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Existing studies on the biological activity of theabrownins are not based on their free state but on the complexes of theabrownins, polysaccharides, proteins, and flavonoids. In this study, theabrownins (TBs-C) were prepared by weak alkali oxidation of tea polyphenols. The ultraviolet-visible scanning spectrum of TBs-C showed two characteristic absorption peaks at 203 and 270 nm. The zeta potential of the TBs-C aqueous solution was negative, and the values varied from - 6.26 to -19.55 mV with a solution pH of 3-9. Storage conditions of pH 5.0-7.0 and around 25 °C were beneficial for the physical and chemical stability of the TBS-C solution. Cells were treated with series concentrations and examined by MTT, HE staining, PI immunofluorescence staining, flow cytometry, and real-time PCR to investigate the antiproliferative effect of TBs-C on human colon cancer HT-29 cells. The results showed that TBs-C, particularly at 500 µg/mL, inhibited cell growth. TBs-C induced HT-29 cell apoptosis, as confirmed by morphological changes, nucleus propidium iodide staining, and distributions of the cell cycle. The apoptotic mechanism may be due to the intracellular redox imbalance induced by TBs-C.

Theabrownins (TBs) are prepared from dark tea and contain a large number of complex heterogeneous components, such as carbohydrates, proteins, and flavonoids, which are difficult to remove. In addition, some toxic and harmful extraction solvents are used to purify TBs. These obstacles hinder the utilization and industrialization of TBs. In this study, tea polyphenols were used as substrates and polyphenol oxidase and sodium bicarbonate (NaHCO3) were used successively to prepare theabrownins (TBs-E). The UV-visible characteristic absorption peaks of the TBs-E were located at 203 and 270 nm and Fourier-transform IR analysis showed that they were polymerized phenolic substances containing the hydroxy and carboxyl groups. The TBs-E aqueous solution was negatively charged and the absolute values of the zeta potential increased with increasing pH. A storage experiment showed that TBs-E were more stable at pH 7.0 and in low-temperature environments around 25°C. HT-29 human colon cancer cells were used to evaluate the biological activity of TBs-E through 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT), H&E staining, propidium iodide immunofluorescent staining, flow cytometry, and real-time PCR assays. The TBs-E significantly inhibited cell growth and caused late apoptosis, particularly at the dose of 500 μg/ml. The TBs-E markedly reduced the expression of antioxidant enzyme genes and increased the generation of reactive oxygen species to break the redox balance, which may have led to cell damage and death. These results will promote research and industrialization of TBs.

Aroma assessment remains difficult and uncertain in the present sensory assessment system. It is highly desirable to develop a new assessment method to discriminate the quality of various teas in the tea market. In the present work, based on linear discriminant analysis and principal component analysis, the aroma of dry and wet samples of different Xi-hu Longjing and Pu-erh teas were tested and differentiated by electronic noses (e-nose). The results confirm that e-nose can discriminate different priced Xi-hu Longjing tea samples in the range of 80-800 RMB/500 g and varying storage years of Pu-erh tea samples. Furthermore, for the detection of both dry and wet samples of Longjing and Pu-erh teas, the results reveal that all samples have specific aroma characteristics that e-nose can recognize. More importantly, contribution analysis in sensors indicates that nitrogen oxides, methane and alcohols are the characteristic components that contribute to the fragrances of different priced Xi-hu Longjing teas, while nitrogen oxides, aromatic benzene and amines make the fragrances of Pu-erh teas with different storage years disparate. PRACTICAL APPLICATION: This work demonstrates that e-nose can rapidly distinguish tea products with different price levels and varying storage years. With the advantages of ease of use, high portability and flexibility, e-nose will be widely expanded and applied in refined processing and the development of flavored foods.

This article reviewed inhibitory activities of green tea catechins (GTCs) against various tumorigenesis and their suppressive effects on cancer cell progression, metastasis, and angiogenesis according to a great number of kinds of literature, and then summarized the mechanisms of tea catechins-mediated cancer prevention in various cancer types. Special emphasis was placed on summarizing recent research highlighting the related techniques in improving GTCs’ effectiveness in the prevention of tumor progression and/or treatment of cancers. Synergistic effects of catechins when combined with other phytochemicals and drugs, nanostructure- based delivery system, and molecular modifications of EGCG and catechins as means were discussed, and thus provide the basis to better utilize GTCs as the main ingredient of functional foods to reduce the risk of human cancer.

As a non-camellia tea with a rich history in Chinese culture that spans several centuries, Apocynum venetum L. tea is a brewed beverage made from the leaves of the Apocynum venetum L. plant. Despite its long history, little research on the polysaccharides in Apocynum venetum L. leaves has been conducted. In this study, polysaccharide conjugates were extracted from Apocynum venetum L. tea residue under alkaline conditions, referred to as ATPC-A. The conjugates comprised polysaccharide moieties covalently bound to protein. Oil-in-water (O/W) emulsions were prepared from the mixtures of the ATPC-A in water and medium-chain triglycerides (MCT). The mean particle diameter (MPD) (d3,2) of the ATPC-A-stabilized emulsions containing 2.00 wt% and 3.00 wt% ATPC-A increased from 0.47 μm to 1.94 μm and 0.37 μm–1.48 μm after storage at 25.0 °C for 10 days. The zeta potentials of the emulsions were also stable around −40.00 mV. Compared to a 5.00 wt% gum arabic (GA)-stabilized emulsion, the ATPC-A-stabilized emulsion containing 1.00 wt% ATPC-A and higher featured smaller particle sizes and stabilities compared to at lower ATPC-A concentrations. Between pH 2.0 and 8.0, the MPD (d3,2) of the ATPC-A emulsions ranged from 21.05 to 5.67 μm, while the zeta potentials ranged from −25.47 to −44.88 mV. Under different concentrations of metal ions (Na+ and Ca2+), the MPD (d3,2) of the ATPC-A emulsion increased from 13.61 to 29.55 μm between 0.10 and 0.50 mol/L Na+) and from 26.60 μm to 43.72 μm between 0.01 and 0.05 mol/L Ca2+. The absolute zeta potential dropped from 35.07 to 32.53 mV (Na+) and from 33.33 mV to 17.63 mV (Ca2+). These results highlighted the utilization of polysaccharide conjugates derived from Apocynum venetum L. leaves and provided a basis for the high-value utilization of Apocynum venetum L. tea residues.

The oil-in-water (O/W) emulsions were prepared from Scutellaria baicalensis polysaccharide conjugates (SBPC) as an emulsifier and medium-chain triglyceride (MCT). Effects of pH, metal ions and heat treatment on the emulsion stability were investigated. Compared to that of 0.20 1.00 wt% SBPC and 2.00 wt% GA, 2.00 wt% and 3.00 wt% SBPC stabilized emulsion droplets had a smaller particle size and were more stable during 10-day storage at 25 °C. The average particle sizes (d32) of emulsions containing metal ions varied from 4.54 to 6.62 μm (0.100–0.500 mol/L Na+), from 2.63 to 3.86 μm (0.010–0.050 mol/L Ca2+), and from 2.66 to 7.89 μm (0.001–0.030 mol/L Al3+), as well as the zeta potential varying from −17.63 to −19.67 mV (Na+), from −16.50 to −18.13 mV (Ca2+) and from −15.02 to −18.56 mV (Al3+). SBPC emulsion possessed stability under pH 3.0–7.0 and thermal treatment at 70–100 °C during the 10-day storage period. Furthermore, SBPC emulsion inhibited oxidative polymerization of EGC. The average retention rate of EGC was 88.28% on the 10th day. This research provides a new way for development and application of SBPC as an emulsifier.

This research investigated the stabilityof Pu’er tea infusion and Fangbao tea infusion and their contents of biochemical components, such as TP (tea polyphenols), caffeine, water-soluble saccharides, free protein, free amino acids. Compared with green tea, there are a small number of TP and free amino acids in the above two kinds of dark tea and no free amino acids were detected in Fangbao tea. Pu’er tea infusion and Fangbao tea infusion were respectively stored at 2, 30 and 60°C, respectively for 1, 2, 6, 12, 16, 24 and 48 h, respectively to evaluate their stability. The turbidity of Pu’er tea infusion and Fangbao tea infusion began to increase after stored for 6 h and its stability was the worst at 30°C.