Comparison of hypoglycemic effects of ripened pu-erh tea and raw pu-erh tea in streptozotocin-induced diabetic rats

Antidiabetic Potential of Tea and Its Active Compounds: From Molecular Mechanism to Clinical Evidence

Diabetes mellitus (DM) is a chronic endocrine disorder that poses a long-term risk to human health accompanied by serious complications. Common antidiabetic drugs are usually accompanied by side effects such as hepatotoxicity and nephrotoxicity. There is an urgent need for natural dietary alternatives for diabetic treatment. Tea (Camellia sinensis) consumption has been widely investigated to lower the risk of diabetes and its complications through restoring glucose metabolism homeostasis, safeguarding pancreatic β-cells, ameliorating insulin resistance, ameliorating oxidative stresses, inhibiting inflammatory response, and regulating intestinal microbiota. It is indispensable to develop effective strategies to improve the absorption of tea active compounds and exert combinational effects with other natural compounds to broaden its hypoglycemic potential. The advances in clinical trials and population-based investigations are also discussed. This review primarily delves into the antidiabetic potential and underlying mechanisms of tea active compounds, providing a theoretical basis for the practical application of tea and its active compounds against diabetes.

Exploring the connection between caffeine intake and constipation: a cross-sectional study using national health and nutrition examination survey data

BACKGROUND

Caffeine has been reported to increase gastrointestinal motility and change intestinal microbiota. Constipation may be caused by colonic motor dysfunction and colonic microbiomeis disturbances. In this study, we aimed to explore the association between caffeine intake and constipation.

METHODS

This was a cross-sectional study based on the National Health and Nutrition Examination Survey (NHANES). Caffeine intake was assessed using 24-h dietary recall method, and constipation was defined based on stool consistency or stool frequency. Logistic regression analysis was used to assess the association between caffeine intake and constipation, and results were expressed as odds ratio (OR) with 95% confidence intervals (95%CI). Subgroup analysis was performed based on age.

RESULTS

A total of 13,816 participants were finally included for analysis. After adjusting potential confounders, high intake of caffeine was found to be associated with the low odds of constipation (Q3: OR = 0.60, 95%CI: 0.49-0.74; Q4: OR = 0.77, 95%CI: 0.59-0.99; Q5: OR = 0.72, 95%CI: 0.56-0.92). The similar association was found in young people and middle-age people (P < 0.05).

CONCLUSION

High caffeine intake was associated with the low odds of constipation. Our finding indicated that individuals should develop consciousness and habit of consuming caffeinated foods and drinks to prevent and relief the constipation.

Ameliorative effects of Scutellaria Pinnatifida subsp. pichleri (Stapf) Rech.f. Extract in streptozotocin-induced diabetic rats: chemical composition, biochemical and histopathological evaluation

BACKGROUNDS

Scutellaria Pinnatifida subsp. pichleri (Stapf) Rech.f. (SP) is used in folk medicine for the treatment of diabetes. The aim of the study was to determine the phenolic profile of SP extract (SPE) by LC-MS/MS and to investigate the antidiabetic, hepatoprotective and nephroprotective effects of SPE in streptozotosin (STZ)-induced diabetic rat model.

METHODS

Forty-two rats were randomly divided into six groups (n = 7): Control (nondiabetic), diabetes mellitus (DM), DM + SP-100 (diabetic rats treated with SPE, 100 mg/kg/day), DM + SP-200 (diabetic rats treated with SPE, 200 mg/kg/day), DM + SP-400 (diabetic rats treated with SPE, 400 mg/kg/day) and DM + Gly-3 (diabetic rats treated with glibenclamide, 3 mg/kg/day). Live body weight, fasting blood glucose (FBG) level, antidiabetic, serum biochemical and lipid profile parameters, antioxidant defense system, malondyaldehyde (MDA) and histopathological examinations in liver, kidney and pancreas were evaluated.

RESULTS

Apigenin, luteolin, quinic acid, cosmosiin and epigallocatechin were determined to be the major phenolic compounds in the SPE. Administration of the highest dose of SP extract (400 mg/kg) resulted in a significant reduction in FBG levels and glycosylated hemoglobin levels in STZ-induced diabetic rats, indicating an antihyperglycemic effect. SPE (200 and 400 mg/kg) and glibenclamide significantly improved MDA in liver and kidney tissues. In addition, SPE contributed to the struggle against STZ-induced oxidative stress by stimulating antioxidant defense systems. STZ induction negatively affected liver, kidney and pancreas tissues according to histopathological findings. Treatment with 400 mg/kg and glibenclamide attenuated these negative effects.

CONCLUSIONS

In conclusion, the extract of the aerial part of Scutellaria pinnatifida subsp. pichleri has hepatoprotective, nephroprotective and insulin secretion stimulating effects against STZ-induced diabetes and its complications due to its antidiabetic and antioxidant phytochemicals such as apigenin, luteolin, quinic acid, cosmosiin and epigallocatechin.

Simultaneous Determination of Pesticide Residues and Mycotoxins in Storage Pu-erh Tea Using Ultra-High-Performance Liquid Chromatography Coupled with Tandem Mass Spectrometry

Mycotoxins and pesticides are the most concerning chemical contaminants that can affect the quality of Pu-erh tea during its production and storage. This study presents a method that can simultaneously determine 31 pesticide residues and six mycotoxins in Pu-erh tea within 11 min using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) after QuEChERS extraction. The lower limit of quantification (LOQ) for all analytes ranged between 0.06 and 50 ppb. Recoveries for each pesticide and mycotoxin ranged between 62.0 and 130.3%, with intra- and inter-day precisions lower than 15%. Good linear relationships were obtained, with correlation coefficients of r2 > 0.991 for all analytes. The established method was applied to 31 Pu-erh tea samples, including raw and ripened Pu-erh tea with different storage times. As a result, pesticide residues were not detected in any of the collected samples, and the mycotoxins detected in the samples were well below the official maximum residue limits (MRLs). Notably, the levels of aflatoxin B1 (AFB1), aflatoxin G1 (AFG1) and aflatoxin G2 (AFG2) were lower than 1 ppb in the samples stored for more than 30 years.

Inonotus obliquus polysaccharide are linear molecules that alter the abundance and composition of intestinal microbiota in Sprague Dawley rats

Introduction

The macromolecular polysaccharide Inonotus obliquus polysaccharide (IOP) is composed of various monosaccharides, and it could modulate the composition and diversity of intestinal flora. However, its impact on the intestinal flora in rats of different genders remains unclear. Therefore, this study aims to investigate the structural changes of IOP and its effects on the intestinal flora after administration in male and female rats.

Methods

In this study, the molecular weight and purity of IOP were analyzed by high-performance gel permeation chromatography (HPGPC) and phenol sulfuric acid method, and NMR was used to confirm the chemical structure of IOP. Sex hormone [testosterone (T) and estradiol (E2)] levels and intestinal microbial changes were detected by enzyme-linked immunosorbent assay (ELISA) and 16S rRNA, respectively, after gavage of IOP (100 mg/kg) in male and female Sprague Dawley (SD) rats.

Results

HPGPC analysis showed that the average molecular weight (Mw) of IOP was 4,828  Da, and the total sugar content of the purified IOP was 96.2%, indicating that the polysaccharide is of high purity. NMR revealed that IOP is a linear macromolecule with an α-D-type glucose backbone. The results of ELISA and 16S rRNA showed that the IOP increased the abundance of beneficial bacteria, such as Clostridia_UCG-014 and Prevotellaceae_NK3B31, and reduced that of harmful bacteria, such as Colidextribacter and Desulfobacterota in the intestine of both male and female rats, and IOP changed the levels of sex hormones in male and female rats. Further analyses revealed that the increase in alpha diversity was higher in male than female rats. α diversity and β diversity revealed a significant difference in the composition of cecal microbiota between male and female rats in the control group, but IOP intake reduced this difference. Meanwhile, α analysis revealed a change in the composition of bacterial flora was more stable in male than female rats.

Conclusions

This study enhances our comprehension of the IOP structure and elucidates the alterations in intestinal flora following IOP administration in rats of varying genders. Nonetheless, further investigation is warranted to explore the specific underlying reasons for these discrepancies.

Analysis of Volatile Profile and Aromatic Characteristics of Raw Pu-erh Tea during Storage Based on GC-MS and Odor Activity Value

Volatile constituents are critical to the flavor of tea, but their changes in raw Pu-erh tea (RAPT) during storage have not been clearly understood. This work aimed to investigate the volatile composition and their changes at various storage durations. The volatile profile of RAPT was determined using headspace solid-phase microextraction in combination gas chromatography-mass spectrometry. A total of 130 volatile compounds were identified in RAPT samples, and 64 of them were shared by all samples. The aroma attributes of RAPT over a storage period ranging from 0 to 10 years were assessed through the combination of odor activity value (OAV), aroma characteristic influence(ACI) value, and multivariate statistical analysis. The results revealed that RAPT exhibited a distinct floral and fruity aroma profile after storage for approximately 3-4 years. A notable shift in aroma was observed after 3-4 years of storage, indicating a significant turning point. Furthermore, the likely notable shift after 10 years of storage may signify the second turning point. According to the odor activity value (OAV ≥ 100), eight key volatile compounds were identified: linalool, α-terpineol, geraniol, trans-β-ionone, α-ionone, (E,E)-2,4-heptadienal, 1-octanol, and octanal. Combining OAV (≥100) and ACI (≥1), five compounds, namely linalool, (E,E)-2,4-heptadienal, (Z)-3-hexen-1-ol, 2,6,10,10-tetramethyl-1-oxaspiro [4.5]dec-6-ene, and octanal, were identified as significant contributors to the aroma. The results offer a scientific foundation and valuable insights for understanding the volatile composition of RAPT and their changes during storage.

Flavor perception and health benefits of tea

As one of the most consumed non-alcoholic beverages in the world, tea is acclaimed for its pleasant flavor and various health benefits. Different types of tea present a distinctive flavor and bioactivity due to the changes in the composition and proportion of respective compounds. This article aimed to provide a more comprehensive understanding of tea flavor (including aroma and taste) and the character of tea in preventing and alleviating diseases. The recent advanced modern analytical techniques for revealing flavor components in tea, including enrichment, identification, quantitation, statistics, and sensory evaluation methodologies, were summarized in the following content. Besides, the role of tea in anti-cancer, preventing cardiovascular disease and metabolic syndrome, anti-aging and neuroprotection, and regulating gut microbiota was also listed in this article. Moreover, questions and outlooks were mentioned to objectify tea products' flavor quality and health benefits on a molecular level and significantly promote our understanding of the comprehensive value of tea as a satisfactory health beverage in the future.

Effects of pile fermentation on the physicochemical, functional, and biological properties of tea polysaccharides

This study investigated the influence of pile fermentation on the physicochemical, functional, and biological properties of tea polysaccharides (TPS). Results indicated that the extraction yield, uronic acid content, and polyphenol content of TPS greatly increased from 1.8, 13.1 and 6.3 % to 4.1, 27.9, and 7.8 %, respectively, but the molecular weight markedly decreased from 153.7 to 76.0 kDa after pile fermentation. Additionally, the interfacial, emulsion formation, and emulsion stabilization properties of TPS were significantly improved after pile fermentation. For instance, 1.0 wt% TPS isolated from dark tea (D-TPS) can fabricate 8.0 wt% MCT oil-in-water nanoemulsion (d₃₂ ≈ 159 nm) with potent storage stability. Moreover, the antioxidant and α-glucosidase inhibitory activities of D-TPS was higher than that of TPS isolated from sun-dried raw tea (R-TPS). Overall, this study indicated that pile fermentation markedly affected the physicochemical and structural characteristics of TPS, thereby improving their functional and biological properties.

Preparation, characterization and antioxidant activity of cobalt polysaccharides from Qingzhuan Dark Tea

The paradoxical effects of cobalt in biological processes have caused controversy regarding the application of cobalt-based biomaterials. Cobalt has recently been shown to be a trace element that promotes bone growth. Qingzhuan Dark Tea polysaccharides (TPS) has been shown to be a biomaterial with antioxidant and immunomodulatory effects. In order to develop a novel immunomodulatory biomaterial, we synthesized polysaccharide cobalt complex (TPS-Co) to prevent the paradoxical effects of cobalt while maintaining its beneficial effects, and evaluated its morphology, structure, and antioxidant activity. Fourier-transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy demonstrated that cobalt complexed successfully with TPS. Scanning electron microscopy and atomic mechanical microscopy demonstrated that TPS-Co has a more homogeneous and concentrated morphological distribution compared to TPS. Thermal performance analysis demonstrated that TPS-Co has higher thermal stability. Atomic absorption spectroscopy showed a cobalt content of 3.8%. Ultraviolet spectroscopy indicated that TPS-Co does not contain nucleic acids and proteins. Antioxidant activity assays showed that TPS-Co has better antioxidant activity than TPS in the concentration range of 0.4-2 mg/mL. Proliferation assay of MC3T3-E1 cells demonstrated that TPS-Co has the best cell proliferation effect at a cobalt concentration of 2 ppm. Therefore, TPS-Co may have potential applications in bone regeneration.

Assembly processes underlying bacterial community differentiation among geographically close mangrove forests

Bacterial communities play pivotal roles in nutrient cycling in mangrove forests. The assembly of mangrove microbial communities has been found to be influenced by complex factors, such as geographic distance, physicochemical conditions, and plant identity, but the relative importance of these factors and how these factors shape the assembling process remain elusive. We analyzed the bacterial communities sampled from three mangrove species (Aegiceras corniculatum, Bruguiera sexangula, and Kandelia obovata) at three locations along the estuarine Dongzhai Harbor in Hainan, China. We revealed larger differences in rhizosphere bacterial communities among geographical locations than among plant species, indicated by differences in diversity, composition, and interaction networks. We found that dispersal limitation and homogeneous selection have substantial contributions to the assembly of mangrove rhizosphere bacterial communities in all three locations. Following the phylogenetic-bin-based null model analysis (iCAMP) framework, we also found dispersal limitation and homogeneous selection showing dominance in some bins. The greater differences among geographic locations may be mainly attributed to the larger proportions of dispersal limitation even at such a short geographic distance. We also found that beta diversity was positively correlated with environmental distances, implying that the more similar environmental conditions (such as rich carbon and nitrogen contents) among plant species may have shaped similar bacterial communities. We concluded that the geographic distances, which are associated with dispersal limitation, played a key role in assembling mangrove rhizosphere bacterial communities, while physicochemical conditions and plant identity contributed less.

Protective effect of rosmarinic acid-rich extract from Trichodesma khasianum Clarke against microbiota dysbiosis in high-fat diet-fed obese mice

Hypertrophy of adipose tissues and dysbiosis are hallmarks of obesity. Although drugs are applied for obesity treatment, side effects limit their use. The anti-obesity capacity of rosmarinic acid (RA) has been documented. Trichodesma khasianum Clarke is an edible RA-rich plant grown in Taiwan. Our previous study found that an 80 % ethanol extract of T. khasianum Clarke leaves (80EETC) ameliorates gastric mucosal damage through its anti-inflammatory, antioxidant, and microbiota modulation abilities. However, the anti-obesity effect of 80EETC remains unclear. Therefore, the objective of this study was to explore the protective effects of low-dose 80EETC (125 mg/kg b.w., 80EETCL) or high-dose 80EETC (250 mg/kg b.w., 80EETCH) on obesity development through gut microbiota modulation in high-fat diet (HFD)-induced C57BL/6 mice. The results showed a high RA content (89.2 ± 7.4 mg/g) in 80EETC. 80EETC administration significantly decreased body weight, body fat ratio, serum lipid levels (TC, TG, and LDL-C), adipose tissue accumulation, malondialdehyde (MDA), and tumor necrosis factor-α (TNF-α) in HFD-fed mice. Furthermore, supplementation with 80EETC reduced the Firmicutes/Bacteroidetes ratio and enhanced the relative abundance of gut microbiota (p_Bacteroidetes, f_Lactobacillus, f_Muribaculaceae, f_Prevotellaceae, g_Lactobacillus, g_Prevotellaceae_NK3B31_group, g_Ruminococcaceae_UCG-013, and g_Ruminococcaceae_UCG-014), which negatively correlated with obesity-related factors such as body weight, energy intake, fat accumulation in adipose tissue, TC, TG, LDL, and MDA. In conclusion, RA-rich 80EETC had a protective effect against obesity development and it has potential in healthy food applications.

Regulation of fungal community and the quality formation and safety control of Pu-erh tea

Pu-erh tea belongs to dark tea among six major teas in China. As an important kind of post-fermented tea with complex microbial composition, Pu-erh tea is highly praised by many consumers owing to its unique and rich flavor and taste. In recent years, Pu-erh tea has exhibited various physiological activities to prevent and treat metabolic diseases. This review focuses on the fungi in Pu-erh tea and introduces the sources, types, and functions of fungi in Pu-erh tea, as well as the influence on the quality of Pu-erh tea and potential safety risks. During the process of fermentation and aging of Pu-erh tea, fungi contribute to complex chemical changes in bioactive components of tea. Therefore, we examine the important role that fungi play in the quality formation of Pu-erh tea. The associations among the microbial composition, chemicals excreted, and potential food hazards are discussed during the pile-fermentation of Pu-erh tea. The quality of Pu-erh tea has exhibited profound changes during the process of pile-fermentation, including color, aroma, taste, and the bottom of the leaves, which are inseparable from the fungus in the pile-fermentation of Pu-erh tea. Specifically, the application prospects of various detection methods of mycotoxins in assessing the safety of Pu-erh tea are proposed. This review aims to fully understand the importance of fungi in the production of Pu-erh tea and further provides new insights into subtly regulating the piling process to improve the nutritional properties and guarantee the safety of Pu-erh tea.

Variation in Volatile Compounds of Raw Pu-Erh Tea upon Steeping Process by Gas Chromatography-Ion Mobility Spectrometry and Characterization of the Aroma-Active Compounds in Tea Infusion Using Gas Chromatography-Olfactometry-Mass Spectrometry

Steeping process is an important factor for aroma release of tea, which has rarely been investigated for the aroma changes of raw Pu-erh tea (RAPT). In addition, the comprehensive aroma characteristics identification of RAPT infusion is necessary. In this study, GC-IMS coupled with principal component analysis (PCA) was used to clarify the difference of volatile profiles during the steeping process of RAPT. Furthermore, the volatiles contained in the RAPT infusion were extracted by three pretreatment methods (HS-SPME, SBSE, and SAFE) and identified using GC-O-MS. According to the odor activity value, 28 of 66 compounds were categorized as aroma-active compounds. Aroma recombination and omission experiments showed that "fatty", "green", "fruity", and "floral" are considered to be the main aroma attributes of RAPT infusion with a strong relationship with 1-octen-3-one, 1-octen-3-ol, (E)-2-octenal, β-ionone, linalool, etc. This study will contribute a better understanding of the mechanism of the RAPT steeping process and volatile generation.

Anti-diabetic and gut microbiota modulation effects of sacha inchi (Plukenetia volubilis L.) leaf extract in streptozotocin-induced type 1 diabetic mice

BACKGROUND

Sacha inchi (Plukenetia volubilis L.) tea has been used as an adjuvant treatment for diabetes in Pu'er, in the Yunnan province of China. The effects of sacha inchi tea on diabetes and the underlying mechanisms remain unknown. This study was conducted to investigate the influence of a water extract of sacha inchi (P. volubilis L.) leaves (PWE) on hypoglycemic activity and gut microbiota composition in mice with streptozotocin (STZ)-induced type 1 diabetes mellitus (T1DM). During the 6 weeks of the study, T1DM mice were administered PWE intragastrically at 400 mg kg^-1 body weight (BW) per day.

RESULTS

Treatment with PWE reduced excessive loss of BW and excessive intake of food. It significantly decreased blood glucose levels and improved oral glucose tolerance. The treatment caused protective histopathological transformations in sections of the pancreas, leading to decreased insulin resistance and improved insulin sensitivity. Treatment with PWE also significantly ameliorated disorders of the gut microbiota structure and increased the richness and diversity of intestinal microbial species in T1DM mice. At the genus level, the populations of several crucial bacteria, such as Akkermansia, Parabacteroides, and Muribaculum increased in the PWE treatment group but the abundance of Ruminiclostridium and Oscillibacter decreased.

CONCLUSIONS

Treatment with PWE can ameliorate hyperglycemic symptoms in STZ-induced T1DM mice, and the anti-diabetic effect of PWE was related to the amelioration of gut microbial structural disorder and the enrichment of functional bacteria. © 2022 Society of Chemical Industry.

LC-Q-TOF-MS/MS detection of food flavonoids: principle, methodology, and applications

Flavonoids have been attracting increasing research interest because of their multiple health promoting effects. However, many flavonoids with similar structures are present in foods, often at low concentrations, which increases the difficulty of their separation and identification. Liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (LC-Q-TOF-MS/MS) has become one of the most widely used techniques for flavonoid detection. LC-Q-TOF-MS/MS can achieve highly efficient separation by LC; it also provides structural information regarding flavonoids by Q-TOF-MS/MS. This review presents a comprehensive summary of the scientific principles and detailed methodologies (e.g., qualitative determination, quantitative determination, and data processing) of LC-Q-TOF-MS/MS specifically for food flavonoids. It also discusses the recent applications of LC-Q-TOF-MS/MS in determination of flavonoid types and contents in agricultural products, changes in their structures and contents during food processing, and metabolism in vivo after consumption. Moreover, it proposes necessary technological improvements and potential applications. This review would facilitate the scientific understanding of theory and technique of LC-Q-TOF-MS/MS for flavonoid detection, and promote its applications in food and health industry.

Gut microbiota as a driver of the interindividual variability of cardiometabolic effects from tea polyphenols

Tea polyphenols have been extensively studied for their preventive properties against cardiometabolic diseases. Nevertheless, the evidence of these effects from human intervention studies is not always consistent, mainly because of a large interindividual variability. The bioavailability of tea polyphenols is low, and metabolism of tea polyphenols highly depends on individual gut microbiota. The accompanying reciprocal relationship between tea polyphenols and gut microbiota may result in alterations in the cardiometabolic effects, however, the underlying mechanism of which is little explored. This review summarizes tea polyphenols-microbiota interaction and its contribution to interindividual variability in cardiometabolic effects. Currently, only a few bacteria that can biodegrade tea polyphenols have been identified and generated metabolites and their bioactivities in metabolic pathways are not fully elucidated. A deeper understanding of the role of complex interaction necessitates fully individualized data, the ntegration of multiple-omics platforms and development of polyphenol-centered databases. Knowledge of this microbial contribution will enable the functional stratification of individuals in the gut microbiota profile (metabotypes) to clarify interindividual variability in the health effects of tea polyphenols. This could be used to predict individual responses to tea polyphenols consumption, hence bringing us closer to personalized nutrition with optimal dose and additional supplementation of specific microorganisms.

Liubao brick tea activates the PI3K-Akt signaling pathway to lower blood glucose, metabolic disorders and insulin resistance via altering the intestinal flora

Diabetes and its related metabolic disorders are worldwide public health issues. Many studies have shown that changes in the structure and composition of the intestinal flora are closely related to the host's physiological and pathological processes. In this study, we aim to explore the effect of Liubao tea (LBT) extract on hyperglycemic mice with metabolic disorders and intestinal flora dysbiosis and to further study its regulatory effect on insulin resistance and its potential regulatory mechanism. Our results show that LBT had a good hypoglycemic effect and could significantly alleviate the metabolic disorder evoked by hyperglycemia. The gut microbial sequencing showed that LBT treatment increased the diversity of intestinal flora, increased the abundance of beneficial bacteria, and reduced the abundance of harmful or conditional pathogenic bacteria, as well as significantly altered 39 of the top 50 OTUs with abundance. Besides, LBT could activate the PI3K-Akt-PPARs-GLUT2 cascade signaling pathway to improve metabolic disorders, thereby alleviating insulin resistance. These results suggest that LBT has excellent potential to become a natural functional food for the prevention of hyperglycemia and insulin resistance.

Dynamic changes of metabolic profile and taste quality during the long-term aging of Qingzhuan Tea: The impact of storage age

Qingzhuan tea (QZT) with longer aging year is usually believed to have higher quality and commercial value. In this study, a 20 years sequence of aged QZT were subjected to an electronic tongue and liquid chromatography-mass spectrometry to investigate the effect of storage age on its metabolic profile and taste quality. The changes in both taste quality and metabolic profile exhibited a parabolic trend in the 20 years of QZT aging and reached the maximum at the 10th year. A total of 47 compounds were identified as critical metabolites responsible for the age variation of QZT quality, with the methylation of catechins, glycosylation of flavonoids, degradation of flavoalkaloids, biosynthesis of triterpenoids, and formation of theabrownins. These results suggested that the taste of QZT was improved after 10 years of storage, with the reduction of bitterness and astringency and a general increase of key quality-related compounds.

Polysaccharide conjugates from Chin brick tea (Camellia sinensis) improve the physicochemical stability and bioaccessibility of β-carotene in oil-in-water nanoemulsions

A natural antioxidant emulsifier, tea polysaccharide conjugate (TPC), was isolated from Chin brick tea. The impact of TPC on β-carotene stability and bioaccessibility in oil-in-water nanoemulsions was assessed. TPC exhibited strong antioxidant activity and could be used to fabricate stable nanoemulsions (d < 140 nm). The extent of lipid digestion was considerably lower for lipid droplets coated by TPC (68%) than Tween 80 (94%) or whey protein isolate (WPI) (89%), probably because TPC formed interfacial layers that hindered the access of lipases to lipids. The chemical stability of β-carotene in TPC-nanoemulsions was markedly higher than in those formulated with Tween 80 or WPI due to the high antioxidant activity of TPC. The bioaccessibility of β-carotene (20-30%) was independent of emulsifier type. TPC from Chin brick tea can therefore be used as a dual-purpose functional ingredient in emulsified foods.

Effects of bioactive components of Pu-erh tea on gut microbiomes and health: A review

Pu-erh tea is a post-fermentation tea with unique flavor and multiple health benefits. Due to the various microorganisms involved in the post-fermentation process, Pu-erh tea contains highly complex components, which have rich interactions with the gut microbiomes (GMs). Because the structure and homeostasis of GMs are closely related to human wellness and the various diseases progress, the beneficial effects of Pu-erh tea on GMs have a great potential for application in health care. However, there is no systematic summary of the bioactive components of Pu-erh tea, and their effects on the GMs. Here, we review the current studies on the effects of Pu-erh tea and its bioactive components on the structure of GMs as well as on health improvement, and further discuss the relevant quality indicators. This "components - function - indicators" clue will hopefully stimulate the standardization of Pu-erh tea fermentation process and the development of its functional products.

Exploring community evolutionary characteristics of microbial populations with supplementation of Camellia green tea extracts in microbial fuel cells

This first-attempt study deciphered combined characteristics of species evolution and bioelectricity generation of microbial community in microbial fuel cells (MFCs) supplemented with Camellia green tea (GT) extracts for biomass energy extraction. Prior studies indicated that polyphenols-rich extracts as effective redox mediators (RMs) could exhibit significant electrochemical activities to enhance power generation in MFCs. However, the supplementation of Camellia GT extract obtained at room temperature with significant redox capabilities into MFCs unexpectedly exhibited obvious inhibitory effect towards power generation. This systematic study indicated that the presence of antimicrobial components (especially catechins) in GT extract might significantly alter the distribution of microbial community, in particular a decrease of microbial diversity and evenness. For practical applications to different microbial systems, pre-screening criteria of selecting biocompatible RMs should not only consider their promising redox capabilities (abiotic), but also possible inhibitory potency (biotic) to receptor microbes. Although Camellia tea extract was well-characterized as GRAS energy drink, some contents (e.g., catechins) may still express inhibition towards organisms and further assessment upon biotoxicity may be inevitably required for practice.

Distinct Changes of Metabolic Profile and Sensory Quality during Qingzhuan Tea Processing Revealed by LC-MS-Based Metabolomics

Qingzhuan tea (QZT) is a unique type of dark tea exclusively produced in Hubei Province of China. In the current study, liquid chromatography-mass spectrometry (LC-MS) coupled with multivariate analysis was applied to characterize the chemical composition of QZT and investigate the effect of QZT processing on its metabolic profile and sensory quality. The contents of polyphenols and flavonoids decreased significantly while the polysaccharides content remained stable, while the theabrownin content inversely increased during QZT processing. LC-MS-based metabolomics analyses revealed that the tea sample after microbial fermentation (MFT) was dramatically different from the sample before microbial fermentation (UFT), while MFT was very similar to QZT. A total of 102 compounds were identified as critical metabolites responsible for metabolic changes caused by QZT processing, with the contents of catechins and flavonoids significantly decreased, and some novel phenolic acids and catechin derivatives were formed. The sensory quality of QZT was mainly formed during microbial fermentation, which greatly reduced the astringency and bitterness of raw tea leaves and produced its characteristic woody and stale aroma as well as mellow taste. These results suggested that microbial fermentation is the critical process in changing the metabolic profile of raw tea leaves and forming the sensory quality of QZT.

Antioxidative stress of oral administration of tea extract granule in chickens

The present study was to evaluate antioxidative effect of tea extract granule (TEG) on oxidative stress induced by cyclophosphamide (Cy) in chickens. In experiment 1, chickens were randomly divided into 5 groups with 10 birds in each. Groups 3 to 5 were orally administered TEG in drinking water for 7 D at doses of 20, 40, and 80 mg/kg body weight, respectively. After that, groups 2 to 5 received intramuscular injection of Cy (100 mg/kg BW) for 3 D. Group 1 was not treated as a control. In experiment 2, chickens were grouped in the same way as in experiment 1. Groups 2 to 5 received intramuscular injection of Cy (100 mg/kg BW) for 3 D. After that, groups 3 to 5 were orally administered TEG in drinking water for 7 D at doses of 20, 40, and 80 mg/kg BW, respectively. Results showed that Cy injection induced significantly decreased body weight and oxidative stress. Oral administration of TEG before or after Cy injection increased body weight, the thymus, bursa, and spleen indices, total antioxidant capacity, and the levels of glutathione; elevated the activity of superoxide dismutase, catalase, and glutathione peroxidase; as well as decreased the protein carbonyl content, lipid peroxide, and malondialdehyde. In addition, TEG administration reduced intracellular reactive oxygen species. Therefore, TEG could be a promising agent against oxidative stress in the poultry industry.

Hypoglycemic effects of phenolic compound-rich aqueous extract from water dropwort (Oenanthe javanica DC.) on streptozotocin-induced diabetic mice

Phenolic compounds in water dropwort aqueous extract were identified, and the IRS-2/PI3K-AKT pathway and GLUT4 translocation were regulated for hypoglycemic action.

Comparison of Potent Odorants in Raw and Ripened Pu-Erh Tea Infusions Based on Odor Activity Value Calculation and Multivariate Analysis: Understanding the Role of Pile Fermentation

Infusions prepared from raw pu-erh tea (RAPT) and ripened pu-erh tea (RIPT) showed remarkable aroma differences. Predominant odorants in RAPT and RIPT infusions were identified and compared by the combined use of gas chromatography-olfactometry, aroma extract dilution analysis, odor activity values (OAVs), and multivariate analysis. A total of 35 and 19 odorants (OAV > 1) were detected in RIPT and RAPT, respectively. Odorants in RAPT and RIPT are significantly different in both odor properties and aroma compound intensities. Overall, RAPT contained a complex variety of chemical classes with diverse odors and moderate odor intensities, while RIPT is dominated by structurally and organoleptically similar compounds with high potency. Specifically, stale and musty smelling methoxybenzenes contributed the most to RIPT, while floral-, sweet-, and woody-smelling terpene alcohols, terpene ketones, and phenolic compounds were the predominant odorants in RAPT. Orthogonal partial least squares discriminant analysis revealed that linalool, α-ionone, 1,2,4-trimethoxybenzene, 1,2,3-trimethoxy-5-methylbenzene, 1,2,3,4-tetramethoxybenzene, and 1,2,3-trimethoxybenzene underwent remarkable changes during pile fermentation and could be used as potential odor-active markers for RIPT and RAPT discrimination. The comprehensive aroma characterization of pu-erh tea and determination of the effect of pile fermentation on odorant alteration herein will provide guidance for pu-erh tea flavor quality control and evaluation.

Effects and Mechanisms of Tea for the Prevention and Management of Diabetes Mellitus and Diabetic Complications: An Updated Review

Diabetes mellitus has become a serious and growing public health concern. It has high morbidity and mortality because of its complications, such as diabetic nephropathy, diabetic cardiovascular complication, diabetic neuropathy, diabetic retinopathy, and diabetic hepatopathy. Epidemiological studies revealed that the consumption of tea was inversely associated with the risk of diabetes mellitus and its complications. Experimental studies demonstrated that tea had protective effects against diabetes mellitus and its complications via several possible mechanisms, including enhancing insulin action, ameliorating insulin resistance, activating insulin signaling pathway, protecting islet β-cells, scavenging free radicals, and decreasing inflammation. Moreover, clinical trials also confirmed that tea intervention is effective in patients with diabetes mellitus and its complications. Therefore, in order to highlight the importance of tea in the prevention and management of diabetes mellitus and its complications, this article summarizes and discusses the effects of tea against diabetes mellitus and its complications based on the findings from epidemiological, experimental, and clinical studies, with the special attention paid to the mechanisms of action.