Theaflavin is a general name for a class of compounds with a benzodiazepine structure formed by the condensation of catechins, which is catalyzed by polyphenol oxidase, during the processing of black tea. Theaflavins are the determinant of the quality of black tea and have been reported to have a variety of biological functions. Theaflavins are called the “soft gold of tea” and have great potential and promising applications in the fields of foods, health products and natural medicine. Theaflavins are sought after by the consumer market because of their various special biological activities, which have attracted the growing interest of researchers in recent years. Numerous studies have shown that theaflavin has a variety of biological activities such as hypolipidemic, anti-tumor, blood glucose regulatory, and anti-aging activities. Their mechanism of action involves a wide range of signaling pathways, including nuclear factor kappa-B (NF-κB), phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), and activating protein-1 (AP-1) signaling pathways, with multi-target, multi-link, multi-effect characteristics. However, the mechanism of action of theaflavins has not yet been clearly investigated due to the inaccessibility of high-purity theaflavins and theaflavin monomers, and the unstable nature and low bioavailability of theaflavins. Therefore, this paper outlines the latest progress in understanding the various biological activities of theaflavins, with the aim of providing a reference for the research and development of natural dietary supplements and functional foods using theaflavins as raw material.

With the accelerated pace of life, diseases caused by long-term high-sugar and high-energy dietary habits and oxidative stress caused by factors such as strenuous exercise may cause damage to the myocardium to varying degrees and consequently affect human health. Tea polyphenols have been reported to be effective in enhancing physical endurance, stimulating skeletal muscle anabolism, and preventing cardiovascular system diseases, but their protective effects on the myocardium and the underlying mechanisms have not yet been reviewed in detail and systematically. Therefore, this article reviews recent progress in research on the effects of tea polyphenols in enhancing and protecting myocardial function and the underlying mechanisms. We hope that exogenous dietary supplementation of tea polyphenols will be applied to prevent, alleviate and even treat myocardial diseases in humans and animals in the future.

In this study, the aroma quality and volatile components of Dancong tea were analyzed by sensory evaluation and gas chromatography-mass spectrometry (GC-MS), respectively, and the aroma components were identified using a variety of statistical analyses. The results showed that the most important volatile substances in Dancong tea were indole, dehydrolinalool, linalool, jasmine lactone, safflower aldehyde and β-cyclic citral, followed by neroliol and benzylacetonitrile and α, 4-dimethyl-3-cyclohexene-1-acetaldehyde. Among these volatile components, alcohols mainly contributing to the floral and fruity aroma were the most abundant, followed by nitrogen-containing compounds. In correlation analysis and cluster analysis, the honeysuckle-like and osmanthus-like aroma types of Dancong tea had unique volatile composition. The honey-like and floral aroma types were well classified by principal component analysis (PCA) and orthogonal partial least square-discriminant analysis (OPLS-DA). The applicability and testing results of the established OPLS-DA model were good. These results provide a scientific basis for evaluating the aroma quality of Dancong tea and improving product quality.

Fu brick tea (FBT) is a unique compressed dark tea in China. The unique fungal fermentation process creates its unique fungal flavor and special health benefits, so FBT is deeply favored by consumers. This paper reviews the research results on the volatile components contributing to the aroma of FBT and the methods for their evaluation. The reported volatile compounds are systematically classified, and the compounds with high detection frequency are elaborated in detail. The methods for the extraction, qualitative and quantitative analysis of the volatile compounds and the methods for the screening and evaluation of the odor-active compounds of FBT are summarized. Meanwhile, the problems with the current studies and the focus of future research are pointed out.

This research was performed in order to investigate the alleviative effect of aged Wuyi rock tea on dextran sulfate sodium (DSS)-induced colitis in mice. Fifty C57BL/6JGpt female mice were randomly and equally divided into five groups: control, DSS, DSS + infusion of 20-year-old Wuyi rock tea (DSS + OT01), DSS + infusion of 10-year-old Wuyi rock tea (DSS + OT11) and DSS + infusion of fresh Wuyi rock tea (DSS + OT20). The physiological and histopathological conditions of mice after Wuyi rock tea interventions, and the changes of serum inflammatory factors and cecal microbiota were analyzed. The results showed that aged Wuyi rock tea could significantly alleviate the symptoms of body mass loss, diarrhea, bloody stool, and colon length shortening, reduce inflammatory cell infiltration, and significantly inhibit the secretion of pro-inflammatory cytokines. In addition, aged Wuyi rock tea could alleviate the disorder of the gut microbiota, significantly down-regulate the relative abundance of Proteobacteria, Enterobacteriaceae and Escherichia, and up-regulate the relative abundance of Verrucomicrobia and Akkermansia. In summary, aged Wuyi rock tea can alleviate DSS-induced colitis in mice, and the tea produced in 2011 is more effective than that produced in 2001, which may be due to proper oxidation of catechins such as epigallocatechin gallate to produce thearubigins, with better anti-inflammatory and antioxidant properties. In addition, aged Wuyi rock tea is able to maintain intestinal homeostasis by regulating the relative abundance of Escherichia and Akkermansia in the intestine, which in turn alleviates the symptoms of DSS-induced colitis in mice such as body mass loss, diarrhea, bloody stool, colon length shortening, mucosal and crypt damage, inflammatory cell infiltration, and serum inflammatory factor overexpression.

The current study was performedin order to explore the effect of Eurotium cristatum LJSC.2001 on the fermentation quality of raw dark tea. Golden flower loose tea was produced by using E. cristatum LJSC.2001 to ferment raw dark tea from the cultivars Zhuyeqi, Yuntaidaye and Taoyuandaye provided by representative manufacturers (Yuntaishan, Yunshang, Baishaxi and Junhe) in Anhua, Hunan province, and comparative analysis of their taste and aroma quality was carried out by sensory evaluation, basic physicochemical analysis, analysis of catechin components by high performance liquid chromatography (HPLC), and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Results showed that after fermentation by E. cristatum LJSC.2001, the dry tea samples were darker in colorand fully covered with golden flower; their infusions were darker in color, and had a strong fungal aroma and a mellow and full taste, and the brewed tea was soft. Raw dark tea from Baishaxi had a stronger fungal aroma after fermentation, while retaining a distinct pine smoke-like aroma. The contents of taste compounds including tea polyphenols, free amino acids, soluble carbohydrates, flavonoids, total catechins, myricetin, quercetin, and kaempferol showed an overall decreasing trend. The content of catechins in Yuntaidaye raw dark tea from Yuntaishan and Yunshang declined most. The relative contents of esters and aldehydes increased after fermentation. There were differences in the content of volatile components among the different fermented tea samples, methyl salicylate and (E,E)-2,4-heptadienal being the major ones. Multivariate statistical analysis showed significant differences in volatile composition between golden flower loose tea and raw black tea. There were 19 characteristic volatile components identified including methyl salicylate, (E,E)-2,4-heptadienal, (E)-linalool 3,7-oxide, (E)-furan oxidized linaloa, acetophenone, (E)-2-, (Z)-6-nonadienal, (E)-2-hexenal, (E,E)-3,5-octadien-2-one and n-tridecane. The contents of the nine volatile components increased significantly after fermentation, and they all contributed to the fungal aroma of golden flower loose tea. It can be seen that fermentation by E. cristatum LJSC.2001 can impart a more mellow and fuller taste and a more prominent fungal aroma to raw black tea.

Tea is one of the most popular beverages in the world, not only for its unique flavor, but also for its various health benefits. Intestinal flora is known as the "second brain" of human being, and it's closely related to the health of the host. Studies have reported that functional components of tea can effectively regulate the disturbance of intestinal flora, promote the growth of beneficial bacteria, inhibit the growth of harmful bacteria and maintain intestinal health, but there is a lack of in-depth research on the corresponding mechanism. Based on the systematic summary of recent studies, this paper formed the regulatory mechanism of "tea and its functional components-intestinal flora-intestinal metabolites-host health", in order to provide new ideas for the study of the healthy function of tea and its functional components.

Hyperuricemia is a disease of increased blood uric acid caused by the disorder of purine metabolism and decreased uric acid excretion in the host. In recent years, studies have reported that tea and its functional components (mainly tea polyphenols and tea pigment compounds) inhibit purine metabolism enzymes to reduce the production of uric acid, and regulate uric acid transporter to increase the excretion of uric acid, thereby exerting a uric acid-lowering effect. This article systematically reviewed the uric acid-lowering effects of tea and its functional components and its mechanism of action, aiming to provide research ideas for the research and development of tea-drinking tea-lowering uric acid and tea functional products.

Inflammation is the first biological response of the immune system to infection, injury or stimulation. The anti-inflammatory effect of tea is achieved by regulating various inflammatory cytokines. Tea has an obvious anti-inflammatory effect. The functional components in tea, such as tea polyphenols (catechins), theaflavins and other substances, can regulate immune cells and reduce the expression of inflammatory cytokines. However, at present, the research on the anti-inflammatory effect of tea and its functional components mainly stays in the stage of in vitro experiments and animal experiments, and there is still a lack of clinical anti-inflammatory activity research. This paper systematically summarized the latest research progress on the anti-inflammatory effect and mechanism of tea and its functional components, in order to provide reference for the in-depth study of the anti-inflammatory mechanism of tea and the development of anti-inflammatory products.

In order to systematically reveal the differences in flavor quality among green, yellow and black vine teas, processed from the young stems and leaves of Ampelopsis grossedentata by different techniques, sensory evaluation, physicochemical analysis and headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) were used to analyze the quality of green, yellow and black vine teas. Sensory evaluation results showed that yellow vine tea was covered by a silver white powder, and its infusion had a bright yellow color, strong fruity aroma and mellow taste; green vine tea had a yellowish-green color, and its infusion had a bright greenish-yellow color, strong stir-fried aroma and slightly bitter taste; black vine tea had a reddish-brown color, and its infusion had a bright orangered color, strong floral and fruity aroma, and mellow taste. Taste composition analysis showed that the contents of soluble sugar, water extract, and dihydromyricetin were all higher in green vine tea than in yellow and black vine teas, while the content of free amino acids in black vine tea was the highest. A total of 56 volatile components were identified in the three vine teas, with hydrocarbons being dominant in green and yellow vine teas while alcohols being dominant in black vine tea. 1,1,6-trimethyl-1,2-dihydronaphthalene, stigmasterol, lauryl alcohol and linalool were closely related to the stir-fried aroma of green vine tea, while phenylacetaldehyde, naphthalene, 2-pentylfuran, P-umbelliferyl hydrocarbons, and n-tetradecane were closely related to the fruity aroma of yellow vine tea, and phenylacetaldehyde, methyl salicylate, 1,1,6-trimethyl-1,2-dihydronaphthalene contributed to the floral and fruity flavor of black vine tea.