Antioxidant Capacity Of Green Tea Research Articles

Effect of Brewing Temperature on the Total Antioxidant Capacity of Green Tea

The relationships between the total available antioxidant capacity of green tea and the brewing temperature and preparation time were studied, with the Trolox equivalent antioxidant capacity (TEAC) assay used to determine the antioxidant levels. The initial green tea mass-to-water volume ratio was set to 10 g/L, %-inhibition values were determined at various concentrations through serial dilution, and the slope of the relationship between %-inhibition and concentration was used to determine the TEAC value. The total antioxidant capacities of green tea determined under the experimental conditions adopted in this study are in the 214-819 μmolTrolox/ggreen tea range, which is significantly higher than previously reported values for various common fruits and vegetables. The total available antioxidant capacity was found to increase with temperature at a rate of approximately 6 (μmolTrolox/ggreen tea)/°C when brewed for 4 min. Green tea concentration, brewing time, and brewing temperature were experimentally determined to be the primary factors that determine the antioxidant capacity.

Antioxidant capacity and characteristics of theaflavin catechins and ginger freeze-dried extract as affected by extraction techniques

ABSTRACT The aim of current research was to determine the effect of different extraction techniques on the antioxidant capacity of green tea, black tea and ginger polyphenols. Initially, the raw materials were subjected to compositional analysis. Afterward, the bioactive moieties from all the samples were extracted through ultrasound and conventional solvent extraction method using different solvents (i.e. ethanol, methanol and water). Furthermore, the functional ingredients, namely, catechins and theaflavins were isolated by solvent partition method from green and black tea, respectively. In addition, the extracts and isolates were analyzed for their total phenolic and antioxidant profile using various spectrophotometric assays. For the quantification of theaflavins and catechins, a reverse phase HPLC system was used. Results showed that ultrasound (P > .005) proved more effectual for the extraction and isolation of polyphenols (757.33 mg/100 g GAE) from the tested materials among the other extraction techniques (741.66 mg/100 g GAE). Likewise, green tea showed better performance than the rest and in solvents ethanol performed better as compared to their counter parts. Similarly, the isolates showed higher antioxidant potential as compared to their extracts and order of effectiveness was catechins > theaflavins > Ginger freeze dried extract (GFDE).

Effects of green tea- and amla extracts on quality and melanosis of Indian white prawn (Fenneropenaeus indicus, Milne Edwards, 1837) during chilled storage

Effect of ethanol extracts of green tea (Camellia sinensis L.) and amla (Phyllanthus emblica Linn) were investigated on quality and melanosis of chilled stored Indian white prawn (Fenneropenaeus indicus) during 28 days. Extracts were subjected to antioxidant assays viz.1,1-diphenyl-2-picryl hydrazyl radical reducing power methods (DPPH), total antioxidant capacity (TAC), total phenolic content (TPC) and ferric reducing antioxidant power(FRAP) to evaluate antioxidant potentiality and fourier-transform infrared spectroscopy (FT-IR) to identify organic constituents. Polyphenol oxidase (PPO) inhibition was assessed to check the efficacy of the extracts as anti-melanogenic agents. Biochemical (total volatile nitrogen, free fatty acid and peroxide values), bacteriological (aerobic counts), melanosis inhibition and sensory quality of chilled stored shrimp were addressed to investigate the efficacy of extracts as preservative and anti-melanogenic remedy. Free reducing power of green tea - and amla extracts were in a range of 28.72–65.67%and 17.38–66.95%, respectively. Phenolic content level was almost same for green tea and amla extract (2.46 ± 0.002 and 2.51 ± 0.036 mg GAE/gram). Total antioxidant capacity of green tea (210.33 ± 4.63 mg EqAsc/g) was slightly higher than that of amla extracts (145.56 ± 1.98 mg EqAsc/g). FRAP value revealed that green tea(477.49 ± 3.25 mgE Fe (II)/g) had more ferric reducing power than amla (324.39 ± 5.85 mgE Fe (II)/g).FT-IR analysis revealed the presence of essential organic bioactive compounds, which play an important role in reducing lipid oxidation and quality loss, and both extracts possess an encouraging PPO inhibition ability. Treatment by green tea - and amla extracts on chilled stored shrimp showed promising effects on biochemical and microbiological parameters followed by melanosis inhibition and enhanced sensory attributes. Treated Indian white prawn with green tea – and amla extract revealed significantly (P < 0.05) lower value of biochemical indices and microbial load during chilled storage compared to untreated sample.

Effect of gamma radiation on antioxidant capacity of green tea, yerba mate, and chamomile tea as evaluated by different methods

Tea is a traditional plant extract with important cultural ties. It is the most widely consumed beverage in the world. Tea consumption has some health benefits including antioxidant stimulus. Gamma radiation is currently used to control of postharvest pathogens on tea herb. However, free radicals can be generated, which consumes antioxidant molecules. A positive relation was found between radiation doses used and free radicals generation in green tea (Camellia sinensis), yerba mate (Ilex paraguariensis), and chamomile tea (Matricaria recutita). Total antioxidant capacity (TAC) of aqueous and methanol extracts of these herbs was determined by various methods to compare the effect of irradiation of herb on antioxidant capacity of the extracts. TAC was evaluated by measuring: total phenols (decreased with irradiation in mate and green teas), total flavonoids (stable in aqueous extracts and decreased with irradiation in methanol extract of mate and chamomile), Trolox equivalent or ABTS (unchanged under irradiation), DPPH* scavenging capacity (stable on aqueous extract but diminished in methanol extract after irradiation), β carotene/acid linoleic ability (stable with the exception of chamomile tea that increased after irradiation) and, capacity to chelate ferrous ions (unchanged with irradiation). In conclusion, gamma irradiation reduced the capacity of some antioxidants but preserved the capacity of others. This study showed that one isolated test does not suffice to perform this evaluation reliably, which is a reflection of the diversity and complexity of the effects of irradiation on antioxidant molecules present in different samples.

The Effect of Green Tea (Camellia sinensis) Extract Against Hepato-Toxicity Induced By Tamoxifen in Rats

The present study was conducted to elucidate the antioxidant capacity of green tea (Camellia sinensis) extract against Tamoxifen citrate-induced liver injury. Four groups containing ten female Wister rats each were selected: Group I, served as control group, Group II, permitted Green Tea Extract (1.5% w/v in water) as the sole drinking fluid, Group III, injured by intraperitoneal injection of Tamoxefin (45 mg/ Kg/day) for 7 successive days and Group IV, permitted green tea extract as a sole source of drinking water (1.5% w/v in water) 4 days prior and 14 days after Tamxifen-intoxication (45 mg/Kg/day for 7 successive days). Hepatic oxidative damage was observed in Tamoxefin treated rats as evidenced via augmentation in liver lipid peroxidation as well as depletion in liver antioxidant enzymes; catalase, superoxide dismutase and glutathione peroxidase with highly degeneration and necrosis of the hepatocytes. Histopathological studies of liver treated with Tamoxefin revealed that supplementation of green tea extract resulted in mild degeneration and necrosis of the hepatocytes. Furthermore, green tea extract had normalized catalase, superoxide dismutase, glutathione peroxidase and liver lipid peroxidation content. In Conclusion, the supplementation of green tea extract appeared to be beneficial to a great extent in attenuating and restoring the damage sustained by Tamoxefin exposure.

Voltammetric evaluation of the antioxidant capacity of tea on electrodes modified with multi-walled carbon nanotubes

The characteristics of the voltammograms of tea polyphenols on a glassy carbon electrode modified with multi-walled carbon nanotubes (MCNT-GCE) were evaluated. With the use of atomic force microscopy, it was found that MCNTs are oriented as rows 0.8–1.0 μm wide with alternating hills to 586 nm in height. Polyphenols other than of tannin are reversibly oxidized at the first step. Corresponding electrode reaction schemes are proposed. A voltammetric procedure for the estimation of the antioxidant capacity (AOC) of tea based on the oxidation of its polyphenol compounds was developed. The voltammograms of tea exhibited clearly defined peaks and oxidation steps whose potentials depend on the type of tea. The area of oxidation peaks was chosen as the parameter that characterizes antioxidant properties. The AOC of tea was expressed in terms of catechin equivalents per 100 mL of a beverage. 27 tea samples were analyzed. It was found that the AOC of green tea is 79% higher than that of black tea (290 ± 40 and 54 ± 22 mg/100 mL, respectively, P 0.05).

Impact of Brewing Conditions on the Antioxidant Capacity of Green Tea

The polyphenolic compounds in green tea, have well established antioxidant activity, which may be responsible for the health benefits of drinking green tea described in research literature.ObjectiveTo measure the impact of infusion conditions on the oxygen radical absorbance capacity (ORAC) of several green teas.MethodsA fluorescence‐based ORAC assay was developed and validated. Infusion conditions were varied systematically; including temperature, duration, source, variety, brewing environment, and preparation method. Antioxidant capacity results were calculated in units of mM Trolox/g tea based on standard Trolox equivalents. We also describe a new measure of total inherent antioxidant potential (TI‐ORAC), defined as the area under the ORAC curve over a standard number of infusions.ResultsBrewing time, and tea source, had a significant impact on single infusion ORAC values, while time between brews and temperature had minimal impact on ORAC. TI‐ORAC varied considerably across varieties of green tea; and between two environments.ConclusionsInfusion conditions impact the ORAC of green tea, which may impact its health benefits. TI‐ORAC may be a novel assay to consider in continued research of tea and other natural products. This research was supported by grant number 5T32 AT00815‐03 from the National Center for Complementary and Alternative Medicine.

The Impact of Packaging Materials on the Antioxidant Phytochemical Stability of Aqueous Infusions of Green Tea (Camellia sinensis) and Yaupon Holly (Ilex vomitoria) during Cold Storage

Ready to drink (RTD) teas are a growing segment in the beverage category, brought about by improvements in the flavor of these products and healthy market trends driven by consumers. The presented results evaluated the antioxidant phytochemical stability of RTD teas from aqueous infusions of traditional green tea (Camellia sinensis) and a botanical tea from yaupon holly (Ilex vomitoria) as influenced by packaging materials during cold storage. Two common packaging materials for RTD products are glass and polyethylene terephthalate (PET) and have been compared to a retortable pouch (RP), an emerging packaging material for various types of food since it is durable, inexpensive, lightweight, and easy to sterilize. Storage stability was then evaluated for each aqueous infusion prepared at 10 g/L at 90 °C for 10 min and evaluated at 3 °C in the absence of light over 12 weeks. Analyses included quantification and characterization of individual polyphenolics by high-performance liquid chromatography-photodiode array and liquid chromatography-electrospray ionization-mass spectrometry as well as changes in total antioxidant capacity. For green tea, concentrations of the three major flavan-3-ols, epigallocatechin gallate, epigallocatechin, and epicatechin gallate were better retained in glass bottles as compared to other packages over 12 weeks. In yaupon holly, chlorogenic acid and its isomers that were the predominant compounds were generally stable in each packaging material, and a 20.6-fold higher amount of saponin was found as compared to green tea, which caused higher stability of flavonol glycosides present in yaupon holly during storage. The antioxidant capacity of green tea was better retained in glass and PET versus RP, whereas no differences were again observed for yaupon holly. Results highlight the superiority of oxygen-impervious glass packaging, but viable alternatives may be utilizable for RTD teas with variable phytochemical compositions.

The influence of domestic culinary processes on the Trolox Equivalent Antioxidant Capacity of green tea infusions

This paper presents an investigation into the influence of several culinary factors, such as water temperature, infusion time, stirring and dosage form, on polyphenol content and antioxidant capacity (TEAC values) during the domestic preparation of green tea. The results obtained show that water temperature and infusion time strongly influence total polyphenol levels and the antioxidant capacity of green tea. Temperatures of 70–80 °C together with infusion times of 3–5 min produced greatest effect, in this respect. At 90 °C, extraction was faster and more effective. However, prolonged infusion at this temperature may cause a loss of polyphenol compounds and, consequently, of antioxidant capacity. Factors such as agitation and dosage form do not seem to have much influence. Furthermore, it was found that pure green tea infusions have higher antioxidant properties than do blends of green tea with aromatic herbs and fruits.

Prediction and interpretation of the antioxidant capacity of green tea from dissimilar chromatographic fingerprints

Previously, multivariate calibration techniques have been successfully applied to model and predict the antioxidant activity of green tea from its chromatographic fingerprint. Since the selectivity differences between dissimilar chromatographic systems have already been valuably used in several applications, in this paper it is studied whether combining the complementary information contained in two dissimilar fingerprints can improve the predictive capacity of the multivariate calibration model. The simplest way of combining the data is concatenating both fingerprints for each sample. The resulting matrix can then be subjected to Orthogonal Projections to Latent Structures (O-PLS). Unfortunately, this approach resulted in a more complex model with a prediction error of about the average of the errors obtained with the individual fingerprints. Secondly, only the peaks with high loading and low orthogonal loading from both chromatograms were included in the O-PLS model. This resulted in a reduced complexity, but not in better predictions, probably due to a lack of complementarity of the information concerning the antioxidant capacity. Finally, the concatenated fingerprints were subjected to stepwise multiple linear regression (MLR) in order to build a model based on the variables most correlated with the antioxidant capacity. The obtained prediction error was lower than those of both previous approaches, but still higher than the error of the model based on a single analysis. This is probably again caused by a lack of complementarity in the variables. Nevertheless, it was advantageous to develop fingerprints on dissimilar system, because it enables to choose the most suited chromatographic profile to build a multivariate calibration model for the considered purpose. In contrast to what was expected, the study showed that the most simple (so the worst separated) fingerprints resulted in the best predictions. On the other hand, a more complex fingerprint in which more compounds are separated is still important to improve the interpretability of the model.

Tea consumption and risk of ovarian cancer

Although the growth inhibitory effects of tea, particularly green tea, and tea polyphenols have been demonstrated in animal models of ovarian cancer, the results of epidemiological studies have been inconclusive. We investigated this issue using data from an Australian population-based, case-control study (1,368 cases; 1,416 controls). We also systemically reviewed all the available evidence regarding the potential association between green tea and risk of ovarian cancer, given the abundance of bioavailable polyphenols and higher antioxidant capacity of green tea than black tea, to provide the best summary estimate of the association. In our case-control study, while we found uniformly inverse odds ratios (OR) for tea drinkers compared to non-tea drinkers [4 + cups/day any tea OR 0.71 (95% CI 0.52-0.97); green tea OR 0.82 (95% CI 0.38-1.79); herbal tea OR 0.77 (95% CI 0.28-2.14): black tea OR 0.88 (95% CI 0.66-1.18)], we saw no dose-response trends. Our meta-analysis provided some evidence that women who drink green tea have a lower risk of ovarian cancer, although the summary estimate did not reach statistical significance (0.58, 95% CI 0.33-1.01 for >or=1 cup/green tea day). This result is consistent with two recent meta-analyses that evaluated the association of tea (all types combined) and ovarian cancer risk. Overall, our findings provide some support for the hypothesis that tea consumption reduces the risk of ovarian cancer.

Exploration of linear multivariate calibration techniques to predict the total antioxidant capacity of green tea from chromatographic fingerprints

Nowadays fingerprinting is a generally applied technique for the identification and quality assessment of herbal products. In this study it was aimed to predict a quantitative property, the antioxidant capacity of green tea, from chromatographic fingerprints. Different linear multivariate calibration techniques, commonly applied on spectral data, were explored and compared. When the chromatograms were appropriately pretreated, all tested techniques were able to predict the total antioxidant capacity with a precision comparable to that of the reference method (Trolox equivalent antioxidant capacity assay). Stepwise multiple linear regression (MLR) however is less recommended because of inadequate variable selection. Principal components regression (PCR) also seems less preferable, because large variations not correlated with the total antioxidant capacity were also included in the model. This problem does not occur with partial least squares (PLS) models. Of all tested PLS methods, orthogonal projections to latent structures (O-PLS) was preferred because of its simplicity, reproducibility, good interpretability of the compounds’ contribution to the antioxidant capacity and its good predictive and describing abilities.

Hepatoprotective Effect of Green Tea (Camellia sinensis) Extract against Tamoxifen-induced Liver Injury in Rats

Tamoxifen citrate (TAM), is widely used for treatment of breast cancer. It showed a degree of hepatic carcinogenesis. The purpose of this study was to elucidate the antioxidant capacity of green tea (Camellia sinensis) extract (GTE) against TAM-induced liver injury. A model of liver injury in female rats was done by intraperitoneal injection of TAM in a dose of 45mg Kg(-1) day(-1), i.p. for 7 successive days. GTE in the concentration of 1.5 %, was orally administered 4 days prior and 14 days after TAM-intoxication as a sole source of drinking water. The antioxidant flavonoid; epicatechin (a component of green tea) was not detectable in liver and blood of rats in either normal control or TAM-intoxicated group, however, TAM intoxication resulted in a significant decrease of its level in liver homogenate of tamoxifenintoxicated rats. The model of TAM-intoxication elicited significant declines in the antioxidant enzymes (glutathione-S-transferase,glutathione peroxidase, superoxide dismutase and catalase) and reduced glutathione concomitant with significant elevations in TBARS (thiobarbituric acid reactive substance) and liver transaminases; sGPT (serum glutamate pyruvate transaminase) and sGOT (serum glutamate oxaloacetate transaminase) levels. The oral administration of 1.5 % GTE to TAM-intoxicated rats, produced significant increments in the antioxidant enzymes and reduced glutathione concomitant with significant decrements in TBARS and liver transaminases levels. The data obtained from this study speculated that 1.5 % GTE has the capacity to scavenge free radical and can protect against oxidative stress induced by TAM intoxication. Supplementation of GTE could be useful in alleviating tamoxifen-induced liver injury in rats.

Effects of iron, ascorbate, meat and casein on the antioxidant capacity of green tea under conditions of in vitro digestion

The hypothesis that interactions of dietary polyphenols with dietary iron occur during digestion and result in a decrease of the post-absorptive antioxidant properties of polyphenols was investigated. The hypothesis was tested in vitro, under conditions that simulate gastrointestinal digestion. Mixtures of green tea, iron, and three dietary factors that modify the form of iron in the lumen, namely ascorbic acid, meat or casein, were subjected to an in vitro gastrointestinal digestion. Antioxidant capacity (FRAP assay), iron concentration (ferrozine assay) and polyphenol concentration (Folin–Ciocalteau assay) were measured in the in vitro digests. The presence of iron decreased the antioxidant capacity and the polyphenol concentration of green tea digests. The presence of ascorbic acid increased, while meat and casein decreased the antioxidant capacity of green tea. The factorial analysis of the data suggests that protein and iron interact with green tea polyphenols during the in vitro digestion and decrease their antioxidant capacity. These results support the aforementioned hypothesis.

On-line high-performance liquid chromatography analysis of the antioxidant activity of phenolic compounds in green and black tea

Teas represent a rich source of dietary antioxidants. This paper describes analysis of the antioxidant potential of individual tea phenolics using an on-line high-performance liquid chromatography (HPLC) method. Tea phenolics from Kenyan green and black teas were identified using liquid chromatography--mass spectrometry (LC-MS(n)) in conjunction with the analysis of their 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS+) radical scavenging ability. Antioxidant potential of flavan-3-ols, caffeoylquinic acids, flavonols, and theaflavins was assessed in comparison to the synthetic vitamin E analogue Trolox. (-)-Epigallocatechin gallate was identified as the most potent antioxidant with a Trolox equivalent antioxidant capacity (TEAC) value of 3.0, contributing approximately 30% of the total antioxidant capacity of green tea. Theaflavins retained antioxidant capacity similar to that of (-)-epicatechin monomers whilst conjugated flavonols did not contribute significantly to the antioxidant capacity of either green or black tea. After HPLC analysis of the antioxidant capacity of phenolics in black tea some 80% of antioxidant activity remained unaccounted for indicating the potential importance of thearubigens as antioxidants in black teas.

Feasibility study for the use of near infrared spectroscopy in the qualitative and quantitative analysis of green tea, Camellia sinensis (L.)

This paper indicates the possibility to use near infrared spectroscopy (NIR) combined with PLS as a rapid method to estimate the quality of green tea. NIR is used to build calibration models to predict the content of caffeine, epigallocatechin gallate (EGCG) and epicatechin (EC) and for the prediction of the total antioxidant capacity of green tea. For the determination of the total antioxidant capacity, the trolox equivalent antioxidant capacity (TEAC) method is used. Until now, the prediction of the antioxidant capacity as such by use of NIR has not been reported. For caffeine and TEAC, models are build for the whole green tea leaves and also for the ground leaves. For the polyphenols (EGCG and EC), only models for the whole leaves are investigated. A partial least squares (PLS) algorithm is used to perform the calibration. To decide upon the number of PLS factors included in the PLS model, the model with the lowest root mean square error of cross-validation (RMSECV) for the training set is chosen. The correlation coefficient ( r) between the predicted and the reference results for the test set is used as an evaluation parameter for the models: for the TEAC results r=0.90 for the model with the whole leaves, r=0.86 for the model with the powdered leaves are obtained. The caffeine prediction model has a correlation coefficient r=0.96 for the whole leaves and r=0.93 for the ground leaves. The correlation coefficient for the EGCG and the EC content models are, respectively 0.83 and 0.44.