A systematic review of published toxicology and human intervention studies was performed to characterize potential hazards associated with consumption of green tea and its preparations. A review of ...toxicological evidence from laboratory studies revealed the liver as the target organ and hepatotoxicity as the critical effect, which was strongly associated with certain dosing conditions (e.g. bolus dose via gavage, fasting), and positively correlated with total catechin and epigallocatechingallate (EGCG) content. A review of adverse event (AE) data from 159 human intervention studies yielded findings consistent with toxicological evidence in that a limited range of concentrated, catechin-rich green tea preparations resulted in hepatic AEs in a dose-dependent manner when ingested in large bolus doses, but not when consumed as brewed tea or extracts in beverages or as part of food. Toxico- and pharmacokinetic evidence further suggests internal dose of catechins is a key determinant in the occurrence and severity of hepatotoxicity. A safe intake level of 338 mg EGCG/day for adults was derived from toxicological and human safety data for tea preparations ingested as a solid bolus dose. An Observed Safe Level (OSL) of 704 mg EGCG/day might be considered for tea preparations in beverage form based on human AE data.
•Published toxicology and human clinical studies were reviewed, and hepatotoxicity identified as the critical effect.•Feeding state, dosing condition and purity of catechins are key determinants of toxicity.•GTEs closely reflecting that of traditional infusions in composition and ingestion mode are safe.•An Observed Safe Level of 704 mg EGCG/day could be considered for GTEs consumed in beverage form.•A safe intake level of 338 mg EGCG/day for adults could be considered for GTE ingested as a concentrated solid bolus dose.
With the increasing environmental concern and consumption demand for fresh food of human being, development of biodegradable and active food packaging films is highly desirable. In this study, an ...active multilayer food packaging film was fabricated using gelatin (GEL) and sodium alginate (ALG) as matrix biopolymer, green tea extract (GTE) derived from green tea waste as cross-linking agent and active ingredient. The film-forming method was based on simple layer-by-layer (LBL) casting. SEM and FTIR demonstrated the good compatibility of the film-forming substances and the formation of a more compact LBL multilayer composite film due to occurrence of increased intermolecular hydrogen bonding, thereby improving UV-shielding, mechanical strength, water vapor and oxygen barrier, water resistance and thermal stability. The multilayer composite film also exhibited high antioxidant and antibacterial activity. Particularly, slow release of GTE from multilayer composite film was observed. Moreover, the preservation study demonstrated that obtained active film could effectively maintain postharvest quality of Boletus bicolor Peck and extend shelf-life to 7 days under 4 °C storage, indicating its promising application potential for food preservation.
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A novel green tea extract–encapsulated silica gel decorated with in situ–generated Pd nanoparticles is reported as an efficient, green heterogeneous catalyst in the Buchwald-Hartwig C–N ...cross-coupling reaction. It was characterized by several analytical techniques. Thereafter, a wide range of aryl amines were synthesized in good to excellent yields by reaction of different substituted aryl halides and secondary amines over the catalyst. The material is sufficiently stable and could be used at least six times in a model Buchwald-Hartwig reaction without noticeable change in its catalytic activity. Heterogeneity of the catalyst was examined by a hot filtration test.
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•In situ–generated palladium nanoparticles anchored to green tea extract–coated silica gel.•Excellent performance as a reusable catalyst in Buchwald-Hartwig C–N cross-coupling reactions.•Excellent yield of the products.•Catalyst used up to six times.
The nano-zero-valent iron composite (nZVI@TP-Mont) was successfully prepared using a low-cost and environmental-friendly green synthesis via tea leaves extract (tea polyphenols, TPs) and the ...montmorillonite (Mont). The batch and column experiments and characterization were conducted to investigate the transport behavior and Cr(VI) remediation by nZVI@TP-Mont in water/soil. Due to its particular surface characteristics and morphology (i.e., the Fe0 core wrapped by TPs, the doped sulfur, and interlayer structure), the nZVI@TP-Mont composite showed a great removal capacity of Cr(VI) and sufficient mobility under different soil conditions. We opine the increase in the Cr(VI) reduction of nZVI@TP-Mont was attributed to the tethering of Fe2O3 on the surface of Fe0 core by the support of Mont interlayer, especially the TP-coverage around nZVI@TP-Mont surface unwrapped, thereby increasing the regenerated reactive Fe2+ and the exposed reaction sites of Fe0 cores to Cr(VI). The increased transportability of nZVI@TP-Mont slightly depends on the heterogeneous soil properties (i.e., ionic strength, sand/soil ratio, and pH). The two-site kinetic attachment model fitting results suggest Cr(VI)/Cr(III) speciation associated with the agglomerated nZVI@TP-Mont were efficiently immobilized in soil. Therefore, this study would benefit the efficient application of the green-synthesized nZVI@TP-Mont in in-situ remediation of soils contaminated by Cr(VI).
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•Synergistic effects of Mont and tea polyphenols increased the dispersibility of nZVI.•TPs-coverage & Mont support inhibited the Fe2O3 formation around Fe0 cores.•Unwrapped TPs-coverage increased Fe0 cores exposure to Cr(VI) reduction.•Sufficient transport of nZVI@TP-Mont was independent of soil heterogeneity.•nZVI@TP-Mont showed excellent remediation of Cr(VI) in both water and soils.
In this work, we modified the NiO-based graphite electrode by a green synthesis nanoparticles composite of magnetite@chitosan for urea electrooxidation (UEO) in 0.5 M KOH solution. Green magnetite ...(Fe3O4) nanoparticles were prepared with green tea extract that acts as a reducing agent. The new composite catalyst Fe3O4@Chitosan performs a dual function to improve the catalytic properties of UEO. The magnetite Fe3O4 nanoparticles increase the active sites by accelerating the electron transfer between Fe3+/Fe2+ions, while chitosan enhances urea adsorption on the electrode surface. Three graphite electrodes were prepared with different NiO and Fe3O4@Chitosan catalysts ratios under optimized conditions and denoted by Ni0.85Fe0.15, Ni0.75Fe0.25, and Ni0.65Fe0.35. The excellent catalytic parameters as maximum current density (35.4 mA cm−2), Tafel slope (69 mVdec−1), diffusion coefficient (5.759 × 10−6 cm2 s−1), and onset potential (446 mV vs. Ag/AgCl) were achieved by Ni0.75Fe0.25 electrocatalyst. The modified NiO/Fe3O4@chitosan electrocatalyst was characterized by XRD and SEM/EDEX-elemental mapping techniques characterized its morphology and chemical structures. Moreover, cyclic voltammetry, double-step Choronoamerometery, and electrochemical impedance were employed to detect the electrodes' catalytic performance. The EIS fitting parameters deduced from R(RQ)& (RQ) equivalent circuits were used to explain how the Ni/Fe ratios' can affect the charge transfer process of UOR at the prepared electrocatalysts surfaces under the applied potentials.
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•The nickel-based electrocatalyst for urea electrooxidation.•Chitosan/magnetite for enhancement of electrochemical oxidation.•NiO–Fe3O4 electrochemical oxidation.•Urea electrooxidation rate constant.•Chitosan composite for urea electrooxidation.
Green tea is one of the most popular and extensively used dietary supplement in the United States. Diverse health claims have made for green tea as a trendy ingredient in the growing market for ...nutraceuticals and functional foods. Green tea extract contains several polyphenolic components with antioxidant properties, but the predominant active components are the flavanol monomers known as catechins, where epigallocatechin-3-gallate and epicatechin-3-gallate are the most effective antioxidant compounds. Additional active components of green tea extract include the other catechins such as epicatechin and epigallocatechin. Among these, epigallocatechin-3-gallate is the most bioactive and the most scrutinized one. Green tea polyphenols are also responsible for distinctive aroma, color and taste. Green tea extract can also be used in lipid-bearing foods to delay lipid oxidation and to enhance the shelf-life of various food products. This review outlines the chemistry, flavour components, antioxidant mechanism, regulatory status, food applications, and stability of green tea extract in food.
Green tea extract (GTE) is one of the most popular beverages globally, traditionally prepared from Camelia sinensis leaves. Therefore, it is beneficial to define the impact of GTE and its ingredients ...on the human organism. Epigallocatechin-3-O-gallate (EGCG) is the most abundant catechin in green tea leaves, belonging to the group of tannins and flavonoids, demonstrating pharmacological activity, but so far, it has not been applied as a drug. This is because EGCG does not present sufficient stability and quickly decomposes through epimerization or autooxidation mechanisms under the influence of light, temperature, changes in pH, or the presence of oxygen. Another limiting factor is EGCG’s low bioavailability after oral administration. Nevertheless, the growing market of dietary supplements together with increasing growing consumption of green tea extracts should prompt us to pay more attention to the safety of both EGCG itself, as well as its influence on other simultaneously used drugs. Previously published data confirm the relationship between healthcare professionals’ access to professional knowledge and their willingness to engage in patient education. For this reason, in this review article, we report the formulations of EGCG and GTE, discuss the data on the safety of EGCG and its possible interactions with drugs, as well as gather various recommendations from medical specialists. Particular attention should be paid to the consumption of green tea during pregnancy and breastfeeding, as well as in the elderly. Patients taking clozapine, digoxin, and warfarin should avoid consuming GTE extracts and dietary supplements containing EGCG. Professional consultation seems especially important for patients treated with statins, calcium channel blockers, or sildenafil.
The antioxidant capability of oil‐soluble green tea extract (OSGT) in canola oil was compared to common synthetic and plant‐derived ingredients with antioxidant function. Three storage conditions ...were included—22–25 °C ambient, 60 °C heated and air‐purging at 22–25 °C. The oxidation process was monitored by electron spin resonance spectroscopy for free radicals, peroxide value for primary oxidative byproducts, proton nuclear magnetic resonance for the loss of oxidatively labile protons, aldehydes as secondary oxidative byproducts and antioxidants residues. Except for tocopherols, the use of antioxidant ingredients improved the stability of the oils under all conditions. However, the extent of improvement differed under different storages for the same ingredients. Evaluating antioxidant ingredients and interpretation of data when using accelerated conditions need caution. Antioxidant level change under different storage conditions provide new insights on the mechanism working of antioxidants in bulk oil. OSGT has comparable performance to TBHQ under ambient temperature conditions. In conclusion, evaluating antioxidant ingredients under accelerated conditions needs caution. Oil‐soluble green tea extract has comparable antioxidative performance to TBHQ in bulk vegetable oil systems without affecting organoleptic properties of the oils under ambient temperature regardless of temperature or oxygen levels.
In this work, we successfully prepare NiAl2O4/NiO nanocomposite with thermal decomposition method by using green tea extract (GTE) as precipitating agent. The biosynthesized NiAl2O4/NiO nanocomposite ...characterize using X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), N2 adsorption (BET), ultraviolet–visible (UV–Vis) spectroscopy, and transmission electron microscopy (TEM). Also, we study the electrochemical hydrogen storage properties of NiAl2O4/NiO nanocomposite porous with different calcination temperature. The discharge capacity of samples with calcination temperature 700, 800 and 900 °C are 450, 325 and 800 mAh/g after 15 cycles, respectively.
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•NiAl2O4/NiO nanocomposition has been prepared using simple thermal decomposition method.•The effects of calcination temperature on morphology, size and optical properties were investigated.•The green tea extract can be used as precipitating agent.•For the first time, the hydrogen storage capacity of NiAl2O4/NiO was studied.
Phyto-synthesis of silver nanoparticles (AgNPs) was achieved using aqueous garlic, green tea and turmeric extracts, and characterized by different spectroscopic techniques. Phytochemical analysis ...revealed the presence of rich amount of biochemicals in these extracts, which serve as reducing and capping agents for converting silver nitrate into AgNPs. FT IR spectroscopy confirmed the role of biomolecules in the bioreduction and efficient stabilization of AgNPs. UV–Vis DRS spectra showed a band around 450 nm characteristics of AgNPs. XRD patterns revealed the crystalline nature of the synthesized AgNPs with fcc structure. SEM and TEM analysis revealed the spherical shape of the synthesized AgNPs with an average particle size of 8 nm. EDX analysis confirmed the purity of the synthesized AgNPs with a strong signal at 3.2 keV. The antioxidant activity was assessed by ABTS, DPPH, p-NDA, H2O2 and DMSO scavenging assays, in which the AgNPs synthesized using green method showed remarkable activity with respect to the standard antioxidants ascorbic acid and rutin. In vitro cytotoxicity activity was tested on four cancer cell lines such as human breast adenocarcinoma (MCF-7), cervical (HeLa), epithelioma (Hep-2) and lung (A549) along with one normal human dermal fibroblasts (NHDF) cell line. The AgNPs synthesized using turmeric extract exhibits excellent antioxidant and cytotoxicity activity compared to that synthesized using other extracts.
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•We report green extracts-mediated phytosynthesis of AgNPs.•XRD patterns confirmed the face centered cubic (fcc) structure of AgNPs.•SEM and TEM analysis confirmed the morphology and size of the AgNPs.•In vitro antioxidant activity was tested by five different assays.•Turmeric extract mediated AgNPs exhibit higher biological activity.
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