• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.173-177
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• 1997

For the utilizing of tannins in the functional foods and natural inhibitor against browning reaction by tyrosinase in foods, inhibition effect against tyrosinase of tannins from Korean green tea was determined. Acetone extract from Korean green tea showed inhibition effect against tyrosinase. The gallocatechin compounds showed higher inhibition effect than the catechin compounds. In terms of stereo isomers, (-)-epicatechin compounds had higher inhibition effect than the (+)-catechin compounds. The monomer had higher inhibition effect than the dimer.

• Food Science and Biotechnology
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• v.16 no.1
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• pp.167-170
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• 2007

(-)-Epigallocatechin-3-gallate (EGCG), a mai or tea catechin has been shown to have many interesting biological activities. In the present study, we studied the effects of green tea catechins, EGCG metabolites, and black tea theaflavins on accumulation of EGCG in HT-29 human colon cells. Intracellular levels of [$^3H$]-EGCG were not changed significantly in the presence of other tea catechins including (-)-epicatechin, (-)-epigallocatechin, and (-)-epicatechin-3-gallate. EGCG methyl metabolites and EGCG 4"-glucuronide did not affect cellular levels of [$^3H$]-EGCG. Black tea theaflavins and theasinensin A (TsA), an EGCG oxidative dimer, however, significantly decreased cellular accumulation of EGCG in HT-29 cells by 31-56%. This decrease was more pronounced when cells were incubated in the presence of theaflavin-3',3"-digallate (TFdiG) or TsA. When EGCG was added separately from TFdiG or TsA, the accumulation of EGCG in HT-29 cells was also significantly decreased regardless of when TFdiG or TsA was added during the uptake study (p<0.01). The results suggest that theaflavins and TsA may interrupt EGCG absorption through the gastrointestinal epithelium.

• Journal of Nutrition and Health
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• v.34 no.4
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• pp.384-392
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• 2001

The purpose of this study was to investigate the effects of green tea catechin on the cadmium accumulation in body, cadmium excretion and detoxification functions in chronic cadmium poisoned rats. Sprague-Dawley male rats weighing 100$\pm$10g were randomly assigned to one normal group and three cadmium poisoned groups. Cadmium groups were classified to catechin free diet (Cd-0C group), 0.25% catechin diet(Cd-0.25C group) and 0.5% catechin diet(Cd-0.5C group) according to the levels of catechin supplement. Animals were maintained on 0, 0.25 and 0.5% catechin diets for 20 weeks and simultaneously administered 50ppm Cd(sup)2+ dissolved in the drinking water. Body weight, food intakes and food efficiency ratio in Cd-0C group was lower than the normal group. The accumulation of cadmium in rat liver, kidney, and blood was reduced by catechin supplementation. The excretion of cadmium in urine and feces was increased by catechin supplementation. The metallothionein(MT) contents in liver and kidney were increased in all cadmium groups compared with that of normal group. The ratios of cadmium absorption and retention ratios were significantly decreased in catechin supplementation groups. Accordingly, catechin supplementation resulted to an excretion of cadmium in urine and feces and a lowered accumulation of cadmium in liver and kidney by increasing methallothionein synthesis that led to the significant decrease in cadmium absorption and retention ratios.(Korean J Nutrition 34(4) : 384~392, 2001)

• Korean Journal of Medicinal Crop Science
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• v.14 no.6
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• pp.322-328
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• 2006

Green tea is of particular source as it has been found to have strong antioxidant activities. The extracts of green tea during the commercial harvest seasons from April, 2003 to August, 2003 were compared. The purpose of this study was to determine the correlation between the polyphenol content of green teas and its antioxidant activities. The con-tent of total polyphenols was analyzed and several antioxidant testings were performed. The levels of total polyphenols were higher in the green teas (e.g. Woojeon, Sejak) harvested during very early spring and lower in the green teas harvested late(eg. Ipha, Yepcha). In particular, the free radical scavenging, the inhibition of LDL oxidation, the cytoprotective effect and the inhibition of DNA damage were correlated with the total polyphenol contents of green tea extracts harvested early spring such as Woojeon, Sejak and Jungjak. The results obtained here show that all extracts of green teas including purified green tea catechin, GTC, have strong antioxidant activities on oxidative stress in vifrθ. The variation in polyphenol content and antioxidant activities among various types of green tea by the harvesting time may provide critical information for investigators and consumers using tea in purposes of nutrition and chemoprevention.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.5
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• pp.901-907
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• 1997

The purpose of this study was to investigate the effects of green tea catechin o n free radical generation system and peroxidative damage in the liver of streptozotocin(STZ)-induced diabetic rats. Spragu-Dawley male rats weighing 150$\pm$10gm were randomly assigned to one normal and three STZ-induced diabetic groups; diabetic groups were classified to catechin free diet(DM-oC group), 0.5% catechin diet(DM-0.5C group) and 1% catechin diet(DM-1C group) according to the levels of dietary catechin supplementation. Diabetes was experimentally induced by intravenous injection of 55mg/kg of body wt of STZ in citrate buffer(pH 4.3) after feeding of three experimental diet for 4 weeks. Animals were sacrificed at the 6th day of diabetic states. Activities of serum glutamic oxaloacetic transaminase(GPT) in DM-oC groups were higher than those of the normal group, and those in catechin supplementation group were similar to those of the normal group. Liver lipid peroxide values increased by 153%, 49%, and 27% in Dm-oC, DM-0.5C and DM-0C and Dm-1C but was not significantly different in catechin supplementation groups compared with the normal group, and liver cytochrome $P_{450}$ contents was similar to result of XOD activity. In electron microscopic examination of liver, lysosome was relatively scattered in Dm-oC and Dm-0.5C group and preserved normal shapes in DM-1C group. The present results indicate that STZ-induced diabetic rats are more sensitive to oxidative stress, leading to the acceleration of lipid peroxidation process, but this was reduced by anti-oxidative effect of high level of dietary catechin. It is concluded that dietary catechin serves as powerful antioxidant against lipid peroxidation in diabetic rats.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.1
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• pp.132-139
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• 2004

This study was peformed in order to compare general components, color, free amino acid, fatty acid and organic acid contents between commercial doenjang (C-1, C-2, C-3) and green tea doenjang (GT). The moisture content in green tea doenjang was higher than that in commercial doenjang, but the contents of crude protein, carbohydrate and energy in commercial doenjang were higher than those in green tea doenjang. The crude lipid and fiber contents of commercial doenjang were similar to green tea doenjang. Catechin content of green tea doenjang was 2.3%. The total content of free amino acids in commercial doenjang ranged from 2,739∼6,380 mg% in which it showed wide variation among samples and the total content of free amino acids in green tea doenjang was 3000 mg%. Glutamic acid was almost high in commercial doenjang except one product but green tea doenjang was low. Linoleic acid (51%) was the highest content among the fatty acids. The major organic acid in both commercial and green tea doenjang was oxalic acid and its content in commercial times higher than in green tea doenjang. The antioxidant activity of green tea doenjang was higher than that of commercial doenjang.

• The Korean Journal of Food And Nutrition
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• v.18 no.1
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• pp.94-101
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• 2005

The present study was conducted to know the physicochemical properties of Korean tea according to degree of fermention. The moisture content of green tea, blue tea, yellow tea and black tea was 2.02∼2.04%. The content of total nitrogen was 3.78 % in green tea and 3.49∼4.03% in fermented tea. The content of the mineral was highest in Ca, Mg. The content of vitamin C was 670.62 mg in green tea and 169.7∼85.03 mg in fermented tea. The content of vitamin C were increased as tea was more fermented. The composition of vitamin E and β-carotene was green tea> blue tea> yellow tea> black tea. The content of the rutin was 0.12 % in green tea and 1.37% in black tea. The content of rutin was increased with fermentation. The content of total amino acid of green tea was 2270.9 mg. The content of main amino acid of Glu, Asp, and Leu was 342.01 mg, 165.32 mg, and 161.69 mg and the hightst content of Glu. The content of total amino acid of black tea was 2,219.08 mg. Total amino acid content of fermented tea increased in the order of black tea> blue tea> yellow tea, and among the tea, the content of black tea was the highest in the fermented tea. The content of caffeine was 1.17% in green tea and 1.05∼1.32% fermented tea. These results were nothing in the content of caffeine during the fermentation. The content of theanine was 0.95% in green tea and 0.73∼1.42% in fermented tea. The content of total catechin was highest in green tea, and decreased sharply as tea was more fermented. Flavonoid content of 1.05% in green tea. DPPH radical scavenge activities of the teas 4.73∼19.5% mg.

• Microbiology and Biotechnology Letters
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• v.44 no.1
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• pp.62-67
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• 2016

Hydrolytic enzyme activities, including those of ${\beta}$-glucosidase, ${\beta}$-glucuronidase, ${\beta}$-xylosidase, ${\beta}$-galactosidase, ${\beta}$-arabinofuranosidase, ${\beta}$-arabinosidase, and ${\beta}$-arabinopyranosidase, which are useful for bioconversion, were explored in lactic acid bacteria isolated from Korean traditional fermented foods. Nine bacterial strains were selected for the fermentation of green tea extract prepared by supercritical fluid extraction. Changes in the concentrations of catechin, epicatechin, epicatechin gallate, epigallocatechin, and epigallocatechin-3-gallate in green tea extract were investigated after fermentation by the selected lactic acid bacteria strains. The strain Leuconostoc mesenteroides MBE1424, which showed the highest ${\beta}$-glucuronidase enzyme activity among the tested bacterial strains, increased the epigallocatechin content of the green tea extract by 60%. In addition, L. mesenteroides MBE1424 was more resistant than the control strain at high temperature and showed a maximum specific growth rate at $40^{\circ}C$. L. mesenteroides MBE1424 was presumed to have an enzyme system containing ${\beta}$-glucuronidase with utility in the bioconversion of green tea extract.

• YAKHAK HOEJI
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• v.53 no.2
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• pp.51-59
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• 2009

Quantitative analysis of (+)-catechin (C), (-)-epigallocatechin (EGC), (-)-epicatechin (EC), (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG) and caffeine in commercial green tea was carried out by HPLC employing gradient elution of 0.1% acetic acid and acetonitrile on ODS column. The optimized HPLC method provided satisfactory linearity, accuracy and precision. The relationship between the concentration of the components and cultivated region of the commercial green tea was not significant, while the concentration of EGCG, ECG and caffeine decreased significantly in the later harvested green tea samples (p<0.01). Multivariate analysis of the components was performed in order to characterize and evaluate the cultivated region and harvest period-related variation. Hierarchical clustering and discriminant analysis were applied to classify the geographical and seasonal origins of the green tea samples. The classification accuracy of the cultivated region and harvest period by discriminant analysis was 95% and 91%, respectively, indicating that this method could be reliable and convenient for the quality control of herbal products with different origin.

• Culinary science and hospitality research
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• v.22 no.5
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• pp.267-276
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• 2016

This study used HPLC to analyze the contents of catechins, alkaloids, and theanine of commercial green tea. Green tea samples were stored for 6 months at five different temperatures, $30^{\circ}C$, $15^{\circ}C$, $4^{\circ}C$, $-15^{\circ}C$ and $-40^{\circ}C$. Catechins change in storage temperature was $30^{\circ}C$ > $15^{\circ}C$ > $4^{\circ}C$ > $-15^{\circ}C$ > $-40^{\circ}C$ stored for 6 months. Total alkaloids content higher levels were CAF(27.49 mg/g) with lower level of TB(2.16 mg/g) and TP(0.28 mg/g). The total alkaloids content decreased in the longer storage periods, a similar case with, although CAF were almost unchanged in all storage temperatures. The results indicate that temperature and storage time are important in the storage of green tea, with refrigerated and frozen conditions as preferable to increase or preserve the chemical compounds of the green tea.