In the present study, four Bacteroides species that could degrade Fuzhuan brick tea polysaccharide-3 (FBTPS-3) were isolated from human feces and identified to be Bacteroides ovatus, B. uniformis, B. fragilis and B. thetaiotaomicron. The four Bacteroides species showed growth on FBTPS-3 as the carbon source, and B. ovatus showed the best capability for utilizing FBTPS-3 among the four species since B. ovatus could utilize more FBTPS-3 during 24 h fermentation. Moreover, the four Bacteroides species could metabolize FBTPS-3 and promote the production of acetic, propionic and isovaleric acids. Transcriptome analysis of B. ovatus revealed that 602 genes were up-regulated by FBTPS-3, including two carbohydrate-active enzyme clusters and four polysaccharide utilization loci (PULs). The PUL 1 contained GH28 family that could hydrolyze rhamnogalacturonan and other pectic substrates, which was in line with our previous work that rhamnose and galacturonic acid were the main component monosaccharides of FBTPS-3. Collectively, the results suggested that FBTPS-3 could be utilized by Bacteroides spp., and it might be developed as a promising prebiotic targeting Bacteroidetes in intestinal environment.

Introduction: Fuzhuan brick tea (FBT) is a worldwide popular beverage which has the appreciable potential in regulating glycometabolism. However, the reports on the hypoglycemic mechanism of FBT remain limited. Methods: In this study, the hypoglycemic effect of FBT was evaluated in a pharmacological experiment based on Kunming mice. Global metabolomics and network pharmacology were combined to discover the potential target metabolites and genes. In addition, the real-time quantitative polymerase chain reaction (RT-qPCR) analysis was performed for verification. Results: Seven potential target metabolites and six potential target genes were screened using the integrated approach. After RT-qPCR analysis, it was found that the mRNA expression of VEGFA, KDR, MAPK14, and PPARA showed significant differences between normal and diabetes mellitus mice, with a retracement after FBT treatment. Conclusion: These results indicated that the hypoglycemic effect of FBT was associated with its anti-inflammatory activities and regulation of lipid metabolism disorders. The exploration of the hypoglycemic mechanism of FBT would be meaningful for its further application and development.

Fuzhuan brick tea (FBT) is a post-fermented tea fermented by the fungus Eurotium cristatum and is mainly produced in Hunan Province, China. Our previous study revealed that FBT extract prevents obesity by increasing energy expenditure and mitochondrial content in mice. Therefore, in this study, we hypothesized that FBT extract could be effective in alleviating obesity-induced muscle atrophy by addressing mitochondrial dysfunction, and aimed to explore the underlying molecular mechanism of FBT extract in high-fat diet-induced obese mice. FBT extract increased skeletal muscle weight and size, myosin heavy chain isoforms, and muscle performance in obese mice. Additionally, FBT extract reduced obesity-induced intramuscular lipids, skeletal muscle inflammation, and the expression of skeletal muscle atrophy markers, and increased the expression of fibronectin type III domain-containing protein 5 in skeletal muscles. Obesity-induced skeletal muscle mitochondrial dysfunction was improved by FBT extract as analyzed through mitochondrial morphology, fatty acid oxidation, respiratory chain complexes, and mitochondrial dynamics and biogenesis. Epigallocatechin, a major bioactive compound in FBT extract, attenuated palmitic acid-induced muscle atrophy by regulating mitochondrial functions in C2C12 cells. In conclusion, FBT extract may prevent obesity-induced muscle atrophy by alleviating mitochondrial dysfunction in mice.

The pile fermentation process of Fuzhuan brick tea is unique in that it involves preheating without the use of starter cultures. The detailed metabolite changes and their drivers during this procedure are not known. Characterizing these unknown changes that occur in the metabolites and microbes during pile fermentation of Fuzhuan brick tea is important for industrial modernization of this traditional fermented food. Using microbial DNA amplicon sequencing, mass spectrometry-based untargeted metabolomics, and feature-based molecular networking, we herein reveal that significant changes in the microbial community occur before changes in the metabolite profile. These changes were characterized by a decrease in Klebsiella and Aspergillus, alongside an increase in Bacillus and Eurotium. The decrease in lysophosphatidylcholines, unsaturated fatty acids, and some astringent flavan-3-ols and bitter amino acids, as well as the increase in some less astringent flavan-3-ols and sweet or umami amino acids, contributed importantly to the overall changes observed in the metabolite profile. The majority of these changes was caused by bacterial metabolism and the corresponding heat generated by it.

Fuzhuan brick tea, a distinctive dark tea fermented by microorganisms, is a traditional beverage in China throughout history. Recently, it has attracted considerable attention owing to its unique quality characteristics and potential health benefits. The aim of this study was to establish a method for the quality control of Fuzhuan brick tea for stable production. Ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry was used to identify Fuzhuan brick tea, and the major components were chosen for further quantitative analysis. Subsequently, a quantification method was developed using ultra-high-performance liquid chromatography coupled with triple-quadrupole mass spectrometry, and its reliability was verified through methodological validation. Finally, a total of 30 compounds were identified, including catechins, flavonoids, alkaloids, and fatty acids. The established method was reliable for methodological validation and was applied to the quantitative analysis of Fuzhuan brick tea. This study provides a fundamental basis for the quality control and further studies on the component analysis of Fuzhuan brick tea.

Fuzhuan brick tea (FBT), a distinctive Chinese dark tea with the predominant fungus of Eurotium cristatum, offered significant health benefits to Chinese people. In the current study, the in vivo bioactivities of E. cristatum (SXHBTBU1934) fermented green tea and spores of E. cristatum fermented on wheat were investigated, respectively. The methanol extract of fermented green tea and spore of E. cristatum both showed potent lipid-lowering activity in the blood of a high-fat diet induced hyperlipidemia model in golden hamsters and significantly reduced the accumulation of fat granules in the liver. These results indicated that the key active components were produced by E. cristatum. Chemical investigations suggested similar components in the two extracts and led to the identification of a new alkaloid, namely variecolorin P (1), along with four known structurally related compounds, (-)-neoechinulin A (2), neoechinulin D (3), variecolorin G (4), and echinulin (5). The structure of the new alkaloid was elucidated by HRESIMS, 1H, 13C, and 2D NMR analysis. The lipid-lowering activity of these compounds was evaluated using an oleic acid-induced HepG2 cell line model. Compound 1 significantly reduced the lipid accumulation in the HepG2 cell line with an IC50 value of 0.127 μM.

Fuzhuan brick tea (FBT), a type of black tea, is a traditional beverage in China, especially popular among frontier ethnic groups. FBT is well-known for its health benefits, such as hypoglycemic, anti-hypertensive, anti-inflammatory, diuretic, and detoxification effects. Nevertheless, the underlying mechanisms on the molecular level are still elusive and the key compounds responsible for the health benefits are unidentified. Previous studies have mainly focused on functional studies of the water extract. However, FBT is typically cooked with butter or milk. Therefore, we hypothesized that some lipophilic components in FBT, which can be absorbed through the co-consumption of butter or milk, may play an important role in the health benefits. The present study aimed to investigate whether the liposoluble extract of FBT alleviates symptoms related to metabolic diseases and to identify the active compounds involved. By comparing the high-performance liquid chromatography (HPLC) profiles of water, milk and hexane extract, some low polarity peaks were observed in the milk and hexane extracts. Furthermore, the hexane extract treatment alleviated body weight gain, serum total cholesterol and triglyceride levels, and inhibited the accumulation of hepatic fat granules in a high-fat diet (HFD)-induced C57BL/6N mouse model. In order to identify the key functional lipophilic compounds in FBT, the hexane extract of FBT was subjected to chemical characterization. Four phenol analogs were characterized, namely, isodihydroauroglaucin (1), dihydroauroglaucin (2), tetrahydroauroglaucin (3), and flavoglaucin (4). Compounds 1 and 4 reduced the levels of total cholesterol and triglyceride in vivo. Both compounds also inhibited the high-fat diet-induced body weight gain and accumulation of fat granules in the liver of C57BL/6N mice. Isodihydroauroglaucin and flavoglaucin have therefore been identified as bioactive ingredients that contribute to the health benefits of FBT.

Fuzhuan brick tea (FBT) is a post-fermented dark tea preferred by consumers for its excellent hypolipidemic activity, and theabrownin (TB) is the main bioactive composition in FBT. This work explored the structural and hypolipidemic properties of TB derived from Pingwu FBT, and investigated whether it exerted hypolipidemic activity by inhibiting intestinal lipid absorption. Structural characterization revealed that TB was an amorphous polymerized phenolic compound rich in hydroxyl and carboxyl groups with good thermostability. In vivo, TB and its fractions with different molecular weights (TB-LT3k, TB-3-10k, TB-10-30k, TB-30-100k, TB-GT100k) significantly reduced the lipid levels of hyperlipidemia zebrafish (P < 0.05). Moreover, TB attenuated hyperlipidemia by inhibiting intestinal lipid absorption, as TB effectively bound to bile acids, inhibited enzymatic activity of pancreatic lipase and cholesterol esterase, influenced micelle formation, and decreased micellar cholesterol solubility. Results facilitated research on TB and offered support for its feasibility as a natural alternative to prevent hyperlipidemia.

The present study investigated the immune-protective effect of polysaccharides from Fuzhuan brick tea (FBTPs) in cyclophosphamide (Cy)-induced immunosuppressive mice. The results showed that high-dose of FBTPs administration remarkably alleviated Cy-evoked immune damage through improving the body features, organ indices, immune responses and oxidative stress in the mice. Further microbiota analysis revealed that FBTPs obviously restored Cy-evoked microbial dysbiosis by increasing several beneficial bacteria Lactobacillus, Allobaculum, Unclassified_f_Lachnospiraceae and norank_f_Lachnospiraceae, while reducing Bacteroides, norank_f_Ruminococcaceae, Colidextribacter, Alloprevotella, norank_f_Desulfovibrionaceae and Helicobacter. Meanwhile, metabolomics analysis found that FBTPs significantly altered a range of microbial metabolites, including inosine, deoxyinosine, taurine, sinapic acid, maltotriose, butyric acid, lysophosphatidyl cholines (LysoPCs), lysophosphatidic acids (LysoPAs) and choline. These altered metabolites were involved in purine metabolism, ABC transporters, sulfur metabolism, neuroactive ligand-receptor interaction, biosynthesis of phenylpropanoids, carbohydrate digestion and absorption, protein digestion and absorption, choline metabolism in cancer and glycerophospholipid metabolism pathways, which were mainly related to immune responses, antioxidant capacity and energy supply of the immunosuppressive mice. Additionally, some significant correlations were observed between the specific microbiota and effective metabolites. These results provide a novel insight into the immune-protective effect of FBTPs on regulating the intestinal microbiota and metabolism, which are helpful for thoroughly understanding the nutrition of FBTPs and providing a solid basis for the deeper utilization of Fuzhuan brick tea (FBT).

The effect of Fuzhuan brick tea (FBT) on metabolism in obese mice is mediated by regulation of N-methyltransferase by aryl hydrocarbon receptor. The expression of the phosphatidylethanolamine N-methyltransferase gene is regulated by many transcription factors, and those specific to this effect need further investigation. Experimental animal studies have been designed to observe the effects of a single drug or the sequential effects of drugs. A washout period should be included if different drugs (e.g., antibiotics and FBT) are given to avoid or reduce additive effects or synergy. Currently, most experimental studies performed in mice used only male animals. However, experience has revealed that the results of using only male mice are very likely to have sex differences.