Our Tea-Drinking Habits: Effects of Brewing Cycles and Infusion Time on Total Phenol Content and Antioxidants of Common Teas

Characterization of phenolic components of black teas of different origins and the effect of brewing duration on quality properties

This research aims to identify the phytochemical constituents of 79 different samples of black tea, including varieties from India, Iran (IrT), Turkey (TT), and Sri Lanka. In addition, this study investigates the effect of varying brewing times on the quality characteristics of tea. Therefore, we analyzed the phytochemical content of tea using a novel LC-MS/MS method that we developed, which identifies 53 different phenolic compounds. Furthermore, objective evaluations were conducted on the total phenolic compound, total flavonoid compound, antioxidant activity, and color values at 15, 30, and 60-min brewing intervals. The prevailing phenolic compounds discovered in the corresponding tea classifications were quantitatively analyzed to be quinic acid, epicatechin gallate, epigallocatechin gallate, epicatechin, epigallocatechin, gallic acid, nicotiflorine, and isoquercitrin. The study found that the TT and IrT groups had the richest phytochemical content and the highest antioxidant activity. The Turkish tea group had the highest measurement for the desired red color, which is considered a sensory property. Infusion color, antioxidant activity, and total phenolic and flavonoid contents showed significant increases with prolonged brewing time. It was important to note that the chemical composition of tea varies according to its origin and brewing conditions. Extending the brewing time improved the quality of the tea. It should be noted, however, that longer brewing times result in a more intense release of flavonoids, and this increase may have a pro-oxidant effect.

Effect of Extraction Period on Total Phenolics, Total Flavonoids, and Antioxidant Capacity of Ugandan Camellia sinensis (L) Kuntze, Black Primary Grades and Green Tea

Introduction. Globally, the consumption and production of tea are on the rise because of its beneficial constituents. Scarce literature exists on the effects of extraction periods on the contents of the biologically important and protective phytochemicals such as phenolics, flavonoids, and antioxidants in locally produced teas in Uganda. Aim. This study determined the effects of extraction periods on the aqueous total phenolic content (TPC) of local Camella sinensis, black primary grades and green tea, and their ecological differences, their total flavonoid content (TFC), and antioxidant capacities (AOC). Methods. Samples of local tea were collected from Kigezi, Ankole, and Buganda regions, and those of green tea were purchased from a local supermarket in Uganda. Four- and 40-minute infusions were separately prepared for each sample. Total phenolic and flavonoid contents were determined using the Folin–Ciocalteu and aluminium chloride methods using garlic acid and quercetin as standards, respectively. Antioxidant content was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and ferric reducing assay power (FRAP) methods, using ascorbic acid as the standard. Results. Green tea had the highest total phenolic content both with four-minute (9.50 ± 0.25 mgGAE/g) and 40-minute (25.81 ± 1.13 mgGAE/g) extractions, followed by D1 (4.14 ± 0.33 mgGAE/g) at four minutes and PF (23.60 ± 2.37 mgGAE/g) at 40 minutes. Regionally, Kigezi (4.71 ± 0.09 and 22.13 ± 0.85 mgGAE/g) at four and 40 minutes, respectively, gave the highest TPC. In TFC, tea from Buganda (4,371 ± 0.00 μgQE/g) was the highest. In DPPH and FRAP, GT (93.82 ± 0.03%, 39.04 ± 0.02 AAEμg/mL) was the best, followed by Buganda tea (88.71 ± 0.03%, 36.99 ± 0.01 AAEµg/mL), respectively. Conclusion. Longer extraction periods increase TPC in all teas. Green tea generates approximately twice the TPC generated by black tea in four-minute infusions. Green tea gives higher TPC, DPPH, and FRAP but less TFC than some black teas and is perhaps the best in terms of protection against oxidative damage to the body.

Comparative Analysis of the Efficiency of Medicinal Plants for the Treatment and Prevention of COVID-19

The COVID-19 pandemic has once again prompted people to resort to the remedies of folk and alternative medicine. Medicinal plants, because of their chemical composition, pharmacological properties, and the action of biologically active substances, can stop and relieve the symptoms of the disease. The purpose of the work is a comparative flora analysis of medicinal plants to identify the most prospective plant and further production of a remedy for the avoidance, treatment, and rehabilitation of COVID-19. The search for prospective medicinal plants was performed by analyzing the literature in online databases: Web of Science, Scopus, Google Scholar, and PubMed, including official WHO media sites. According to recent studies related to COVID-19, a significant number of medicinal plants with anti-inflammatory, antiviral, and immunostimulatory effects have been identified. A comparative study of nine medicinal plants was conducted to determine the most suitable medicinal plant to treat coronavirus infection. According to the results of the comparative analysis, Chamaenerion angustifolium Seg. showed itself as the most prospective medicinal plant with the greatest pharmacological effect compared with other types of medicinal plants. Its therapeutic properties allow physiological relief of 18 symptoms of coronavirus infection. It is advisable to conduct further clinical trials for the treatment and rehabilitation of COVID-19 using preparations from this plant.

Evaluation of the Brewing Characteristics, Digestion Profiles, and Neuroprotective Effects of Two Typical Se-Enriched Green Teas

As a functional beverage, selenium (Se)-enriched green tea (Se-GT) has gained increasing popularity for its superior properties in promoting health. In this study, we compared the brewing characteristics, in vitro digestion profiles, and protective effects on neurotoxicity induced through the amyloid-beta (Aβ) peptide of two typical Se-GTs (Enshi Yulu (ESYL) and Ziyang Maojian (ZYMJ), representing the typical low-Se green tea and high-Se green tea, respectively). ESYL and ZYMJ showed similar chemical component leaching properties with the different brewing methods, and the optimized brewing conditions were 5 min, 90 °C, 50 mL/g, and first brewing. The antioxidant activities of the tea infusions had the strongest positive correlation with the tea polyphenols among all of the leaching substances. The tea infusions of ESYL and ZYMJ showed similar digestive behaviors, and the tea polyphenols in the tea infusions were almost totally degraded or transferred after 150 min of dynamic digestion. Studies conducted in a cell model of Alzheimer’s disease (AD) showed that the extract from the high-Se green tea was more effective for neuroprotection compared with the low-Se green tea. Overall, our results revealed the best brewing conditions and digestion behaviors of Se-GT and the great potential of Se-GT or Se-enriched green extract (Se-GTE) to be used as promising AD-preventive beverages or food ingredients.

Effect of brewing time and temperature on the physical properties, antioxidant activities and sensory of the kenaf leaves tea

Kenaf (Hibiscus cannabinus L.), an annual herbaceous plant in the Malvaceae family, has become a multifunctional crop in Malaysia due to its large number of industrial applications for its fibrous stem. Recently, its kenaf leaves that have high antioxidant properties are getting more attention to be developed into tea. Therefore, this research aims to determine the best brewing time and temperature based on the physical properties, antioxidant activities and sensory of kenaf leaves tea (KLT). The kenaf leaves powder which was infused in hot (80 °C or 100 °C; 5 min or 10 min) or cold water (room temperature; 60 min or 120 min) were analysed. Results demonstrated that the KLT brewed at 80 °C for 10 min and 100 °C for 10 min showed the highest antioxidant activities in most of the antioxidant analysis conducted. Moreover, the colour of cold-brewed KLT was much lighter than the hot-brewed KLT and the cold-brewed KLT (room temperature; 120 min) can likely be a new trend for the consumer since it contained high antioxidising capabilities. However, the pH, greenness, yellowness, sensory results in KLT were not affected significantly by both brewing time and temperature (p > 0.05). The antioxidant test was correlated positively with the phytochemical contents but insignificant relationship with most of the colour parameters. Overall, the optimum temperature and time for brewing KLT was 80 °C at 10 min because it saved energy and extracted the highest amount of antioxidants while retaining similar sensory taste with other brewing conditions.

Effect of Different Durations of Solid-Phase Fermentation for Fireweed (Chamerion angustifolium (L.) Holub) Leaves on the Content of Polyphenols and Antioxidant Activity In Vitro

Fireweed has recently been recognized as a plant with high antioxidant potential and phenolic content. Its leaves can be fermented to prepare an infusion with ideal antioxidant activity. The aim of this study was to investigate and to determine the influence of solid-phase fermentation of different durations on the variation of polyphenols in the leaves of fireweed. Laboratory experiments were conducted in 2017-2018. The leaves of fireweed, naturally growing, were fermented for different periods of time: not fermented (control) and fermented for 24 and 48 h. The evaluation of polyphenols and antioxidant activity in leaves was performed using high- performance liquid chromatography (HPLC). Additionally, principal component analysis was used to characterize differences in bioactive compounds between fireweed samples fermented at different durations. Solid-phase fermented leaves were characterized by higher contents of oenothein B, quercetin and benzoic acid but had lower contents of quercetin-3-O-rutinoside, luteolin and chlorogenic and gallic acids. Antioxidant activity in short- (24 h) and long-term (48 h) fermentation (compared to control) gave the highest level of regression in 2017, but in 2018 the effect was observed only with short-term fermentation and control. In conclusion, solid-phase fermentation can be used to modulate biologically active compounds in fireweed leaves.