Evaluation of the antioxidant properties of fruit and flavoured black teas

Caffeoylquinic acid profiling: comparative analysis in yerba mate, Indian camphorweed, and stevia extracts with emphasis on the influence of brewing conditions and cold storage in yerba mate infusion

Herbal infusions exhibit diverse pharmacological effects, such as antioxidant, anti-inflammatory, anticancer, antihypertensive, and antineurodegenerative activities, which can be attributed to the high content of phenolic compounds (e.g., caffeoylquinic acids (CQAs)). In this study, we used ultraperformance liquid chromatography to determine the content of CQAs in the methanolic extracts of model herbs, namely, yerba mate (Ilex paraguariensis), stevia (Stevia rebaudiana), and Indian camphorweed (Pluchea indica (L.) Less.). The results revealed that yerba mate had the highest total CQA content (108.05 ± 1.12 mg/g of dry weight). Furthermore, we evaluated the effect of brewing conditions and storage at 4 °C under dark and light conditions on the antioxidant property and total phenolic and CQA contents of a yerba mate infusion. The analysis of the yerba mate infusions prepared with different steeping times, dried leaf weights, and water temperatures revealed that the amount of extracted CQAs was maximized (∼175 mg/150 mL) when 6 g of dried leaves were steeped in hot water for 10 min. A total of 10-day refrigerated storage resulted in no significant changes in the antioxidant activity and total phenolic and CQA contents of an infusion kept in a brown container (dark). However, the antioxidant properties and total phenolic and CQA contents were negatively affected when kept in a clear container, suggesting the detrimental effect of light exposure. Our study provides practical recommendations for improving the preparation and storage of herbal infusions, thus catering to the needs of consumers, food scientists, and commercial producers. Moreover, it is the first study of the influence of light exposure on the content of crucial quality attributes within plant-based beverages.

Herbal Polyphenols as Selenium Reducers in the Green Synthesis of Selenium Nanoparticles: Antibacterial and Antioxidant Capabilities of the Obtained SeNPs

Selenium is an essential trace element for the proper functioning of the human body. In recent years, great attention has been paid to selenium nanoparticles (SeNPs) due to their potential for medicinal applications. In this study, herbal extracts were used in the green synthesis of SeNPs. The influence of herbal species, the ratio of the reagents, and post-reaction heating on the antibacterial and antioxidant properties of obtained SeNPs were investigated. The relationship between these properties and the physical parameters of obtained nanoparticles (e.g., size, shape) was also studied. It has been proven that SeNPs showed higher antioxidant and antibacterial properties in comparison to herbal extracts taken for their synthesis. Heating of the post-reaction mixture did not affect the SeNP size, shape, or other studied properties.

Effect of the type of brewing water on the sensory and physicochemical properties of light-scented and strong-scented Tieguanyin oolong teas

Variations in the quality of brewing water profoundly impact tea flavor. This study systematically investigated the effects of four common water sources, including pure water (PW), mountain spring water (MSW), mineral water (MW) and natural water (NW) on the flavor of Tieguanyin tea infusion. Brewing with MW resulted in a flat taste and turbid aroma, mainly due to the low leaching of tea flavor components and complex interactions with mineral ions (mainly Ca2+, Mg2+). Tea infusions brewed with NW exhibited the highest relative contents of total volatile compounds, while those brewed with PW had the lowest. NW and MSW, with moderate mineralization, were conducive to improving the aroma quality of tea infusion and were more suitable for brewing both aroma types of Tieguanyin. These findings offer valuable insights into the effect of brewing water on the sensory and physicochemical properties of oolong teas.

Does the Type Matter? Verification of Different Tea Types' Potential in the Synthesis of SeNPs

Selenium nanoparticles (SeNPs) are gaining popularity due to their potential biomedical applications. This work describes their green synthesis using various types of tea. Black, green, red and white tea infusions were tested for the content of polyphenolic compounds and antioxidant properties and then used in the synthesis of SeNPs. In each of the syntheses, nanoparticles with dimensions ranging from 3.9 to 12.5 nm, differing in shape and properties, were obtained. All of them were characterized by a very high ability to neutralize hydroxyl radicals, which was about three-times higher than for the tea infusions from which they were obtained. The main inconvenience in obtaining SeNPs was the difficulties with their purification, which should be a further stage in the described research.

Dual effect of the herbal matcha green tea (Camellia sinensis L. kuntze) supplement in EA.hy926 endothelial cells and Artemia salina

ETHNOPHARMACOLOGICAL RELEVANCE

Matcha green tea (Camellia sinensis) based-supplements have been widely used since they present a greater content of phenolic compounds than traditional green tea, which is popularly used in the treatment of diabetes. However, there are few studies on the effectiveness and safety of matcha supplements.

AIM OF THE STUDY

This work aimed to evaluate the efficacy and safety of this supplement in endothelial cells (EA.hy926) in the hyperglycemic model and in vivo Artemia salina.

MATERIALS AND METHODS

To assess the effect of Matcha herbal supplement (MHS), EA. hy926 endothelial cells were treated with 20 μg/mL of MHS for 24 h, in a hyperglycemic medium with 35 mM glucose. After treatment, cells were trypsinized and centrifuged at 4 °C and 47×g for 5 min. The pellet was used to determine the reaction products to thiobarbituric acid and the levels of nitric oxide. Electron transport chain activity and ATP levels were also evaluated. Intracellular pH, apoptosis, and mitochondrial membrane depolarization were evaluated by flow cytometry. MHS chemical characterization was performed by HPLC-UV and total phenolic content analysis. The evaluation of the antioxidant capacity of MHS was performed by 2,2-diphenyl-1-picrylhydrazyl radical scavenger assay. To determine the in vivo acute toxicity of MHS, an A. salina assay was conducted, using 0,2 mL of different concentrations of MHS (10, 50, 100, 250, 500, 750 and 1000 μg/mL). The LD₅₀ values were obtained by interpolation of 50% (y = 50) of the dead individuals in the trend curves.

RESULTS

Our data showed that MHS was able to avoid oxidative and nitrosative stress induced by hyperglycemia, demonstrating important antioxidant activity. However, it was observed that MHS reduced up to 90% the activity of the four-electron transport complexes, reducing the ATP production of the endothelial cells. In the toxicity assay performed in Artemia salina, MHS showed mild toxicity (LD₅₀ = 0,4 mg/mL). The major compounds found in MHS were epigallocatechin gallate, epicatechin, rutin, kaempferol, and quercetin.

CONCLUSIONS

This data draws attention to the fact that supplements with high content of phenolic compounds, capable of avoiding oxidative and nitrosative stress can have a dual effect and, simultaneously to antioxidant activity, can induce toxicity in different cell types.

Exploration of chemical markers using a metabolomics strategy and machine learning to study the different origins of Ixeris denticulata (Houtt.) Stebb

As a generally edible plant, Ixeris denticulata (Houtt.) Stebb is widely distributed in China. Its medicinal value has attracted much attention in recent years. However, the chemical markers that cause quality and taste differences in I. denticulata from different regions are currently unclear. In this study, samples from 8 different origins were collected and analysed by UPLC-Q-TOF/MS. A metabolomics data processing strategy and machine learning method were established to explore the reasons for the difference in quality and taste of different origins from the perspective of chemical composition. With the established strategy, 10 characteristic chemical markers were identified that could be used to distinguish the origins of I. denticulata. The strategy proposed in this study could provide a certain basis for quality control and reasonable consumption of I. denticulata and additional food and medicinal homologous species.

The anticancer potential of the dietary polyphenol rutin: Current status, challenges, and perspectives

Rutin is one of the most common dietary polyphenols found in vegetables, fruits, and other plants. It is metabolized by the mammalian gut microbiota and absorbed from the intestines, and becomes bioavailable in the form of conjugated metabolites. Rutin exhibits a plethora of bioactive properties, making it an extremely promising phytochemical. Numerous studies demonstrate that rutin can act as a chemotherapeutic and chemopreventive agent, and its anticancer effects can be mediated through the suppression of cell proliferation, the induction of apoptosis or autophagy, and the hindering of angiogenesis and metastasis. Rutin has been found to modulate multiple molecular targets involved in carcinogenesis, such as cell cycle mediators, cellular kinases, inflammatory cytokines, transcription factors, drug transporters, and reactive oxygen species. This review summarizes the natural sources of rutin, its bioavailability, and in particular its potential use as an anticancer agent, with highlighting its anticancer mechanisms as well as molecular targets. Additionally, this review updates the anticancer potential of its analogs, nanoformulations, and metabolites, and discusses relevant safety issues. Overall, rutin is a promising natural dietary compound with promising anticancer potential and can be widely used in functional foods, dietary supplements, and pharmaceuticals for the prevention and management of cancer.

Rapid LC-MS/MS Determination of Hesperidin in Fermented Tea Prepared from Unripe Satsuma Mandarin (Citrus unshiu) Fruits and Third-crop Green Tea (Camellia sinensis) Leaves

For improving quality control in the fermented tea production process and advancing the corresponding food labeling with function claims, a rapid and robust hesperidin analysis method using LC-MS/MS with the sample dilution approach was developed by following internationally accepted criteria of the Association of Official Analytical Chemists (AOAC). The linear correlation coefficient (r²) of the regression line was 0.9997 in the concentration range of 0.025 - 2.5 mg/L. The matrix effect evaluated using regression line slope values was negligible. The recovery rate of 100.7% indicated improved trueness. The performance of the newly developed method in determining the hesperidin content of fermented tea samples did not significantly vary from that of a well-established, conventional method. The HorRat values of intra- and inter-laboratory reproducibility studies were both within the acceptable range, indicating sufficient accuracy of the newly developed method according to the AOAC criteria.

Quantification of Polyphenols and Metals in Chinese Tea Infusions by Mass Spectrometry

Chemical compounds within tea (Camellia sinensis) are characterized by an extensive heterogeneity; some of them are crucial for their protective and defensive role in plants, and are closely connected to the benefits that the consumption of tea can provide. This paper is mainly focused on the characterization of polyphenols (secondary metabolites generally involved in defense against ultraviolet radiation and aggression by pathogens) and metals, extracted from nine Chinese tea samples, by integrating different mass spectrometry methodologies, LC-MS/MS in multiple reaction monitoring (MRM) and inductively coupled plasma mass spectrometry (ICP-MS). Our approach allowed to identify and compare forty polyphenols differently distributed in tea infusions at various fermentation levels. The exploration of polyphenols with nutraceutical potential in tea infusions can widely benefit especially tea-oriented populations. The worldwide consumption of tea requires at the same time a careful monitoring of metals released during the infusion of tea leaves. Metal analysis can provide the identification of many healthy minerals such as potassium, sodium, calcium, magnesium, differently affected by the fermentation of leaves. Our results allowed us: (i) to draw up a polyphenols profile of tea leaves subjected to different fermentation processes; (ii) to identify and quantify metals released from tea leaves during infusion. In this way, we obtained a molecular fingerprint useful for both nutraceutical applications and food control/typization, as well as for frauds detection and counterfeiting.

Effect of drying methods and parameters on the antioxidant properties of tea (Camellia sinensis) leaves

Background

Conventional drying using heated air oven is commonly used as a method for preserving the product but often affects the nutritional value, taste, and texture. However, the heat from the drying method can oxidize and destroy heat-sensitive compounds. Superheated steam (SHS) drying uses superheated steam instead of hot air or combustion gases in a direct dryer and was reported better at preserving the nutritional values of food products.

Aim

To evaluate the effect of SHS drying on antioxidant properties of tea leaves. The study also compared SHS drying with conventional and freeze-drying methods.

Results

Tea leaves dried using freeze drying retained the highest level of antioxidant properties compared to other drying methods. The leaves dried using SHS exhibited significantly higher radical scavenging activity, ORAC and FRAP values compared to oven drying method. At different drying temperatures (150 °C and 175 °C), oven dried leaves showed significantly higher (p < 0.05) antioxidant properties than that of SHS dried ones. Tea leaves dried for 60, 75, and 90 min using SHS showed significantly higher (p < 0.05) FRAP and ORAC values, and also total phenolic content compared to oven dried tea leaves.

Conclusion

Tea leaves dried using SHS drying method retained higher level of antioxidant properties compared to oven drying. The drying method also retained lower antioxidant properties as drying time increased. Further study involving SHS drying in food-related fields should be conducted to support its usefulness.

Graphical abstract

Regardless of the Brewing Conditions, Various Types of Tea are a Source of Acetylcholinesterase Inhibitors

Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized, among others, by abnormally low levels of the neurotransmitter acetylcholine in the brain. Acetylcholinesterase (AChE) plays a significant role in the process through hydrolysis of the acetylcholine neurotransmitter. Currently, the main method for treatment of AD at a symptomatic stage entails administration of AChE inhibitors to patients diagnosed with the disease. However, it is also possible to take certain steps to treat AD by delivering inhibitors with food. There is a growing body of evidence to suggest that tea (Camellia sinensis) shows numerous beneficial properties, including improving cognitive abilities. This is particularly important in the case of AD patients. The study assessed the impact of brewing conditions on the inhibition of AChE activity observed in tea extracts (black, white, or fruit). Our study revealed that neither temperature nor time of brewing influenced the respective infusions’ ability to inhibit the activity of AChE. Anticholinesterase activity was observed in most of the different types of tea that were analyzed, with the highest rate of inhibition (30.46%–48.54%) evidenced in the Biofix Tea Wild Strawberry brand. The results of our research show that tea may be used as a rich source of cholinesterase inhibitors which play a significant role in AD treatment.

Antioxidant Activity and Main Chemical Components of a Novel Fermented Tea

In the present study, we aimed to develop a novel fermented tea (NFT) product and to evaluate their in vitro antioxidant potential and chemical composition. We found that NFT contained a high level of total phenolic compounds (102.98 mg gallic acid equivalents/g extract) and exhibited diverse antioxidant activities, such as scavenging of 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and hydroxyl radicals, as well as reducing power. The total catechins in NFT were comparable to those of Lipton black tea (LBT), but lower than those of Boseong green tea (BGT) or Tieguanyin oolong tea (TOT). Among all catechins tested, epigallocatechin (EGC) and epigallocatechin-3-O-gallate (EGCG) were the predominant compounds in NFT. In particular, the contents of total theaflavins (TFs), theaflavin (TF), theaflavin-3-gallate (TF3G), and theaflavin-3'-gallate (TF3'G) in NFT were significantly higher than that of BGT, TOT, or LBT. NFT had the highest level of total essential amino acid and γ-aminobutyric acid (GABA) compared with BGT, TOT and LBT. Furthermore, the sensory evaluation results showed that NFT had satisfactory color, aroma, taste, and overall acceptability scores. Our results highlight the potential usefulness of this novel fermented tea as a nutraceutical food/ingredient with special functional activities.

UPLC-Q-TOF/MS-based untargeted metabolomics coupled with chemometrics approach for Tieguanyin tea with seasonal and year variations

The taste and aroma quality of Tieguanyin tea fluctuate seasonally and yearly. However, the compounds responsible for the seasonal and year variations of metabolic pattern and its sensory quality are far from clear. 60 Tieguanyin tea samples harvested in different years and seasons were analyzed by ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) and chemometrics. Principal component analysis (PCA) explained 33.2% of the total variance, while orthogonal projection to latent structures discriminate analysis (OPLS-DA) can obtain potential metabolites with better discrimination, and with R²X and Q² of cross-validation as 0.974 and 0.937, respectively. Subsequently, heat map analysis (HCA) visualized relationships between Tieguanyin teas with these significantly different potential metabolites by Mann-Whitney U test (p < 0.05). Furthermore, the best discriminate metabolites contributing to different sensory qualities were revealed by stepwise liner discrimination analysis (SLDA) with 100% accuracy rate. The present strategy also exhibited great potential for untargeted metabolomics of other foods.

A novel design to screen chlorogenic acid-producing microbial strains from the environment

The present study aimed to develop a plate-screening method, based on the specific color development of complexes formed between chlorogenic acid, a valuable plant-derived compound, and aluminum (III), to detect chlorogenic acid-producing microbial strains. Modified media with 0.75 mM aluminum chloride were developed to identify CGA-producing bacteria (based on beef extract agar medium) or fungi (based on the potato dextrose agar medium). Compared with conventional screening, the modified media let to 3.3 times more CGA producers from plants, at 90.9% selective accuracy. Novel chlorogenic acid-biosynthesizing strains included Brevibacillus borstelensis B14, Bacillus amyloliquefaciens B17, Bacillus badius B19, Sphingomonas yabuuchiae N21, Enterobacter tabaci N22, and Lodderomyces elongisporus S216 and P212. Strain S216 produced the highest chlorogenic acid yield (23.39 mg L⁻¹). This study provides a highly efficient and low-cost tool for quick detection and subsequent identification of several newly isolated strains with chlorogenic acid-producing potential.

Bioactive compounds from extra virgin olive oils: Correlation between phenolic content and oxidative stress cell protection

When compared with other edible vegetable oils, the extra virgin olive oil (EVOO) exhibits excellent nutritional properties due to the presence of biophenolic compounds. Although they constitute only a very small amount of the unsaponifiable fraction of EVOO, biophenols strongly contribute to the sensorial properties of this precious food conferring it, for example, the bitter or pungent taste. Furthermore, it has been found that biophenols possess beneficial effects against many human pathologies such as oxidative stress, inflammation, cardiovascular diseases, cancer and aging-related illness. In the present work, the biophenolic content of 51 Italian and Spanish EVOOs was qualitatively and quantitatively identified and their antioxidant ability analyzed by oxygen radical absorbance capacity (ORAC) assay. Results indicated that the maximum relationship can be found if the ORAC value is correlated with the concentration of the large family composed by ligstroside and oleuropein derivatives together with their degradation products, hydroxytyrosol and tyrosol. Then, selected biophenolic extracts were tested in NIH-3T3 cell line to verify their ability in the recovery of the oxidative stress revealed by DCFH-DA assay. Results were linearly correlated with the concentration of ligstroside aglycone (aldehyde and hydroxyl form).

Concentration of Tea Extracts by Osmotic Evaporation: Optimisation of Process Parameters and Effect on Antioxidant Activity

In this work, the concentration process of three different tea extracts (medicinal Rosil No. 6, Black, and Forest Fruit teas) using the osmotic evaporation (OE) process, was studied. The effect of the OE process on the content of phenolic compounds and antioxidant activity was evaluated. The concentration process was carried out in a hollow-fibre membrane contactor with an effective surface area of 0.54 m². The tea extract was circulated through the shell side of the contactor, while a concentrated osmotic solution (CaCl₂ 5 M) was circulated inside the fibres. The flux, the driving force, and the mass transfer coefficient were evaluated. A decrease of the water flux over time was observed and was attributed only to the decrease of the driving force, caused by the dilution of the osmotic solution. Using a surface area/feed volume ratio of 774 m²·m⁻³, it is possible to reach a tea concentration of 40% (w/w) in 5 h, with a constant water flux and without losing the phenolic content and antioxidant potential in most teas.

New Sample Preparation Method for Quantification of Phenolic Compounds of Tea (Camellia sinensis L. Kuntze): A Polyphenol Rich Plant

Chemical analysis of the Sri Lankan tea (Camellia sinensis, L.) germplasm would immensely contribute to the success of the tea breeding programme. However, the polyphenols, particularly catechins (flavan-3-ols), are readily prone to oxidation in the conventional method of sample preparation. Therefore, optimization of the present sample preparation methodology for the profiling of metabolites is much important. Two sample preparation methodologies were compared, fresh leaves (as in the conventional procedures) and freeze-dried leaves (a new procedure), for quantification of major metabolites by employing two cultivars, one is known to be high quality black tea and the other low quality black tea. The amounts of major metabolites such as catechins, caffeine, gallic acid, and theobromine, recorded in the new sampling procedure via freeze-dried leaves, were significantly higher than those recorded in the conventional sample preparation procedure. Additionally new method required less amount of leaf sample for analysis of major metabolites and facilitates storage of samples until analysis. The freeze-dried method would be useful for high throughput analysis of large number of samples in shorter period without chemical deterioration starting from the point of harvest until usage. Hence, this method is more suitable for metabolite profiling of tea as well as other phenol rich plants.

Tea consumption and mortality of all cancers, CVD and all causes: a meta-analysis of eighteen prospective cohort studies

Epidemiological studies have demonstrated inconsistent associations between tea consumption and mortality of all cancers, CVD and all causes. To obtain quantitative overall estimates, we conducted a dose-response meta-analysis of prospective cohort studies. A literature search in PubMed and Embase up to April 2015 was conducted for all relevant papers published. Random-effects models were used to calculate pooled relative risks (RR) with 95 % CI. In eighteen prospective studies, there were 12 221, 11 306 and 55 528 deaths from all cancers, CVD and all causes, respectively. For all cancer mortality, the summary RR for the highest v. lowest category of green tea and black tea consumption were 1·06 (95 % CI 0·98, 1·15) and 0·79 (95 % CI 0·65, 0·97), respectively. For CVD mortality, the summary RR for the highest v. lowest category of green tea and black tea consumption were 0·67 (95 % CI 0·46, 0·96) and 0·88 (95 % CI 0·77, 1·01), respectively. For all-cause mortality, the summary RR for the highest v. lowest category of green tea and black tea consumption were 0·80 (95 % CI 0·68, 0·93) and 0·90 (95 % CI 0·83, 0·98), respectively. The dose-response analysis indicated that one cup per d increment of green tea consumption was associated with 5 % lower risk of CVD mortality and with 4 % lower risk of all-cause mortality. Green tea consumption was significantly inversely associated with CVD and all-cause mortality, whereas black tea consumption was significantly inversely associated with all cancer and all-cause mortality.

Occurrence of 15 + 1 EU priority polycyclic aromatic hydrocarbons (PAH) in various types of tea (Camellia sinensis) and herbal infusions

For the analysis of 15 + 1 EU priority PAH in tea and herbal infusions, an online-SPE-LVI-GC-MS method was developed. This method includes sample extraction of the tea and herbal infusions with saponification followed by an automated SPE clean-up step. For brews a liquid-liquid extraction with cyclohexane was performed before an automated SPE clean-up. Gas chromatographic separation was done using an Agilent J&W Select PAH (15 m × 0.15 mm × 0.10 µm) column, which allows the separation of the three benzofluoranthenes as well as triphenylene from chrysene. Method performance criteria such as method linearity, limit of quantitation (LOQ) and repeatability were determined and demonstrated that the method was fit for purpose. The method was used to analyse 15 + 1 EU priority PAH in 91 tea and herbal infusion samples. The levels of PAHs ranged from below 0.5 (LOQ) to 460 µg kg⁻¹, with a median of 4.7 µg kg⁻¹ and a mean of 39 µg kg⁻¹ for BaP, and from below 1.0 (LOQ) to 2700 µg kg⁻¹, with a median of 39 µg kg⁻¹ and a mean of 250 µg kg⁻¹ for total PAH, which were in good agreement with other studies reported in the literature. For the brews prepared under normal house preparation (20 g material in 2 L boiling tap water for 10 min), no total 15 + 1 PAH could be detected above the LOQ. With an extended brewing time of 30 min, a transfer rate between 0.25% and 0.52% could be determined, which results in no exceeding of the maximum limits given by the European Union directive for drinking water (EU Council Directive 98/83/EC).

A Comparison of Total Antioxidant Capacities of Concord, Purple, Red, and Green Grapes Using the CUPRAC Assay

Considering how popular grapes are in terms of their antioxidant benefits, we compared concord, purple, red, and green grapes for total antioxidant capacity (TAC) and carbohydrate concentration. All grapes were acquired from commercial sources and samples of each were separated into skinned and not skinned groups. Each whole grape and the skins were individually homogenized and then separated into pulp and supernatant fractions. Each fraction was analyzed for total TAC and carbohydrates. The concord grapes and purple grapes had significantly higher TAC in the homogenates than did the red or green grapes. The concord grapes and green grapes had significantly higher TAC in the pulp than in the cytosol whereas the red and purple grapes had approximately the same amount. The majority of the TAC of the purple and red grapes was in the skin whereas the concord and green grapes had approximately the same TAC in the skin and pulp. The concord and purple grapes had the highest TAC when compared to the red and green grapes, whereas the red and green grapes had approximately the same total TAC.

Evaluation of Antioxidant Properties and Phenolic Composition of Fruit Tea Infusions

The popularity of fruit tea is increasing in the world because of its antioxidant properties and attractive taste. The aim of this study was to determine and compare the antioxidant property and phenolic composition of 16 different fruit teas. The antioxidant property and total phenol content of fruit teas depending on the extraction condition (water temperature) were examined using the ABTS (2,2-azinobis[3-ethylbenzothiazoline-6-sulphonic acid]) method and the Folin-Ciocalteu method, respectively. The contents of total flavonoid and total anthocyanin of fruit teas was determined by using the UV/Vis spectrophotometric method. The phenolic composition was determined and quantified by using high performance liquid chromatography and photodiode array detection (HPLC-PDA). The highest total phenol content and antioxidant capacity were determined in pomegranate (I). The highest contents of total flavonoid and total anthocyanin were determined in peach (III) and blackberry (I), respectively. Chlorogenic acid, quercetin, myricetin, rutin, rosmarinic acid and ferulic acid were determined in fruit teas. A water temperature of 100 °C was the most effective to extract the highest contents of total phenols, total flavonoids, total anthocyanins and the highest antioxidant capacity in 16 different fruit teas. The purpose of this study was to determine the effect of water temperature on the extraction and quantify the various phenolic compounds in fruit teas by HPLC method for industrial application in producing the extracts.

Disposable biosensor based on platinum nanoparticles-reduced graphene oxide-laccase biocomposite for the determination of total polyphenolic content

A disposable amperometric biosensor was developed for the detection of total polyphenolic compounds from tea infusions. The biosensor was designed by modifying the surface of a carbon screen-printed electrode with platinum nanoparticles and reduced graphene oxide, followed by the laccase drop-casting and stabilization in neutralised 1% Nafion solution. The obtained biosensor was investigated by scanning electron microscopy and electrochemical techniques. It was observed that platinum nanoparticles-reduced graphene oxide composite had synergistic effects on the electron transfer and increased the electroactive surface area of the carbon screen-printed electrode. The constructed analytical tool showed a good linearity in the range 0.2-2 μM for caffeic acid and a limit of detection of 0.09 μM. The value of Michaelis-Menten apparent constant was calculated from the electrochemical version of Lineweaver-Burk equation to be 2.75 μM. This disposable laccase biosensor could be a valuable tool for the estimation of total polyphenolic content from tea infusions.

Polyphenolic content and comparative antioxidant capacity of flavoured black teas

The content of selected flavonoids and phenolic acids of 12 commercial flavoured black tea infusions was determined by high-performance liquid chromatography with tandem mass spectrometry in the negative electrospray ionization mode. Assays for the evaluation of their antioxidant capacity were carried out by cupric ion reducing antioxidant capacity, Folin-Ciocalteu assay, cyclic voltammetry and potentiometry. Flavonoids were predominantly present as glycosides in the studied infusions. Only quercetin as a free aglycone was found at trace levels. Notable amount of naringin and hesperidin was determined in teas with citrus aromas or fruits. These compounds were not found in premium black tea. Two principal groups of the studied teas were found using cluster analysis in relation to the values of their antioxidant activities.

Relationships between black tea consumption and key health indicators in the world: an ecological study

OBJECTIVES

The aim of this study was to investigate potential statistical relationships between black tea consumption and key health indicators in the world. The research question is: Does tea consumption is correlated with one or more epidemiological indicators?

DESIGN

Ecological study using a systematic data-mining approach in which the unit of the analysis is a population of one country.

SETTING

Six variables, black tea consumption data and prevalence data of respiratory diseases, infectious diseases, cancer, cardiovascular diseases and diabetes, have been studied at a global level.

PARTICIPANTS

Data from 50 participating countries in the World Health Survey were investigated. PRIMARY AND SECONDARY OUTCOMES MEASURES: Level of statistical relationships between variables.

RESULTS

Principal component analysis established a very high contribution of the black tea consumption parameter on the third axis (81%). The correlation circle confirmed that the 'black tea' vector was negatively correlated with the diabetes vector and was not correlated with any of the other four health indicators. A linear correlation model then confirmed a significant statistical correlation between high black tea consumption and low diabetes prevalence.

CONCLUSIONS

This innovative study establishes a linear statistical correlation between high black tea consumption and low diabetes prevalence in the world. These results are consistent with biological and physiological studies conducted on the effect of black tea on diabetes and confirm the results of a previous ecological study in Europe. Further epidemiological research and randomised studies are necessary to investigate the causality.