Oolong Tea Extract Research Articles

Influence of varied processing methods on the antioxidant capacity, antibacterial activity, and bioavailability of Iranian black, oolong, and green leafy teas

In this study, the impact of various tea preparation techniques on the content of bioactive compounds, antioxidant capacity, antibacterial properties, and polyphenol bioavailability in green, black, and oolong tea infusions was examined. The findings demonstrated that the fermentation process significantly influences the levels of bioactive compounds, with green tea infusions exhibiting the highest, and black tea the lowest, content of phenolic compounds. A positive correlation was observed between the content of the phenolic compound and both antioxidant and antibacterial activities. Additionally, the microwave brewing method was identified as the most effective preparation technique for maximizing the bioactive compound content and bioavailability. The inclusion of skim milk powder was found to further enhance the bioavailability of phenolic compounds during digestive process. The research suggests that green tea infusions prepared using the microwave brewing method and supplemented with the skim milk powder, could serve as a functional beverage offering enhanced health benefits.

Development of analytical “aroma wheels” for Oolong tea infusions (Shuixian and Rougui) and prediction of dynamic aroma release and colour changes during “Chinese tea ceremony” with machine learning

The flavour of tea as a worldwide popular beverage has been studied extensively. This study aimed to apply established flavour analysis techniques (GC–MS, GC-O-MS and APCI-MS/MS) in innovative ways to characterise the flavour profile of oolong tea infusions for two types of oolong tea (type A- Shuixian, type B- Rougui). GC–MS identified 48 aroma compounds, with type B having a higher abundance of most compounds. GC-O-MS analysis determined the noticeable aroma difference based on 20 key aroma compounds, facilitating the creation of an analytical “Aroma Wheel” with 8 key odour descriptors. APCI-MS/MS assessed real-time aroma release during successive brews linked with the “Chinese tea ceremony” (Gongfu Cha). Multivariate Polynomial Regression (MPR) and Long Short-Term Memory (LSTM) network approaches were applied to aroma and colour data from seven successive brews. The results revealed a progressive decline in both colour and aroma with seven repeated brews, particularly notable after the fourth brew.

Enhancement of cytotoxic and apoptotic activity through oolong tea extract-mediated CuO/Cu2O nanoparticles

The development of multifunctional nanoformulations with enhanced anticancer activity and drug delivery potential is of increasing scientific importance. In this study, we synthesized and characterized copper oxide nanoparticles mediated by oolong tea extract (OE-CuO/Cu2O NPs) using a variety of techniques, including TEM, XRD, FTIR, and UV–Vis spectroscopy, to assess their physical and chemical properties. Remarkably, the results revealed that OE/CuO NPs exhibited significantly enhanced anticancer activity compared to OE alone. The effects of OE and OE-CuO/Cu2O NPs were on cytotoxicity, apoptosis, and cell cycle progression. Furthermore, we assessed the impact of these nanostructures on CD44/24 antibodies, known as aggressive cell markers, following treatment. The green OE-CuO/Cu2O NPs displayed remarkable inhibitory effects on colon cancer HCT116 and breast cancer cells MCF-7 cells. It was shown that OE-CuO/Cu2O NPs reduced the production of the CD44 antibody, provided cell cycle arrest, and encouraged apoptosis. More specifically, it was discovered that these NPs caused MCF-7 cells to undergo apoptosis and G2/M phase cell cycle arrest. Additionally, drug delivery investigations were conducted to evaluate the potential of OE-CuO/Cu2O NPs as drug nanocarriers, further underscoring their promise in developing novel anticancer agents with significant cytotoxic, apoptotic, and drug delivery properties.

Aged oolong tea manages type 2 diabetes mellitus by inhibiting fat ectopic deposition and alleviating insulin resistance in db/db mice

AbstractAn important concern for tea consumers is whether appropriate storage can effectively improve the ability of oolong tea to alleviate type 2 diabetes mellitus (T2DM). In this study, the antidiabetic effects of three aged oolong tea (2001, 2011, and 2020) extracts (aged TEs) in db/db T2DM mice were investigated and compared for the first time. The results showed that aged oolong tea extracts (aged TEs) alleviated the abnormal fasting blood glucose levels, lipid profiles, insulin resistance, and reduced ectopic fat deposition in liver. Moreover, aged TEs alleviated T2DM‐related tissue damage and activated insulin receptor (INSR)/insulin receptor substrate (IRS)/phosphatidylinositol‐3 kinase (PI3K)/phosphatidylinositol‐3 kinase (AKT)/glycogen synthase kinase 3 beta (GSK‐3β)/glycogen synthase (GYS)‐mediated hepatic glycogen synthesis signaling pathway. In addition, aged TEs altered gut microbiota composition and gut metabolite profiles associated with T2DM. Together, all three aged TEs (400 mg/kg/day in mice, a human equivalent dose of 7 g/60 kg/day), especially 2011, can effectively alleviate T2DM, and proper storage can effectively improve the ability of oolong tea to alleviate T2DM.

Phenolic Compounds, Free Radical Scavenging Activity and α-Glucosidase Inhibition Properties of Green, Oolong and Black Sacha Inchi Tea Extract

Sacha Inchi leaves may possess antioxidant function which is naturally rich in bioactive ingredients and has been widely processed into herbal teas that has many benefits to human health. According to the global data from the World Health Organization (WHO), there has been a rise in the frequency of diabetes mellitus (DM) among adults. Sacha Inchi tea was prepared using several methods, with green tea not fermented, oolong partially fermented, and black tea completely fermented. The phenolic compounds (total phenolic content (TPC), total flavonoid content (TFC), tannin), free radical scavenging activity (DPPH) and inhibition properties of α-Glucosidase on green, oolong and black Sacha Inchi tea extract were determined. The green Sacha Inchi tea extract displayed the highest TPC and TFC values among the oolong and black Sacha Inchi tea extracts at a concentration of 500µg/mL, with values of 2.10±0.01 µg GAE/mL and 3.23±0.20 µg QE/mL, respectively. Meanwhile, at a concentration of 500µg/mL, Sacha Inchi black tea extract demonstrated strong antioxidant activity by DPPH with radical scavenging activity (%) (89.4±0.45). Furthermore, at a concentration of 15.625 µg/mL, black, oolong, and green tea extracts exhibited stronger inhibitory effects on α-Glucosidase (95%, 95%, 92%, respectively) than acarbose (90%). Therefore, the processing steps involved in tea production impact the phenolic compounds, free radical scavenging activity, and the ability to inhibit α-Glucosidase in green, oolong, and black tea extracts.

Effects of brewing water on the volatile composition of tea infusions.

There is a huge demand for brewing water in tea consumption, and the sensory flavor of tea infusion is significantly affected by the water used for brewing. To investigate the impact of brewing water on the aroma of tea infusions made from Camelia senensis, the three tea infusions of green, oolong and black tea brewed by six different drinking waters were analyzed by sensory evaluation, solid-phase microextraction, gas chromatography-mass spectrometry, and chemometrics. Brewing water with high pH values (>8.10) and high TDS content (>140ppm) resulted in a lower overall aroma acceptability for tea infusion, where HCO3-, Ca2+ and Mg2+ were key influencing ions. A total of 86, 106, and 131 volatiles were identified in green, oolong and black tea infusions, respectively, which were strongly influenced by six different brands of waters. Decanal, dimethyl sulfide, β-ionone and linalool were potent volatiles in tea aroma changes caused by brewing water.

High Gamma-Aminobutyric Acid (GABA) Oolong Tea Alleviates High-Fat Diet-Induced Metabolic Disorders in Mice.

Obesity and overweight are associated with an increasing risk of developing health conditions and chronic non-communicable diseases, including cardiovascular diseases, cancer, musculoskeletal problems, respiratory problems, and mental health, and its prevalence is rising. Diet is one of three primary lifestyle interventions. Many bioactive components in tea especially oolong tea, including flavonoids, gamma-aminobutyric acid (GABA), and caffeine were reported to show related effects in reducing the risk of obesity. However, the effects of GABA oolong tea extracts (OTEs) on high-fat diet (HFD)-induced obesity are still unclear. Therefore, this study aims to explore whether the intervention of GABA OTEs can prevent HFD-induced obesity and decipher its underlying mechanisms using male C57BL/6 J mice. The result indicated that GABA OTEs reduced leptin expression in epididymal adipose tissue and showed a protective effect on nonalcoholic fatty liver disease. It promoted thermogenesis-related protein of uncoupling protein-1 and peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α), boosted lipid metabolism, and promoted fatty acid oxidation. It also reduced lipogenesis-related protein levels of sterol regulatory element binding protein, acetyl-CoA carboxylase, and fatty acid synthase and inhibited hepatic triglyceride (TG) levels. These data suggest that regular drinking of GABA oolong tea has the potential to reduce the risk of being overweight, preventing obesity development through thermogenesis, lipogenesis, and lipolysis.

Targeted HPLC-UV Polyphenolic Profiling to Detect and Quantify Adulterated Tea Samples by Chemometrics.

Tea can be found among the most widely consumed beverages, but it is also highly susceptible to fraudulent practices of adulteration with other plants such as chicory to obtain an illicit economic gain. Simple, feasible and cheap analytical methods to assess tea authentication are therefore required. In the present contribution, a targeted HPLC-UV method for polyphenolic profiling, monitoring 17 polyphenolic and phenolic acids typically described in tea, was proposed to classify and authenticate tea samples versus chicory. For that purpose, the obtained HPLC-UV polyphenolic profiles (based on the peak areas at three different acquisition wavelengths) were employed as sample chemical descriptors for principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) studies. Overall, PLS-DA demonstrated good sample grouping and discrimination of chicory against any tea variety, but also among the five different tea varieties under study, with classification errors below 8% and 10.5% for calibration and cross-validation, respectively. In addition, the potential use of polyphenolic profiles as chemical descriptors to detect and quantify frauds was evaluated by studying the adulteration of each tea variety with chicory, as well as the adulteration of red tea extracts with oolong tea extracts. Excellent results were obtained in all cases, with calibration, cross-validation, and prediction errors below 2.0%, 4.2%, and 3.9%, respectively, when using chicory as an adulterant, clearly improving on previously reported results when using non-targeted HPLC-UV fingerprinting methodologies.

Effect of tea extract on starch gelatinisation, gluten aggregation and quality characteristics of dry yellow alkaline noodle

SummaryThree kinds of tea extracts (green tea extract, black tea extract and oolong tea extract) were incorporated into a dry yellow alkaline noodle (YAN) at a concentration of 0.5%–2.0% to investigate their effects on starch gelatinisation, gluten aggregation and noodle quality characteristics. Due to the starch–polyphenol interaction, the temperature and enthalpy required for starch gelatinisation were decreased by 0.90–1.10 °C and 2.85–3.31 J/g, respectively, when 2.0% tea extract was added compared with the control. Furthermore, the dry noodles showed lower starch pasting viscosities (reduced by 28.35%–55.20%) and increased resistance to breakdown and retrogradation. Through the hydrogen bonding between gliadins and tea polyphenols, the conformation of gluten was modified (15.41%–24.62% and 15.19%–22.95% increases in α‐helix and β‐sheet contents, respectively) and its structure was strengthened. The combined effect of tea extracts on starch gelatinisation and gluten formation behaviour resulted in the restricted water permeability and mobility in the structure of cooked noodles, which was associated with increased hardness (13.15–16.34 N), cohesiveness (0.63–0.69), chewiness (7.47–10.88) and resilience (0.34–0.42). It also decreased the absolute adhesiveness (0.11–0.13 N.sec) of cooked YANs. In the alkaline noodle system, three kinds of tea extracts exhibited similar effects on the quality characteristics of YAN. The results suggest that tea extracts are capable of improving YAN texture.

UV-blocking properties of carboxymethyl cellulose film integrated with oolong tea extracts as eco-friendly packaging film

The preparation of biodegradableUV protective carboxymethyl cellulose (CMC) films using extracted phenolic compounds fromoolong tea (O) as bio-fillers to improve UV-blocking capability has been studied.The properties of the CMC and CMC/O films including color,transmission infrared spectra,moisture uptake, water vapor permeability, thermal properties, tensile properties, %reduction of UV transmittance and biodegradability were examined The total amount of phenolic compounds fromoolong teaextracts was determined as 0.1577 ± 0.0018 g of compound per 15 g of oolong tea powder.The addition ofoolong teaextracts to CMC matrices improved the reduction of UV transmittance of the films. It wasobservedthat CMC/Ofilms with2 % v/voolong teaextracts gave a %reduction of UV transmittance for all UVC, UVB and UVA ranges comparable to that of the oolong teaextracts. Moreover, the addition ofoolong teaextracts led to a decreasein water vapor permeability of the CMC/Ofilms.The results indicated that carboxymethyl cellulosefilms filled withoolong teaextracts have potential for an application of UV radiation reduction packaging.

Synthesis of Manganese Nanoparticles of Oolong Tea Extract by Sonication Method for a Natural Oral Contrast Media on Magnetic Resonance Cholangiopancreatography (MRCP)

Synthesis of Manganese Nanoparticles of Oolong Tea Extract by Sonication Method for a Natural Oral Contrast Media on Magnetic Resonance Cholangiopancreatography (MRCP)

Synthesis of manganese nanoparticles of Oolong tea extract by sonication method for a natural oral contrast media on magnetic resonance cholangiopancreatography

Introduction: Magnetic resonance cholangio-pancreatography examination using natural contrast media has not provided an optimal image of gastroduodenal suppression that covers the image of the biliary system. Natural materials used as contrast media continue to be developed with various previous studies, but not many have been associated with using, nanoparticles as natural contrast media materials. This study aims to make manganese nanoparticles in oolong tea extract is used as an oral contrast medium.

Evaluation of Oolong Tea Extract Staining of Brain Tissue with Special Reference to Smooth Endoplasmic Reticulum

Evaluation of Oolong Tea Extract Staining of Brain Tissue with Special Reference to Smooth Endoplasmic Reticulum

Understanding Young Taiwanese Consumers' Acceptance, Sensory Profile, and Drivers of Liking for GABA Oolong Tea Beverages with Cold Infusions.

The sensory qualities of Taiwanese teas are evaluated by the experts from the Tea Research and Extension Station (TRES) at tea competitions held annually. The prices of Taiwanese teas are also influenced by the results of these tea competitions. However, a tea winning an award and having a high sensory quality and price does not mean that it is liked by Taiwanese consumers. The check all that apply method (CATA) is a scientific method of sensory evaluation. It is able to evaluate the sensory characteristics with consumers and is cheap and time-saving. Twelve samples of γ-aminobutyric acid (GABA) Oolong tea made by the Taiwan Tea No. 12 cultivar were selected from the first Taiwanese GABA tea competition in 2020. The aim of this research was to study young Taiwanese consumers’ acceptability for GABA Oolong tea infusions, and their opinions towards the sensory qualities of teas through questionnaires composed of CATA questions and hedonic scales. Based on the results, the CATA method identified 21 important descriptive terms for GABA tea that were selected by over 20% of consumers. It was found that the consumers like GABA Oolong teas with 13 specific sensory characteristics, but dislike the ones with another 6 specific sensory characteristics. We conjecture that the different process of tea production will affect consumers’ preference for GABA Oolong tea. Overall, GABA Oolong tea has the same delightful sensory characteristics as traditional Taiwanese specialty Oolong teas, and is liked by the young Taiwanese consumers.

Green and Oolong Tea Extracts With Different Phytochemical Compositions Prevent Hypertension and Modulate the Intestinal Flora in a High-Salt Diet Fed Wistar Rats.

Green tea (GT) and oolong tea (OLT) are widely consumed beverages, and their preventive and regulatory effects on hypertension have been reported. However, the interventional effects of GT and OLT on hypertension induced by a high-salt diet and its mechanism have not been fully explored. This study evaluated the anti-hypertensive effects of GT and OLT and their underlying mechanisms. The in vivo anti-hypertensive effects of GT and OLT and their capability to prevent hypertension and regulate the intestinal microbiota in Wistar rats fed with a high-salt diet were evaluated. Our results show that GT and OLT supplementations could regulate oxidative stress, inflammation, gene expression, and parameter levels related to blood pressure (BP) and prevent the increase in BP induced by a high-salt diet. Furthermore, both GT and OLT boosted the richness and diversity of intestinal microbiota, increased the abundance of beneficial bacteria and reduced the abundance of harmful bacteria and conditionally pathogenic bacteria, and regulated the intestinal microbial metabolism pathway related to BP. Among them, OLT presented better effects than GT. These findings indicate that GT and OLT can prevent hypertension caused by high-salt diets, which may be due to the regulation of intestinal flora by GT and OLT.

Selenium-enriched oolong tea (Camellia sinensis) extract exerts anti-inflammatory potential via targeting NF-κB and MAPK pathways in macrophages

Both tea polyphenols and selenium (Se) have been suggested to exert the health benefits via the regulatory capacities of chronic inflammation, which make Se-enriched oolong tea a promising beverage as an anti-inflammatory diet. The aim of this study is to investigate the anti-inflammatory effects of Se-enriched oolong tea extract (Se-TE) and underlying mechanism in lipopolysaccharide (LPS)-induced RAW264.7 cells. Se-TE treatments (50 and 150 μg/mL) significantly suppressed the over-production of nitric oxide (NO) and prostaglandin E2 (PGE2) in LPS-stimulated macrophages via downregulating the expression of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Moreover, Se-TEs also effectively inhibited the productions of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β). Furthermore, Se-TE could block mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways through the inhibition of the phosphorylation of key proteins (IκB-α, p65, p38, ERK, and JNK) and the translocation of the p65 subunit into the nucleus. Collectively, our results indicated that Se-TE may have the potential to be used as a novel food ingredient for the development of various anti-inflammatory foods and the treatment and prevention of chronic inflammation-related diseases.

Oolong tea extract alleviates weight gain in high-fat diet-induced obese rats by regulating lipid metabolism and modulating gut microbiota.

Obesity is a serious global health issue, and the societal interventions during the COVID-19 pandemic may have perturbed energy homeostasis, which affects the condition of obesity. Tea is a traditional beverage in Asia and has been shown to provide many beneficial health effects. Oolong tea is semifermented, with its chemical composition comprising features of green (unfermented) and black (fermented) tea. Although green tea has anti-obesity properties, studies on the anti-obesity ability of oolong tea are still scarce. In this study, we analyzed the chemical composition of oolong tea extract (OTE) and investigated the effects of OTE on high-fat diet-induced obese rats. OTE contained more (-)-epigallocatechin-3-gallate, (-)-epigallocatechin, and (-)-gallocatechin-3-gallate than theaflavins and theasinensins. Rats fed with a high-fat diet (HFD) and treated with 0.5% OTE exhibited significantly reduced body weight and visceral fat weight compared with the HFD-only group. OTE also decreased adipocyte size, lipogenesis-related protein sterol regulatory element-binding protein 1 (SREBP1) and fatty acid synthase (FASN) protein expression and increased thermogenesis-related protein peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) and uncoupling protein 1 (UCP1) protein expression in epididymal adipose tissue compared with the HFD group. Moreover, the OTE groups had a significantly higher abundance of Candidatus arthromitus and Hydrogenoanaerobacterium and a lower abundance of Ruminococcus1, Oscillibacter, and Odoribacter compared with the HFD group. All these results show that OTE can alleviate weight gain by regulating lipid metabolism and modulating the distribution of the gut microbiota to decrease lipid accumulation in adipose tissue.

Tieguanyin extracts ameliorated DSS-induced mouse colitis by suppressing inflammation and regulating intestinal microbiota.

Previous studies have shown that a typical kind of oolong tea, Tieguanyin, has multiple health benefits, while there is no research investigating its effects on inflammatory bowel disease (IBD). In this study, we aimed to explore the alleviation effects of Tieguanyin water (TWE) and ethanol (TES) extracts on IBD. Physiological activity status, colitis severity (disease activity index (DAI), colon and spleen weight), inflammatory cytokines (interleukin (IL)-4, interferon-γ (IFN-γ), IL-17, transforming growth factor-β (TGF-β), and IL-10) and microbiota composition were measured in experimental colitis mice induced by dextran sulfate sodium (DSS). TWE and TES exerted remarkable protective effects against experimental colitis, showing decreased colitis severity and improved colon morphology. TES also suppressed colonic inflammation via downregulation of pro-inflammatory cytokines (IL-4, IFN-γ, IL-17, and TGF-β) and upregulation of the anti-inflammatory cytokine IL-10. In addition, TWE and TES treatment caused significant alterations in the gut microbiota. Oolong tea extract treatment reduced the community abundance of pernicious bacteria Escherichia-Shigella from 21.6% (DSS) to 0.9% (TES) and 1.2% (TWE), and elevated that of probiotics Lachnospiraceae_NK4A136_group from 2.2% to 15.2% (TES) and 11.9% (TWE). Therefore, TWE and TES both remarkably ameliorated DSS-induced colitis, which suggested oolong extracts could be a candidate for IBD treatment.

The inhibitory action of purple tea on in vivo starch digestion compared to other Camellia sinensis teas

In order to contribute to improve knowledge about the actions of Camellia sinensis extracts on starch digestion, several varieties were compared. The latter were green, oolong, white, black, and purple teas. The results are hoped to contribute to our understanding of the mode of action and potency of the various tea preparations as possible adjuvants in the control of post-prandial glycemia. The extracts were prepared in way similar to their form of consumption. All extracts decreased starch digestion, but the purple tea extract was the strongest inhibitor, their inhibitory tendency started at the dose of 50 mg/kg and was already maximal with 250 mg/kg. Maltose tolerance was not significantly affected by the extracts. Glucose tolerance was not affected by purple tea, but black tea clearly diminished it; green tea presented the same tendency. Purple tea was also the strongest inhibitor of pancreatic α-amylase, followed by black tea. The green tea, oolong tea, and white tea extracts tended to stimulate the pancreatic α-amylase at low concentrations, a phenomenon that could be counterbalancing its inhibitory effect on starch digestion. Based on chemical analyses and molecular docking simulations it was concluded that for both purple and black tea extracts the most abundant active component, epigallocatechin gallate, seems also to be the main responsible for the inhibition of the pancreatic α-amylase and starch digestion. In the case of purple tea, the inhibitory activity is likely to be complemented by its content in deoxyhexoside-hexoside-containing polyphenolics, especially the kaempferol and myricetin derivatives. Polysaccharides are also contributing to some extent. Cyanidins, the compounds giving to purple tea its characteristic color, seem not to be the main responsible for its effects on starch digestion. It can be concluded that in terms of postprandial anti-hyperglycemic action purple tea presents the best perspectives among all the tea varieties tested in the present study.

Oolonghomobisflavans from Camellia sinensis increase Caenorhabditis elegans lifespan and healthspan

Tea polyphenols are widely considered as excellent antioxidant agents which can contribute to human health and longevity. However, the identification of the active biomolecules in complex tea extracts that promote health and longevity are not fully known. Here we used the nematode Caenorhabditis elegans to analyze the health benefits and longevity effects of Camellia sinensis oolong tea extracts (QFT, NFT, and CFT) and oolonghomobisflavan A and oolonghomobisflavan B, which are present in oolong tea extracts. Our results showed that oolong tea extracts and oolonghomobisflavans prolong lifespan and improved healthspan by curtailing the age-related decline in muscle activity and the accumulation of age pigment (lipofuscin). We found that the lifespan and healthspan promoting effects of oolong tea extracts and oolonghomobisflavans were positively correlated with the stress resistance via DAF-16/FOXO transcription factor. Furthermore, oolong tea extracts and oolonghomobisflavans displayed protective effects against Aβ- and polyQ-induced neuro/proteotoxicity. Overall, our study provides new evidence to support the health benefits of oolong tea and importantly identify oolonghomobisflavans as potent bioactive molecules that promote health when supplemented with a normal diet. As such, oolonghomobisflavans represent a valuable new class of compounds that promote healthy aging.