowers and seeds). Phenetic analyses resulted in groupings of samples that were partly congruent with species but not with morphological groupings within the genus. Although different provenances of the same species were sometimes found to be very variable, Principle Component Analysis (PCA) indicated that a combination of compounds have some (albeit limited) potential as diagnostic characters at species level. 74 Phenolic compounds are presented, many of which were identified for the first time in Cyclopia species, with nine of these being responsible for the separation between samples in the PCAs. Full article

Aspalathin, the main polyphenol of rooibos (Aspalathus linearis), is associated with diverse health promoting properties of the tea. During fermentation, aspalathin is oxidized and concentrations are significantly reduced. Standardized methods for quality control of rooibos products do not investigate aspalathin, since current techniques of aspalathin detection require expensive equipment and expertise. Here, we describe a simple and fast thin-layer chromatography (TLC) method that can reproducibly visualize aspalathin in rooibos herbal tea and plant extracts at a limit of detection (LOD) equal to 178.7 ng and a limit of quantification (LOQ) equal to 541.6 ng. Aspalathin is a rare compound, so far only found in A. linearis and its (rare) sister species A. pendula. Therefore, aspalathin could serve as a marker compound for authentication and quality control of rooibos products, and the described TLC method represents a cost-effective approach for high-throughput screening of plant and herbal tea extracts. Full article

Catechins belonging to polyhydroxylated polyphenols are the primary compounds found in green tea. They are associated with many physiological properties. Epicatechin (EC) is a non-gallate-type catechin with four phenolic hydroxyl groups attached. The changes in EC treated with color light illumination in an alkaline condition were investigated by chromatographic and mass analyses in this study. In particular, the superoxide anion radical (O₂•⁻) was investigated during the EC photolytic process. EC is unstable under blue light illumination in an alkaline solution. When EC was treated with blue light illumination in an alkaline solution, O₂•⁻ was found to occur via a photosensitive redox reaction. In addition, the generation of monomeric, dimeric, and trimeric compounds is investigated. On the other hand, epigallocatechin gallate (EGCG), which is a gallate-type catechin, is stable under blue light illumination in an alkaline solution. Adding EGCG, during the blue light illumination treatment of EC decreased photolytic formation, suggesting that gallate-type catechins can suppress the photosensitive oxidation of EC. Gallate-type catechins are formed via the esterification of non-gallate-type catechins and gallic acid (GA). The carbonyl group on the gallate moiety of gallate-type catechins appears to exhibit its effect on the stability against the photosensitive oxidation caused by blue light illumination. Full article

Amyloid-β, one of the hallmarks of Alzheimer’s disease (AD), is toxic to neurons and can also cause brain cell death. Oxidative stress is known to play an important role in AD, and there is strong evidence that oxidative stress is associated with amyloid-β. In the present study we report the protective effect of Zijuan Pu’er tea water extract (ZTWE) and the mixture of main ingredients (+)-catechins, caffeine and procyanidin (MCCP) in ZTWE on β-amyloid-induced toxicity in transgenic Caenorhabditis elegans (C. elegans) CL4176 expressing the human Aβ_1–42 gene. ZTWE, (+)-catechins, caffeine, procyanidin and MCCP delayed the β-amyloid-induced paralysis to different degrees. The MCCP treatment did not affect the transcript abundance of amyloid-β transgene (amy-1); however, Thioflavin T staining showed a significant decrease in Aβ accumulation compared to untreated worms. Further research using transgenic worms found that MCCP promoted the translocation of DAF-16 from cytoplasm to nucleus and increased the expression of superoxide dismutase 3 (SOD-3). In addition, MCCP decreased the reactive oxygen species (ROS) content and increased the SOD activity in CL4176 worms. In conclusion, the results suggested that MCCP had a significant protective effect on β-amyloid-induced toxicity in C. elegans by reducing β-amyloid aggregation and inducing DAF-16 nuclear translocation that could activate the downstream signal pathway and enhance resistance to oxidative stress. Full article

Hawk tea is a rich and edible resource, traditionally used as a beverage in South China. This drink has many pharmacologic effects, such as acting as an antioxidant and reducing blood sugar and lipids. The objective of this work was to explore the active compound contents, bioactivities and their monthly changes, and optimize the harvest time. In the present study, Hawk tea from each month in 2017 was collected and extracted with 70% (v/v) ethanol. The contents of the total flavonoids and total phenols were determined using the colorimetric method. We determined the contents of seven characteristic active substances—hyperin, isoquercitrin, trifolin, quercitrin, astragalin, quercetin, and kaempferol—using high-performance liquid chromatography. The crude extract was tested for its antioxidant and inhibitory properties on enzymes involved in metabolic syndrome. Specifically, 2,2-diphenyl-1-picrylhydrazyl, 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid), ferric-reducing power assay, and the inhibition capacity test on α-glucosidase and lipase were conducted to determine the antioxidant effect in vitro, as well as the reduction of blood sugar and lipids. Monthly variations in activities and components were determined by numeric analysis and comparison. Correlation analysis revealed that antioxidant effects are significantly correlated with the total flavonoids. The hierarchical cluster analysis of bioactivities and their contents indicates that October and November are the best harvesting months, which differs with the habitual collection of Hawk tea. Full article

Theanine, a unique amino acid in Camellia sinensis, accounts for more than 50% of total free amino acids in tea and has a significant contribution to the quality of green tea. Previous research indicated that theanine is synthesized from glutamic acid (Glu) and ethylamine mainly in roots, and that theanine accumulation depends on the availability of ethylamine which is derived from alanine (Ala) decarboxylation catalyzed by alanine decarboxylase (AlaDC). However, the specific gene encoding AlaDC protein remains to be discovered in tea plants or in other species. To explore the gene of AlaDC in tea plants, the differences in theanine contents and gene expressions between pretreatment and posttreatment of long-time nitrogen starvation were analyzed in young roots of two tea cultivars. A novel gene annotated as serine decarboxylase (SDC) was noted for its expression levels, which showed high consistency with theanine content, and the expression was remarkably high in young roots under sufficient nitrogen condition. To verify its function, full-length complementary DNA (cDNA) of this candidate gene was cloned from young roots of tea seedlings, and the target protein was expressed and purified from Escherichia coli (E. coli). The enzymatic activity of the protein for Ala and Ser was measured in vitro using ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS). The results illustrated that the target protein could catalyze the decarboxylation of Ala despite of its high similarity with SDC from other species. Therefore, this novel gene was identified as AlaDC and named CsAlaDC. Furthermore, the gene expression levels of CsAlaDC in different tissues of tea plants were also quantified with quantitative real-time PCR (qRT-PCR). The results suggest that transcription levels of CsAlaDC in root tissues are significantly higher than those in leaf tissues. That may explain why theanine biosynthesis preferentially occurs in the roots of tea plants. The expression of the gene was upregulated when nitrogen was present, suggesting that theanine biosynthesis is regulated by nitrogen supply and closely related to nitrogen metabolism for C. sinensis. The results of this study are significant supplements to the theanine biosynthetic pathway and provide evidence for the differential accumulation of theanine between C. sinensis and other species. Full article

Nitrogen (N) forms are closely related to tea quality, however, little is known about the characteristics of quality chemical components in tea under the spatial heterogeneity of different N forms. In this study, a split-root system, high performance liquid chromatography (HPLC), and root analysis system (WinRHIZO) were used to investigate free amino acids (FAAs) and root length of tea plants under the spatial heterogeneity of different N forms. Uniform. (U.) ammonium (NH₄⁺) (both compartments had NH₄⁺), U. nitrate (NO₃⁻) (both compartments had NO₃⁻), Split. (Sp.) NH₄⁺ (one of the compartments had NH₄⁺), and Sp. NO₃⁻ (the other compartment had NO₃⁻) were performed. The ranking of total FAAs in leaves were as follows: U. NH₄⁺ > Sp. NH₄⁺/Sp. NO₃⁻ > U. NO₃⁻. The FAA characteristics of Sp. NH₄⁺/Sp. NO₃⁻ were more similar to those of U. NO₃⁻. The contents of the important FAAs (aspartic acid, glutamic acid, and theanine) that determine the quality of tea, increased significantly in U. NH₄⁺. The total root length in U. NH₄⁺ was higher than that in the other treatments. More serious root browning was found in U. NO₃⁻. In conclusion, NH₄⁺ improved the accumulations of FAAs in tea leaves, which might be attributed to the root development. Full article

Chrysanthemum morifolium Ramat is a perennial flowering plant widely cultivated for use in a tea infusion and as a popular beverage. To identify and evaluate the tea infusion made with a γ-irradiated mutant chrysanthemum cultivar with dark purple petals (cv. ARTI-Dark Chocolate), its phytochemical composition and antioxidant activity were tested and compared with those of the commercially available chrysanthemum cultivar with yellow petals (cv. Gamguk) by HPLC-DAD-ESIMS, as well as DPPH and ABTS radical scavenging assays. The purple chrysanthemum tea contained anthocyanins and linarin, which were not detected in the yellow chrysanthemum tea and the content of chlorogenic acid, acacetin-7-O-β-glucoside, and luteolin was higher compared with the yellow chrysanthemum tea. In contrast, the yellow chrysanthemum tea had higher luteolin-7-O-β-glucoside, 3,5-dicaffeoylquinic acid, apigenin-7-O-β-glucoside, and apigenin contents in comparison with the purple chrysanthemum tea. In addition, the content and antioxidant activity of the two chrysanthemum teas were investigated according to different water temperatures and infusing time. The yellow chrysanthemum tea did not show any significant differences according to infusing time and temperature, while the purple chrysanthemum tea was more influenced by the infusing time than water temperature, showing the highest total compound content in the infusing condition of 100 °C and 4 min. Moreover, the floral scent volatiles of the two chrysanthemum tea sources were analyzed using HS-SPME-GC-MS. In the DPPH radical scavenging assay, the purple chrysanthemum tea broadly showed greater antioxidant activity than did the yellow chrysanthemum tea, corresponding to the high content of anthocyanins known as the powerful antioxidant. Further, both chrysanthemum flower teas exhibited strong ABTS radical scavenging effects ranging from 76% to 61% under all infusing conditions. Therefore, the purple chrysanthemum cultivar, ARTI-Dark Chocolate, is worthy of breeding as a new tea cultivar. Full article

We have previously found two novel monoterpene glycosides, liguroside A and liguroside B, with an inhibitory effect on the catalytic activity of the enzyme leukocyte-type 12-lipoxygenase in the Qing Shan Lu Shui tea. Here, two new monoterpene glycosides, liguroside C and liguroside D which inhibit this enzyme, were isolated from the same tea. The spectral and chemical evidence characterized the structures of these compounds as (5E)-7-hydroperoxy-3,7-dimethyl-1,5-octadienyl-3-O-(α-l-rhamnopyranosyl)-(1′′→3′)-(4′′′-O-trans-p-coumaroyl)-β-d-glucopyranoside and (2E)-6-hydroxy-3,7-dimethyl-2,7-octadienyl-3-O-(α-l-rhamnopyranosyl)-(1′′→3′)-(4′′′-O-trans-p-coumaroyl)-β-d-glucopyranoside, respectively. These ligurosides, which irreversibly inhibited leukocyte-type 12-lipoxygenase, have a hydroperoxy group in the monoterpene moiety. Additionally, monoterpene glycosides had the same backbone structure but did not have a hydroperoxy group, such as kudingoside A and lipedoside B-III, contained in the tea did not inhibit the enzyme. When a hydroperoxy group in liguroside A was reduced by using triphenylphosphine, the resultant compound, kudingoside B, showed a lower inhibitory effect on the enzyme. These results strongly suggest the involvement of the hydroperoxy group in the irreversible inhibition of the catalytic activity of leukocyte-type 12-lipoxygenase by the monoterpene glycosides contained in the Qing Shan Lu Shui tea. Full article

Pu’er tea produced from Camellia sinensis var. assamica is a widely appreciated and consumed beverage that can be divided into two kinds of tea depending on the different fermentation processed used, the special sensory characteristics, and their chemical composition. However, authentication seems to be very important for such teas, as they are traded to comparatively high prices, especially in Europe. The results for selected biochemical markers showed that aged raw pu’er tea contained 210.2 mg GAE/g polyphenols, of which 2.2 mg/g were gallic acid, 16.1 mg/g theogallin, 35.1 mg/g (−)-epigallocatechin gallate, and 40.1 mg/g (−)-epicatechin gallate, on average. Young ripened pu’er tea contained about 104.6 mg GAE/g polyphenols, of which 5.5 mg/g gallic acid, 0.9 mg/g theogallin, 0.7 mg/g (−)-epigallocatechin gallate, and 1.8 mg/g (−)-epicatechin gallate, on average. An additional objective of the present study was to unravel the best brewing conditions for optimal extraction of the bioactive compounds. Infusions of nineteen commercial teas (from pu’er cakes) were obtained at different time-temperature ratios for studying the content of bioactive compounds (flavan-3-ols, flavonols, caffeoylquinic acids, methylxanthines). Brewing at 90 °C for 5 min was the best condition to obtain a high content of total polyphenols in ripened pu’er tea. Principal component analysis and hierarchical cluster analysis showed, that young ripened and aged raw pu’er tea can be successfully differentiated by the analyzed chemical compounds. Principal component analysis results indicated that young ripened pu’er tea has higher contents of gallic acid, quercetin, and kaempferol than aged raw pu’er tea. Full article