Compositional variation among black tea across geographies and their potential influence on endothelial nitric oxide and antioxidant activity

Development of Promising Flower-like Ag/SrFeO3 Nanosheet Electrode Materials: An Efficient and Selective Electrocatalytic Detection of Caffeic Acid in Coffee and Green Tea

The development of highly efficient electrocatalytic sensors is necessary for detection in various paramedical and industrial applications. Motivated by this concept, we demonstrate flower-like Ag/SrFeO3 nanostructures prepared by a facile route to modify electrocatalyst material for the detection of caffeic acid (CA). The surface morphology, phase structure, particle size, and pore volume were investigated through different physicochemical analytical techniques. The cyclic voltammetry technique was employed to evaluate the electrochemical behavior of both glassy carbon and modified Ag/SrFeO3 electrodes toward CA. The study revealed that the modified electrode shows excellent electrocatalytic activity toward CA compared to the reported values, with a wide linear range of 1-15 nM, a detection limit of 23 nM, good stability, and excellent repeatability. The superior results are attributed to numerous factors such as rapid electron transfer ability, tunable texture, high surface area, and good conductivity. The created Ag/SrFeO3 nanostructure-based electrochemical biosensor is a potential candidate for real-time analytical performance to directly detect CA in commercially available coffee and green tea without any pre-treatment.

Effects of Key Components on the Antioxidant Activity of Black Tea

Many components (such as tea polyphenols, catechins, theaflavins, theasinensins, thearubigins, flavonoids, gallic acid, etc.) in black tea have antioxidant activities. However, it is not clear which components have a greater influence on the antioxidant activity of black tea. In this study, the antioxidant activity and contents of tea polyphenols, catechins, theaflavins, thearubigins, theabrownins, TSA, total flavonoids, amino acids, caffeine, and total soluble sugar were analyzed in 51 black teas. Principal component analysis (PCA), orthogonal partial least-squares discrimination analysis (OPLS-DA), and the correlation analysis method were used for data analysis. The results showed that catechins in tea polyphenols were the most important components that determine the antioxidant activity of black tea. Among them, epicatechin gallate (ECG), epi-gallocatechin gallate (EGCG), epicatechin (EC), and epi-gallocatechin (EGC) were significantly positively correlated with the antioxidant activity of black tea, and theabrownin was negatively correlated with the antioxidant activity of black tea. Furthermore, this study analyzed the correlation between the changes in catechin and its oxidized polymers with antioxidant activity during black tea fermentation; it verified that catechins were significantly positively correlated with the antioxidant activity of black tea, and theabrownin showed a negative correlation. And the antioxidant activity of catechins and their oxidation products in vitro and their correlation in black tea processing were used as validation. This study provides a comparison method for comparing the antioxidant activity of black tea.

Effects of Infusion and Storage on Antioxidant Activity and Total Phenolic Content of Black Tea

This study determined antioxidant activity in terms of the 1,1-Diphenyl-2-picrylhydrazyl (DPPH) scavenging ability and total phenolic content of black tea under different infusion and storage conditions. High performance liquid chromatography analysis identified caffeine, (−)-epigallocatechin, (−)-epicatechin-3-gallate, (−)-epigallocatechin-3-gallate and (−)-gallocatechin-3-gallate in the tea sample. The water–tea leaves weight ratio did not affect the DPPH scavenging ability. However, infusion temperature affected the DPPH scavenging activity and the total phenolic content. In the present study, the 50% inhibitory concentrations (IC50) for DPPH of black tea infused at 60 to 100 °C ranged from 100.0 ± 13.7 to 28.4 ± 4.8 μg/mL. The total phenolic content of black tea steeped at 60 to 100 °C ranged from 50.4 ± 5.2 to 178.6 ± 16.4 mg gallic acid equivalent/g dry leaf. Black tea exhibited increased antioxidant activity when the infusion temperature was increased. Regarding short-term storage, the DPPH scavenging ability and total phenolic content of black tea did not significantly change within 15 days. This result was consistent for storage temperatures of 4, 9, and 25 °C.

Uncovering the antioxidant characteristics of black tea by coupling in vitro free radical scavenging assay with UHPLC-HRMS analysis

Black tea (BT) is rich in dietary antioxidants, but its antioxidant composition has not been fully understood. To identify the true antioxidants occurring in BT, we established an approach based on 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay coupled with ultra-high performance liquid chromatography-high resolution mass spectrometry (DPPH-UHPLC-HRMS). The employment of HRMS enable us to detect trace antioxidants, resolve co-eluted antioxidants, and characterize chemical structures of unknown antioxidants. In total, 56 phenolic compounds were screened as potential antioxidants from 106 compounds identified in BT. Catechol and pyrogallol were revealed as the key substructures in enhancing the antioxidant abilities of phenolic compounds. During BT brewing, high temperature with extended time promote antioxidant leaching but may induce the degradation of esterified and glycosylated compounds such as theaflavin-3-gallate and rutin. In conclusion, this work identified the true antioxidant constituents of BT, their structural characteristics, and their dynamic changes under various brewing conditions.

A combination of Citrus reticulata peel and black tea inhibits migration and invasion of liver cancer via PI3K/AKT and MMPs signaling pathway

Liver cancer, one of the most common malignancies, is the second leading cause of cancer death in the world. The citrus reticulate peel and black tea have been studied for their beneficial health effects. In spite of the many studies have been reported, the underlying molecular mechanisms underlying its health benefits are still not fully understood. In present study, we developed a unique citrus reticulate peel black tea (CRPBT) by combined citrus reticulate peel and black tea and assessed its active ingredients, anti-oxidant and anti-liver cancer effects in vitro. The results suggested that CRPBT exhibited antioxidant capacity and effectively inhibited proliferation and migration of liver cancer cells in a dose- and time- dependent manner. Mechanistically, CRPBT significantly down-regulated phosphorylation of PI3K and AKT, and up-regulated the ratio of Bax/Bcl-2, and suppressed the expression of MMP2/9, N-cadherin and Vimetin proteins in liver cancer cells. Taken together, CRPBT has good effect on inhibiting migration, invasion, proliferation, and inducing apoptosis in liver cancer cells.

Anti-oxidative effects of safranal on immobilization-induced oxidative damage in rat brain

Safranal, a major constituent of saffron, possesses antioxidant and anti-apoptotic properties showing considerable neuroprotective effects. The present study was designed to investigate the effects of safranal against restraint stress induced oxidative damage in the rat brain. For inducing the chronic restraint stress, rats were kept in the restrainers for 1h every day, for 21 consecutive days, then, the animals received systemic administrations of vehicle (0.1% DMSO) acted as the control group or safranal daily for 21days. Results indicated that the rats submitted to restraint stress showed an increase in the immobility time versus the non-stress rats. In addition, stress decreased number of crossing in the rats submitted to restraint stress versus the non-stress animals. Treatment with safranal (0.75mg/kg) showed a significant reduction in the immobility time compared to the non-treated stress group, while, the treatment improved the number of crossing in rats submitted to restraint stress versus the vehicle-treated stress rats. In the stressed animals that received vehicle, the MDA level was significantly higher and the levels of GSH and antioxidant enzymes were significantly lower than the non-stressed rats. Safranal ameliorated the changes in the stressed animals as compared with the control groups. The present findings indicate that safranal might be effective against depressant-like effects induced by chronic stress via modulating brain oxidative response.

Voltammetric determination of polyphenolic content as rosmarinic acid equivalent in tea samples using pencil graphite electrodes

The quasi-reversible, diffusion controlled behavior of rosmarinic acid (RA) on a disposable pencil graphite electrode (PGE) was established by cyclic voltammetry. Using the anodic oxidation peak presented by RA on the PGE a differential pulse voltammetric (DPV) method was developed for the quantitative determination of RA. The linear range was 10(-8) - 10(-5) M RA and the detection and quantification limits were 7.93 × 10(-9) M and 2.64 × 10(-8) M RA, respectively. The applicability of the developed method was tested by recovery studies and by the assessment of the total polyphenolic contents (TPCDPV) of green, white and black Turkish teas, which were found to be 40.74, 30.04 and 23.97 mg rosmarinic acid equivalent/g dry tea, respectively. These results were in good agreement with those obtained by the Folin-Ciocalteu method. The developed method is a sensitive and cheap tool for the rapid and precise evaluation of TPCDPV of tea samples.

Effects of alternative steeping methods on composition, antioxidant property and colour of green, black and oolong tea infusions

Cold water steeping is reported to maximise tea health benefits, but requires long infusion time. In this work, the employment of a brief hot infusion step followed by ice addition was evaluated. The comparison of this innovative method with hot and cold steeping was investigated on green, black and oolong teas. Catechins, xanthines and gallic acid content, antioxidant power, total phenolics and colour analysis were evaluated. Hot infusion shown rapid extractive power, but relevant compound degradation. On the contrary, cold infusion extracted higher level of healthy molecules with slow kinetic. The innovative method achieved in short time similar properties of cold infusion in terms of antioxidant power. As for bioactive compounds, such as gallic acid and epigallocatechin gallate, highest values, about double than in hot infusion, were recorded for green and black teas. This steeping method may represent an alternative approach for industrial beverage preparation.

Rapid determination of total polyphenolic content in tea samples based on caffeic acid voltammetric behaviour on a disposable graphite electrode

The present paper describes the voltammetric behaviour and the quantitative determination of caffeic acid (CA) on a disposable pencil graphite electrode (PGE). The anodic peak current of CA recorded by differential pulse voltammetry (DPV) varies linearly with CA concentration in the range 1×10(-7)-3×10(-3) M. The detection and quantification limits were 8.83×10(-8) M and 2.94×10(-7) M caffeic acid, respectively. The mean recoveries of CA from Turkish green, white and black teas were 98.30%, 99.57% and 91.46%. For these three tea types the corresponding total polyphenolic contents (TPCs) evaluated by DPV on PGE were 35.81, 34.59 and 31.21 mg caffeic acid equivalent/g tea, respectively. These TPC values were in good accordance with those obtained by the Folin-Ciocalteu method. The developed DPV on PGE method constitutes a simple and inexpensive tool for the rapid assessment of TPC of tea samples.

The role of phytochemicals as micronutrients in health and disease

PURPOSE OF REVIEW

Intake of dietary phytochemicals has frequently been associated with health benefits. Noninfectious diseases including cardiovascular disease (CVD), cancer and diabetes are major causes of death, whereas dementia cases are also increasing to 'epidemic' proportion. This review will focus on recent progress on mechanisms underlying the potential role of dietary phytochemicals in CVD, diabetes, cancer and dementia, with consideration of the latest clinical data.

RECENT FINDINGS

The association of tea (Camellia sinensis), particularly catechins, with reported mechanistic effects for CVD, diabetes, cancer and cognition contributes to our understanding of the suggested benefits of tea consumption on health from limited and inconclusive clinical trial and epidemiological data. Resveratrol, which occurs in grapes (Vitis vinifera) and wine, and curcumin, a component of turmeric (Curcuma longa), are also emerging as potentially relevant to health, particularly for CVD and dementia, with some promising data also concluded for curcumin in cancer. Other phytochemicals mechanistically relevant for health include anthocyanins, isoflavones and glucosinolates, which are also discussed.

SUMMARY

Evidence for the role of phytochemicals in health and disease is growing, but associations between phytochemicals and disease need to be more firmly understood and established from more robust clinical data using preparations that have been phytochemically characterized.