Commercial Tea Samples Research Articles

Commercial peppermint (Mentha × piperita L.) teas: Antichlamydial effect and polyphenolic composition

The qualitative and quantitative polyphenolic contents in the infusions of the commercial peppermint tea (Mentha×piperita L.) samples (n=27) from different countries were studied using HPLC–UV-MS/MS analysis. The most abundant polyphenolics in the peppermint infusion were eriocitrin, 12-hydroxyjasmonate sulfate, luteolin-O-rutinoside and rosmarinic acid. In order to evaluate the content of samples by finding chemosystematic markers, the essential oil composition was studied by GC. The analyses showed that the 24 (89%) peppermint tea samples contained peppermint, whereas three samples may contain Mentha spicata, different from that claimed on the package.The effects of seven peppermint tea extracts against respiratory tract pathogen Chlamydia pneumoniae were investigated in vitro. All seven selected tea extracts were active against C. pneumoniae, the growth inhibition ranging from 20.7% to 69.5% at extract concentration of 250μg/ml. In most cases, the antichlamydial activity was related to the peppermint teas having also high content of luteolin and apigenin glycosides. This study supports the consumption of peppermint tea to potentially elicit beneficial health effects on acute respiratory tract infections.

Modified QuEChERS method for the analysis of 11 pesticide residues in tea by liquid chromatography–tandem mass spectrometry

An accurate, rapid and reliable method for the simultaneous determination of 11 pesticide residues in tea by liquid chromatography–electrospray ionization tandem mass spectrometry has been established. Samples were purified by a modified QuEChERS method, followed by analysis by LC–ESI(+)-MS/MS and quantification using isotope internal standards. In this study, different extraction conditions, such as soaking time, extraction time of pesticides from the real tea samples and spiked samples, were optimized and compared. It was found that pesticides in real tea needed more time to be soaked and extracted than those in spiked tea for complete extraction. In order to eliminate the matrix effect and obtain satisfactory recoveries, the dosage of sorbents PSA (125, 250, 400, 600, 800, 1000, 1200 mg) and GCB (0, 25, 50, 250, 500 mg) was optimized in this study, and 800 mg PSA, 25 mg GCB, 750 mg MgSO4 were used in the purification process. In addition, the use of isotope internal standards and blank matrix matched standard calibration are discussed in depth. When the concentration range of 11 pesticides was 1–500 ng g−1, the linear correlation coefficients were 0.9981–0.9999. At the low, medium and high fortification levels of 2–100 ng g−1 (n = 6), recoveries were within 88–103%. The relative standard deviation was between 0.2% and 7.6%, and the limits of detection (LODs) ranged from 0.02 to 0.38 ng g−1 for 11 pesticides. It was found that the method was successfully applied to the qualitative and quantitative analysis of pesticides in actual commercial tea samples.

Analysis of metabolic markers of tea origin by UHPLC and high resolution mass spectrometry

Tea is an infusion made from the dried leaves of Camellia sinensis L. and is the second most consumed beverage in the world. It has been shown that factors such as fermentation methods, cultivar, geographical origin and season can affect the biochemical composition of tea. In this study, the biochemical composition of green, oolong and black commercial tea samples from around the world was studied using a non-targeted method utilising reversed phase ultra high pressure liquid chromatography (UHPLC) and high resolution mass spectrometry. Principal component analysis of green, oolong and black tea extracts clearly showed that fermented tea can be resolved from non-fermented tea. When the non-targeted data were combined with the supervised multivariate technique, partial least squares discriminant analysis, the method was able to clearly distinguish ‘country of origin’ within green tea and to a lesser extent within a black tea sample set, plus provide indicative marker ions for the country of origin. Many of the significant components detected in this study are unknowns, emphasising the importance of un-biased non-targeted analytical techniques. This study highlights the potential efficacy of non-targeted UHPLC–mass spectrometry when combined with multivariate statistics to differentiate fermented from non-fermented tea and provide potential indicators of provenance of tea samples for further examination.

Analysis of some selected catechins and caffeine in green tea by high performance liquid chromatography

Green tea seems to have a positive impact on health due to the catechins-found as flavanols. Thus, the present study was aimed to develop a low cost reversed phase high performance liquid chromatographic (HPLC) method for simultaneous determination of flavanol contents, namely catechin (C), epicatechin (EC), epigallocatechin (EGC), epicatechin 3-gallate (ECG) and epigallocatechin 3-gallate (EGCG) and caffeine in 29 commercial green tea samples available in a Saudi Arabian local market. A C-18 reversed-phase column, acetonitrile-trifluoroacetic acid as a mobile phase, coupled with UV detector at 205 nm, was successfully used for precise analysis of the tested analytes in boiled water of digested tea leaves. The average values of N (No. of theoretical plates), HETP (height equivalent of theoretical plates) and R(s) (separation factor) (at 10 μg ml(-1) of the catechins EC, EGC, EGCG and ECG) were 2.6×10(3)±1.2×10(3), 1.7×10(-3)±4.7×10(-4) cm and 1.7±5.53×10(-2), respectively. The developed HPLC method demonstrated excellent performance, with low limits of detection (LOD) and quantification (LOQ) of the tested catechins of 0.004-0.05 μg ml(-1) and 0.01-0.17 μg ml(-1), respectively, and recovery percentages of 96-101%. The influence of infusion time (5-30 min) and temperature on the content of the flavanols was investigated by HPLC. After a 5 min infusion of the tea leaves, the average concentrations of caffeine, catechin, EC, EGC, ECG and EGCG were found to be in the ranges 0.086-2.23, 0.113-2.94, 0.58-10.22, 0.19-24.9, 0.22-13.9 and 1.01-43.3 mg g(-1), respectively. The contents of caffeine and catechins followed the sequence: EGCG>EGC>ECG>EC>C>caffeine. The method was applied satisfactorily for the analysis of (+)-catechin, even at trace and ultra trace concentrations of catechins. The method was rapid, accurate, reproducible and ideal for routine analysis.

Simultaneous determination of methylxanthines in different types of tea by a newly developed and validated TLC method

The aim of this paper is to develop a new simple, fast and economical method for simultaneous quantitative determination of methylxanthine compounds based on TLC combined with image analysis. To obtain certain results, both extraction and chromatographic separation were optimized. The optimum extraction conditions were maceration in ethanol-water 8:2, v/v. The chromatographic separations were done on the silica gel F(254) TLC plates developed with chloroform-dichloromethane-isopropanol, 4:2:1 v/v/v. Detection was performed under UV lamp at 254 nm and the evaluation of the chromatographic plate was based on digital processing of chromatographic images. The developed TLC method was validated for parameters such as specificity, linearity and range, LOD and LOQ, precision, robustness and accuracy. This method was then applied for determination of caffeine, theobromine and theophylline in different types of tea, commercially available. Moreover, the content of methylxanthines detected and determined in commercial tea samples can be used as chemical marker in quality control.

Significance of Chromatographic and Voltammetric Data for the Classification of Green Teas in Türkiye: A Principle Component Analysis Approach

Tea (Camellia sinensis) is one of the most popular beverages in Anatolia; it provides a significant source of phenolic compounds in the Turkish diet. All around Anatolia, tea traditionally is usually served black but in recent years green tea is becoming a popular alternative, mostly due to its higher content of antioxidant compounds. The growing green tea consumption resulted in the appearance of commercial green tea brands with different additives. In this study, the flavonoid content of methanol extracts of various commercial green tea samples was determined by HPLC analysis. Rutin, apigenin, luteolin, luteolin-4-glucoside, naringenin, quercetin, isoquercitrine, and quercetin-4-glucoside were studied as model bioactive flavonoid compounds successfully separated and detected. HPLC detection was performed under isocratic conditions through a C18 analytical column with methanol and 0.01 M orthophosphoric acid (pH 7) (50:50, v/v) as the mobile phase. Variable wavelength UV-Vis (230 nm), fluorescence (Ex: 250 nm, Em: 450 nm), and a programmable electrochemical detector (+ 1.30 V vs. Ag/AgCl) were employed for detection. Based on the chemometric tools (principle component analysis, PCA), the flavonoid patterns of the samples were used successfully to identify and classify the commercial brands with additives from unmodified ones. This might help to make a very easy and rapid classification simply based on rough data without focusing on detailed analysis methods. Additionally, cyclic voltammetry (CV) data of the samples was obtained and used again in PCA to identify the commercial brands. Also, based on the CV data, the samples were sorted according to their anodic oxidation potential, which is a measure of the free radical scavenging (antioxidant) capacity of the samples.

Potentiometric flow-injection estimation of tea fermentation degree

A potentiometric flow-injection (FI) system was developed for estimating tea fermentation degrees; the method is based on the redox potentials of tea infusions. The infusions were extracted with phosphate buffer (10 mM, pH7.0), and injected (200 μL) into the FI system (1 mL min −1). The redox potentials ( vs. Ag/AgCl) of carrier stream were monitored with a home-made electrochemical flow cell equipped with a platinum indicating electrode. Flow-injection strategy successfully decreased the problem of electrode fouling with increased reproducibility (S.D. < 1.5 mV) and elevated sample throughput (>20 determination h −1). During indoor withering process (0–24 h) for making pouching tea, the redox potential of tea infusions rose (110–130 mV) along with the depletion of tea catechins (100–75 mg g −1 dry tea powder, by HPLC). The system can also be used to estimate the fermentation degrees of commercial tea samples. For commercialization, the platinum electrode can be replaced with a screen-printed carbon-paste disposable electrode with similar performance.

English

In the present study, twelve different types of commercial tea samples were assayed to determine their phenolic composition and antioxidant activity. Reverse phase high performance liquid chromatography using a binary gradient system was used for the identification and quantification of individual catechins. Subsequently, total phenolic content was determined spectrophotometrically according to the Folin-ciocalteus method. Total theaflavins and thearubigins were also determined. The radical scavenging behavior of the polyphenols on 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) was also studied spectrophotometrically. The results showed that total polyphenols, total catechins and antioxidant activity were significantly (P<0.05) different in the commercial tea samples. Green tea had the highest levels of catechins, total polyphenols and total antioxidant activity. White tea (silvery tip) a rare specialty type of tea was not significantly different from green tea. Statistical analysis showed an essential catechin content influence of the tea extracts on antioxidant activity. Epigallocatechin gallate (EGCG) was the most potent catechin and the most potent in antioxidant activity (r = 0.989***). Epigallocatechin (EGC) (r = 0.787, P<0.001), epicatechin (EC) + catechin (+C) and epicatechigallate (ECG) also showed significant (P<0.05) antioxidant activity. Black tea contained high levels of theaflavins and thearubigins, which accounted for most of the antioxidant potential in this type of tea product (r = 0.930*** and r = 0.930*** respectively). These results suggest that conversion of catechins during black tea processing did not affect the free-radical potency of black tea. Gallic acid (GA) also showed significant(r = 0.530*) contribution to the antioxidant activity in black tea. Green, black and white tea products processed from Kenyan tea cultivars originally selected for black tea had significantly (P<0.05) higher antioxidant activity than green tea processed from tea cultivars from Japan and China. These results seem to suggest that the cultivar type is critical in determining the antioxidant potency of tea product and that black teas processed from suitable cultivars could be potent in antioxidant activity when compared to green teas.

Selective square wave voltammetric determination of (+)-catechin in commercial tea samples using beta-cyclodextrin modified carbon paste electrode

Osteryoung square wave cathodic or anodic voltammetry has been used for the determination of (+)-catechin (CAT) at physiological pH in the presence of 0.05 mol · L−1 phosphate/borate buffer using beta-cylcodextrin modified carbon paste electrode. A linear range up to 70.0 µg · mL−1 CAT in cathodic voltammetry and up to 45.0 µg · mL−1 CAT in anodic voltammetry was achieved. The method gave reproducible and reliable results with 1.35 µg · mL−1 CAT as a detection limit with R.S.D. less than 2%. The proposed electrode was applied successfully for the determination of CAT in commercial tea samples with acceptable recovery range (98–102%). The extraction of CAT from commercial tea samples was rather simple, making it suitable for studies with a large number of commercial tea samples giving high accuracy of the proposed method.

Dynamic Ultrasound‐Assisted Extraction of Catechins and Caffeine in Some Tea Samples

A novel dynamic ultrasound-assisted extraction (DUAE) device has been constructed for extraction of five catechins and caffeine in solid sample. The accurate, simple, reproducible and sensitive method for the determination of five catechins and caffeine has been developed and validated. A comparison has been made of the efficiencies by employing DUAE and conventionally static ultrasound-assisted extraction (UAE). The proposed method can not only improve extraction efficiency but also decrease time and solvent consumption. The commercial Chinese tea samples, involving green and black teas, are rapidly analyzed by the proposed DUAE method. The linearity, range, selectivity, precision, accuracy, and robustness also showed acceptable values.

Determination of Theanine in Commercial Tea by Liquid Chromatography with Fluorescence and Diode Array Ultraviolet Detection

Two liquid chromatographic methods that involve precolumn derivatization with o-phthaladehyde (OPA) and phenylisothiocyanate (PITC) with fluorescence and diode array UV detection for the determination of theanine have been developed. The chromatographic separations were achieved by reverse-phase high-performance liquid chromatography using octadecyl columns and gradient elution. The methods were applied to evaluate the theanine content of commercial tea leaves. The coefficient of variation of the peak area repeatability for within day (n = 8) and between day (n = 8 over 10 days) was lower than 3% for both of the methods. The estimated limit of detection (LOD) and limit of quantitation (LOQ) for the OPA method was 0.12 and 0.35 microg theanine, respectively. The PITC method was 500-fold more sensitive with LOD and LOQ values of 0.25 and 0.75 ng, respectively. The theanine content of the commercial tea samples varied from 2-5 mg/g leaf. The overall % recoveries for these methods ranged from 93-99.3. The sensitivity and simplicity of the method render them suitable for use in quality control laboratories.

Stir bar sorptive extraction and high-performance liquid chromatography–fluorescence detection for the determination of polycyclic aromatic hydrocarbons in Mate teas

A simple procedure based on stir bar sorptive extraction (SBSE) and high-performance liquid chromatography–fluorescence detection (HPLC–FLD) is presented for the determination of 15 polycyclic aromatic hydrocarbons (PAHs) in herbal tea prepared with Mate leaves ( Ilex paraguariensis St. Hil.). The influence of methanol and salt addition to the samples, the extraction time, the desorption time and the number of desorption steps, as well as the matrix effect, were investigated. Once the SBSE method was optimised (10 mL of Mate tea, 2 h extraction at room temperature followed by 15 min desorption in 160 μL of an acetonitrile (ACN)–water mixture), analytical parameters such as repeatability (≤10.1%), linearity ( r 2 ≥ 0.996), limit of detection (LOD, 0.1–8.9 ng L −1), limit of quantitation (LOQ, 0.3–29.7 ng L −1) and absolute recovery (24.2–87.0%) were determined. For calibration purposes, a reference sample was firstly obtained by removing the analytes originally present in the lowest contaminated Mate tea studied (via SBSE procedure) and then spiked at 1–1200 ng L −1 range. The proposed methodology proved to be very convenient and effective, and was successfully applied to the analysis of 11 Mate tea samples commercialised in Brazil. The results of the commercial Mate tea samples found by the SBSE approach were compared with those obtained by liquid–liquid extraction (LLE), showing good agreement.

On‐Line Preconcentration of Cadmium in Commercial Tea Samples using Polyurethane Foam as Filter Associated with Ultrasonic Nebulization‐Inductively Coupled Plasma Optical Emission Spectrometric Detection

Tea is the most popular beverage, next to water, consumed by over two‐thirds of the world's population. The present paper proposes an on‐line preconcentration procedure for cadmium determination in tea samples (Camellia sinensis) by ultrasonic nebulization associated with inductively coupled plasma optical emission spectrometry (USN‐ICP‐OES). It is based on the precipitation of cadmium(II) ion onto a conical minicolumn packed with polyurethane foam using 2‐(5‐bromo‐2‐pyridilazo)‐5‐diethylaminophenol (5‐Br‐PADAP) as precipitating reagent. The collected analyte precipitate was quantitatively eluted from the minicolumn with 20% (v/v) nitric acid. An enhancement factor of 240‐fold (20 for preconcentration and 12 for USN) was obtained. The detection limit (DL) value for the preconcentration of 10.0 mL of sample was 4.0 ng L−1. The precision for 10 replicate determinations at 0.1 µg L−1 cadmium levels was 3.2% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the preconcentration system for cadmium was linear with a correlation coefficient of 0.9998, at levels near the detection limits up to at least 500 µg L−1. The preconcentration procedure was successfully applied to the determination of cadmium in tea samples.

Application of a potentiometric electronic tongue as a classification tool in food analysis

This paper reports on the application of a potentiometric sensor array to the food analysis field, in order to distinguish simple tastes and to classify food samples. This array is formed by a set of non-specific all-solid-state potentiometric sensors and has been used in combination with principal component analysis (PCA) for the classification of food samples in batch and in flow injection mode. First attempt was to classify synthetic samples prepared with controlled variability. Once this ability is proven, satisfactory classification results are presented for commercial waters, orange-based drinks and tea samples. An interesting correlation is achieved between the natural juice content and its first calculated component, which allows for a very simple tool for screening purposes.

Electroanalytical Determination of the Herbicide Paraquat in Natural Water and Commercial Tea Samples with Gold Electrodes Obtained from Recordable Compact Disc

This work describes the application of gold electrodes constructed from recordable compact discs for the analytical determination of the herbicide paraquat in natural water samples using square wave voltammetry. The detection limit for pure water (laboratory samples) was 21 µg L−1, lower than the EPA limit for drinking water (100 µg L−1). The experimental quantification limit was determined as 73 µg L−1. In polluted creek water samples the detection limit rose to 76.4 µg L−1 and is shown to be dependent on BOD and COD values. Recovery measurements in tea and natural water samples were approximately 95%, which indicates that the methodology can be employed to analyze paraquat in such matrices. The authors acknowledge the financial support of FAPESP and CNPq.

Survey of Catechins, Gallic Acid, and Methylxanthines in Green, Oolong, Pu-erh, and Black Teas

An isocratic HPLC procedure was developed for simultaneous determination of six catechins, gallic acid, and three methylxanthines in tea water extract. A baseline separation was achieved on a Cosmosil C18-MS packed column with a solvent mixture of methanol/doubly distilled water/formic acid (19.5:80.2:0.3, v/v/v) as mobile phase. A gradient HPLC procedure was also provided for the separation of these tea components. The contents of catechins, gallic acid, and methylxanthines have been measured in infusions of a range of green tea, oolong tea, and pu-erh tea products sold and consumed in the China, Japan, and Taiwan. When 15 Chinese green tea and 13 Japanese green tea products were analyzed by the HPLC method, the mean levels of the total catechins, (−)-epigallocatechin 3-gallate, (+)-catechin, and caffeine were found to be very similar in these two groups, but other minor catechins such as (−)-epigallocatechin, (−)-epicatechin, and (−)-gallocatechin 3-gallate were found to be higher in Japanese green tea products, whereas (−)-epicatechin 3-gallate, gallic acid, theophylline, and theobromine were found to be higher in Chinese green tea products. Oolong tea products possessed lower levels of catechins, whereas pu-erh tea products contained negligible amounts of these constituents. The new HPLC method is rapid, reliable, and reproducible and should be highly recommended to tea industries for routine analysis of commercial tea samples. Keywords: Catechins; gallic acid; caffeine; theophylline; theobromine; green tea; oolong tea; paochong tea; pu-erh tea; black tea; isocratic HPLC

The modulatory effect of phenolic extracts on smooth muscle cell activity

Green tea seems to have a positive impact on health due to the catechins-found as flavanols. Thus, the present study was aimed to develop a low cost reversed phase high performance liquid chromatographic (HPLC) method for simultaneous determination of flavanol contents, namely catechin (C), epicatechin (EC), epigallocatechin (EGC), epicatechin 3-gallate (ECG) and epigallocatechin 3-gallate (EGCG) and caffeine in 29 commercial green tea samples available in a Saudi Arabian local market. A C-18 reversed-phase column, acetonitrile–trifluoroacetic acid as a mobile phase, coupled with UV detector at 205 nm, was successfully used for precise analysis of the tested analytes in boiled water of digested tea leaves. The average values of N (No. of theoretical plates), HETP (height equivalent of theoretical plates) and Rs (separation factor) (at 10 μg ml−1 of the catechins EC, EGC, EGCG and ECG) were 2.6 × 103 ± 1.2 × 103, 1.7 × 10−3 ± 4.7 × 10−4 cm and 1.7 ± 5.53 × 10−2, respectively. The developed HPLC method demonstrated excellent performance, with low limits of detection (LOD) and quantification (LOQ) of the tested catechins of 0.004–0.05 μg ml−1 and 0.01–0.17 μg ml−1, respectively, and recovery percentages of 96–101%. The influence of infusion time (5–30 min) and temperature on the content of the flavanols was investigated by HPLC. After a 5 min infusion of the tea leaves, the average concentrations of caffeine, catechin, EC, EGC, ECG and EGCG were found to be in the ranges 0.086–2.23, 0.113–2.94, 0.58–10.22, 0.19–24.9, 0.22–13.9 and 1.01–43.3 mg g−1, respectively. The contents of caffeine and catechins followed the sequence: EGCG > EGC > ECG > EC > C > caffeine. The method was applied satisfactorily for the analysis of (+)-catechin, even at trace and ultra trace concentrations of catechins. The method was rapid, accurate, reproducible and ideal for routine analysis.

Tranquilizers: Therapeutic use and pharmacology

Linden tea has been used in Serbian folk medicine for centuries to induce sweating for colds, relieve throat irritation and cough, reduce blood pressure, as well as a diuretic, spasmolytic, and as a sedative. The main aim of this study was to determine the comprehensive metabolite profile, free radical scavenging activity, and antimicrobial activities against 23 human and plant pathogens of both commercial and field-collected linden tea samples from Serbia. Developed high-performance thin-layer chromatography (HPTLC) method allowed identification of eight major metabolites in investigated samples, while forty-six metabolites were tentatively identified using high resolution mass spectrometry (HRMS): 14 phenolic acids and their derivatives, 15 glycosides, 9 flavonoids, and 8 procyanidins. Both commercial and field-collected linden tea samples showed similar total phenolic content and radical scavenging activity. Seven compounds such as p-hydroxybenzoic acid 4-O-hexoside, caffeic acid cinnamyl ester, pinocembrin, galangin, luteolin 7-O-glucuronide (and its isomer), isorhamnetin hexosyl hexoside were found in Tilia samples for the first time. Radical reagent 2,2-Diphenyl-1-picrylhydrazyl· (DPPH·) was used in DPPH-HPTLC assay which identified chlorogenic acid, caffeic acid, astragalin, quercitrin, tiliroside, and rutin as compounds that exhibit radical scavenging activity. Tilia samples showed inhibitory effect overwhelming only on Gram-positive bacteria, especially on Bacillus subtilis with the lowest MIC values observed, as well as towards Staphylococcus aureus and oral cavity isolates of Streptococcus pyogenes and Streptococcus mutans. Vaginal isolate of Candida glabrata showed more susceptibility than Candida albicans isolate. Generally, extract from Tilia cordata Miller (L4) showed the highest antimicrobial activity against the most of the tested pathogens, among all field-collected Tilia samples.

Discriminant analysis of black tea by near infrared reflectance spectroscopy

A new method for the discrimination of commercial black tea samples using near infrared (NIR) reflectance spectroscopy has been investigated. NIR data at four wavelengths (1660, 1720, 2050 and 2300 nm) corresponding to maximum variation in the intensity of absorption bands in the spectra of black teas were used to calculate Mahalanobis distances. A cut-off point in the values of these distances was determined by means of which two sets of black teas with differing sensory properties could be discriminated with a 91% success rate.

Folacin content of tea

Total folacin and free folacin activities of 22 commercial tea samples, involving 5 types and 14 brands, were determined by a microbiological assay, using Lactobacillus casei (ATCC 7469). Substantially higher amounts of folacin were found in tea leaves than had been reported previously, due to an improved assay method with added ascorbic acid to protect the labile folate forms. Tea brews made from green and black teas contained approximately three to four times more folacin than the brews made from oolong tea, herb tea, and instant tea powders. Tea brews made from loose leaf teas and tea bags did not differ appreciably in folacin content. However, the tea bag itself inhibited folacin extraction. A range of 3% to 25% of the RDA for folacin can be met by consuming five servings (5 to 6 oz. per serving) of tea daily.