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Natural dye sensitizers are substances that are sensitive to light colour and can be classified into several classes based on their chemical structure. Theaflavin pigments are unexplored natural dyes used as light sensitizers derived from black tea waste. However, the efficiency of natural dye-sensitized solar cells (DSSC) is lower than that of synthetic ones. To increase the efficiency, an amine donor molecule, a thiophene bridge, and a cyanoacrylic acid anchoring group were added. This improvement was achieved by comparing the LHE values, absorption shifts towards the red spectrum, and electronic parameters before and after modification of the theaflavin structure. This study aimed to analyze the effect of a fused thiophene bridge on the colour pigment of theaflavin on the electronic and optical properties of DSSC. TDDFT was employed with the hybrid functional B3LYP and def2-SVP. The calculated results concluded that adding fused thiophene can shift the wavelength with a maximum value of 256 nm and an increase in LHE of 40%. The addition of five thiophenes can shift the absorption wavelength closer to the red spectrum and satisfy the electronic properties of the DSSC, and the number of electron donor and acceptor sites obeying the law of conservation of charge. [ABSTRACT FROM AUTHOR]

The corona virus disease 2019 (COVID-19) pandemic, which originated in the city of Wuhan, China, has rapidly spread to various countries, with many cases having been reported. Some existing antiviral agents showed positive results to inhibit the infection and transmission of the novel corona virus 2019 (2019-nCoV) in vitro. Covaxin is India's first indigenous COVID-19 vaccine. In this paper, we introduce the Gourava and hyper-Gourava polynomials of a graph. We compute the Gourava and hyper-Gourava polynomials of some specific class of graphs. Further, we obtain the Gourava and hyper-Gourava polynomials of some chemical structures viz., chloroquine, hydroxychloroquine, remdesivir and theaflavin which were used in the treatment of COVID-19. The Gourava and hyper-Gourava indices are investigated for the aforesaid antiviral drugs using polynomial approach. The Indian Council of Medical Research and Bharat Biotech announced that Phase 3 results of covaxin, developed by them, have shown an interim vaccine efficacy of 81 percent. So, the results obtained may be useful for finding the design of new medicine for the treatment of COVID-19. [ABSTRACT FROM AUTHOR]

The novel coronavirus disease 2019 (COVID-19) emerged in Wuhan, China, and has spread rapidly to nearly every part of the world. Unfortunately, no drug or vaccine has been accepted for the treatment of this pandemic. Researchers have established the efficacy of some existing antiviral drugs to control COVID-19 in vitro. Some of them are remdesivir (GS-5734), chloroquine, hydroxychloroquine, theaflavin. Topological indices are mathematical interpretations of a molecule generated by an algorithm implemented to a given molecular representation. Topological indices are used to model different physicochemical properties and biological activities of chemical compounds. In this work, some degree-based and neighborhood degree sum-based topological indices are investigated for the aforesaid antiviral drugs using polynomial approach. The results obtained can aid in the design of new medicine for the treatment of COVID-19. [ABSTRACT FROM AUTHOR]

Objectives: The present study was to evaluate the effect of theaflavin on the activities of key enzymes of carbohydrate metabolism in high fat diet and streptozotocin – induced diabetic rats. Methods: Diabetes was induced in male albino Wistar rats by feeding them with high fat diet comprising of standard laboratory rat chow 84.3%, lard 5%, egg yolk powder 10%, cholesterol 0.2% and bile salt 0.5% for 2 weeks. After 2 weeks, the animals were kept in an overnight fast and injected with low dose of streptozotocin (40 mg/kg b.w). Results: Theaflavin (100 mg/kg b.w /day) was administered orally to diabetic rats for 30 days. At the end of the experimental period, diabetic control rats showed significant increase in plasma glucose, homeostatic model assessment of insulin resistance (HOMA-IR), glycosylated hemoglobin (HbA1c) with concomitant decrease in plasma insulin, total hemoglobin and body weight. The activities of key enzymes of carbohydrate metabolism, lipid peroxidation markers, antioxidant enzymes, glycogen content and glycogen synthase and glycogen phosphorylase were also altered in diabetic rats. Discussion: Oral administration of theaflavin to diabetic rats significantly ameliorated all the biochemical alterations to near normal levels. The results of the present study suggest that theaflavin exhibits antidiabetic effect through its antioxidant activity. [ABSTRACT FROM AUTHOR]

The manuscript deals with the optimization of simple, rapid, sensitive and economic HPLC method for estimation of Theaflavin in Camellia sinensis extract and Theaflavin loaded nanoformulation. The preliminary screening was performed employing fractional factorial (25-1) design with mobile phase pH, flow rate, column temperature, injection volume, and acetonitrile concentration as independent variables while tailing factor as the dependent variable. The separation was achieved using the isocratic system as mobile phase, flow rate of 1 ml/min, and ultraviolet detection at 275 nm. Upon further evaluation, the method revealed a high degree of linearity, accuracy, precision, sensitivity and robustness, while, forced degradation studies indicated stability of Theaflavin at pH 3-6 in an air tight, light-protected container. The method when applied towards estimation of Theaflavin in C. sinensis extract and Theaflavin loaded nanoformulation, indicated no significant change in retention time. Thus, a HPLC method for rapid estimation of Theaflavin with an understanding of influencing variables for enhancing the method performance was developed. [ABSTRACT FROM AUTHOR]

Dietary interventions are among the emerging trends to curtail physiological malfunctioning like cancer, diabetes, cardiac complications, etc. The essence of phytonutrients has developed the concept of nutraceuticals at the junction of diet health linkages. In this context, theaflavin & thearubigins are the oxidized derivatives of black tea catechins during fermentation having nutraceutical potential owing to esterification of hydroxyl ring with digallate esters. Theaflavin may influence activation of transcription factors such as NFnB or AP-1 that ultimately hinder the formation of nitric oxide expression gene. Likewise, black tea contains a unique amino acid theanine acts as neurotransmitter owing to its ability to cross the blood–brain barrier. Moreover, it boasts immunity by enhancing the disease-fighting ability of gamma delta T cells. Theaflavin & thearubigins act as safeguard against oxidative stress thereby effective in the cardiac functioning. The mechanistic approach of these antioxidants is likely to be associated with inhibition of redox sensitive transcription factors & pro-oxidant enzymes such as xanthine oxidase or nitric oxide synthase. However, their involvement in antioxidative enzyme induction as in glutathione-S-transferases is also well documented. They act as curative agent against numerous pathological disorders by disrupting the electron chain thus inhibiting the progression of certain ailments. Black tea polyphenols established themselves as strong antioxidants due to their standard one-electron potential, and their vitality is dependent on the concentration of polyphenols and pH for their inclusive execution. Present review is an attempt to enrich the readers regarding the health promoting aspects of black tea polyphenols. Concomitantly, it needs core attention of researchers for the exploitations of black tea flavanols as an important dietary constituent for the vulnerable segment. [ABSTRACT FROM PUBLISHER]

Black Tea (Camellia sinensis) is an important source of phytochemicals with proven health benefits. The core objective of the present investigation was to characterize some promising commercial tea brands available in Pakistan for their active ingredients with special reference to flavanols. The results indicated that total phenolic contents were in the range of 26.42 to 29.74 g/100 g liquid tea, while antioxidant activity and DPPH reduction was in the range from 45 to 50 g/100 g liquid tea and 47 to 50 g/100 g liquid tea, respectively. Tea quality parameters including theaflavins, thearubingins, and theabronins were observed to be 1.71–1.79, 1.74–1.83, and 17.05–20.22 g/100 g liquid tea. Likewise, total catechins and caffeine were 1.01–1.28 and 1.22–1.25 g/100 g liquid tea, respectively. Tea extract of commercial brands containing a larger particle size exhibited better quality. [ABSTRACT FROM PUBLISHER]

Theaflavin (TF1), theaflavin-3-gallate (TF2A), theaflavin-3'-gallate (TF2B), and theaflavin-3,3'-digallate (TF3) are the major theaflavins, which mostly contribute to the quality and bioactivity of black tea. In this study, a rapid isolation and purification of the four major individual theaflavins from crude theaflavins mixture was established. The crude theaflavins mixture was prepared by enzymatic oxidation of tea polyphenols using immobilized polyphenol oxidase and then fractionated using a Mitsubishi SP-207 resin chromatography with an elution gradient of 20%, 30%, 40%, 50%, and 70% aqueous ethanol to obtain a mixture of theaflavins with 80% purity (TF80). The TF80 was further purified using a semi-preparative high performance liquid chromatography (HPLC) equipped with a C18 column using isocratic elution with water/acetonitrile/glacial acetic acid (73.5:26:0.5, v/v/v) at a flow rate of 5 mL/min as optimized operating conditions. The purity of the isolated individual theaflavins were 92.48% for TF2A, 90.05% for TF2B, 92.40% for TF3, and 73.02% for TF1, respectively. [ABSTRACT FROM AUTHOR]

A theaflavin-related benzotropolone pigment formed between procyanidin B-1 and (-)-epigallocatechin was synthesized enzymatically for the first time. The condensation occurred regioselectively at the extension (upper) unit of the procyanidin, probably due to a steric effect. [ABSTRACT FROM AUTHOR]