Article

Multivariate effects of Chinese keemun black tea grades (Camellia sinensis var. sinensis) on the phenolic composition, antioxidant, antihemolytic and cytotoxic/cytoprotection activities

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Abstract

The main objectives of the study were to compare the phenolic composition, chemical and biological antioxidant activities, and cytotoxicity towards IMR90, HCT8, and A549 cell lines of eight grades of Chinese keemun black tea (Camellia sinensis var. sinensis) using a statistical approach. No cytotoxic effects were observed on IMR90 normal cells. Our results all together show that the chemical antioxidant capacity of high-grade black teas measured by DPPH, FRAP, and total reducing capacity assays was correspondingly higher than the mean values of low-grade teas and these antioxidant assays were not associated with cytotoxicity towards cancerous cell lines (HCT8 and A549). High grades of Chinese keemun black teas contained higher contents of total phenolics, flavonoids and ortho-diphenols than lower grades and theaflavin-3,3'-di-gallate could only be detected in high black tea grades (T1 and T2). Intermediate-high keemun black tea grades - C1, C3, T1, and T2 - which also had the highest mean values of TPC, flavonoids, o-diphenols, theaflavin-3-gallate, theaflavin-3'-gallate, Fe2+ chelating ability, and chemical antioxidant activity, presented the highest inhibition of Wistar rat's brain oxidation. No clear differentiation and trend were observed between erythrocyte protection and Chinese black tea grades as results clearly showed that intermediate black tea grades (C3 and C4) protected more the human erythrocytes against mechanical stress. Our study shows that although higher Chinese keemun black tea grades (T1 and T2) presented the highest TPC, flavonoids, and chemical antioxidant activity, these in vitro chemical assays were not translated into higher biological activity.

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... In the FRAP assay, the corresponding values of BT was 0.4977. Our results on the antioxidant activity are in-line with those of Zhang et al. [14] for FRAP and DPPH, which indicated black teas presented free-radical scavenging and ferric reducing properties. ...
... Among the polyphenolic compounds, all the catechins showed the strong association with DPPH activity at a statistical significant level (Table S1). Zhang et al. [14] has concluded that the black teas with higher phenolic contents present higher antioxidant. Our results were in agreement with the data exhibited by Zhang et al. [14], which presented a relative strong correlation between phenolic content with the chemical antioxidant activity. ...
... Zhang et al. [14] has concluded that the black teas with higher phenolic contents present higher antioxidant. Our results were in agreement with the data exhibited by Zhang et al. [14], which presented a relative strong correlation between phenolic content with the chemical antioxidant activity. No trend was established between amino acids and DPPH, but L-theanine expressed a high correlation to DPPH. ...
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... Several substances such as butadiene, rutin, and flavonoids can stabilize erythrocyte membranes that undergo hypotonic hemolysis. It is also associated with the anti-inflammatory activity of triterpene compounds against cell membranes [124][125][126]. Table 9 compiles the antihemolytic activities in several edible flowers. ...
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... The fluorescence intensity was measured at an excitation wavelength of 485 nm and at an emission wavelength of 538 nm. The data were expressed as percentage of fluorescence intensity [33]. ...
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... It is also an important cash crop in Qingyuan City, Guangdong Province, China, and dominates local agriculture as a characteristic industry [3,4]. Tea polyphenols, caffeine, free amino acids, total sugars, and other tea components have anti-oxidative, anti-cancerous, and anti-obesity characteristics, lower blood pressure, and prevent cardiovascular diseases [5][6][7][8][9][10]. In addition, the content of these components determines the qualities of taste, aroma, and appearance of tea [11], which, in turn, determine the tea quality and value [12]. ...
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The evaluation of Chinese dianhong black tea (CDBT) grades was an important indicator to ensure its quality. A handheld spectroscopy system combined with chemometrics was utilized to assess CDBT from eight grades. Both variables selection methods, namely genetic algorithm (GA) and successive projections algorithm (SPA), were employed to acquire the feature variables of each sample spectrum. A partial least‐squares discriminant analysis (PLS‐DA) and support vector machine (SVM) algorithms were applied for the establishment of the grading discrimination models based on near‐infrared spectroscopy (NIRS). Comparisons of the portable and benchtop NIRS systems were implemented to obtain the optimal discriminant models. Experimental results showed that GA‐SVM models by the handheld sensors yielded the best predictive performance with the correct discriminant rate (CDR) of 98.75% and 100% in the training set and prediction set, respectively. This study demonstrated that the handheld system combined with a suitable chemometric and feature information selection method could successfully be used for the rapid and efficient discrimination of CDBT rankings. It was promising to establish a specific economical portable NIRS sensor for in situ quality assurance of CDBT grades. The handheld near‐infrared spectroscopy (NIRS) system combined with a suitable chemometric and feature information selection method could successfully be used for the rapid and efficient discrimination of Chinese dianhong black tea (CDBT) grades. It was promising to establish a specific economical portable NIRS sensor for in situ quality assurance of CDBT grades.
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BACKGROUND Grading represents an essential criterion for the quality assurance of black tea. The main objectives of the study were to develop a highly robust model for Chinese black tea of seven grades based on cognitive spectroscopy. RESULTS Cognitive spectroscopy was proposed to combine near‐infrared spectroscopy with machine learning and evolutionary algorithms, selected feature information from complex spectral data and showed the best results without human intervention. The NIRS measuring system was used to obtain the spectra of Chinese black tea samples of seven grades. The spectra acquired were preprocessed by standard normal variate transformation (SNV), multiplicative scatter correction (MSC) and min/max normalization (MIN/MAX), and the optimal pretreating method was implemented using principal component analysis combined with linear discriminant analysis algorithm. Three feature selection evolutionary algorithms, which were a genetic algorithm (GA), simulated annealing (SA) and particle swarm optimization (PSO), were compared to search the best preprocessed characteristic wavelengths. Cognitive models of Chinese black tea ranks were constructed using extreme learning machine (ELM), K‐nearest neighbor (KNN) and support vector machine (SVM) methods based on the selected characteristic variables. Experimental results revealed that the PSO‐SVM model showed the best predictive performance with the correlation coefficients of prediction set (Rp) of 0.9838, the root mean square error of prediction (RMSEP) of 0.2460, and the correct discriminant rate (CDR) of 98.70%. The extracted feature wavelengths were only occupying 0.18% of the origin. CONCLUSION The overall results demonstrated that cognitive spectroscopy could be utilized as a rapid strategy to identify Chinese black tea grades. This article is protected by copyright. All rights reserved.
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Parasitic diseases have attracted worldwide attention of their consequent impact on mortality and morbidity. Accordingly, several plants have been screened for antiparasitic activity aiming to create new alternatives for treatment. These diseases have been neglected and have not attracted worldwide attention (nowadays), the health concerns are focused in chronic diseases, but it is necessary to focus on parasitic diseases and look for prophylactic alternatives, such as plant extracts. Although camu-camu (Myrciaria dubia) seeds are a rich source of antioxidant antimutagenic, cytotoxic, anti-inflammatory, antimicrobial, antihypertensive and neuroprotective compounds, nothing is known about their antiparasitic effects. Thus, in the present study we aimed to evaluate five extracts of camu-camu seeds (100% water, 100% ethyl alcohol, 50% water + 50% ethyl alcohol, 25% water + 75% ethyl alcohol, and 75% water + 25% ethyl alcohol) in relation to their in vitro antimalarial, antischistosomicidal, leishmanicidal and anti-hemolytic effects. The extracts exhibited antischistosomicidal (ED50 values from 418.4 to >1000.0 µg/mL) and antimalarial activities (IC50 values from 24.2 to 240.8 µg/mL) for both W2 and 3D7 strains in all intra-erythrocytic stages. Correlation analysis showed that the toxic effects may mainly be attributed to methylvescalagin (r= -0.548 to -0.951, p<0.05) and 2,4-dihydroxybenzoic acid (r= -0.612 to -0.917, p<0.05) contents. Moreover, the anti-hemolytic effect was associated to methylvescalagin (r= -0.597, p<0.05). No toxic effects were observed for leishmaniasis and IMR90 normal cells. Herein, methylvescalagin was the bioactive compound of greatest interest once it presented simultaneous relation with antiparasitic and anti-hemolytic activities.
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Perfluorodecanoic acid (PFDA) is a highly toxic food contaminant that is extensively used in food applications as surface antifouling agent. In this present study, we aimed to assess whether green tea polyphenols (GTPs) and epigallocatechin-3-gallate (EGCG) exert protective effects against PFDA-induced liver damage and inflammation in mice. A mouse model to evaluate liver toxicity was established by giving mice drinking water containing different concentrations of PFDA. GTPs or EGCG (0.32%, w/v) were co-administered to mice exposed to PFDA in drinking water. Overall, GTPs and EGCG extended the survival time and inhibited weight loss among mice who received a lower dose of PFDA. Moreover, GTPs and EGCG ameliorated hepatic oxidative stress, cell apoptosis, necrosis, steatosis, edema, and degeneration, reduced hepatic inflammation and NLRP3 inflammasome activation caused by a moderate dose of PFDA. Taken together, these results show that GTPs or EGCG (or green tea intake) supplements can be beneficial for people exposed to PFDA.
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Withering process is one of the most crucial steps in Keemun black tea (KBT) manufacturing, which is the foundation of quality formation. This study investigated the effects of conventional static withering and innovative dynamic withering on the volatile and nonvolatile compounds of KBT. Overall, 79 volatile compounds were identified in five tea samples (FL: fresh leaf for control; SW7h, SW15h: leaves of static withering 7 h and 15 h; and DW7h, DW15h: leaves of dynamic withering 7 h and 15 h) by using HS-SPME/GC-MS. Orthogonal projections to latent structures discriminant analysis (OPLS-DA) were used to classify samples, and 36 key markers in volatile compounds were selected. Quantitative descriptive analysis (QDA) of KBT aroma showed that in dynamic withering, dense, floral and fruity aroma were significantly improved. The 14 odor-active compounds were speculated as the cause of QDA differences in aroma between dynamic and static withering. Meanwhile, theaflavins were generated and accumulated earlier in dynamic withering. Notably, the contents of aspartic acid, serine, glycine, arginine, cysteine, methionine, lysine, isoleucine, and leucine significantly increased after dynamic withering. Our study provides a comparative investigation metabolite of dynamic and static withering processes, offering innovative dynamic withering methods to improve the quality of KBT.
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To explore the impact of harvest season in white tea, high-performance liquid chromatography (HPLC) and amino acid analyzer were developed for the determinations of 17 phenolic compounds, 3 purine alkaloids, 19 amino acids, γ-aminobutyric acid (GABA) and 4 main quality components in 18 Bai mudan sub-type of Xinyang white teas harvested in spring, summer and autumn seasons, respectively. Additionally, the in vitro antioxidant capacity was evaluated by 5 various assays. Principal component analysis (PCA), hierarchical cluster analysis (HCA) and partial least squares-discriminant analysis (PLS-DA) could completely classify these white teas by the harvest season, and indicated its profound impact on chemical composition in white tea. 14 Characteristic compounds (VIP ≥1.0), such as (−)-epigallocatechin (EGC), gallic acid, caffeine, l-theanine, conduced to identify the harvest season of white tea. Through comparison, the spring tea was observed to possess the highest amino acids, catechins contents and in vitro antioxidant capacity. (−)-Epicatechin (EC), EGC, (−)-epicatechin gallate (ECG) and (−)-epigallocatechin gallate (EGCG) were considered as the major antioxidants in white tea due to their highly significantly (p < 0.01) positive correlations. Overall, the research results provided support for the identification of harvest season in white tea.
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The aims of this study were to quantify and optimize the extraction of total phenolic content (TPC), total flavonoids (TF) and antioxidant activity (AA) of aqueous pu-erh (Camellia sinensis var. assamica) extracts, as well as to compare the optimized pu-erh tea extract (OPT) with toasted mate (Ilex paraguariensis), black and green (Camellia sinensis) teas. The optimization process increased the TPC and the ferric reducing antioxidant power (FRAP). The results showed that the green tea extract presented the highest values for TPC and antioxidant capacity. The pasteurized OPT showed lower TPC and TF, and higher FRAP, DPPH and Cu2+ chelating ability compared to the non-pasteurized OPT. The lyophilized OPT showed inhibition of lipid peroxidation in Wistar rat brain homogenate and displayed antibiofilm activity against Enterococcus faecalis ATCC 25212 and 19433, and Staphylococcus aureus ATCC 25923. Additionally, lyophilized OPT presented cytotoxic and antiproliferative effects against tumor cell lines (Caco-2, A549 and HepG2), inhibited the production of reactive oxygen species in A549 and IMR90 cells, and presented antihemolytic activity in human erythrocytes. The lyophilized OPT inhibited α-glucosidase (IC50 = 47.0 µg/mL) and α-amylase at 30.0 mg/mL. The main compounds detected in OPT were gallic acid, caffeine and theobromine.
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Food companies should comply with the requirements of a zero‐waste concept to adapt to the circular economy requirements. In fruit companies, usually seeds are discarded without proper utilization and extraction of the bioactive compounds. Fruit seeds are sources of chemical compounds that can be extracted, studied, and applied in high value‐added products. Thus, in this work the experimental conditions for the water extraction of phenolic compounds from camu‐camu (Myrciaria dubia ) seed coat were optimized using a central composite deign and the desirability function. Total phenolic content (TPC), and condensed tannins (CT), DPPH radical scavenging activity, ferric reducing antioxidant capacity (FRAP), Folin‐Ciocalteu reducing capacity (FCRC), and Cu²⁺chelating ability were assessed. Seed coat extracted for 51.1 min using a 1:34.1 solid:liquid ratio of was the optimal condition to extract 6,242 mg gallic acid equivalent (GAE)/100 g of TPC and 695 mg catechi0n equivalent (CE)/100 g of CT. The optimized extract displayed free‐radical scavenging activity, reducing properties and ability to chelate Cu²⁺, and inhibited the growth of Listeria monocytogenes , Pseudomonas aeruginosa , Salmonella Typhimurium, Salmonella Enteritidis, Bacillus cereus , and Staphylococcus aureus . Additionally, the lyophilized water extract inhibited the in vitro activity of α‐amylase, α‐glucosidase, and angiotensin converting enzyme and showed cytotoxic effects towards Caco‐2, A549, and HepG2 cancer cells, but no cytotoxicity towards IMR90 cells. Vescalagin, castalagin, and 3,4‐dihydroxybenzoic acid were the major phenolic compounds identified in the optimized extract. In conclusion, the optimized camu‐camu seed coat water extract is a rich source of phenolic compounds with antioxidant, antidiabetic, antihypertensive, and antiproliferative effects. Practical Application Camu‐camu fruit pulp and seeds have been studied for their phenolic composition and bioactivity. However, seeds are usually discarded and represent an environmental problem in South American countries. We presented a methodological overview on the extraction optimization of the phenolic compounds from camu‐camu seed coat and studied the bioactivity of the optimized extract using chemical, enzymatic, and cell‐based experiments. Results can be used by camu‐camu processors to obtain a phenolic‐rich extract for industrial applications, without any further processing.
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The main objectives of the study are to understand and explore critical feature wavelengths of the obtained near-infrared (NIR) data relating to dianhong black tea quality categories, we propose a multi-variable selection strategy based on the variable space optimization from big to small which is the kernel idea of a variable combination of the improved genetic algorithm (IGA) and particle swarm optimization (PSO) in this study. A rapid description based on the NIR technology is implemented to assess black tea tenderness and rankings. First, 700 standard samples from dianhong black tea of seven quality classes are scanned using a NIR system. The raw spectra acquired are preprocessed by Savitzky-Golay (SG) filtering coupled with standard normal variate transformation (SNV). Then, the multi-variable selection algorithm (IGA-PSO) is applied to compare with the single method (the IGA and PSO) and search the optimal characteristic wavelengths. Finally, the identification models are developed using a decision tree (DT), partial least-squares discriminant analysis (PLS-DA), and support vector machine (SVM) based on different kernel functions combined with the effective features from the above variables screening paths for the discrimination of black tea quality. The results show that the IGA-PSO-SVM model with a radial basis function achieves the best predictive results with the correct discriminant rate (CDR) of 95.28% based on selected four characteristic variables in the prediction process. The overall results demonstrate that NIR combined with a multi-variable selection method can constitute a potential tool to understand the most important features involved in the evaluation of dianhong black tea quality helping the instrument manufacturers to achieve the development of low-cost and handheld NIR sensors.
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The antimicrobial and antileukemic effect of a purified fraction of flavonoids from the leaves of Camellia sinensis was evaluated. An extraction yield of 9.77 mg.g-1 total flavonoids was recovered through a pressurized liquid extraction associated with solid-phase extraction. This fraction was tested against pathogenic microorganisms (Staphylococcus, Salmonella, and Enterococcus), considering the minimum inhibitory concentration. In addition, the human monocyte cell line THP-1, derived from a patient with acute monocytic leukemia, was used for the antitumor assay. The results show that the flavonoid-rich fraction obtained by coupling a Pressurized Liquids Extraction in-line with a Solid Phase Extraction (PLE-SPE) has a high antimicrobial effect and resulted in cell cycle blockage G0 / G1, increased DNA fragmentation, and altered leukemic cell morphology. These results suggest that a flavonoid-rich fraction obtained from Camellia sinensis can be applied as potential adjuvants in chemotherapy treatment to mitigate the side effects caused by chemotherapy or even as a supplement to cancer therapy.
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A large number of plants produce secondary metabolites known as allelochemicals that are capable of inhibiting the germination of competitive species. This process is known as allelopathy and is mediated by several classes of chemicals, among which phenolic compounds are the most frequent. Thus, plant allelochemicals can be used to control weeds in agricultural systems. In the present work, we analyzed the phenolic profile and phytotoxic potential of different extracts (pure water or water: ethanol 50:50) from Scrophulariastriata plants that were collected from two ecological regions in Iran (Pahleh and Lizan). The total polyphenolic content (TPC), as evaluated by the Folin-Ciocolteau method, ranged from 28.3 mg/g in the aqueous extract obtained from the Lizan ecotype to 39.6 mg/g in the hydroalcoholic extract obtained from the Pahleh ecotype. Moreover, HPLC analysis was aimed at determining the content of eight phenolic compounds, namely eugenol, rosmarinic acid, hesperetin, hesperedin, trans-ferulic acid, vanillin, and caffeic acid. According to the results, rosmarinic acid appeared to be the most abundant component. The phytotoxic activities of S.striata extracts were examined on the seed germination of a crop species, Lepidium sativum, and two weeds, Chenopodium album and Malva sylvestris. All extracts showed inhibitory effects on these species. The efficiency of these inhibitory effects depended on the type of plant species, origin, and concentration of extract. The highest phytotoxic activity was caused by approximately 1% concentration of extract. The most susceptible weed was M. sylvestris. The extracts that were obtained from the Pahleh ecotype, notably the hydroalcoholic ones, showed higher phytotoxicity against L. sativum, C. album and M. sylvestris. These results encourage further studies to support the use of S. striata as a source of bioherbicides.
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Ripened Pu-erh tea is a traditional microbial-fermented tea with multiple beneficial effects and the genus Aspergillus were considered as the dominant fungi. In this study, six Aspergillus and one Penicillium fungi, abbreviated as AniPT1, AsyPT2, ApaPT3, AsePT4, PmaPT5, AusPT6 and AtaPT7, were inoculated into sun-dried green tea-leaves for the microbial fermentation. Based on 42 chemical components belonging to several classes as polyphenols, amino acids and purine alkaloids, PCA and HCA revealed the significant differences in tea-leaves microbial fermentation of seven tea-derived fungi. Most of catechins, flavonoids and free amino acids were decreased highly significantly (p < 0.001), while theabrownins, theaflavins and gallic acid contents were increased highly significantly (p < 0.001) in all microbial fermentation. Additionally, several tea-derived fungi contributed to the accumulation of (+)-catechin, (-)-epicatechin, kaempferol, myricetin, theophylline, L-methionine, L-tryptophan, L-cysteine, L-histidine and γ-aminobutyric acid, and the improvement of antioxidant activity in tea-leaves after inoculated fermentation. Particularly, AsyPT2 converted caffeine into theophylline mainly. The bivariate correlation analysis confirmed the extremely significantly (p < 0.001) positive correction of gallic acid and kaempferol to antioxidant activity in fermented tea-leaves. This study provided reference for the application of tea-derived fungi in ripened Pu-erh tea.
Chapter
Phenolic compounds have demonstrated several in vitro beneficial properties by acting as antioxidant and pro-oxidant agents. This chapter approaches the relationship among oxidative stress, cancer, phenolic compounds and antiproliferative activity. Moreover, it discusses in vitro techniques and their biological applications, regarding cell viability and intracellular measure of reactive oxygen assays. The in vitro methods are important tools for screening and understanding the pathways involved on antiproliferative and antioxidant/pro-oxidant effects of phenolic compounds. These findings open avenues for the development of innovative food, chemical structures, technological applications and future perspectives in this research field.
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Ora-pro-nobis (Pereskia aculeata Miller) is a non-conventional food plant common in Brazil. The objective of this study was to optimize the extraction of bioactive phenolic compounds from ora-pro-nobis leaves by employing solvent mixtures. Ten extracts were obtained with water, ethanol, acetone, and their binary and ternary mixtures, evaluating the chemical composition, antioxidant activity and bioactivities in vitro. The response surface methodology was applied to model the results and calculate the optimal solvent composition, which is 60% water, 40% ethanol and 0% acetone. The optimized extract is rich in phenolic compounds (64 mg GAE/g) and proteins (823 mg/g) and presents antioxidant activity (in intracellular media as well) and inhibits lipid peroxidation (32%) along with h ypotonic hemolysis (H50 = 0.339%), it does not present toxicity in vitro against cancer and normal cells. This is the first report of chicoric, caffeoyl-hexaric and coumaroyl-hexaric acids and some glycosylate derivatives of flavonols in ora-pro-nobis leaves.
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The rapid and scientific method for monitoring the quality of black tea fermentation is of great significance to the quality control of black tea production. This study proposed a novel method for evaluating the fermentation quality of black tea by using hyperspectral imaging technology with self-assembled nanoporphyrin (N-TPP) dyes, which were used as aroma capture probes in the black tea fermentation process. Scanning electron microscopy and ultraviolet–visible spectroscopy were performed to characterize the N-TPP. Then, the results of the colorimetric sensor array (conventional camera color method) and the proposed hyperspectral methods were compared. Finally, the hyperspectral information of N-TPP with higher sensitivity was collected, and the qualitative models of evaluating black tea fermentation quality were established using support vector machine (SVM), extreme learning machine, and linear discriminant analysis. Among these models, the SVM model exhibited the highest discriminant accuracy. The accuracy of the SVM model based on the hyperspectral information of the self-assembled N-TPP array was 98.85%, which was considerably higher than that (68.97%) of the SVM model based on the color information of the porphyrin array. The results revealed that the proposed method can effectively improve the monitoring accuracy of black tea fermentation quality.
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Hydroxycinnamoyl quinic acids are important phenolic acids in tea, particularly fermented teas. However, there have been fewer studies that have confirmed their taste properties. The aim of this study was to investigate the astringent compounds in Keemun congou black tea (KBT) using a combination of mass spectrometry, turbidity analysis, and sensory evaluation. Turbidity analysis determined that p-coumaroylquinic acids were the astringent contributing compounds in KBT. Moreover, the separated compound D16 was identified as trans-4-O-p-coumaroylquinic acid (trans-4-O-pCoQA) by nuclear magnetic resonance spectroscopy and first confirmed to be the astringent contributing compound in KBT by sensory evaluation. Its astringent threshold concentration was tested to be 38 µM. The trans-4-O-pCoQA content in eight KBT samples of various grades ranged from 40.20 ± 0.15∼65.53 ± 0.22 µM. Turbidity analysis combined with sensory evaluation could be a powerful tool for identifying critical compounds responsible for the astringent taste.
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Authentication of food geographic origin improves traceability, quality control, and brand protection. In this study, elemental fingerprints of 27 mineral elements from 104 samples of Keemun black tea from its core (Qimen) and traditional (Dongzhi and Guichi) production regions were analyzed using inductively coupled plasma - mass spectrometry (ICP-MS) coupled with chemometrics to determine the narrow-geographic origin. Variance analysis revealed that Keemun black teas from different regions had their own elemental fingerprints. Although the orthogonal partial least squares-discriminant analysis (OPLS-DA) presented a satisfactory performance, the discrimination of teas based on linear discriminant analysis (LDA) had 100% accuracy and 99% cross-validation, and thus outperformed OPLS-DA. Similarly, support vector machines was able to differentiate 100% of teas from all geographical origins. The results indicate that elemental fingerprints coupled with chemometrics can be used to authenticate the narrow-geographic origins of Keemun black teas.
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Black tea natural dye is usually recognised to contain functional colouring matters, which has long been used for the coloration of textile materials. However, due to poor binding and colour fastness, a large number of mordants have been used in the dyeing process, leading to serious environmental problems. To address these issues, we have developed a no-mordant pad-dry dyeing strategy for dyeing flax fabrics with functional components of Keemun black tea (KBT) waste. The dyed flax fabrics showed outstanding colour fastness to perspiration, rubbing, and washing. Moreover, increasing the KBT extract concentration, dyeing time, and temperature, and decreasing the pH level could significantly enhance the K/S values. Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) results revealed that theaflavin compounds dyed thoroughly the fibres successfully through hydrogen bonding force, and the theaflavin compounds could be bound to fibres stably through van der Waals and hydrogen bonding forces based on Independent Gradient Model (IGM) calculations. In addition, the dyed flax fabrics possessed good ultraviolet (UV) protection and antibacterial performance. This work proposes novel approaches for the reuse of KBT waste and the simultaneous coloration and functionalisation of flax fabric.
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Rapid monitoring of fermentation quality has been the key to realizing the intelligent processing of black tea. In our study, mixing ratios, sensing array components and reaction times were optimized before an optimal solution phase colorimetric sensor array was constructed. The characteristic spectral information of the array was obtained by UV-visible spectroscopy and subsequently combined with machine learning algorithms to construct a black tea fermentation quality evaluation model. The competitive adaptive reweighting algorithms (CARS)-support vector machine model discriminated the black tea fermentation degree with 100% accuracy. For quantification of catechins and four theaflavins (TF, TFDG, TF-3-G, and TF-3'-G), the correlation coefficients of the CARS least square support vector machine model prediction set were 0.91, 0.86, 0.76, 0.72 and 0.79, respectively. The results obtained within 2 minutes enabled accurate monitoring of the fermentation quality of black tea, which provides a new method and idea for intelligent black tea processing.
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Phenolic acids, including benzoic acid and hydroxycinnamic acid derivatives, are the main compounds of black tea. An efficient and accurate analytical method to quantify ten phenolic acids was established and validated by ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-QQQ-MS/MS). The chemical shifts during the processing of Keemun black tea were analyzed and the phenolic acids were quantified. Compared with fresh tea leaves, after processing, the contents of free phenolic acids, including gallic acid, salicylic acid, p-coumaric acid, and ferulic acid, increased markedly. Still, the contents of soluble conjugated phenolic acids, including p-coumaroylquinic acid isomers and chlorogenic acid isomers, decreased. Furthermore, the total contents of lignin, and insoluble bonded phenolic acids decreased. The adduct of (-)-epigallocatechin gallate and 3-caffeoylquinic acid was detected in tea samples, and its content increased highly after rolling. The developed and validated analytical method can be used to monitor the manufacturing process of black tea.
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Tea cream is a kind of turbid substance commonly existing in tea infusion and tea beverage upon cooling. Herein, a comparative study was conducted on the supernatant and cream from black tea infusion in terms of antioxidant, anti-inflammatory and enzyme inhibitory activities, and chemical composition. Ultraviolet-visible (UV-vis) spectrometry and high-performance liquid chromatography (HPLC) analysis showed that the contents of protein, polyphenols, theaflavins, thearubigins, theabrownins, and caffeine in cream were significantly higher than those in the supernatant. The contents of Al, Ca, Cu, and Fe elements in cream were higher than those in the supernatant. However, higher levels of monosaccharides and free amino acids were detected in the supernatant compared with cream. The ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) based metabolomics analysis revealed that the main marker compounds between the supernatant and the cream were organic acids, phenolic acids, and flavan-3-ols and their oxidation products, flavonol glycosides and amino acids. The cream showed better antioxidant and anti-inflammatory, as well as α-amylase and α-glycosidase inhibitory activities than the supernatant, because it contained higher contents of polyphenols than the supernatant. The present study expanded the new vision towards the cream of black tea infusion.
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Tea quality is generally assessed through panel sensory evaluation, which requires elaborate sample preparation steps. Here, a novel and low-cost evaluation method of using smartphone imaging coupled with micro-near-infrared (NIR) spectrometer based on digital light processing is proposed to classify the quality grades of Keemun black tea. RGB color information was obtained by Image J software, eight texture characteristics, including scheme, contrast, dissimilarity, entropy, correlation, second moment and variance, and homogeneity were obtained by ENVI software based on co - occurrence method from smartphone images, and spectral data were preprocessed with standard normal variate. A principal component analysis (PCA)–support vector machine (SVM) model was established to analyze the color, texture, and spectral data. Low-level and middle-level fusion strategies were introduced for analyzing the fusion data. The results indicated that the accuracy of the SVM model on mid-level data fusion (100.00%, 94.29% for calibration set and prediction set, respectively) was higher than that obtained for separate color (97.14%, 88.57%), texture (84.29%, 60%), spectrum (74.29%, 68.57%) evaluation, or low-level data fusion (88.57%, 82.86%). The best SVM model yielded satisfactory performance with 94.29% accuracy for the prediction sets. These results suggested that smartphone imaging coupled with micro-NIR spectroscopy is an effective and low-cost tool for evaluating tea quality.
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The antioxidant and anticandidal activities of leaves obtained fromCamellia sinensis by non-fermentation (green and white teas), semi-fermentation (red tea) and fermentation method (black tea) were investigated. It was evaluated the total phenolic content by Folin-Ciocalteau assay; antioxidant capacities were evaluated in vitro using DPPH and ABTS radicals, hypochlorous acid and superoxide anion scavenger assays, induced hemolysis, lipid peroxidation by conjugated diene formation and myeloperoxidase activity. Anticandidal activity was performed on three strains of Candida spp. The results showed that non-fermented teas have a higher concentration of phenolic compounds, and then presented the best inhibitory activity of AAPH-induced hemolysis, the best inhibition of conjugated diene formation and more pronounced antioxidant activity in all tests. The highest anticandidal activity was obtained from fermented tea, followed by non-fermented tea. These results indicate that the antioxidant activity demonstrated has no direct relation with the anticandidal activity.
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In vitro cell proliferation, cell cycle arrest and induction of apoptosis were investigated, using three human head and neck squamous cell carcinoma (HNSCC) cell lines (OSCC-3, SCC-61, and SQ-20B). Aqueous extracts of Camellia sinensis, Ilex paraguariensis, and Ardisia compressa were tested and (−) epigallocatechin-3-gallate (EGCG) was used for comparison. For EGCG the IC50 values were between 80 and 166μM and for the extracts among 75 and 505μM eq. (+) catechin, with C. sinensis demonstrating dominant cytotoxicity. There was not a correlation between antioxidant capacity and cytotoxicity. Flow cytometry analysis revealed similarities in response for EGCG and C. sinensis. The A. compressa extract altered DNA distribution (P<0.05) and was the most effective in induction of apoptosis via caspases (P<0.05). Not all HNSCC cells tested responded to the same preventive agents. The fact that A. compressa inhibits HNSCC cell proliferation makes this aqueous extract a potential source of chemopreventive agents.
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Berries and berry production are an important economic factor. Berries contain nutritive components but also pertinent non-nutritive bioactives like phenolic-type phytochemicals. It is well accepted that consumption of bioactives from berries prevent or delay chronic and degenerative diseases. Therefore, a thorough evaluation of bioactive compounds is of utmost interest to assess berry quality. The most accepted photometric methods for the determination of bioactive compounds are presented for conventional cuvette and modern microplate applications. All methods are precisely described and advantages of the microplate methods are discussed. Cuvette and microplate methods show slightly different sensitivity and limits of detection depending on concentrations used for reagents and standard compounds. In general, with microplate methods reagents can be saved up to 12-fold and less time to perform the analyses is needed (up to factor 33). Applicability of all the methods has been shown with selected berry juices. Among all analysed commercial juices, blueberry juice had the highest content of total polyphenols, flavonoids, proanthocyanidins, while the lowest content was observed in pomegranate juice. Blueberry juice had also the highest antioxidant capacity measured by TEAC by ABTS, FRAP and ORAC method when compared to the cranberry, açai, goji and pomegranate juice.
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The research compared antidiabetic activity of snake fruit Kombucha, black tea Kombucha and metformin in streptozotocin-induced diabetic rats. Snake fruit Kombucha, black tea Kombucha and metformin were orally administered to the diabetic rats daily during a 28-day experiment. Fasting plasma glucose (FPG) levels, superoxide dismutase (SOD) activities, malondialdehyde (MDA) levels and lipid profiles (total triglyceride, total cholesterol, LDL-cholesterol and HDL-cholesterol) of the blood plasma were investigated. Pancreas immunohistochemical study and β-cells quantification were also conducted. The products significantly (p < 0.05) reduced fasting plasma glucose levels (67–76%) and improved oxidative stress indices and lipid profiles. From immunohistochemical staining of pancreatic tissues, pancreatic β-cells were also improved in the diabetic rats by the products. The snake fruit Kombucha compared with the metformin but better than the black tea Kombucha as a diabetes therapy agent.
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This review summarises 25 years of investigations on antioxidants research in foods and biological fluids and critically analyses the merits and limitations of using the total antioxidant capacity (TAC) measurement in the metabolomic era. An enormous bulk of knowledge was produced on the antioxidant capacity of foods and large TAC databases were developed. A direct link between a food TAC value and any health benefit is erroneous and had led to several cases of consumers’ deception. However, the striking epidemiological evidence associating a high dietary TAC with some disease prevention and the availability of well‐done TAC databases deserve attention and must be taken into account to establish the usefulness of measuring TAC in both foods and biological samples. The in vivo measure of TAC, usually performed in plasma, is influenced by many external factors, such as dietary habits, environmental and behavioural factors, that are integrated towards a homeostatic control by fine physiological mechanisms with a high inter‐individual variability. Therefore, plasma TAC cannot be considered a unique biomarker of individual antioxidant status. However, the combined evaluation of plasma TAC with known markers of disease, individual metabolism, inflammation, and genetics as well as with markers of gut microbiota composition and activity may lead identifying populations that are more responsive to foods/diets TAC. In this framework, appropriate use of TAC measurement both in food and in vivo can still provide support for the interpretation of complex phenomena and be a tool for sample screening to take quick decision to orientate deeper research investigations. This article is protected by copyright. All rights reserved.
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Bioactive compounds are associated with decreased in oxidative stress, inflammation and consequently in risk of non-communicable diseases. Polyphenols have demonstrated potential biological activity in many diseases, such as cancer, diabetes, inflammation, obesity-related diseases, neurodegenerative disorders, bacterial and viral infections or cardiovascular diseases due to antioxidant and prooxidant capacities. Indeed, these compounds may still have many applications in the pharmaceutical and food industries, with potential functional properties in vivo. This review article discusses the relationship between polyphenols, their antiproliferative effects and the mechanisms involved, oxidative stress, technological applications and future perspectives in this research field.
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Sea buckthorn (Hippophaë rhamnoides, SB) leaves contain wide-ranging bioactive compounds. Processing of the leaves into beverages/food presents great potential for supporting human health. The research aimed to investigate the impact of different processing methods on phenolic compounds and antioxidant activities of tea-type infusions prepared from SB leaves. Leaves of two SB cultivars, ‘Terhi’ and ‘Tytti’, were processed with different methods commonly used for tea processing. Phenolic compounds in the infusions were analyzed with High-Performance Liquid Chromatography-Diode-Array Detection and High-Performance Liquid Chromatography Electrospray Ionization-Tandem Mass Spectrometry. Isorhamnetin-3-O-glucoside-7-O-rhamnoside, isorhamnetin-3-O-rutinoside and kaempferol-3-O-hexoside-7-O-rhamnoside were the three major flavonol glycosides, stachyurin and casuarinin were the most abundant ellagitannins. The infusions of ‘Tytti’ contained more total phenolics than those of ‘Terhi’ (p < 0.05). High temperature processing resulted in higher content of total phenolics and ellagitannins in the infusions compared with low temperatures (p < 0.05). Thermal processing decreased the antioxidant activities of the infusions.
Article
Camu-camu (Myrciaria dubia) pulp, seeds, and skin are widely known because of their nutritional properties. However, the seed coat has never been studied as a source of bioactive compounds. Herein, we characterized the phenolic composition, the antioxidant activity, and inhibition of angiotensin-converting enzyme (ACE) of three different extracts (water, propanone, and ethanol) from this residue and assessed the structure-activity using bivariate and multivariate statistical approaches. Phenolic acids and flavonoids were quantified by highperformance liquid chromatography while the ferric reducing antioxidant power (FRAP), inhibition of lipid peroxidation using egg yolk and Wistar rat brain, scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH*) radical, Folin-Ciocalteu reducing capacity (FCRC), and the inhibition of angiotensin-converting enzyme (ACE) by the extracts were also analyzed. t-Resveratrol was found in camu-camu seed coat for the first time. The aqueous extract had the highest total phenolic content, FRAP, DPPH*, FCRC, and inhibition of lipid oxidation using both chemical and biological assays, while the propanone extract showed the opposite behavior but it presented higher in vitro antihypertensive activity. The ethanolic extract exhibited intermediate values for the responses. The association between chemical composition and the functional properties of the camu-camu seed coat extracts were revealed using correlation analysis and principal component analysis.
Article
This study aimed to optimise the experimental conditions of extraction of the phytochemical compounds and functional properties of Centaurea cyanus petals. The following parameters were determined: the chemical composition (LC-ESI-MS/MS), the effects of pH on the stability and antioxidant activity of anthocyanins, the inhibition of lipid peroxidation, antioxidant activity, anti-hemolytic activity, antimicrobial, anti-hypertensive, and cytotoxic/cytoprotective effect, and the measurements of intracellular reactive oxygen species. Results showed that the temperature and time influenced (p ≤ 0.05) the content of flavonoids, anthocyanins, and FRAP. Only the temperature influenced the total phenolic content, non-anthocyanin flavonoids, and antioxidant activity (DPPH). The statistical approach made it possible to obtain the optimised experimental extraction conditions to increase the level of bioactive compounds. Chlorogenic, caffeic, ferulic, and p-coumaric acids, isoquercitrin, and coumarin were identified as the major compounds in the optimised extract. The optimised extract presented anti-hemolytic and anti-hypertensive activity in vitro, in addition to showing stability and reversibility of anthocyanins and antioxidant activity with pH variation. The C. cyanus extract exhibited high IC50 and GI50 (>900 μg/mL) values for all cell lines, meaning low cytotoxicity. Based on the stress oxidative assay, the extract exhibited pro-oxidant action (10-100 μg/mL) but did not cause damage or cell death.
Article
As many studies are exploring the association between ingestion of bioactive compounds and decreased risk of non-communicable diseases, the scientific community continues to show considerable interest in these compounds. In addition, as many non-nutrients with putative health benefits are reducing agents, hydrogen donors, singlet oxygen quenchers or metal chelators, measurement of antioxidant activity using in vitro assays has become very popular over recent decades. Measuring concentrations of total phenolics, flavonoids, and other compound (sub)classes using UV/Vis spectrophotometry offers a rapid chemical index, but chromatographic techniques are necessary to establish structure-activity. For bioactive purposes, in vivo models are required or, at the very least, methods that employ distinct mechanisms of action (i.e., single electron transfer, transition metal chelating ability, and hydrogen atom transfer). In this regard, better understanding and application of in vitro screening methods should help design of future research studies on ‘bioactive compounds’.
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A statistical optimization study was conducted to obtain a tea containing fermented rooibos (Aspalathus linearis), white tea (Camellia sinensis var. sinensis), and roasted mate (Ilex paraguariensis). An optimal combination of these species was proposed. This optimized tea inhibited 64% the lipoperoxidation in vitro and presented a high phenolic content, especially kaempferol, (+)-catechin, (−)-epicatechin, rutin, (−)-epigallocatechin, and (−)-epicatechin-2-O-gallate. Indeed, the antioxidant effect was confirmed by decreasing 30% the reactive oxygen species generation in human hepatoma carcinoma cells (HepG2, 100 and 240 µg/mL). In the cell viability assay, the GI50 for human colorectal adenocarcinoma epithelial cells (Caco-2) was about 547 µg/mL and 481 µg/mL for HepG2. The pasteurization process (65 °C/30 min) did not affect the total phenolic content and antioxidant activity of the optimized tea formulation. The sensory test indicated an acceptability index of 78%, showing that the analytical approach adopted was feasible to develop a phenolic-rich beverage.
Article
Hibiscus sabdariffa calyx is a rich source of anthocyanins and other bioactive compounds but no study reported the effects of experimental conditions on the extraction of these chemical compounds. Therefore, the effects of time and extraction temperature on the bioactive compounds and antioxidant activity of Hibiscus sabdariffa calyx were evaluated. In addition, the effects of copigmentation and pH on the stability of anthocyanins were assessed and the cytotoxic effects (LC50, IC50, and GC50) of the extracts were determined in relation to tumor cell lines - Caco-2, HepG-2, HCT8, and A549. The temperature significantly influenced the total anthocyanins and flavonoids contents. The interaction between time/temperature influenced the total phenolic content and ascorbic acid. The t1/2 and the percentage of colour retention decreased markedly at temperatures above 80 °C. Variations in pH conserved the antioxidant activity of the anthocyanins, and the protonation-deprotonation process of the extract was reversible. The treatment of cells with purified anthocyanin extract or crude extracts at 5-800 μg mL-1 did not show significant cytotoxic effects on the cell lines, corroborating the chemical antioxidant effect of the extracts (DPPH assay). Cyanidin-3-glucoside, delphinidin-3-sambubioside, delphinidin-3-glucoside, and cyanidin-3-sambubioside were identified in the extracts by LC-ESI-MS.
Article
Quantitative analysis and untargeted liquid chromatography mass spectrum (LC–MS) based metabolomics of different grades of Keemun black tea (KBT) were conducted. Quantitative analysis did not show tight correlation between tea grades and contents of polyphenols, but untargeted metabolomics analysis revealed that high-grades KBT were distinguished from the low-grades. S-plot and Variable Importance (VIP) analysis gave 28 marker compounds responsible for the discrimination of different grades of KBT. The inhibitory effects of KBT on α-amylase and α-glucosidase were positively correlated to tea grades, and the correlation coefficient between each marker compound and inhibitory rate were calculated. Thirteen compounds were positively related to the anti-glycemic activity, and theasinensin A, afzelechin gallate and kaempferol-glucoside were confirmed as grade-related bioactive marker compounds by chemical and bioassay in effective fractions. This study suggested that combinatory metabolomics and bioactivities assay provided a new strategy for the classification of tea grades.
Article
Tea polyphenols have been a topic of discussion due to their health benefits. Nevertheless, detailed studies on the antioxidant capacity and polyphenol contents of teas in relation to factors including geographical locations, plantation elevations and leaf grades have been limited. In this study, 53 tea samples were analysed to determine the individual and total catechin and theaflavin contents by HPLC and the total antioxidant capacity by Oxygen Radical Absorbance Capacity (ORAC) methods. Results show that the polyphenol (catechins and theaflavins) contents were significantly influenced by plantation location. Black tea from low plantation elevation contained 22–28% more polyphenols than those from high elevation. Small tea leaves had up to 15% more polyphenols than larger leaves from similar elevation. The results were further confirmed by Principal Composition Analysis (PCA), which grouped the black and green tea samples into 3 different clusters, respectively.
Article
Available online A B S T R A C T The inhibitory activities of three tea extracts (TEs) and individual phenolic compounds in TEs against porcine pancreatic α-amylase (PPA) were studied by measuring their half in-hibitory (IC50) concentrations. The kinetics of inhibition by these extracts and compounds were investigated through Dixon, Cornish-Bowden, and Lineweaver–Burk plots. The results showed that green, oolong and black tea extracts, epigallocatechin gallate, theaflavin-3, 3′-digallate and tannic acid were competitive inhibitors of PPA, whereas epicatechin gallate, theaflavin-3′-gallate and theaflavin were mixed-type inhibitors with both competitive and uncompetitive inhibitory characteristics. Only catechins with a galloyl substituent at the 3-position showed measurable inhibition. The competitive inhibition constants (Kic) were lower for theaflavins than catechins, with the lowest value for theaflavin-3, 3′-digallate. The lower Kic than the uncompetitive inhibition constant for the mixed-type inhibitors suggests that they bind more tightly with free PPA than with the PPA–starch complex. A 3 and/ or 3′-galloyl moiety in catechin and theaflavin structures was consistently found to increase inhibition of PPA through enhanced association with the enzyme active site.
Article
Aiming to standardize the experimental protocols to assess the ability to chelate Fe²⁺ and Cu²⁺ using 96-well microplates, we analyzed Brazilian coffees (n = 20) as a study-case in relation to their antioxidant activity using conventional methods (DPPH and FRAP assays) and correlated the results with the total phenolic content (TPC) using bivariate and multivariate statistical approaches. Complementarily, we assessed the repeatability, reproducibility, recovery, and linearity of both methods. Data showed that the proposed assays presented a good repeatability and reproducibility (<7% RSD) and mean recovery values of 96.66% and 98.91% for the iron and copper assays, respectively. Both methods were linear in the range of 0–100 mg EDTA equivalents/L. Cu²⁺-chelating ability was significantly correlated to FRAP, DPPH, and TPC, while sparse (p < 0.05) correlations were obtained with Fe²⁺-chelating ability. Overall, both micro assays can be used to assess the ability of plant-based extracts to chelate Fe²⁺ and Cu²⁺ in vitro.
Article
The effects of farming system, geographical origin, and grape variety on the in vitro antioxidant capacity, some physicochemical properties and chemical composition were investigated. Major and minor phenolic compounds, reducing and antioxidant assays using chemical and biological systems were determined in n = 62 100% purple grape Brazilian juices (Vitis labrusca L.) from organic and conventional systems from the three largest producing regions. Results were subjected to ANOVA, MANOVA, and principal component analysis. No distinction was observed between organic and conventional grape juices regarding the in vitro antioxidant/reducing capacities, but only through the analysis of individual phenolic acids. The geographical origin and grape variety played a more important role in distinguishing Brazilian grape juices according to the antioxidant activity and some chemical markers. MANOVA was applied and the combined effect of farming system and geographical origin was only significant for tonality (p = 0.044) and protocatechuic acid content (p = 0.030). Correlation analysis was performed and results showed that total phenolic content, total flavonoids, flavonols, anthocyanins, and condensed tannins were statistically associated (p < 0.05) with FRAP, ABTS, and reducing potential of the hydrophilic phenolic compounds (RPHPC). Ascorbic acid did not seem to be involved in the antioxidant potential of the selected purple grape juices. Protocatechuic acid was statistically correlated to FRAP (r = 0.4636, p < 0.001), ABTS (r = 0.3298, p = 0.010), and RPHPC (r = 0.3623, p = 0.004), while ferulic acid correlated with FRAP (r = 0.3410, p = 0.008) and RPHPC (r = 0.2662, p = 0.040). The inhibition of lipid peroxidation conducted at 37 °C in a biological system buffered at pH 7.4 was significantly (p < 0.05) correlated to RPHPC (r = 0.533, p = 0.013) and to the scavenging activity toward ABTS radical (r = 0.505, p = 0.020). In addition, principal component analysis revealed that the inhibition of lipid peroxidation caused by grape juice was associated with higher contents of total phenolic content, flavonoids, anthocyanins, flavonols, condensed tannins, and protocatechuic acid. Additionally, both spectrophotometric and chromatographic data regarding the phenolic composition seemed to be suitable approaches to differentiate Brazilian organic and conventionally-produced purple grape juices using PLS-DA as the classification efficiency in the calibration and validation steps were 78% and 75%, respectively.
Article
Folin-Ciocalteu colorimetric assay (FC) is the most widely used assay to estimate the total phenolic content in foods, beverages, herbs and other plant extracts, but many chemical compounds may act as interfering agents, producing inaccurate estimations of the real concentration of phenolic compounds in the matrix. Based on this limitation, the objective of this study was to compare, quantitatively, the Folin-Ciocalteu and Prussian Blue (PB) assays in estimating the total phenolic content in purple grape juices (n = 20; Vitis labrusca L.) and teas (n = 25) from different botanical origins using 96-well microplates. PB assay presented a low limit of detection (PB = 0.27 mg/L; FC = 0.25 mg/L) and quantification (PB = 0.92 mg/L; FC = 0.82 mg/L), showing its suitability in screening the total phenolic content in grape juices and teas. FC and PB assays presented a high association (P < 0.0001) for teas (r = 0.887) and grape juices (r = 0.923). The advantages of PB over FC assay are its simplicity, low time consumption (15 min reaction as compared to 60 min reaction for the FC assay), lower usage of reagents (solutions are prepared in a mM base), and higher selectivity. Additionally, PB assay was proven to be reproducible and repeatable and, therefore, may be used as an alternative to FC assay.
Article
Reactive oxygen species (ROS) play a major role in carcinogenesis: pro-oxidant agents like tobacco smoke, asbestos or N-nitrosamines, are known as mutagenic and carcinogenic, and cancer cells show increased levels of ROS and redox deregulation. However, pro-oxidant molecules can also act as selective cytotoxic agents against cancer cells by achieving toxic levels of ROS. Although polyphenols are well-known as potent antioxidants, a pro-oxidant effect has been associated with their pro-apoptotic effect in various types of tumor cells. The aim of the present review is to present the main evidences of the pro-oxidant-related cytotoxic activity of naturally occurring polyphenols and their underlying mechanisms. Copyright © 2015. Published by Elsevier Inc.
Article
This work aimed at using a simplex-centroid design to model the effects of green, yellow, and red teas mixtures (Camellia sinensis var sinensis) on metal chelation activity, phenolic composition, antioxidant activity, and instrumental taste profile. The regression models that described the extraction of flavan-3-ols, o-diphenols, total phenolic compounds (TPC), free-radical scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), cupric-ion reducing antioxidant activity (CUPRAC), and ferric reducing antioxidant power (FRAP) were significant and data were fit satisfactorily (R2>80%). A mixture of green and red teas had a synergism in CUPRAC and TPC, while a mixture of yellow and red teas had a positive effect on CUPRAC and DPPH. An optimization was performed to maximize the antioxidant activity, flavan-3-ol content and to render a tea with mild bitterness and results showed that a mixture of 14.81% green, 56.86% yellow and 28.33% red teas would be the most suitable combination of factors.
Article
Polyphenols are naturally-occuring compounds, reported to be biologically active, and through their interactions with cell membranes. Although association of the polyphenols with the bilayer has been reported, the detailed mechanism of interaction is not yet well elucidated. We report on spatio-temporal real-time membrane dynamics observed in the presence of polyphenols. Two distinct membrane dynamics, corresponding to the two classes of polyphenols used, were observed. Flavonoids (epi-gallocatechin-3-gallate, gallocatechin, theaflavin and theaflavin-3-gallate) caused lipid membrane aggregation and rigidification. As simple structural modification through opening of the aromatic C-ring into an olefin bond, present in trans-stilbenes (resveratrol and picead), completely changed the membrane properties, increasing fluidity and inducing fluctuation. There were differences in the membrane transformations within the same class of polyphenols. Structure-dependent classification of membrane dynamics may contribute to a better understanding of the physicochemical mechanism involved in the bioactivity of polyphenols. In general, an increase in the number of hydrophilic side chains (galloyl, hydroxyl, glucoside, gallate) increased the reactivity of the polyphenols. Most notable was the difference observed through a simple addition of the gallate group. Unraveling the importance of these polyphenols, at a functional group level further opens the key to tailored design of bioactive compounds as potential drug candidates.
Article
The protective effect of water extracts of white tea (WEWT) on oxidative stress in vitro is investigated. WEWT, like water extracts of green tea (WEGT) and water extracts of Pu-erh tea (WEPT), demonstrates a marked inhibition of the oxidation of liposome, albumin and LDLmodel systems. WEWT protects against H2O2-induced cytotoxicity, in a dose-dependent manner. The inhibition of ROS generation and MDA formation by WEWT in H2O2-induced Clone 9 cells parallels the effects on cell viability. Moreover, GSH and antioxidant enzymes may play an important role in the protective effect that is associated with H2O2-induced oxidative stress. The HPLC-DAD and HPLC-MS/MS analysis, shows that sixteen bioactive compounds are present in WEWT, which may partially account for its protective effect against oxidative insult. These results suggest that the mechanism of the protective actions of WEWT is related to its antioxidant potential and the maintenance of the normal redox status of the cell.
Article
The antiradical activities of various antioxidants were determined using the free radical, 2,2-Diphenyl-1-picrylhydrazyl (DPPH*). In its radical form. DPPH* has an absorption band at 515 nm which dissappears upon reduction by an antiradical compound. Twenty compounds were reacted with the DPPH* and shown to follow one of three possible reaction kinetic types. Ascorbic acid, isoascorbic acid and isoeugenol reacted quickly with the DPPH* reaching a steady state immediately. Rosmarinic acid and δ-tocopherol reacted a little slower and reached a steady state within 30 min. The remaining compounds reacted more progressively with the DPPH* reaching a steady state from 1 to 6 h. Caffeic acid, gentisic acid and gallic acid showed the highest antiradical activities with a stoichiometry of 4 to 6 reduced DPPH* molecules per molecule of antioxidant. Vanillin, phenol, γ-resorcylic acid and vanillic acid were found to be poor antiradical compounds. The stoichiometry for the other 13 phenolic compounds varied from one to three reduced DPPH* molecules per molecule of antioxidant. Possible mechanisms are proposed to explain the experimental results.
Article
A mechanism of hemolytic hole formation during rapid hemolysis in a hypotonic medium has been investigated using eosin-5-maleimide (EMI) as a probe. The EMI-labeled erythrocytes revealed a distinct cluster and/or ring of intense fluorescence staining in a hypotonic 5 mM Hepes buffer (pH 7.4), but not in an isotonic buffer containing 150 mM KCl. This EMI cluster indicates an association of band 3 proteins, which correspond to a hemolytic hole. The hole was confirmed by an atomic force microscopy image. The erythrocytes showed a single large hole in the membrane. By the use of EMI-labeled ghosts, it was observed that the lateral clustering of band 3 was accompanied by a biphasic change of fluorescence intensity of EMI. This biphasic change is interpreted as the hemolytic hole formation by band 3, followed by a disappearance of the hole accompanied by band 3 diffusion or distribution within membrane. The latter event corresponds to a spontaneous membrane seal. When a cytoplasmic domain of band 3 was digested with trypsin, or when SH groups in the cytoplasm-facing components of the membrane were also labeled by EMI, no fluorescence change was observed. These results suggest that the association and/or dissociation of band 3 proteins in a hypotonic medium are strongly influenced by cytoplasmic domains. The apparent biphasic change of the fluorescence intensity in the hypotonic medium was well explained by assuming three events: swelling, clustering of band 3, and sealing accompanied by band 3 redistribution.
Article
A simple, automated test measuring the ferric reducing ability of plasma, the FRAP assay, is presented as a novel method for assessing "antioxidant power." Ferric to ferrous ion reduction at low pH causes a colored ferrous-tripyridyltriazine complex to form. FRAP values are obtained by comparing the absorbance change at 593 nm in test reaction mixtures with those containing ferrous ions in known concentration. Absorbance changes are linear over a wide concentration range with antioxidant mixtures, including plasma, and with solutions containing one antioxidant in purified form. There is no apparent interaction between antioxidants. Measured stoichiometric factors of Trolox, alpha-tocopherol, ascorbic acid, and uric acid are all 2.0; that of bilirubin is 4.0. Activity of albumin is very low. Within- and between-run CVs are <1.0 and <3.0%, respectively, at 100-1000 micromol/liter. FRAP values of fresh plasma of healthy Chinese adults: 612-1634 micromol/liter (mean, 1017; SD, 206; n = 141). The FRAP assay is inexpensive, reagents are simple to prepare, results are highly reproducible, and the procedure is straightforward and speedy. The FRAP assay offers a putative index of antioxidant, or reducing, potential of biological fluids within the technological reach of every laboratory and researcher interested in oxidative stress and its effects.
Article
The antihemolytic activity of Rooibos and black tea on Japanese quail erythrocytes was studied. Peroxide and hypotonic hemolysis of the red blood cells of quails, either fed with Rooibos tea supplemented food or fed without tea, was performed. Long-term consumption of Rooibos tea did not change the erythrocyte fragility to either peroxide or hypotonia induced hemolysis. However, Rooibos and black teas decreased peroxide induced hemolysis of erythrocytes incubated with each of them, but not hemolysis induced by hypotonic NaCl solution. Stronger inhibition of hemolysis has been obtained when a boiled water extract of Rooibos tea was used for the inhibition. The degree of inhibition was comparable with the effect of ascorbic acid.
Article
Antioxidative activities of volatile extracts from six teas (one green tea, one oolong tea, one roasted green tea, and three black teas) were investigated using an aldehyde/carboxylic acid assay and a conjugated diene assay. The samples were tested at levels of 20, 50, 100, and 200 micrograms/mL of dichloromethane. The results obtained from the two assays were consistent. All extracts except roasted green tea exhibited dose-dependent inhibitory activity in the aldehyde/carboxylic acid assay. A volatile extract from green tea exhibited the most potent activity in both assays among the six extracts. It inhibited hexanal oxidation by almost 100% over 40 days at the level of 200 micrograms/mL. The extract from oolong tea inhibited hexanal oxidation by 50% in 15 days. In the case of the extract from roasted green tea, the lowest antioxidative activity was obtained at the level of 200 micrograms/mL, suggesting that the extract from roasted green tea contained some pro-oxidants. The extracts from the three black teas showed slight anti- or proactivities in both assays. The major volatile constituents of green tea and roasted green tea extracts, which exhibited significant antioxidative activities, were analyzed using gas chromatography-mass spectrometry. The major volatile chemicals with possible antioxidative activity identified were alkyl compounds with double bond(s), such as 3,7-dimethyl-1,6-octadien-3-ol (8.04 mg/kg), in the extract from green tea and heterocyclic compounds, such as furfural (7.67 mg/kg), in the extract from roasted green tea. Benzyl alcohol, which was proved to be an antioxidant, was identified both in a green tea extract (4.67 mg/kg) and in a roasted tea extract (1.35 mg/kg).
Article
Application of taste dilution analyses on freshly prepared black tea infusions revealed neither the high molecular weight thearubigen-like polyphenols nor the catechins and theaflavins, but a series of 14 flavon-3-ol glycosides as the main contributors to the astringent taste perceived upon black tea consumption. Among these glycosides, the apigenin-8-C-[alpha-l-rhamnopyranosyl-(1-->2)-O-beta-d-glucopyranoside] was identified for the first time in tea infusions. Depending on the structure, the flavon-3-ol glycosides were found to induce a velvety and mouth-coating sensation at very low threshold concentrations, which were far below those of catechins or theaflavins; for example, the threshold of 0.001 micromol/L found for quercetin-3-O-[alpha-l-rhamnopyranosyl-(1-->6)-O-beta-d-glucopyranoside] is 190000, or 16000 times below the threshold determined for epigallocatechin gallate or theaflavin, respectively. Moreover, structure/activity considerations revealed that, besides the type of flavon-3-ol aglycon, the type and the sequence of the individual monosaccharides in the glycosidic chain are key drivers for astringency perception of flavon-3-ol glycosides.
Article
A quantitative method for four theaflavins and two methylated theaflavin derivatives in black tea leaves was developed by solid-phase extraction and a high-performance liquid chromatographic method with photodiode array detection. The theaflavins in black tea leaves were extracted three times with 40 vol 50% aqueous ethanol (mg dry tea powder/mL) containing 2% ascorbic acid. The ethanol extracts were diluted 4-fold with distilled water. All diluted extracts were directly applied to the solid-phase C18 cartridge column without concentration. The fraction of theaflavins was obtained by 40% ethanol extraction after rinsing with water followed with 15% ethanol extraction. An aliquot of theaflavins after concentration was injected onto an ODS C18 reversed-phase column, and four theaflavins and two methylated theaflavins were sufficiently separated by a linear gradient system using distilled water and acetonitrile with 0.5% acetic acid. This analytical method is sensitive for the determination of a small amount of methylated theaflavins, since various interfering substances produced during the fermentation process were eliminated in advance by solid-phase extraction. Using this analytical method, we also demonstrated that methylated theaflavins were easily produced during the manufacture of black tea.
Article
This work analyzed the effects of the aqueous crude extracts of Artemisia absinthium L., Lippia sp., Bryophyllum sp., Solidago microglossa DC, Cymbopogon citratus DC and Mentha x villosa HUDSON on the osmotic stability of human erythrocytes. Hemolysis was monitored by measurement of absorbance at 540 nm following addition of erythrocytes to NaCl solutions of varying concentration. Absorbance was fitted to sigmoid regression curves given by the Boltzmann equation, and hemolysis was characterized by the NaCl concentration leading to lysis of 50% of cells (H(50)), and by the intensity (H) and the amplitude (dS) of the lysis effect. The parameters were determined in the absence and presence of the crude extracts. The extracts of Artemisia absinthium, Lippia sp., C. citratus and M. villosa protected human erythrocytes against hypotonic shock, as evidenced by a decrease in the values of H and H(50) compared to the control solution (p<0.05). The extracts of Bryophyllum sp. and S. microglossa enhanced hemolysis, since their H(50) values were higher than in the control group (p<0.05), but they also showed protective effects, as evidenced by a decrease in H and an increase in dS.