• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.3
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• pp.356-362
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• 2003

The present study was conducted to know the physicochemical properties of non fermented tea and fermented teas with the fermented time of 0 hr (non fermented tea), 10 hrs, 17 hrs (semi-fermented tea), 24 hrs (black tea), respectively The moisture content of non fermented tea, semi fermented, and black tea was 3.01% ~ 3.29%. The contents of reducing sugar, crude lipid, crude protein were increased and that of ascorbic acid was decresed with fermentation. The total contents of those increased as tea was more fermented. The contents of the citric acid and the malic acid were increased with fermentation, but the content of the succinic acid was decreased. However, the total content of organic acid was generally increased with fermentation. The total content of the amino acid was increased with fermentation. In non fermented tea, Thr+theanine, the Asp, and the Glu, were determined in order of content. In semi-fermented tea and black tea, Ter+theanine, Glu, and Asp were determined in order of content. The rate of essential amino acid in the total content of free amino acid was increased with fermentation. The content of theanine was 1.21% in non fermented tea and 1.50% in black tea. The contents of theanine were increased as tea was more fermented. The content of caffein was 3.57% in non fermented tea and 3.55 ~ 3.60% in semi-fermented tea and black tea. These results were inconsistent in the content of caffein. Five kinds of catechin, that is, cathechin, epigallocathechin, epicathechin, epigallocathechin gallate, and epicathechin gallate were extracted. The content of catechin was 14.18% in non fermented tea, but decreased sharply as tea was more fermented.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.4
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• pp.1649-1654
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• 2016

Tea derived from the leaves and buds of Camellia sinensis (Theaceae) is consumed worldwide. Green tea contains various components with specific health-promoting effects, and is believed to exert protective effects against diseases including cancer, diabetes and hepatitis, as well as obesity. Of the various tea components, the polyphenol catechins have been the subject of extensive investigation and among the catechins, (-)-epigallocatechin gallate has the strongest bioactivity in most cases. Our research group has postulated that hepatocyte nuclear factor-$4{\alpha}$, sterol regulatory element-binding proteins, and tumor necrosis factor-${\alpha}$ are targets of green tea constituents including (-)-epigallocatechin gallate for their anti-diabetes, anti-obesity, and anti-hepatitis effects, respectively. Published papers were reviewed to determine whether the observed changes in these factors can be correlated with anti-cancer effects of green tea. Two major action mechanisms of (-)-epigallocatechin gallate have been proposed; one associated with its anti-oxidative properties and the other with its pro-oxidative activity. When reactive oxygen species are assumed to be involved, our findings that (-)-epigallocatechin gallate downregulated hepatocyte nuclear factor-$4{\alpha}$, sterol regulatory element-binding proteins, and tumor necrosis factor-${\alpha}$ may explain the anti-cancer effect of green tea as well. However, further studies are required to elucidate which determinant directs (-)-epigallocatechin gallate action as an anti-oxidant or a pro-oxidant for favorable activity.

• The Korean Journal of Food And Nutrition
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• v.28 no.5
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• pp.766-773
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• 2015

This study analyzes the chemical composition of green tea, white tea, yellow tea, oolong tea and black tea with respect to extraction temperature and time. The optimum extraction conditions for these teas were determined by assessing the chemical composition of tea brewed at different temperature (50, 60, 70, $80^{\circ}C$) and extraction times (1, 3, 5, 10 minute). Catechins contents were the largest at 5 minutes and generally declined by 10 minutes. Green tea catechins contents were highest when brewed at $70^{\circ}C$ and besides other teas a change of the trend variation at 70 and $80^{\circ}C$. These temperatures did not extract theaflavins in green tea. Extract temperature and time did not significantly affect theaflavins content of white tea, yellow tea, and oolong tea. Black tea, however, was noticeably dependent on extract conditions, which were most effective at $70^{\circ}C$, brewed for 5 minutes. Caffeine content of green tea, yellow tea, and oolong tea was highest at 5 minutes, but temperature did not appear to affect the content. White tea and black tea caffeine content was highest when brewed at $70^{\circ}C$ for 5 minutes. Theobromine content of green tea, yellow tea, oolong tea, and black tea did not show major differences between the study times or temperature, though the content in white tea increased with higher temperatures when brewed for 5 minutes. The extraction of phenolic compounds increased until 5 minutes, and showed not further increase at 10 minutes. Antioxidant capacity of green tea, white tea, and yellow tea were maximized at $70^{\circ}C$ for 5 minutes or $80^{\circ}C$ for 3 minutes, while oolong and black tea were reached maximum antioxidants at $70^{\circ}C$ for 5 minutes. In general, to optimize the beneficial chemical content of brewed tea, a water temperature of $70^{\circ}C$ for 5 minutes is recommended.

• Korean Journal of Medicinal Crop Science
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• v.12 no.3
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• pp.183-190
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• 2004

The major compositions of leaf tea and flower tea were investigated to develope as a new functional tea using Korean native Camellia japonica L. Most of leaf teas, except flower tea, were considered as good materials with basic conditions for tea manufacture because water content was below 6%. Crude protein was the greatest component in roasted young leaf tea (RYLT), crude fats in roasted mature leaf tea (RMLT) and ashes in fermented young leaf tea (FYLT). Caffein were present as the highest amount (5.18%) in steamed mature leaf tea (SMLT), showing less amount than green tea. Catechin were contained as the highest amount in all kinds of teas, especially FYLT was the highest (9.57%). Tannin, which highly related with tea quality including astringent taste, color and perfume, were present as the highest amount in FYLT. Vitamin C was highly detected in the tea from flowers (22.7 mg/l00 g) rather than in the tea from leaves. The content of theanine were found in flower tea by 1,074 mg/l00 g, and had about twofold of FYLT and RYLT. Among free amino acids, glutamic acid and aspartic acid were higher detected in SMLT and RMLT while asparagine was present as higher amounts in RYLT and FYLT, expecting these components can improve tea taste. Nucleic acids and their derivatives including GMP, hypoxanthine and AMP were detected as the higher amounts by 7.86, 8.57, and $12.67\;{\mu}mol/g$, respectively, however IMP content was even reduced by all manufacturing processes. In all kinds of tea, sugars such as glucose, fructose, sucrose and maltose were detected, specially glucose and fructose were found as highest amount in RFT by 65.5 and 59.6 nmol/0.1 mg, respectively.

• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.12
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• pp.1807-1813
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• 2010

To manufacture the fermented tea with hygienic quality, green tea was fermented using Bacillus subtilis, Saccharomyces cerevisiae and Lactobacillus bulgaricus and chemical composition and sensory changes were evaluated during fermentation period. The lightness of the fermented samples decreased; in contrast, redness and yellowness increased. Especially, the color change of the fermented tea using B. subtilis was higher than those of control and other samples with different microorganisms during fermentation period. Chlorophyll contents were decreased by similar level regardless of fermentation treatments. The fastest decrease of total catechins contents were found in the tea fermented with B. subtilis and significantly reduced by increase of fermentation period. However, total catechin contents of the tea fermented by L. bulgaricus were not decreased. The caffeine contents of the microbial fermented teas were more decreased than that of control, even though the decrease was slight. Sensory panelists preferred the tea fermented by B. subtilis to those of control or other fermentation treatment.

• Food Science and Biotechnology
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• v.17 no.2
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• pp.408-412
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• 2008

Determining the elution of water-soluble substances from herbal teas is an important factor in their efficient use in terms of taste, perfume, and content of health-related components. The antioxidant activity and content of catechins in commercial Chrysanthemum indicum (gamguk) teas were determined for optimum elution conditions. The water extract of gamguk teas did not differ significantly in yield compared to methanol extracts and showed stronger antioxidant activity. Catechin contents in gamguk teas were 8-18% of the extracts when individual peaks in high-performance liquid chromatography analysis were compared to standard catechin peaks. Gamguk teas exhibited faster release of antioxidants, and the antioxidant activity was positively correlated with the thermal treatments. Gukhwacha (GC) was the best tea for rapid release (30 sec) of antioxidants with the $50^{\circ}C$ treatment, whereas antioxidants in other teas were relatively slower released.

• Food Science and Biotechnology
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• v.16 no.4
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• pp.501-508
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• 2007

Proanthocyanidins (PACs), also named condensed tannins, are polymers of flavan-3-ols such as (+ )-(gallo)catechin and (-)-epi(gallo)catechin. A proper analysis of the PACs, with difficult challenges due to their complex structures, is crucial in studies of cancer chemoprevention. Cancer is a leading cause of mortality around the world. Many experimental studies have shown that dietary PACs are potential chemopreventive agents that block or suppress against multistage carcinogenesis in both in vitro and in vivo models. Cancer chemoprevention by dietary PACs has been shown effective through different mechanisms of action such as antioxidant, apoptosis-inducing, and enzyme inhibitory activities. Good sources of dietary PACs are nuts, fruits, beans, chocolate, fruit juice, red wine, and green tea. The chemopreventive potential of dietary PACs should be considered together with their bioavailability in humans. The safety issues regarding carcinogenesis and gastrointestinal disorder are also reviewed.

• Food Science and Biotechnology
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• v.17 no.3
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• pp.464-469
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• 2008

In human beings, it is known that there is a correlation between the occurrence of acne and the ability to suppress sebum. Sebosuppression may be related to the inhibition of sebocyte proliferation, differentiation, and lipogenesis in sebaceous glands. To investigate the skin sebosuppressive activity of green tea extract, the in vivo effects of its flavonoid compounds on the androgen-dependent stimulation of pigmented macules in hamsters and performed in vitro experiments with human primary sebocytes were examined. Our results imply a dual activity of skin sebosuppression by green tea flavonoids; some catechins including epigallocatechin-3-gallate (EGCG) and gallocatechin-3-gallate (GCG) may reduce the differentiation of sebocytes by inhibiting PPAR-${\gamma}1$ mRNA expression, whereas some flavonol glycosides including kaempferol may inhibit lipogenesis in sebaceous glands by decreasing levels of the mature form of sterol-sensitive response elements binding protein-1c (SREBP-1c). Therefore, green tea is a potentially effective material for use in the development of health foods or cosmetics for skin sebosuppression.

• Natural Product Sciences
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• v.22 no.2
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• pp.87-92
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• 2016

Endothelial dysfunction in atherosclerosis is associated with increasing oxidative stress that could be reversed by antioxidant. Therefore epigallocatechin gallate (EGCG), epicatechin gallate (ECG), epigallocatechin (EGC) and catechin (C) of tea flavonoids were investigated for their roles in regenerating endothelial cell. Peripheral blood mononuclear cells (PB-MNCs) were isolated, plated and cultured in medium with/without treatment of EGCG, ECG, EGC and C. Results showed that among all EGCG, ECG, EGC and C concentrations tested, $12.5{\mu}mol/L$ was not cytotoxic for peripheral blood-derived endothelial progenitor cells (PB-EPCs). Treatment of EGCG, ECG, EGC or C increased the percentages of CD34, CD133, VEGFR-2 expressions and suppressed hydrogen peroxide-induced percentages of reactive oxygen species (ROS) level in PB-EPCs. Taken together, our current results showed that EGCG, ECG, EGC or C of tea flavonoids could induce differentiation of PB-MNCs into PB-EPCs as well as protect PB-EPCs from oxidative damage by suppresing the intracellular ROS levels.

• Journal of Pharmacopuncture
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• v.19 no.4
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• pp.312-318
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• 2016

Objectives: Bacterial resistant infections have become a global health challenge and threaten the society's health. Thus, an urgent need exists to find ways to combat resistant pathogens. One promising approach to overcoming bacterial resistance is the use of herbal products. Green tea catechins, the major green tea polyphenols, show antimicrobial activity against resistant pathogens. The present study aimed to investigate the effect of catechins, green tea extract, and methylxanthines in combination with gentamicin against standard and clinical isolates of Staphylococcus aureus (S. aureus) and the standard strain of Pseudomonas aeruginosa (P. aeruginosa). Methods: The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) values of different agents against bacterial strains were determined. The interactions of green tea extract, epigallate catechin, epigallocatechin gallate, two types of methylxanthine, caffeine, and theophylline with gentamicin were studied in vitro by using a checkerboard method and calculating the fraction inhibitory concentration index (FICI). Results: The MICs of gentamicin against bacterial strains were in the range of $0.312-320{\mu}g/mL$. The MIC values of both types of catechins were $62.5-250{\mu}g/mL$. Green tea extract showed insufficient antibacterial activity when used alone. Methylxanthines had no intrinsic inhibitory activity against any of the bacterial strains tested. When green tea extract and catechins were combined with gentamicin, the MIC values of gentamicin against the standard strains and a clinical isolate were reduced, and synergistic activities were observed (FICI < 1). A combination of caffeine with gentamicin did not alter the MIC values of gentamicin. Conclusion: The results of the present study revealed that green tea extract and catechins potentiated the antimicrobial action of gentamicin against some clinical isolates of S. aureus and standard P. aeruginosa strains. Therefore, combinations of gentamicin with these natural compounds might be a promising approach to combat microbial resistance.