Chemical Composition Of Tea Research Articles

HPLC-DAD method for simultaneous determination of gallic acid, catechins, and methylxanthines and its application in quantitative analysis and origin identification of green tea

The high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD) was optimized for the simultaneous determination of 11 compounds, belonging to polyphenols (gallic acid and seven catechins) and methylxanthines (caffeine, theobromine, and theophylline). The results obtained for all the validation parameters of the HPLC-DAD method showed that the method is sensitive enough for routine analysis with basic chromatographic equipment, thus it has a significant potential to be highly applicable in common laboratory practice. The method was used in the analysis of 60 green tea infusions originating from four tea-producing countries. The dataset contributes to enhancing current data on green tea. The analysis of green tea extracts revealed significant differences depending on the origin of the samples. Linear Discriminant Analysis (LDA) was applied to test the accuracy of identification of the origin of the tea samples, based on the chemical composition of tea with a focus on polyphenolic compounds and methylxanthines analysed in this study. Based on cross-validation results, the model showed 93.75 % accuracy in the classification of green tea originating from Japan, China (Mainland), China (Taiwan) and South Korea.

Identification of markers for tea authenticity assessment: Non-targeted metabolomics of highly similar oolong tea cultivars (Camellia sinensis var. sinensis)

Tea authenticity assessment remains a challenge because of various cultivars and similar chemical profiles among tea cultivars. Unique oolong tea cultivars (YaShiXiang (YSX)) were used as models in the present study to identify potential markers for tea authenticity assessment via non-targeted metabolomics. With chemometric analysis, a total of ten markers were found to differ significantly among YSX and the high similarity cultivar tea samples, which were up-regulated in YSX. Based on the ten markers, classification model for discrimination of YSX were developed with different combinations of markers. All models were able to classify YSX samples correctly (93.0%–100% for internal cross-validation; 80.5%–99.0% for external validation). The simultaneous determination of metabolites in this study suggested that a combination of non-targeted metabolomics and chemometric methods could provide high resolution markers for tea authenticity assessment, and which can serve as a basis for further quality evaluation and breeding of tea cultivars in the future. • Highly similar oolong tea cultivars were analyzed for tea authenticity assessment. • Chemical composition of tea were analyzed by UHPLC Q-Exative Orbitrap MS. • Ten markers were identified to evaluate the authenticity of oolong tea.

Chemical compositions of Pu'er tea fermented by Eurotium Cristatum and their lipid-lowering activity

In order to reveal the effect of microorganisms on the chemical composition of tea and their lipid-lowering function, Pu'er raw tea (PR) made from sun-dried leaves of Yunnan large-leaf tea cultivars was processed through a period of flowering fermentation mainly facilitated by Eurotium cristatum, and thus converted into flowering Pu'er tea (FP) in the present study. Tea aqueous extracts were successively extracted by chloroform, ethyl acetate and n-butyl alcohol. Afterwards, non-volatile and volatile compounds of PR and FP were identified and compared through high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometer (GC-MS), respectively. Furthermore, high lipid HepG2 cells induced by OA were treated by those extracts of different polar to explore their impact on lipid-lowering. It can be observed that the contents of tea polyphenols (TPs) and amino acids of FP significantly decreased whereas the total amount of flavonoids significantly increased, compared to those of PR. Besides, the ethyl acetate fraction of FP (EAF-FP) was of the most prominent effect on lipid-lowering, and its optium effective concentration was 80 μg/mL.

The aroma, taste, color and bioactive constituents of tea

The genus Camellia sinensis belongs to the family of Theaceae of the flowering plants. The leaves and leaf buds of C. sinensis are used to produce tea. The chemical composition of tea leaves has been thoroughly studied and the main constituents belong to the polyphenol group accounting for 25 to 35% on a dry weight basis. C. sinensis also contains various chemical constituents including methylxanthines, amino acids, chlorophyll, carotenoids, lipids, carbohydrates, vitamins, and more than 600 volatile compounds. Literature reports indicated that consumption of tea protects from various physiological and pharmacological effects which could be because of the presence of crucial therapeutic compounds which are more bio-stable and direct acting than those present in other medicinal plants. The activities of the compounds from tea are so pervading that they are virtually broad spectrum in their actions. This article provides a critical review of different phytochemicals isolated from tea and their associated medicinal properties as well as the chemical constituents responsible for aroma, taste and color. Key words: Tea, Camellia sinensis, chemical constituents, biological activity, aroma, taste, color.

IDAS: a Windows based software package for cluster analysis

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text, comprising the main article and one appendix, is accompanied by two installation diskettes with the software package and data files. The main article discusses the chemometric aspects of the package and explains its purpose. The IDAS software package combines three cluster analysis methods (hierarchical, non-hierarchical and fuzzy) and runs under MS Windows. Modified algorithms for non-hierarchical and fuzzy clusterings are described. The interpretation of the clustering results is facilitated by the extensive use of different types of graph. New approaches to the graphical representation of the results of fuzzy clustering are proposed. Two data sets, the Iris data by Fisher and a data set on the chemical composition of tea, are used to demonstrate the capabilities of the software.

V. Chemical composition of tea

Abstract Abstract Different classes of compounds found in tea are discussed: poly‐phenols, amino acids, caffeine, nucleotides, carbohydrates, lipids, organic acids, chlorophyll, carotenoids, unsaponifiable compounds, saponins, minerals, and volatile compounds.