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Epigenetic alterations, broadly divided into DNA methylation, Histone modifications and interference by non-coding RNAs can often lead to carcinogenesis. Alterations in epigenetic machinery may be due to numerous factors, including exposure to toxic chemicals. These toxicants include heavy metals as well. The metalloid arsenic is an environmental pollutant and its chronic exposure causes cancer. Etiology of arsenic induced cancer includes epigenetic alterations, among others. Inorganic-arsenic is the lead cause of hypermethylation of tumor-suppressor genes and hypomethylation of genes involved in cell proliferation, growth and invasion. It can induce histone methylations and acetylations along with modulation of miRNAs, promoting cancer. Therefore, control of epigenetic alterations is vital. Chemoprevention using phytochemicals is an effective strategy to mitigate the deleterious effect of chronic arsenic exposure. Flavonoids, a group of phytochemicals have shown numerous evidences of epigenetic modulations halting carcinogenesis. Catechins represent one of the most active groups of flavonoids. Tea, a popular beverage, is one of the richest sources of catechins. Green tea contains highly active catechins like epigallocatechin-3-gallate (EGCG), epigallocatechin (EGC), epicatechingallate (ECG) etc. while black tea contains oxidized polymeric catechins like theaflavin and thearubigin. Green tea catechins have elicited their potential as an epigenetic modulator, establishing their chemopreventive attributes. Therefore, administration of tea may be an effective strategy to mitigate the epigenetic alterations, induced by chronic exposure to arsenic, in individuals of endemic areas.

Black tea accounts for 70-80% of world tea production, and the polyphenols therein are produced by enzymatic oxidation of four tea catechins during tea fermentation. However, only limited groups of dimeric oxidation products, such as theaflavins, theasinensins, and theacitrins, have been isolated from black tea and chemically characterized. This is largely because of the complexity and heterogeneity of the oxidation products. To determine structures and production mechanisms of uncharacterized black tea polyphenols,in vitro model fermentation experiments using pure catechins and polyphenol oxidase have been applied, and basic oxidation mechanisms have been established. Contemporary methods, such as LC-MS, are also effective to identify catechin oxidation products in black tea. Despite ongoing efforts, almost 60% of the solids in black tea infusion remain uncharacterized. These compounds include the so-called thearubigins, which are a heterogeneous mixture of uncharacterized catechin oxidation products with oligomeric structures. This review summarizes the current knowledge of the production mechanisms of representative black tea polyphenols and presents recent progress in characterization of thearubigins.

Black tea accounts for 70-80% of world tea production, and the polyphenols therein are produced by enzymatic oxidation of four tea catechins during tea fermentation. However, only limited groups of dimeric oxidation products, such as theaflavins, theasinensins, and theacitrins, have been isolated from black tea and chemically characterized. This is largely because of the complexity and heterogeneity of the oxidation products. To determine structures and production mechanisms of uncharacterized black tea polyphenols,in vitro model fermentation experiments using pure catechins and polyphenol oxidase have been applied, and basic oxidation mechanisms have been established. Contemporary methods, such as LC-MS, are also effective to identify catechin oxidation products in black tea. Despite ongoing efforts, almost 60% of the solids in black tea infusion remain uncharacterized. These compounds include the so-called thearubigins, which are a heterogeneous mixture of uncharacterized catechin oxidation products with oligomeric structures. This review summarizes the current knowledge of the production mechanisms of representative black tea polyphenols and presents recent progress in characterization of thearubigins., Chemical & pharmaceutical bulletin, 68(12), pp.1131-1142; 2020

Coffee wastewater contains a high amount of caffeine, which causes adverse effects on the environment. Current treatment strategies focus majorly on overall chemical oxygen demand (COD) reduction and do not focus on caffeine degradation in wastewater. Though several techniques are available to degrade caffeine, biological methods are preferred as they are economical and eco-friendly. In this study, Pseudomonas strain NCIM 5235 was evaluated for its potential to degrade caffeine in synthetic coffee wastewater. Uninduced cells degraded caffeine completely in 36 h. Sucrose in the medium did not affect caffeine degradation and remain unconsumed by the bacteria. Under optimal cell loading of 10 × 1011 CFU/L, complete degradation of caffeine was achieved in 2 h. Traces of theaflavin and thearubigin were degraded, whereas other polyphenols remain unaffected and were monitored by UV-visible spectrophotometer. Induced cells also displayed the ability of simultaneous degradation of theobromine present in wastewater. Results showed that caffeine degradation is unaffected at adverse pH, indicating its effectiveness in industrial waste treatment where complete reduction of caffeine and its metabolite theobromine can be achieved by induced cells.

As the most abundant component in black tea, thearubigins (TRs) contribute a lot to black tea's characteristic color, mouthfeel, and potential health benefits. But compared to lower molecular weight black tea polyphenols, there are fewer researches that focus on TRs because of their heterogeneity. This review summarized recent research progress on (1) isolation method of TRs; (2) structure analysis and formation mechanism of TRs; (3) biofunctions of TRs, including antioxidation, antimutagenic and anticancer effects, effects on mitochondrial activation, gastrointestinal motility and skeletal health, to show some future research aspects and prospects of TRs.

BACKGROUND The phenol oxidative pathway during fermentation remains unclear. To elucidate the effect of fermentation on phenol conversion, we investigated the effects of fermentation temperature and duration on the conversion of catechins and the formation of theasinensins (TSs), theaflavins (TFs), thearubigins (TRs), and theabrownins (TBs). RESULTS During fermentation, TSs formation increased initially and then decreased. Long fermentation durations were unfavorable for liquor brightness (LB) and resulted in the production of large amounts of TRs and TBs. Low fermentation temperatures (20 °C and 25 °C) favored the maintenance of polyphenol oxidase activity and the continuous formation of TFs, TSs, and TRSI (a TRs fraction), resulting in better LB and liquor color. Higher temperatures (30 °C, 35 °C, and 40 °C) resulted in higher peroxidase activity, higher oxidative depletion rates of catechins, and excessive production of TRSII (a TRs fraction) and TBs. Analysis of the conversion pathway of polyphenolic compounds during fermentation showed that, during early fermentation, large amounts of catechins were oxidized and converted to TFs and theasinensin B. As fermentation progressed, considerable amounts of theaflavin-3'-gallate, theasinensin A, theaflavin-3-gallate, theaflavin-3,3'-digallate, and theasinensin C were produced and then converted to TRSI; in the final stage, TRSII and TBs were converted continuously. CONCLUSION Different fermentation temperature and duration combinations directly affected the type and composition of phenolic compounds. The key conditions for controlling phenolic compound conversion and fermentation direction were 60 or 90 min and 25 or 30 °C. Our study provides insights into the regulation of phenolic compound conversion during black tea fermentation. © 2021 Society of Chemical Industry.

The instability of tea shoots supply from the plantation to the factory was often a problem. In the flush season where tea shoots are abundant, an overcapacity often leads to the uncontrollable withering process. This problem was the cause of the decreased quality of black tea. Theaflavin (TF) and Thearubigin (TR) were chemical substances that positively correlated to the black tea quality. This research conducted to characterize TF and TR quality in two-stages chemical withering. This research treatment consists of two treatments, namely treatment A (plus season), treatment B (minus season), and one control/routine production (treatment C). Treatment A and B used 25 kg of fresh tea shoots to be withered, the first stage was to wither the leaves until it reached 60%, 65%, and 70% of water content. The second stage was to blended those leaves at the first stage and withered it until it reached about 54-56%. For treatment A and B, the enzymatic oxidation (fermentation) time used 90 minutes. Treatment C used 25 kg of fresh tea shot that processed as normal routine production of black tea orthodox-rotor vane process, with enzymatic oxidation time 110 minutes. Every treatment was repeated 3 times. Treatment A produced TF of 0,97% d.b and TR of 15,39 d.b. (ratio 1:15,97). And treatment C produced TF of 0,92% d.b and TR of 13,69% d.b. (ratio 1:14,82). It was concluded that two-stage chemical withering was able to maintain the chemical and organoleptic qualities of black tea.

BACKGROUND: Orthodox tea is known for its distinct aroma and superior quality. However, the oxidation step that is most crucial for developing these attributes needs precise control and is also time consuming. In the present study, a super‐atmospheric oxidation chamber (SOC) was designed to address this issue. Oxidation of hand‐rolled tea leaves was performed at an elevated oxygen concentration inside the SOC. Both pressure and processing time were varied over the ranges 101–303 kPa and 0–150 min, respectively. Theaflavin (TF), thearubigin (TR) and total color (TC) were determined experimentally and then predicted through artificial neuron network (ANN) modeling. RESULTS: An increasing oxygen concentration and attainment of 100% relative humidity in the compressed air was recognized at elevated air pressure. The observed rate of formation or depletion in TF, TR and TC values was faster with compression of the ambient air. The experimental data points were predicted based on an ANN network containing 18, 10 and 16 neurons in the hidden layer since lowest mean square error and mean absolute error values were observed for the given experimental TF, TR and TC values respectively. CONCLUSION: Considering the significant decrease in oxidation duration and minimal mechanized complexity of the design, the set‐up developed in the present study can be upscaled for industrial application in orthodox tea processing. © 2019 Society of Chemical Industry

Flavonoid consumption has reported health benefits such as reducing cardiovascular disease risk factors, improving endothelial function, and delaying age-related cognitive decline. However, there are little dietary intake data for Australians, which limit our ability to make dietary recommendations to increase intakes to a level where health benefits are seen. The aim of this cross-sectional study was to determine the intake of flavonoids, flavonoid classes, and flavonoid subclasses of 1183 Australians aged 39 to 65 years using a validated 215-item food frequency questionnaire. Based on limited global flavonoid intake data, flavanols are the major dietary flavonoid and are found predominantly in tea and cocoa. As Australians are large tea drinkers, we anticipated that flavanols would be the major flavonoid in the Australian diet. The flavonoid content of foods was determined using a combination of the United States Department of Agriculture Databases and the Phenol-Explorer Database. One-way analysis of variance was undertaken to examine differences between flavonoid intake between men and women. Total flavonoid intake was 626 ± 579 mg/d. Men and women consumed 566 ± 559 mg and 660 ± 588 mg of total flavonoids per day, respectively. Thearubigin accounted for 58% of the flavonoid intake. Women consumed more total flavonoids, thearubigins (both P .01), anthocyanidins (P .0001), flavan-3-ols, flavones, and flavonols (all P .05) than men, whereas men consumed more flavanones than women (P = .01). There was no difference between sexes for the consumption of isoflavones. The data indicated that flavan-3-ols, predominantly thearubigin from tea, were the main flavonoid consumed by Australians. This information contributes to population flavonoid intakes, which should be considered when exploring flavonoid and health relationships.

Biochemical means of tea quality evaluation is quite accurate, but it requires very costly instruments and takes a long time to conduct the experiment. Researches show that thearubigin (TR) and theaflavin (TF) are the two most important biochemical compounds present in tea liquor on which liquor characteristics of black CTC tea depends. Consequently, this fact may be the basis of determining tea quality by assessment of TR and TF via electronic tongue (ET) response. This technique is free from subjective factors. In literature, there are only two research works using this technique so more research work is required to address the problem. This chapter proposes a modeling technique of ET response using sparse decomposition technique to estimate TR and TF content in a given tea sample. For each tea sample, sparse model coefficients obtained from the ET response is considered as a characteristic attribute of it. Experimental results using dissimilar regression models show high prediction accuracies which justify the efficacy of the proposed method.

Tea is a popular drink with refreshing and functional properties. Bud, 1st leaf, and 2nd leaf of five varieties of tea clones (Gumti Takda-78, Ambari, Chiniya, and Tinali, which are popular in tea plantation area of Nepal) were collected and used for preparing green and orthodox black tea to study antioxidant activity, phytochemicals profile, chemical content, and sensory parameters. One or two leaves were hand-plucked from each bush to get a sample of about 100 leaves and processed for green and orthodox black tea for different clones of tea plants. Phytochemicals, antioxidant activity, and caffeine content were found higher in bud followed by 1st leaf and 2nd leaf for all clones of tea plants. Both types of tea (green and black) from Gumti were significantly (p<0.05) higher having tannin content, flavonoid content, total polyphenol content, caffeine content, and IC50 value of 49.15 and 36.23 (mg GAE/g dry extract), 358.9 and 350.4 (mg QE/g dry extract), 590.5 and 570 (mg GAE/g dry extract), 2.85 and 2.94%, and 45.15 & 51.88 μg/mL, respectively. Green and orthodox tea from Takda-78 was found higher in caffeine content and the least in Tinali for both types of tea. Moisture, water extract, total ash, acid-insoluble ash, and crude fiber content in tea (green and black) from Gumti were found to be 5.4% & 5.37%, 65.89% & 71.46%, 5.524% & 6.52%, 0.46% & 0.57%, and 7.96% & 10.27%, respectively. The ratio of theaflavin and thearubigin (TF : TR) was found 1 : 8.61, 1 : 9.36, 1 : 9.70, 1 : 12.87, and 1 : 6.36 in Takda-78, Ambari, Gumti, Chiniya, and Tinali respectively. The total quality score in green tea (85.13%) and black tea (85.78%) from Gumti was significantly higher than others. Phytochemicals and antioxidant properties of green tea were significantly (p<0.05) higher than those of orthodox black tea for all clones of tea plant. This study suggests Gumti variety to be used in green and orthodox black tea processing for higher phytochemical, chemical, sensory quality, and antioxidant activity.

Based on the electrical characteristic detection technology, the quantitative prediction models of sensory score and physical and chemical quality Index (theaflavins, thearubigins, and theabrownins) were established by using the fermented products of Congou black tea as the research object. The variation law of electrical parameters during the process of fermentation and the effects of different standardized pretreatment methods and variable optimization methods on the models were discussed. The results showed that the electrical parameters vary regularly with the test frequency and fermentation time, and the substances that hinder the charge transfer increase gradually during the fermentation process. The Zero-mean normalization (Zscore) preprocessing method had the best noise reduction effect, and the prediction set correlation coefficient (Rp) value of the original data could be increased from 0.172 to 0.842. The mixed variable optimization method (MCUVE-CARS) of Monte Carlo uninformed variable elimination (MC UVE) and competitive adaptive reweighted sampling (CARS) was proved that the characteristic electrical parameters were the loss factor (D) and reactance (X) of the low range. Based on the characteristic variables screened by MCUVE-CARS, the quantitative prediction models for each fermentation quality indicator were established. The Rp values of the sensory score, theaflavin, thearubigin and theabrownins of the predicted models were 0.924, 0.811, 0.85 and 0.938 respectively. The relative percent deviation (RPD) values of the sensory score, theaflavins, thearubigins and theabrownins of the predicted models were 2.593, 1.517, 1,851 and 2.920 respectively, and it showed that these models have good performance and could realize quantitative characterization of key fermentation quality indexes.

Theanaphthoquinone (TNQ) is the initial and main oxidation product of theaflavin, a representative black tea pigment. Nevertheless, TNQ is virtually undetected in the high-performance liquid chromatography analysis of black tea leaves using photodiode array detection. To elucidate the degradation mechanism of theaflavin in the black tea production process, this study investigated the reaction of TNQ with epigallocatechin-3-O-gallate (EGCg), which is the most abundant polyphenol in tea leaves. In citrate–phosphate buffer solution at pH 6 and room temperature, TNQ reacted nonenzymatically with EGCg to afford three products, whose structures were determined on the basis of spectroscopic data. The results indicated that the double bond of the ortho-naphthoquinone moiety in TNQ reacted with the autoxidation product of EGCg. This study demonstrates novel reactions occurring in the process of theaflavin degradation, which might be involved in the formation of thearubigins, the major black tea pigments composing oligomeric catechin oxidation products.

The effect of altitude, shooting period, and tea grade on the catechins and caffeine contents of Turkish black tea was investigated. The experimental factors significantly affected all of the parameters analyzed. Epigallocatechin gallate was the major catechin of black tea (0.719-1.007 g 100 g(-1) dm) followed by epigallocatechin (0.627-0.791 g 100 g(-1) dm). Additionally, caffeine (1.810-2.175 g 100 g(-1) dm), theaflavin (3.201-6.000 mu mol g(-1)), and thearubigin (8.577-12.635 g 100 g(-1) dm) contents were determined. Samples of tea grown at high altitude generally produced a considerably greater amount of the catechins that improve tea quality. Shooting period, which is specific to tea cultivation in Turkey, significantly affected almost all of the quality parameters of black tea. Tea produced in the first shooting period contained more catechins than the samples plucked in the following shooting periods. Dust and orange pekoe 1 contained the most catechins of the tea grades analyzed.

Theaflavin (TF) is a product of catechin oxidation that give contribution to golden yellow color, brightness, briskness of black tea and has a potential as natural antioxidant activity. TF has a higher superoxide radical capture rate than EGCG (Epigallocatechin gallate). The study was to synthesize TF components in the form of extracts that have high antioxidants. Materials used in this research is bud+3 leaves from RITC clone (GMB 7). The research were caried out used 15 liters of tea leaves pulp per treatment, fermentation using fermentor with 15 L/min, 20 L/min and 25 L/min airflow treatment, separation of TF from thearubigin (TR) used 2.5% NaHCO3, and isolation of TF from impurity compounds used silica gel column with ethyl acetate/hexane as eluent, and DPPH (1,1-diphenyl-2-picryl hydrazyl) for antioxidant activity. The result showed that TF synthesis of fresh tea leaf catechin at water-air rate of 25 liters/minute could produced TF extract and yield TF purity extract with 1.01% and 39.15% in dry weight respectively after isolation by silica gel column. Antioxidant activity by DPPH from TF extract showed the smallest value of EC50 is 12.16 mg/L at 150 mg dose and its activity increased with the addition of concentration of TF extract.

Liquor characteristics of black cut, tear, and curl tea mostly depend on two biochemical components like theaflavin (TF) and thearubigin (TR). Evaluation of tea quality can be done efficiently by estimating the concentration of TF and TR without using biochemical tests as it takes much time, which requires laborious effort for sample preparation, storage, and measurement. Moreover, the required instruments for this test are very costly. In this paper, we have proposed an efficient method of TF and TR prediction in a given tea sample using electronic tongue (ET) signal. Combinations of transformed features, like discrete cosine transform, Stockwell transform (ST), and singular value decomposition, of ET signals are fused to develop regression models to predict the contents of TF, TR, and TR/TF. Three different regression models such as artificial neural network, vector-valued regularized kernel function approximation, and support vector regression are used to evaluate the performance of the proposed method. High prediction accuracy using fusion of features ensures the effectiveness of the proposed method for prediction of TF and TR using ET signals.

Summary Herbal drinks have been considered among the known groups of functional drinks. The aim of this study was to encapsulate green tea and orange peel extracts using double emulsion followed by complex coacervation to be used in the preparation of a functional drink. All of the microcapsule formulations were spherically prepared without cracks in the walls and their sizes increased by decreasing the ratio of the core to the wall. Microcapsules under the best conditions of this study were used to coat the paper of a bag containing black tea. The results showed that theaflavin and its ratio to thearubigin as the quality indices for black tea have increased in comparison with the sample without encapsulation. This study resulted in the production of encapsulated mixed extracts of green tea and orange peel that can be used later for the preparation of a functional drink.

A comparative study was undertaken to determine the difference in quality, antioxidant activity, and mineral content of northern and southern Indian tea varieties. The results showed that the antioxidant activity, theaflavin and thearubigin content, color particle size and total soluble solids influence the tea leaf and tea dust. Assam leaf showed higher values for all the physico-chemical properties followed by Darjeeling leaf. In addition, the mineral composition of the tea infusion was also influenced. The preparation method, including the amounts of tea and water used, infusion time was shown to be a major determinant of the component concentrations of tea beverages as consumed. An illustration of the variation introduced by these varieties of tea is provided by comparing solids, caffeine, minerals and antioxidant activity of black teas available locally.

This study was undertaken to investigate the effect of natural bioactive compound thearubigin on neonatal acute lung injury (ALI) using LPS-induced ALI as a model. We also attempted to understand the possible underlying mechanism. The effect of thearubigin on lung wet-to-dry weight ratio, the activity of LDH, lung histopathology, BALF protein levels, the activity of MPO, production and extravasation of cytokines and oxidative stress were studied. The results showed that thearubigin caused a significant reduction in lung inflammation as evident from lung wet-to-dry weight ratio, BALF protein levels and MPO activity and histopathological analysis. It was further observed that the attenuation in inflammation happened due to a significant reduction in cytokine levels in alveolar cavities. Thearubigin also showed strong antioxidant properties as evidenced by reduced levels of oxygen species such as H(2)O(2), MDA and OH ion. Additionally, the antioxidant response element nuclear factor erythroid-2-related factor 2 (Nrf2) pathway was found to be activated in thearubigin-treated group. These results provided a possible mechanism of antioxidant activity of thearubigin in neonatal ALI. Overall, this study showed that thearubigin can be a natural alternative for the treatment of neonatal ALI. However, further studies are required to understand its mechanism antioxidant and anti-inflammatory action. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13205-019-1986-z) contains supplementary material, which is available to authorized users.

Analysis of four different catechins, four theaflavins (TF), and thearubigin (TR) in oxidizing macerated CTC (crush–tear–curl) and rolled orthodox leaves of TV25 clone was done. Tea leaves were oxidized at different air temperatures (20, 25, 30, and 35°C) and thickness of oxidizing leaf bed (2 and 5 cm). Rate of depletion of catechins was modeled using Michaelis–Menten equation. Depletion of dihydroxylated catechins (EC, ECG) was found to be more affected by change in air temperature than trihydroxylated catechins (EGC, EGCG). Amount of maximum total TF at different temperatures was in the range of 1.19%–1.3% for CTC‐macerated leaves and 0.33%–0.43% for rolled orthodox leaves. Quadratic and linear regression equations, developed to model the change in TF and TR contents, respectively, were good fit. Bed thickness does not have any significant effect on TF content in both CTC and orthodox leaves as revealed from ANOVA. PRACTICAL APPLICATIONS: Oxidation or fermentation of macerated leaves is a crucial step in black tea processing that needs to be carefully monitored. Tea processing facilities maintain only air humidity level during fermentation. Air temperature is also an important factor affecting the degradation of catechins and formation of different pigment compounds. Optimum amount of unoxidized catechins and oxidized compounds TF and TR affects the quality of final product. Modeling of catechin, TF, and TR contents in oxidizing leaves will help to manipulate processing conditions such as air temperature, duration, and bed thickness to produce good quality black tea.

Fermentation is a key process that affects the quality of black tea. In this study, we discussed the changes and influencing factors of key endoplasmic components at different positions of stacked fermented leaves, and the effects of different preprocessing, variable selection and intelligent algorithm on the model performance are compared, the quantitative prediction model of main endoplasmic components of Congou black tea under different fermentation time series was established, finally, the content distribution is depicted in different colors. The results show that the RPD values of the random forest (RF) prediction model constructed using the optimal variables of theafuscin, thearubigin, catechin, caffeine, and soluble sugar were 3.40, 2.21, 5.71, 1.46, and 2.89, respectively. The RPD values of the support vector machine (SVR) prediction model constructed using the optimal variables of theaflavin and the phenol ammonia ratio were 3.78 and 2.91, respectively. Furthermore, the visualization process successfully displayed the distribution of various quality indicators of the samples at different time periods. These research results lay a theoretical foundation for advancing the judicious processing of black tea.

Tea quality assessment methods generally require elaborate sample preparation steps and often yield in consistent results. Over the last two decades, the diffuse reflectance spectroscopy (DRS) is emerging as a rapid and non-invasive tool for assessing quality parameters of several materials. In this study¸ we examined the DRS approach by creating a reflectance spectral imaging of 81 black crush, tear and curl (CTC) tea samples and eight tea quality parameters. Spectral models for each parameter were developed using the partial-least-squares regression (PLSR) approach. The ratio of performance deviation (RPD) was used to assess such spectral models. Results showed that moisture content, thearubigin components of TRSI and TRSII, total polyphenol contents and liquor brightness were accurately predicted with RPD values 3.63, 2.32, 2.24, 2.23 and 2.02, respectively. Prediction accuracies were moderate for thearubigin, total liquor color and theaflavin. The variable important projection (VIP) showed the wavelengths around near-infrared and shortwave-infrared regions strongly influence spectral reflectance of black tea.

The effect of various foliar diseases such as blister blight, brown blight, grey blight, bird’s eye spot and sooty mould on physiological functions, important biochemical, volatile and quality parameters of green and black teas were compared and evaluated. The results revealed that there was a considerable reduction in physiological activities such as photosynthetic and transpiration rates. Under natural condition, the diseases caused significant decrease in polyphenols, catechins, and aminoacids contents of green leaf which are known to be important precursors determining the quality of black tea. Consequently, a drastic variation existed between volatile flavor components of diseased leaves when compared to healthy ones. A corresponding decrease in the principal tea quality constituents like theaflavin and thearubigin were substantially reduced in made tea. Due to pathogen invasion in tea leaves, the degree of tea quality is varied in varying levels. Among the various tea pathogens, Exobasidium Vexans affected the overall tea quality extensively when compared to other tea pathogens. In addition, the infestation of diseases declined flavour index value and created difficulty in withering and fermentation during tea processing which ultimately affect the overall quality of tea.

Progress in analytical tools have led to a deeper insight into the chemical constitution and reaction pathways during the tea manufacture. However, the challenges have also changed as "new" teas are traded internationally which makes the authentication much more complicated. This micro-review demonstrates that despite all the achievements in the field of validated methods, authenticity, non-targeted methods we still have some gaps. New reactions products have been detected and those might be useful for authenticity purposes. As regards definitions of certain types of tea it makes sense to combine compositional data generated by validated targeted methods with non-targeted work to get a clearer view. Some more work seems to be necessary to get e.g. a deeper insight in the fate of proanthocyanidins during different types of processing and to develop a concept to quantify the thearubigins. There was progress in our knowledge of the thearubigin fraction in the last decade, however, there are still concepts to develop.

Three different methods from the literature for the fractionation and isolation of thearubigins in black tea (Roberts’ fractionation via liquid–liquid extraction, caffeine precipitation and high-speed countercurrent chromatography) were compared. The fractions were analyzed by both normal phase high-performance liquid chromatography (HPLC) on a diol-column and reverse phase HPLC. The methods were compared with regard to time consumption, yield and purity, showing that Roberts’ fractionation yielded the largest fractions while the caffeine precipitation demanded the least time. The purest TR fraction was obtained via high-speed countercurrent chromatography. Based on these results the isolation of thearubigins via countercurrent chromatography was selected for further investigations. Different techniques (high-speed-, spiral-coil- and high-performance-countercurrent chromatography) were applied, the established method was modified and an additional solvent system was developed to receive well-purified thearubigin fractions.

A field study was conducted to evaluate the efficacy of indigenous biocontrol agents such as Streptomyces griseus and Streptomyces lydicus along with Bacillus subtilis and Trichoderma harzianum for controlling red root rot disease of tea plants. In response to biological treatments, disease incidence, green leaf yield, biometric and physiological parameters and organoleptic characters of made tea were assessed. Among the thirteen treatments tested, soil drenching of carbendazim was superior in terms of reducing red root rot incidence followed by combination of S. griseus and T. harzianum recorded in two consecutive field experiments. In contrast, the maximum green leaf yield and plant growth was achieved in soil application of these biocontrol agents. However, the performance of this dual combination of biocontrol agents was on par with systemic fungicide in terms of disease control. Correspondingly, the biometric, physiological and biochemical parameters were also considerably increased in biologically treated plants when compared to untreated control. The disease increased from 38.7% to 47.6% in untreated control plots and those plants were unhealthy in terms of leaf yellowing, stunted growth with heavy flowering, drying of branches and sudden death of bushes. The tea quality parameters such as theaflavin and thearubigin contents were significantly increased in the range of 0.75–1.43% and 10.38–13.22% respectively in biocontrol treated plants. This was also reflected in tea liquor characteristics. Our results suggested that the combination of biocontrol agents represent a promising alternative for effective management of red root rot disease in tea plants.

Five different popular marketed brands of tea produced in Bangladesh viz; Tetley-Premium, Lipton-Taaza, Finlay-Premium, HRC-Clevedon, Ispahani-Blender's choice were studied before expiry dates to evaluate their status of qualitative parameters viz; Caffeine, Total Polyphenol Content (TPC), Theaflavin (TF), Thearubigin (TR), Highly Polymerized Substances (HPS), Total Liquor Colour (TLC), Briskness Index (BI) and Colour Index (CI). All the studied parameters were found to have been varied with brands. The values of caffeine and TPC were found to be varied from 2.65% (Finlay-Premium) to 3.28% (Tetley-Premium) and 24.58% (Lipton-Taaza) to 12.76% (Tetley-Premium) respectively. Similarly, the estimated values of TF, TR and TLC were detected to be maximum in Lipton-Taaza tea but maximum HPS was in Finlay-Premium tea whereas minimum TF and TLC was in Tetley-Premium tea and minimum TR and HPS was in HRC-Clevedon tea. In contrast, BI and Cl were found to be the highest in Ispahani-Blender's choice and HRC-Clevedon tea respectively and the lowest in Tetley-Premium tea. The present study concludes that the Lipton-Taaza tea is superior over the other brands in respect to qualitative status and all the studied brands may, therefore, be ranked as: Lipton-Taaza > Finlay-Premium > Ispahani-Blender's choice > HRC-Clevedon > Tetley-premium.